ASME Conference Presenter Attendance Policy and Archival Proceedings

2018;():V003T00A001. doi:10.1115/IMECE2018-NS3.

This online compilation of papers from the ASME 2018 International Mechanical Engineering Congress and Exposition (IMECE2018) represents the archival version of the Conference Proceedings. According to ASME’s conference presenter attendance policy, if a paper is not presented at the Conference by an author of the paper, the paper will not be published in the official archival Proceedings, which are registered with the Library of Congress and are submitted for abstracting and indexing. The paper also will not be published in The ASME Digital Collection and may not be cited as a published paper.

Commentary by Dr. Valentin Fuster

Biomedical and Biotechnology Engineering: Biomaterials and Tissue: Modelling, Synthesis, Fabrication, and Characterization

2018;():V003T04A001. doi:10.1115/IMECE2018-86630.

In recent years, plasma activated medicine using non-thermal atmospheric-pressure plasma (NTAPP) has attracted great interest for chemotherapy. In this study, we aim to develop a chemotherapy system with reactive species generated in a plasma activated medium (PAM) for PC12 treatment. We observe the morphology change of PC12 cells and evaluate the effectiveness of PAM and the reactive species on axonal-extension enhancement.

First, we measured the amount of reactive species, such as H2O2, NO2, and NO3 in PAM. Second, we confirmed the stimulation effect of PAM on PC12 by measuring the axonal extension length of a 72-h culture after PAM stimulation. Experiments were conducted under 20 conditions to find an optimal condition. Using the grid method, significant axonal extension was confirmed. Next, the optimal conditions to promote PC12 axonal-extension was determined using the response surface method. Promotion of axonal extension was not confirmed in the cell culture using only H2O2. As a result, we presumed that the enhancement of axonal-extension was induced by the coupling effects of NO2, NO3 and H2O2, which are active species produced in PAM. Finally, we were able to declare that PAM exhibits a selective cell activation property for the chemotherapy of the central nervous system.

Commentary by Dr. Valentin Fuster
2018;():V003T04A002. doi:10.1115/IMECE2018-86637.

Numerous studies of electrical stimulation effects on the nerve regeneration have been carried out. However, there were very few investigations which adopt the 3D culture that mimics the in vivo environment. In this study, we designed and fabricated a new 3D direct current electric field (DCEF) stimulation bio-reactor and investigated the effectiveness on the axonal outgrowth enhancement. We searched an optimum structure using the finite element (FE) analyses to obtain a uniform DCEF in the culture region. A measurement result of DCEF strength showed an agreement with FE results. The rat phenocromocytoma cells (PC12) were disseminated in the collagen gel and 3D culture was performed. We observed the morphologies of cell bodies and neurites using the multiphoton excitation fluorescence microscope (MPM). Both increases in 11.3% of mean axonal length and in 4.2% of axogenesis rate, under the condition of 5.0 mV/mm on 6 hours a day for 4 days, were obtained. Further, there was a tendency of longer connecting distance between cell bodies in the DCEF group than one in the Control group. As a result, we validated the efficacies of our stimulation, both for the axonal extension and the neural network generation, using our newly developed bio-reactor.

Commentary by Dr. Valentin Fuster
2018;():V003T04A003. doi:10.1115/IMECE2018-86643.

Enhancement of nerve axonal extension by using the extracellular environmental stimulation were reported. In this study, we focused on the stretch stimulation, and developed a 3D cell culture system to mimic the in vivo extracellular matrices and investigated the fundamental mechanism of axonal extension enhancement.

Firstly, we fabricated the stretch stimulation device. The rat phenocromocytoma cells (PC12), the nerve-like cells, embedded in the collagen gel were poured into the stretch chamber. It was set in the stretch stimulation device, which could load the strain to the collagen gel. Secondly, we determined the structure of the stretch chamber to implement the uniform strain distribution in the culture region. Using the finite element (FE) analyses, we confirmed that the uniform strain is assigned in a region of 2.7 × 3.0 × 0.5 mm in the culture region, which is the candidate for the observation region. Thirdly, PC12 cells axonal extension under uniaxial cyclic stretch stimulation (4% strain, 1 Hz) of 24 hours was carried out. After 96 hours’ culture, we observed the 3D morphology of PC12 cells by the multiphoton excitation fluorescence microscope (MPM). Finally, we confirmed the availability of our stretch stimulation device and the enhancement effect of axonal extension.

Commentary by Dr. Valentin Fuster
2018;():V003T04A004. doi:10.1115/IMECE2018-86648.

In this paper, a pneumatic soft gripper is proposed with inspiration from sea anemone. The gripper is composed of an actuator and several silicone tentacles. With the power of compressed air, the soft actuator expands and folds the tentacles. The gripper wraps tentacles around the object and highly compliant tentacles conforms to the shapes of an object, enveloping and holding it. The physical model is fabricated with 3D printed PLA mold and silicone gel. The gripping mechanics are analyzed according to the experimental gripping operations. On basis of the experimental and analysis result, the compliant gripping is realized while the stability is to be increased. So the tentacle structure is then improved by multi-chamber soft body and vacuum jamming bag. The jamming bag is combined to the end of each tentacle, where the bag is filled with particles to conform to the object shape. Therefore, a reliable constraint is realized between the gripper and the object under vacuum conditions. The bending motion and shaping effect are verified through theoretical and experimental approaches. The important parameters in the vacuum jamming process are also obtained. With such device, soft adaptive bodies enlarges the contact area to adapt to the work-piece where vacuum jamming bags increase the gripping force and stability. It is convenient for universal gripping operation for objects with different shapes.

Commentary by Dr. Valentin Fuster
2018;():V003T04A005. doi:10.1115/IMECE2018-86653.

In the clinical application, the mechanical stimulation against the damaged brain tissue is adopted as the kinesitherapy for the nerve regeneration. Nevertheless, the fundamental mechanism to repair the damaged nerve cell has not been revealed yet. Recently, the cyclic stretch stimulation has been reported as the efficacious treatment method to enhance the axonal extension for regenerative therapy of injured nerve cell. Therefore, we try to develop a new cellular automaton (CA) finite element (FE) hybrid method to predict the axonal extension and nerve network generation, which can evaluate the effect of stretch stimulation on the cell body, axon and dendrites.

In the FE results, the stress concentration occurred at the junction of the axon and cell body. The maximum stress value in the axon was 8.2 kPa which is about twice as large as that of the cell body. CA adopted to predict the morphological evolution of nerve cells under the mechanical stimulation. It was confirmed that the stress affects to accelerate the axonal extension as experimentally suggested. As a result, our CAFE can be employed to simulate the axonal extension and generation of nerve network system under the condition of extra cellular mechanical stimulation.

Commentary by Dr. Valentin Fuster
2018;():V003T04A006. doi:10.1115/IMECE2018-87242.

The thickening of the aortic wall is a mechanical adaptation to the prolonged increase in intravascular pressure resulting from hypertension, which is regulated by the smooth muscle cell layer (SML) and the elastic lamina (EL). Herein, we built a simplified computational model of the aortic media composed of SML and EL and simulated the phenomenon of EL undulation or EL buckling at no-load condition (in vitro) by releasing compressive prestress assigned to the EL. Using the design of experiments approach, we found that the prestress assigned to the EL, the thickness of the EL, and a coupled or interspace connecting length between the SML and the EL are significantly influential factors in representing EL buckling at the unloaded state. We also found that the degree of EL waviness and the change in residual stresses within the SML and the EL are inversely correlated. Furthermore, by increasing the stiffness of the SML, we successfully reconstructed the disappearance of EL undulation at 25% stretch, replicating the dilation of a normal aorta under physiological loading conditions. It can be expected that these findings will help unveil the roles of the SML and the EL in maintaining the mechanical homeostasis of the arterial wall.

Commentary by Dr. Valentin Fuster
2018;():V003T04A007. doi:10.1115/IMECE2018-87406.

In this article, the nano and microhardness and the elastic modulus of the human elbow bones (humerus, ulna and radius) were studied. The nano properties were studied using load controlled technique with a load of 20 mN, while the micro properties were studied under 1 N load. A total of nine bone samples from three cadavers of ages between 45 and 55 years were tested. The measurements were carried out on both osteonal and interstitial bone in the longitudinal direction. The nanoindentation results indicated higher values for interstitial bone (hardness: 0.74 ± 0.09 GPa, elastic modulus: 19.05 ± 1.92 GPa) than for osteonal bone (hardness: 0.53 ± 0.05 GPa, elastic modulus: 16.66 ± 1.55 GPa). Consistent results were obtained at a depth of penetration between 1.1 μm to 1.5 μm in nanoindentation. In the case of microindentation, the microhardness and elastic modulus of interstitial bone was found to be 0.65 ± 0.07 GPa and 20.60 ± 2.27 GPa. Whereas for osteonal bone it was observed to be 0.60 ± 0.08 GPa and 14.56 ± 1.42 GPa respectively. The depth of penetration varies between the 8 μm to 11 μm for microindentation studies. In both measurement scales, a noticeable difference was observed between the osteonal and interstitial bone properties. As bone is a hierarchical structure, identifying the mechanical properties at the lamellar level helps in understanding the local mechanical environment of basic elements of the bones and predicting the behavior of the bone due to physiological loading.

Commentary by Dr. Valentin Fuster
2018;():V003T04A008. doi:10.1115/IMECE2018-87600.

This paper presents the findings of destructive compression testing on Formlabs© CLEAR Resin FLGPCL02 and TOUGH Resin FLTOTL03. Compression testing ASTM D695-15 was chosen because of the extreme fragility of the Clear Resin which did not allowed proper tensile testing with our equipment. The material was subjected to a steadily increasing compressive load until complete failure occurred. Five mechanical properties were extracted from stress versus strain curves. The five experimental properties, of Formlabs© CLEAR resin, found were young’s modulus (1.52 GPa) (std = 71 MPa), yield strength (39.6 MPa) (std = 2 MPa), ultimate strength (255 MPa) (std = 35 MPa), strain at fracture (0.509 m/m) (std = 0.0159 m/m), and toughness (49.1 J/m−3) (std = 3.9 J/m−3). The five experimental properties, of Formlabs© TOUGH resin, found were secant modulus (73.9 MPa) (std = 0.87 MPa), yield strength (42.8 MPa) (std = 3.03MPa), ultimate strength (587 MPa) (std = 61 MPa), strain at fracture (0.686 m/m) (std = 0.0097 m/m), and toughness (65 J/m−3) (std = 6 J/m−3). These were then compared to Formlabs© public released values.

Commentary by Dr. Valentin Fuster
2018;():V003T04A009. doi:10.1115/IMECE2018-87719.

GUR1050 is a medical grade variety of ultra-high molecular weight polyethylene (UHMWPE) intended for use on total joint prosthesis and implants. Probes of this material were characterized on a compression test following ASTM norms and lineaments.

Available data from these mechanical tests is fitted on multiple material models. Achieved results on numerical solutions of finite element modeling (FEM) of the tests are discussed, looking for the best one available in order to simulate with accuracy GUR1050 behavior, with specific interest on the load curve results, showing the pertinence of using certain models on different conditions.

It was found that the use of a bilinear isotropic hardening model assures the best fit for GUR1050 behavior in uniaxial compression under a constant strain rate.

Commentary by Dr. Valentin Fuster
2018;():V003T04A010. doi:10.1115/IMECE2018-88482.

Engineered tissue constructs are assembled through combining scaffolds, cells and biologically active molecules for restoring, maintaining, or improving damaged tissues or whole organs. Cells in engineered tissue constructs often experience mechanical forces during the fabrication process, maturation process, and under in vivo conditions. These mechanical forces/stimuli induce cellular responses and affect cell viability, proliferation, and differentiation. While it is critical to understand the mechanical milieu of cells in tissue constructs, it is also extremely challenging due to the time and length scale span. Multiscale modeling approaches have been emerged to provide linkage among different length scale. One of the approaches is continuum based multiscale modeling to link organ, tissue and cellular levels. A representative volume element (RVE) with periodic or random microstructure serves as a vehicle to connect different length scales. This study focuses on effects of RVE selection, microstructure, and boundary conditions on the mechanical environment at cellular level. In particular, cell embedded alginate tissue constructs were studied. Hyperelastic models were used for modeling alginate and cells. Multi-cellular FE models were generated. The results of the average properties and the stress/strain experienced by cells were compared under different conditions.

Commentary by Dr. Valentin Fuster

Biomedical and Biotechnology Engineering: Biomedical Devices

2018;():V003T04A011. doi:10.1115/IMECE2018-86009.

Research in the field of blood glucose monitoring systems has led to incredible advancements over the past several decades. The blood glucose level of a diabetic patient is vital to monitor since large swings in blood sugar can cause life threatening damage to the individual. The importance of blood glucose monitoring increases when a patient experiences hypoglycemia, which can be very dangerous. The objective of this project is to create a low cost portable device that utilizes the modular bio-signal sensor kit BITalino and Arduino Uno microcontroller to measure and process the electrodermal activity (EDA) and electrocardiography (ECG) signals that can be associated with a drop in the subject’s blood glucose level to detect hypoglycemia in diabetics.

Commentary by Dr. Valentin Fuster
2018;():V003T04A012. doi:10.1115/IMECE2018-86013.

Several types of implants, plates, and screws have been developed for corresponding bone fractures at different sites. To understand the mechanical behavior of a bone plate and to provide surgeons with suggestions for selecting screw positions, this study aimed to create an APP to provide pre-surgical planning using a computed tomography (CT)-based finite element model. This model was validated using a compression test of synthetic sawbones. Furthermore, the specific APP was established using the COMSOL application builder to calculate the stress and strain of the implant under different screw positions. This APP reveals how the number and location of screws affect the stress distribution of the implant. It can provide clinicians with preliminary reference information before surgery.

Commentary by Dr. Valentin Fuster
2018;():V003T04A013. doi:10.1115/IMECE2018-86031.

The heart health monitoring system is a combination of electronics, wireless communication, computer, and information technologies, which allows an individual to measure and analyze their heart rate in real time and also notifies them about any abnormal cardiac events. This project was performed with an objective of developing and validating a low-cost, portable system that will successfully detect symptomless Atrial Fibrillation (AF), which is considered to be one of the most common and frequent cardiac disorders. The prototype device will measure and analyze the heart beat variations and varying-time period between successive R peaks (RR intervals) of the ECG signal and will compare the results with the normal heart rate and RR intervals. Upon exceeding the threshold values, this device will create an alert to notify about the potential AF detection.

Commentary by Dr. Valentin Fuster
2018;():V003T04A014. doi:10.1115/IMECE2018-86120.

This paper presents a novel medical device developed using shape memory polymer (SMP) foams for the endovascular treatment of intracranial aneurysms (ICAs). The SMP foam is fabricated, characterized, and experimentally investigated to better understand their potential for endovascular embolization of ICAs. Polyurethane-based SMP is successfully synthesized and characterized. The SMP foam is manufactured using cast molding, and characterized using an electro-thermal triggering mechanism to fully understand their shape recovery capability. The successful completion of this work will serve as a solid foundation for the development of new biomedical devices to treat intracranial aneurysms and develop an optimal releasing procedure for future animal study.

Commentary by Dr. Valentin Fuster
2018;():V003T04A015. doi:10.1115/IMECE2018-86345.

Laparoscopic Devices are known to be used in Minimal Invasive Surgeries. However, the devices are unable to transmit the spectrum of feedback of the tissue to the hands of the surgeon, which makes the surgical procedure difficult. We have demonstrated a parameterization for the loss in feedback due to backlash and friction. Backlash is correlated to the joint clearances while friction correlates to joint clearance as well as the surface finish of mating pairs, though joint clearances don’t affect the friction coefficient largely. The laparoscope behavior has been dynamically modeled to understand and predict the behavior. Also, the cost to manufacture the graspers has been weighed against force bandwidth and reliability of improving the joint tolerances of the device so that it is able to transmit the desired force bandwidth. We conclude that to achieve kHz force bandwidth through purely mechanical means would entail prohibitively expensive manufacturing means and hence, we propose an alternate design. The alternate design makes the system deterministic without uncertainty in the position of the joint pins. The kinematically constrained joints in the new device completely transmit the input force spectrum at frequencies of multiple kHz. The non-sophisticated alteration in the original device doesn’t significantly alleviate the cost and eludes the loss of tactile sensation.

Commentary by Dr. Valentin Fuster
2018;():V003T04A016. doi:10.1115/IMECE2018-86450.

Background: Pressure distribution for transtibial amputees (TTA) patients varies at the limb socket interface according to several factors. Although socket technology is getting more advanced, the majority of researchers are still facing problems with relief areas.

Objectives: This study focused on the theoretical and experimental aspects of the design to figure out patients’ sensitivity to pain when wearing sockets. Relief areas were analyzed using data collected from patients’ centers and optimized under different static and dynamic conditions.

Methods: Finite element trials and DOE optimization using Design Expert 8 software and analysis of variance (ANOVA) revealed that holes with relief areas are appropriates for lower extremities patients where scanning electron images (SEM) of the worn areas show direct relations between relieved sockets with holes at fibula head (FH) and patient lifestyle and activity.

Clinical Relevance: A patient that moves rather slowly, as a result of old age or sedentary level of activity would greatly benefit from the FH socket hole implementation, and thus reduces the wear of socket materials after longer period of time and increases the level of comfort of patient skins. the interviews conducted were evident that patients endured pain at the PT and FH. Moreover, further studies were performed on the FH, and results revealed that lateral forces play a major role and is influenced by the lifestyle of the patient.

Commentary by Dr. Valentin Fuster
2018;():V003T04A017. doi:10.1115/IMECE2018-86507.

Lung supportive devices (LSD) are widely used for respiratory ventilation and therapy to help provide breathing support for patients with various lung diseases including Obstructive Sleep Apnea. These devices deliver air to the patient through a nasal or facial mask, and the use of these devices normally results in dryness in the upper airways. However, the exhaled air consists of very high humidity content. The question raised, is it possible to recover some of the moisture content of this air to reuse in the inhalation process.

This research focuses on developing an element which can recover the moisture from the exhaled air and the possibility of using it for re-inhalation. The main component is made up of a fibrous cotton fabric polymerized with Poly (N-isopropylacrylamide) (PNIPAM) and sewed with a resistor filament to control the temperature. The results show a viable element which is able to trap water molecules from the expiration airflow and release them into the inspiration airflow.

Commentary by Dr. Valentin Fuster
2018;():V003T04A018. doi:10.1115/IMECE2018-86593.

In this work, the authors first study different designs of prosthetic ankles. Then, a new design is proposed, and its dynamics are discussed. Various experiments are conducted to verify the concept. The results of the experiments are discussed, and a conclusion is drawn based on the discussion. An OpenSim simulation is run to emulate the effects of the prosthesis on an amputee’s residual leg. Further iterations of the same design are then discussed and presented. Finally, a conclusion is drawn on the usability of the ankle along with some suggestions for future research.

Commentary by Dr. Valentin Fuster
2018;():V003T04A019. doi:10.1115/IMECE2018-86620.

The paper presents the design of a smart glove with flexible sensors integrated with wireless technology to measure the signals of grabbing and grasping. The sensor technology is structured into three phases: sensor calibration, amplification and digitizer of the wearable sensors. The real-time raw data is collected, filters are designed to remove the noise and relay the information to the developed application via Bluetooth. The Bluetooth module communicates with an android mobile application through the Bluetooth networks known as the piconets. Piconets use a master/slave model with a Bluetooth module to control and send data that communicates with a smart device. The mobile application sends and receives information to/from the Bluetooth module and the mobile device. This allows the user to analyze the forces applied in each finger for various operations. The interactive glove interfaced with mobile technology provides gesture recognition and maps the finger orientation. The purpose of designing such a glove is to train the user how to improve their hand defense mechanism as the mobile device informs about the multi finger gripper control. To improve the quality of hand rehabilitation, the proposed design can provide physicians an efficient tool to evaluate the recovery of patient’s hand injury.

Topics: Design , Grippers
Commentary by Dr. Valentin Fuster
2018;():V003T04A020. doi:10.1115/IMECE2018-86766.

This paper presents a small radio frequency sensor namely multi-slot antenna for liver tumor ablation at microwave spectrum. A computer simulation model was developed to validate the proposed antenna. The authors tested the proposed antenna on pig liver tissue samples. Both simulation and experimental results showed that the proposed multi-slot antenna has the potential for liver cancer treatment in the future.

Commentary by Dr. Valentin Fuster
2018;():V003T04A021. doi:10.1115/IMECE2018-86893.

There remains a need for a cost-effective, sensitive and on-site analytical technique which requires minimal technical skills for monitoring chemical contaminants in water. This research work presents a smartphone-based colorimetric detection of trace chemical pollutants in water. Components of the Hue, Saturation and Value (HSV) color space within a global region of interest (ROI) of analytes’ image were utilized in developing an algorithm for the quantitative detection of target ions. Calibrations were conducted with Chromium (VI) and Nitrite analytes ranging between 0–250 ppb and 0–3000 ppb respectively. The calibration equation and coefficient of correlation as obtained were HS2 = −0.00918C+6.46003; R2 = 0.9997 and HS2 = −0.00584C+4.85119; R2 = 0.98228 respectively. The smartphone-based monitoring system was utilized to systematically obtain the concentration of target ions in arbitrary solutions. Limits of detection of the system for Nitrite and Chromium (VI) which are within USEPA specification were approximately 285 ppb and 16 ppb respectively. Appreciable agreements between conventional and proposed techniques were obtained with a maximum percentage difference of 8.21% in the concentration of an arbitrary sample.

Topics: Water , Pollution
Commentary by Dr. Valentin Fuster
2018;():V003T04A022. doi:10.1115/IMECE2018-87097.

Infection after joint arthroplasty is the most devastating complication that can occur. As a result, antibiotic eluting biomaterials have been created using three-dimensional printing to prevent these infections. The goal of this study was to investigate the ability of an SLA printer to create accurate internal geometries capable of carrying antibiotics. The maximum amount of unwanted polymer was 0.9 g, which did not vary with resin viscosity or internal void size. This suggests SLA printing may have potential to create accurate, drug eluting biomaterials in a wide variety of polymers and geometries.

Topics: Canals , Design , Printing
Commentary by Dr. Valentin Fuster
2018;():V003T04A023. doi:10.1115/IMECE2018-87669.

This paper presents a numerical study of the influence of different factors on tumor detection via a 2D tactile sensor. The 2D tactile sensor entails a polydimethylsiloxane (PDMS) microstructure embedded with a 3 × 3 sensing-plate/transducer array. By pressing the sensor against a tissue region with a predefined indentation depth pattern, the tissue stiffness distribution is extracted from the measured slopes of the deflections of the sensing-plate array versus the indentation depth. In this work, we numerically investigate the influence of curved tissue surface, curved substrate and tissue viscoelasticity on the measured sensor deflection distribution, which is representative of the tissue stiffness distribution. A set of numerical models are created in COMSOL Multiphysics to investigate the influence of the above-mentioned factors separately. A purely elastic numerical model with a flat substrate and a flat tissue surface is created as the reference model. Two other numerical models are created with one having a curved surface and the other having a curved substrate. The same tumor is embedded in these three models. Given the same 2D sensor, how the measured sensor deflection distribution is affected by different curved surfaces and curved substrates is compared with the results from the reference model. The three tumor parameters (elasticity, size and depth) are also varied for their influence on the measured results. A separate viscoelastic numerical model is created to study how the time-dependent behavior of a tumor varies with its viscoelasticity. This model provides the guidance on tailoring the testing parameters in a pre-defined indentation protocol for quantitatively maximizing the difference in viscoelasticity among different tumors.

Commentary by Dr. Valentin Fuster
2018;():V003T04A024. doi:10.1115/IMECE2018-87905.

Many lower limb disabled, elderly subjects prefer wheelchairs as mobility devices. Transferring such subjects from the wheelchair to and from the bed/toilet seat is one everyday challenge. Caregivers provide manual transfer support to such subjects which increase their caregiver dependence. Lower back pains of caregivers, injury incidences during transfer support are related issues regarding manual caregiver transfer support. Long-time wheelchair users are generally exposed to many health problems associated with idle seated posture in a wheelchair for a long time. The wheelchair with a standing facility allows the user to be able to adjust him to different heights giving enhanced navigations in different situations. Thus, reconfigurable wheelchair built-in with sit-to-stand and sit-to-sleep capabilities can be a handy assistive device for a long time wheelchair users. Thus, the paper presents the design and development of a reconfigurable wheelchair with stand-sit-sleep configurations. Key areas focused on maximizing safety, optimizing the size with minimizing the cost and weight of the wheelchair. The developed model will help in improving the functional capabilities of wheelchair users allowing enhanced independence and quality of life (QoL).

Commentary by Dr. Valentin Fuster
2018;():V003T04A025. doi:10.1115/IMECE2018-87963.

Intra-operative medical imaging based on magnetic resonance imaging (MRI) coupled with robotic manipulation of surgical instruments enables precise feedback-driven procedures. Electrically powered non-ferromagnetic motors based on piezoelectric elements have shown to be well suited for MRI robots. However, even avoiding ferrous materials, the high metal content on commercially available motors still cause distortions to the magnetic fields. We construct semi-custom piezoelectric actuators wherein the quantity of conductive material is minimized and demonstrate that the distortion issues can be partly addressed through substituting several of these components for plastic equivalents, while maintaining motor functionality. Distortion was measured by assessing the RMS change in position of 49 centroid points in a 12.5mm square grid of a gelatin-filled phantom. The metal motor caused a distortion of up to 4.91mm versus 0.55mm for the plastic motor. An additional SNR drop between motor off and motor spinning of approximately 20% was not statistically different for metal versus plastic (p = 0.36).

Commentary by Dr. Valentin Fuster
2018;():V003T04A026. doi:10.1115/IMECE2018-88156.

Dielectrophoresis (DEP) has been demonstrated as an effective mechanism for cell sorting in microfluidic settings. Many existing methods utilize sophisticated microfluidic designs that require complicated fabrication process and operations. In this paper, we present a microfluidics-based cell sorter that is capable of sorting microparticles continuously in a simple straight channel, thus facilitating easier fabrication and operation. An array of indium-tin oxide (ITO) electrodes are embedded on the bottom surface of the straight channel to generate a DEP force field. This force results in deviation of the particles with different dielectric properties from their paths that are hydrodynamically focused in the channel. Particle trajectories are predicted by numerical simulation at different flow rates and field strengths using COMSOL. Separation of red blood cells from polystyrene beads is demonstrated and numerical prediction is validated experimentally. High separation efficiency for the two particle types is confirmed by counting the concentrations of particles collected at the respective collection outlet.

Commentary by Dr. Valentin Fuster
2018;():V003T04A027. doi:10.1115/IMECE2018-88383.

Recently there has been a growing interest to develop innovative surgical needles for percutaneous interventional procedures. Needles are commonly used to reach target locations inside of the body for various medical interventions. The effectiveness of these procedures depends on the accuracy with which the needle tips reach the targets, such as a biopsy procedure to assess cancerous cells and tumors. One of the major issues in needle steering is the force during insertion, also known as the insertion (penetration) force. The insertion force causes tissue damage as well as tissue deformation. It has been well studied that tissue deformation causes the needle to deviate from its target thus causing an ineffective procedure. Simulation of surgical procedures provides an effective method for a robot-assisted surgery for pre- and intra-operative planning. Accurate modeling of the mechanical behavior on the interface of surgical needles and organs, specifically the insertion force, has been well recognized as a major challenge. Overcoming such obstacle by development of robust numerical models will enable realistic force feedback to the user during surgical simulation. This study investigates feasibility of predicting the insertion force of bevel-tip needles based on experimental data using neural network modeling. Simulation of the proposed neural network model is performed using Kera’s Python Deep Learning Library with TensorFlow as a backend. The insertion forces of needles with different bevel-tip angles in gel tissue phantom are measured using a specially designed automated needle insertion test setup. Input-output datasets are generated where the inputs are defined as bevel-tip angles and gel tissue phantom stiffness, and the output is defined as the insertion force. A properly trained neural network then maps the input data to the output data and the input-output dataset is supplied to train a neural network. Its performance is then evaluated using different and unseen input-output dataset. This paper shows that the proposed neural network model accurately predicts the insertion force.

Commentary by Dr. Valentin Fuster

Biomedical and Biotechnology Engineering: Biomedical Imaging and Tissue Characterization

2018;():V003T04A028. doi:10.1115/IMECE2018-86233.

It is widely recognized that bone mineral content is a main contributor to cortical bone stiffness. Previous works by the authors revealed that stiffness of mid-diaphysis cortical bone increases with increasing radial position from interior to exterior regions. In this work, we correlate this radial cortical stiffness to the chemical composition of several bone rings cut from 2-year old bovine cow femur (collected fresh from butcher). This mineralization is quantified using energy-dispersive X-ray (EDX) spectroscopy. On each bone ring, five regions are assigned along a 4 mm radial line covering the entire cortical wall thickness. Locations along the radial distance are assigned to acquire the chemical analysis spectrum. Calcium (Ca) and Phosphorus (P) elements chemical elements are traced/detected. Measured mineralization results are expressed as per weight percent concentration (wt %). These elemental results for Calcium (Ca) and Phosphorus (P) are correlated to radial position and stiffness values using statistical analysis (SPSS®). Calcium (Ca) and Phosphorus (P) elements were positively correlated with stiffness values and radius whilst Ca/P ratio was almost constant with the radius. Findings suggest that with increasing radius, Ca (wt%) and P (wt %) showed a fairly increasing trend that correlates to increasing stiffness values proving that increased bone mineralization would contribute to cortical bone stiffness.

Commentary by Dr. Valentin Fuster
2018;():V003T04A029. doi:10.1115/IMECE2018-86765.

This paper presents the development of a deep convolutional neural network (CNN) method namely super-solution CNN to produce a high-resolution microwave breast image from a low-resolution model, which helps to improve the accuracy and efficiency of breast lesion detection within microwave image. Various experiments are conducted to validate the proposed method. Experimental results show that the proposed approach has the potential to produce a high-resolution breast image with high-accuracy.

Commentary by Dr. Valentin Fuster
2018;():V003T04A030. doi:10.1115/IMECE2018-87259.

Mechanical properties of biomaterials are difficult to characterize experimentally because many relevant biomaterials such as hydrogels are very pliable and viscoelastic. Furthermore, test specimens such as blood clots retrieved from patients tend to be small in size, requiring fine positioning and sensitive force measurement. Mechanobiological studies require fast data recording, preferably under simultaneous microscope imaging, in order to monitor events such as structural remodeling or localized rupture while strain is being applied. A low-profile tensile tester that applies prescribed displacement up to several millimeters and measures forces with resolution on the order of micronewtons has been designed and tested, using alginate as a representative soft biomaterial. 1.5% alginate (cross-linked with 0.1 M and 0.2 M calcium chloride) has been chosen as a reference material because of its extensive use in tissue engineering and other biomedical applications. Prescribed displacement control with rates between 20 μm/s and 60 μm/s were applied using a commercial low-noise nanopositioner. Force data were recorded using data acquisition and signal conditioning hardware with sampling rates as high as 1 kHz. Elongation up to approximately 10 mm and force in the range of 250 mN were measured. The data were used to extract elastic and viscoelastic parameters for alginate specimens. Another biomaterial, 2% agarose, was also tested to show versatility of the apparatus for slightly stiffer materials. The apparatus is modular such that different load cells ranging in capacity from hundreds of millinewtons to tens of newtons can be used. The apparatus furthermore is compatible with real-time microscope imaging, particle tracing, and programmable positioning sequences.

Commentary by Dr. Valentin Fuster
2018;():V003T04A031. doi:10.1115/IMECE2018-87362.

Endovascular treatment has become the standard for intracranial aneurysm management. In vitro systems including an artery model are required for devices evaluation and clinician training. Although silicone is usually use for such model, its compliance is known to be lower than blood vessels. The purpose of this study was to analyze the influence of model material compliance on flow properties.

Silicone and 12 [wt%] poly (vinyl alcohol) hydrogel (PVA-H) were used to create two box-shaped models of significantly different compliance. The inner lumen geometry was a 4 [mm] diameter straight tube (parent vessel) and a 10 [mm] diameter sphere representing the aneurysm. A blood-mimicking fluid made of a mixture of glycerin, water and sodium iodide was used to reproduce the viscosity and density of blood and fit models refractive index. The circulation system consisted of a pulsatile blood pump and resistance valve. A flow rate of 250±50 [ml/min] and pressure from 75 to 115 [mmHg] were set inside the model. Pressure and flow rate sensors were used to monitor flow conditions before and after the model. Particle image velocimetry (PIV) was performed to record the difference of flow patterns inside the aneurysm of both model using a Nd:YAG solid laser system and fluorescent particles.

Results revealed a significant change of flow conditions due to model compliance. Attenuation of the flow rate pulse was recorded between the inlet and the outlet of the both model. This attenuation was 51% for PVA-H model. Moreover, a time lag between outlet pressure and outlet flow rate curves was recorded in both model. This time lag was longer with the PVA-H model, as this model exhibit a greater compliance.

PIV experiments revealed significant changes of flow patterns and velocity inside the aneurysm. Because of its high compliance, PVA-H model walls moved under the pulsatile conditions. A change of flow direction and decrease of its velocity were observed near the proximal wall of the aneurysm, compared to the silicone model. Such differences might modify the stress on the wall of the aneurysm.

To conclude, our experiments revealed that compliance has significant impacts on flow properties and should be taken into account for in vitro vascular model manufacturing.

Topics: Flow (Dynamics)
Commentary by Dr. Valentin Fuster
2018;():V003T04A032. doi:10.1115/IMECE2018-87563.

In the United States, Alzheimer’s disease (AD) affects one in ten people ages 65 and older. In most patients, the first indication of AD is the inability to remember new information, and symptoms grow to include behavior changes and increasing confusion and suspicions surrounding loved ones and daily events. As the disease progresses, the cortex and hippocampus regions of the brain decrease in size, allowing the fluid-filled ventricles within the brain to increase. New and innovative therapies to delay the onset of the disease and progression of the symptoms are being discovered. For example, the antibody solanezumab is undergoing clinical trials to determine its ability to reduce the levels of beta-amyloid in the brain, a known risk factor of AD. Consequently, the ability to identify patients who could benefit from the therapies will be invaluable. The purpose of this study is to determine if the digital volume correlation (DVC) algorithm can detect and track the onset and progression of AD using magnetic resonance imaging (MRI) scans of the head. DVC measures the deformation and strain of the volumetric MRI dataset by tracking the changes in its grey value pattern. A collection of MRI datasets of a patient’s head, which include scans from a baseline visit and visits at 6 months, 12 months, and every 12 months thereafter, is used in our analysis. A strain is applied to each set of MRI scans prior to implementation of the digital volume correlation algorithm. The DVC algorithm is then applied to the dataset and the resulting error between the expected and calculated strain is computed. A decrease in the contrast of the MRI dataset will correlate to additional error by the algorithm. As a result, an increase in the calculated strain error is anticipated to correlate with an increase in the ventricles in the brain, or progression of the disease, over the time period of interest.

Topics: Algorithms , Diseases
Commentary by Dr. Valentin Fuster

Biomedical and Biotechnology Engineering: Biotransport (Fluid, Heat, and Mass)

2018;():V003T04A033. doi:10.1115/IMECE2018-86216.

We consider modeling of single phase fluid flow in heterogeneous porous media governed by elliptic partial differential equations (PDEs) with random field coefficients. Our target application is biotransport in tumors with uncertain heterogeneous material properties. We numerically explore dimension reduction of the input parameter and model output. In the present work, the permeability field is modeled as a log-Gaussian random field, and its covariance function is specified. Uncertainties in permeability are then propagated into the pressure field through the elliptic PDE governing porous media flow. The covariance matrix of pressure is constructed via Monte Carlo sampling. The truncated Karhunen–Loève (KL) expansion technique is used to decompose the log-permeability field, as well as the random pressure field resulting from random permeability. We find that although very high-dimensional representation is needed to recover the permeability field when the correlation length is small, the pressure field is not sensitive to high-oder KL terms of input parameter, and itself can be modeled using a low-dimensional model. Thus a low-rank representation of the pressure field in a low-dimensional parameter space is constructed using the truncated KL expansion technique.

Commentary by Dr. Valentin Fuster
2018;():V003T04A034. doi:10.1115/IMECE2018-86485.

A numerical analysis is conducted to study the thermal behavior of human healthy and cancerous tissues during magnetic nanoparticle hyperthermia treatment. A transient multi-layer two-dimensional model is developed using commercial CFD package, ANSYS-FLUENT 18.1. The impact of therapeutic heat generation rate and various tissue cooling conditions on the thermal response of the tumor and normal tissues are investigated. It was found that the tumor temperature is not affected by different cooling conditions while the temperature of healthy tissues around tumor is significantly impacted. The results also demonstrated that the effective tumor temperature can be achieved in approximately ten minutes by using therapeutic heat generation rate of 150 kW/m3 in all three cooling conditions.

Commentary by Dr. Valentin Fuster
2018;():V003T04A035. doi:10.1115/IMECE2018-86809.

Influence of the rheological model selection on the flow and mass transfer behavior of human blood in a separated and reattached flow region is investigated. Newtonian and non-Newtonian hemorheological models that account for the yield stress and shear-thinning characteristics of blood are used. The conservation of mass, momentum, and species equations as well as the Herschel-Bulkley constitutive equation are solved numerically using a finite-difference scheme. A parametric study is performed to reveal the impact of flow restriction and rheological modelling on blood-borne oxygen exchange with the confining walls. The wall mass transfer rates within the separated and reattached regions display a strong dependency on the used hemorheological model. Newtonian and non-Newtonian models result in a peak wall mass transfer rate within the recirculation region. However, non-Newtonian models that account for the yield stress and shear-thinning effects predict a substantial, highly localized, drop in the wall mass transfer rates of oxygen, at the reattachment point.

Commentary by Dr. Valentin Fuster
2018;():V003T04A036. doi:10.1115/IMECE2018-87552.

Soil is a vital natural resource that regulates our environment sustainability and provide essential resources to humans and nature. Nowadays, with an increasingly populated and urbanized world, pollution is widely recognized as a significant challenge to soil and groundwater resources management. The most common chemicals found in soils and water plumb in a dissolved state and considered as potential pollutants are heavy metals, dyes, phenols, detergents, pesticides, polychlorinated biphenyls (PCBs), and others organic substances, such as organic matter. Unlike organic contaminants, heavy metals are not biodegradable and tend to accumulate in living organisms and many heavy metal ions are known to be toxic or carcinogenic. Toxic heavy metals of particular concern zinc, copper, nickel, mercury, cadmium, lead and chromium. Electrokinetic remediation deserves particular attention in soil treatment due to its peculiar advantages, including the capability of treating fine and low permeability materials, and achieving consolidation, dewatering and removal of salts and inorganic contaminants like heavy metals in a single stage.

In this study, the remediation of artificially chromium contaminated soil by electrokinetic process, coupled with Eggshell Inorganic Fraction Powder (EGGIF) permeable reactive barrier (PRB), was investigated. An electric field of 2 V cm−1 was applied and was used an EGGIF/soil ratio of 30 g kg−1 of contaminated soil for the preparation of the permeable reactive barrier (PRB) in each test.

Results proved that the study of chromium mobility revealed the predominance in its transportation through the soil towards the anode, due essentially to the existence of chromium in the form of oxyanions (chromate and dichromate), which confers a negative charge to the molecule. Chromium removal by electrokinetic remediation was faster in low levels of concentration and the utilization of citric acid as buffer and complexing agent allowed to maintain pH of soil below the precipitation limit for this element. It was obtained high removal rates of chromium in both experiments, especially near the anode. In the normalized distance to cathode of 0.8 it was achieved a maximum removal rate of chromium of 55, 59 and 60% in initial chromium concentration of 500 mg kg−1, 250 mg kg−1 and 100 mg kg−1, respectively.

The viability of the new coupling technology developed (electrokinetic with EGGIF permeable reactive barrier) to treat low-permeability polluted soils was demonstrated. Based on the proved efficiency, this remediation technique has to be optimized and applied to real soils in order to validate it as a large-scale solution.

Topics: Electrokinetics , Soil
Commentary by Dr. Valentin Fuster

Biomedical and Biotechnology Engineering: Clinical Applications of Bioengineering

2018;():V003T04A037. doi:10.1115/IMECE2018-86749.

At least 2 billion people worldwide drink water from sources contaminated with feces, in other words, sources contaminated with E. coli. The traditional method for detecting E. coli, among other limitations, detects only culturable bacteria and takes about 24–48 hours to yield a result. Consequently, the aim of this work is to develop a rapid diagnostic procedure for E. coli by combining immunofluorescence and optoelectrokinetic patterning to specifically target and sensitively trap the whole organism. This is to ensure the populace have timely access to sustained “E. coli-free” water for both domestic and recreational activities.

The procedure involves conjugation of streptavidin functionalized superparamagnetic fluorescent micro-beads with biotin-labelled anti-E. coli polyclonal antibody. The conjugate is introduced into a water sample containing E. coli among other contaminants, where it specifically and sensitively targets the bacteria in the sample solution which is quantified using an optoelectrokinetic patterning technique by introducing the targeted organism in a fabricated microfluidic chip and trapping it with an application of both laser beam and AC electric field simultaneously. Preliminary experiments have shown that increasing concentrations of E. coli in the microfluidic chamber varies directly with the electrical resistance of the entire system. This on-going research has the potential of sensitively isolating E. coli from a large pool of organic and inorganic contaminants in water in less than 4 hours.

Topics: Water
Commentary by Dr. Valentin Fuster
2018;():V003T04A038. doi:10.1115/IMECE2018-86815.

The purpose of this study was to investigate the effects of utilizing sensory (i.e., vision and touch), as well as static and dynamic base of support training on the balance of senior participants aged 60–80 years old. For each participant, there were several weeks of training, two sessions per week and assessments every two weeks. Training included walking and standing exercises on a hard surface, compliant and stiffer foam walking and standing balance training, and navigating obstacles. Within each session, to modify vision, all training included eyes-open and closed. Further, there were increases in training difficulty as the sessions progressed.

It was observed that training over several weeks resulted in increases in stability, as observed by the decreases in Balance Error Scoring System (BESS) assessment results. However, increases in balance confidence, as observed by the Activities-Specific Balance Confidence (ABC) scale were less certain in this healthy elderly (or senior) population. It is an interesting and positive finding that, in doing relatively simple, but targeted exercises and training, senior individuals can have moderate improvements in their balance and, perhaps ultimately, reduce their fall-risk.

Topics: Stability , Errors , Risk
Commentary by Dr. Valentin Fuster
2018;():V003T04A039. doi:10.1115/IMECE2018-87064.

Deep hole drilling is required to install prosthetic devices in surgical implantation. Compared to the common bone drilling processes, deep hole bone drilling is performed with a larger hole depth (i.e., up to a depth of approximately 35 mm in cochlear implantation) using a high ratio of the length to diameter of the drill bit. For successful outcomes from this process, forces must be controlled adequately to avoid other complications such as drill-bit breakage or thermal necrosis. This study investigates the thrust force and torque generated in bone drilling process of up to 36 mm drilling depth. Drilling tests were performed on bovine cortical bone using 2.5 mm diameter twist drill bit with a spindle speed of 3000 rpm, and feed rates of 0.05, 0.075, and 0.1 mm/rev. Two distinct states in both the thrust force and torque data were observed for all conditions, which are called normal and abnormal states in this study. At an early stage of the drilling process, the force signals showed the traditional trend, reaching a constant value once the tip of the drill bit was fully engaged in bone cutting up to a certain depth. After that, both thrust force and torque kept increasing rapidly until the final drilling depth. This study also observed that the chip morphology varies with increasing drilling depth, showing fragmented chips at the normal state and powdery chips at the abnormal state. Chip clogging and increased frictional force between chips, tool, and hole wall with larger drilling depth may cause the abrupt increase in forces and variation in chip morphology.

Topics: Drilling , Bone
Commentary by Dr. Valentin Fuster
2018;():V003T04A040. doi:10.1115/IMECE2018-87390.

Previous studies have shown that microwave imaging offers an alternative or additional way for early diagnosis of breast cancer. Microwave antenna plays an important role in a microwave imaging system. The paper presents a wideband microwave antenna for medical microwave breast imaging application. Various simulations were conducted to validate the proposed antenna. Results show that the proposed antenna has the potential for application in a microwave imaging system to identify breast lesions.

Topics: Microwaves , Cancer
Commentary by Dr. Valentin Fuster
2018;():V003T04A041. doi:10.1115/IMECE2018-87674.

Breastfeeding provides both nutrients and immunities necessary for infant growth. Understanding the biomechanics of breastfeeding requires capturing both positive and negative pressures exerted by infants on the breast. This clinical experimental work utilizes thin, flexible pressure sensors to capture the positive oral pressures of 7 mother-infant dyads during breastfeeding while simultaneously measuring vacuum pressures and imaging of the infants oral cavity movement via ultrasound. Methods for denoising signals and evaluating ultrasound images are discussed. Changes and deformations on the nipple are evaluated. The results reveal that pressure from the infant’s maxilla and mandible are evenly distributed in an oscillatory pattern corresponding to the vacuum pressure patterns. Variations in nipple dimensions are considerably smaller than variations in either pressure but the ultrasound shows positive pressure dominates structural changes during breastfeeding. Clinical implications for infant-led milk expression and data processing are discussed.

Commentary by Dr. Valentin Fuster
2018;():V003T04A042. doi:10.1115/IMECE2018-87906.

Ankylosing spondylitis (AS) is a degenerative rheumatological disorder that mainly affects the spine. It has been reported that different degrees of human resting myofascial tone (HRMT) would affect spinal stability and may predispose to the respective curvature deformities of adolescent idiopathic scoliosis (AIS) and the enthesopathy of ankylosing spondylitis (AS). Although osteoligamentous impacts are prominently recognized in many chronic spine and low back conditions, no research has been performed on the possible role of passive axial (spinal) myofascial tone as a causative factor. In this particular study, the passive muscle properties of the lower lumbar regions of 24 healthy adults and 24 adult AS subjects were examined. Our recent publications examined the linear elastic properties among normal and AS subjects. In this study, those analyses are expanded to include detailed analysis and correlations of the linear elastic property of stiffness to two viscoelastic properties: stress relaxation time (SRT) and creep. Analyzed data supports the hypothesis that resting muscle properties of the lower lumbar muscles hold significance in differentiation of human back health between healthy and diseased subjects, but more testing should be performed to support this study’s results.

Commentary by Dr. Valentin Fuster
2018;():V003T04A043. doi:10.1115/IMECE2018-88259.

Successful outcomes from the use of orthodontic devices are underpinned on their effective anchorage and the loading that they apply to the underlying facial structures. Anchorage plays an important role in determining the point of application of the corrective forces and subsequently the orientation of the resultant of these forces, which in-turn governs the outcome of treatment. Therefore, patient-specific design of anchors and their placement may benefit significantly from personalization using patient-specific and three-dimensional (3D) cephalometry. 3D cephalometry is therefore a first step to personalization of orthodontic treatment. In this feasibility study, we demonstrate the viability a novel image processing and surface analysis pipeline to quantify facial symmetry about the mid-sagittal facial plane, which may offer insight into optimal placement and orientation for implantation of orthodontic anchors, starting with patient-specific cone beam computed tomography (CBCT) images. Typical assessments of geometrical features/attributes of face include size, position, orientation, shape, and symmetry. Using 3D CBCT images in the DICOM image format, skull images were first segmented using a basic iso-contouring approach. To quantify symmetry, we split the skull along the mid-sagittal plane and used an iterative closest point (ICP) approach in order to rigidly co-register the left and right sides of the skull, optimizing for rotation, translation and scaling, after reflection of one half across the mid-sagittal plane. This was accomplished using an in-house plugin is developed for the open-source visualization toolkit (VTK) based 3D visualization tool, Paraview (Kitware Inc.). Finally, using a signed regional distance mapping plugin we were able to assess the regional asymmetry of regions of the skull (e.g. upper and lower jaw – specific targets for therapy) using colormaps of regional asymmetry (in terms of left-v/s-right side surface distance) and visualized the same as vector glyphs. The direction of these vectors is synonymous with anticipated regional forces required in order to achieve left-right symmetry, which in-turn may have value in surgical planning for orthodontic implantation. In sum, we demonstrate a workflow for computer-aided cephalometry to assess the symmetry of the skull, which shows promise for personalized orthodontic anchor design.

Commentary by Dr. Valentin Fuster
2018;():V003T04A044. doi:10.1115/IMECE2018-88267.

Microfabrication-free methods such as wax printing and hydrogel molding have been developed in recent years for fabricating microfluidic devices to enable the applications of microfluidic devices to a broader range. A process has been developed to fabricate electrospun fiber embedded microfluidic devices by integrating hydrogel molding (HGM) and electrospinning (ES), and the feasibility of this integrated method has been demonstrated through our initial study. In particular, agarose gels with various concentrations have been used to generate the channel molds inside PDMS. Recently, a 3D printer kit based on Fuse-deposition method (FDM) was modified to directly deposit hydrogel mold. The current study focuses on how to control the dispensing rate and the extruder motion of the 3D printer for this application. The paper presents a characterization process for determining optimal work ranges in terms of dispensing rate and the moving rate of the x-y table. Specifically, for a given hydrogel material and needle gauge, consistent dispensing volume rate was determined via varying the flow rate of syringe pump and analyzing recorded images. The ranges of the moving rate of the x-y table and the extrusion rate were then determined to generate the previous determined volume rate based on the experimental measurements. As the printer kit is controlled via open source software, the developed method will be applicable to characterization of depositing different material system.

Commentary by Dr. Valentin Fuster
2018;():V003T04A045. doi:10.1115/IMECE2018-88479.

This study tests a custom-designed knee implant made of an FDA approved biomaterial, Chronoflex AR. The implant is designed to cushion the damaged cartilage at the distal end of the femur to reduce knee pain without the removal of cartilage and bone. A patient’s MRI scan was used to render a 3D computer graphic design of the knee. The manufacturing of the implant is conducted by 3D printing the shape of the distal end of the femur and coating it with the biomaterial. This is a preliminary fabrication method. Ultimately, the implant material will be 3D printed or cast in 3D printed molds. A successful implementation of this sort of custom-designed implant would reduce the invasiveness of knee correcting procedures, enable the patient to retain the shape of his or her femoral and tibial anatomy, and reduce the possibility of revision surgeries. A custom knee implant testing machine was designed and fabricated to measure the force, elastic deformation, plastic deformation, wear and fatigue of the component after performing lab tests simulating a normal walking pattern while adhering to ISO standards.

Commentary by Dr. Valentin Fuster

Biomedical and Biotechnology Engineering: Computational Modeling in Biomedical Applications

2018;():V003T04A046. doi:10.1115/IMECE2018-86502.

Innate immunity depends on the coordinated activity of multiple leukocytes at or near the site of tissue injury. Previous numerical studies have shown that an adherent leukocyte can hydrodynamically recruit a free-stream leukocyte towards the endothelial surface. Using a computer model we created, we numerically investigated the hydrodynamic recruitment of circulating cells due to the presence of a nearby adherent deformed cell. For circulating cells positioned one diameter or more above the reactive surface and subsequently involved in a glancing (out-of-plane) collision with an adherent cell, the simulation indicated that the free-stream cell could be driven closer to the surface. This behavior was seen to depend, in part, on the offset glancing distance. Furthermore, for a deformed adherent cell a similar effect was observed, but beginning at smaller offset glancing distances. We also examined the binary interaction for a free-stream cell initially less than one diameter above the surface. For fixed offset glancing distances, the binary interaction with a more significantly deformed adherent cell resulted in enhanced recruiting effectiveness, as quantified by the time needed for the cell to descend to a height where receptor-ligand interactions were possible.

Topics: Leukocytes
Commentary by Dr. Valentin Fuster
2018;():V003T04A047. doi:10.1115/IMECE2018-86545.

Radiative-thermal models of light transport in tissue are presented that stimulates the thermal effects of pulsed laser radiation on very thin scattering and absorbing biological layers. Thermal therapies require a firm understanding of temperature-depth relationship for tissue modification or destruction, especially through very thin layers that are characterized by contrasting opto-thermal properties. Temperature distribution in biological layers of thicknesses in the order of their mean free path or less are evaluated before the onset of thermal diffusion for both the traditional model of Monte Carlo simulation and that with new features tailored for very thin layers. Temperature dynamics in very thin layers such as skin in dermatology is a typical example. For instance, during the heating of small volumes of tissue as in fractional photothermolysis, nonablative dermal remodeling and ablative skin resurfacing, short pulse lasers are used by choosing pulse length sufficiently short that will not damage the surrounding healthy tissue, but sufficiently long enough to allow damage, necrosis or coagulation over the entire target area. This is in contrast to the situation where thermal dissipation due to heat conduction is the principal determinant of tissue damage. Numerical results obtained from both models differ significantly. While the model designed specifically for very thin scattering layers tends to confine temperature rise to specific layers, the traditional model have a tendency to misjudge the layers of interest thereby giving rise to temperature increase in undesired locations. These results will advance our understanding of radiation transport in layers that are extremely very thin, and help develop better treatment modules for laser therapeutic treatment regimes in surgery and dermatology.

Commentary by Dr. Valentin Fuster
2018;():V003T04A048. doi:10.1115/IMECE2018-86559.

Influenza is an important public health concern. Influenza leads to the death or hospitalization of thousands of people around the globe every year. However, the flu-season varies every year viz. when it starts, when it peaks, and the severity of the outbreak. Knowing the trajectory of the epidemic outbreak is important for taking appropriate mitigation strategies. Starting with the 2013–2014 flu season, the Influenza Division of the Centers for Disease Control and Prevention (CDC) has held a “Predict the Influenza Season Challenge” to encourage the scientific community to make advances in the field of influenza forecasting. A key observation from these challenges is that a simple average of the submitted forecasts outperformed nearly all of the individual models. Further, ongoing efforts seek ways to assign weights to individual models to create high-performing ensemble models. Given the sheer number of models, as well as variation in methodology followed among teams contributing influenza-risk forecasts, multiple forecasting models can be combined, by capturing human judgment, to outperform a simple average of these same models. This project exploits such a “wisdom of crowds” approach, using public votes acquired with the help of an R/Shiny based web-application platform in order to assign weights to individual forecasting models on a week-over-week basis, in an effort to improve overall ILI risk prediction accuracy. We describe a strategy for improving the accuracy of influenza risk forecast modeling based on a crowd-sourced set of team-specific forecast votes and the results of the 2017–2018 season. Our approach to assigning weights based on crowd-sourced votes on individual models outperformed an average forecasts of the individual models. The crowd was statistically significantly more accurate than the average model and all but one of the individual models.

Commentary by Dr. Valentin Fuster
2018;():V003T04A049. doi:10.1115/IMECE2018-86848.

A novel approach for the analysis of the non-linear behavior of bio-structures is presented here. This method is developed in the framework of the Carrera Unified Formulation (CUF), a higher-order 1D theory according to which the kinematics of the problem depends on the arbitrary expansion of the generalized unknowns. Taylor-like (TE) and Lagrange-like expansion functions (LE) are employed to describe the kinematic field along the cross-section and, the finite element method (FEM) is used to formulate the governing equations. In this work, the effects of material nonlinearities are investigated and, the problem is solved by using the Newton-Raphson method. An atherosclerotic plaque of an artery is introduced as a typical bio-structure with complex geometry and studied for both linear and non-linear material cases. The results from the proposed technique highlight the accuracy of the in-plane and out-of-plane stress/strain distributions for different 1D models. The 3D-like accuracy of local effect predictions, the possibility of dealing with complex geometries, and low computational costs of nonlinear analyses make the present formulation appealing for biomechanical applications.

Commentary by Dr. Valentin Fuster
2018;():V003T04A050. doi:10.1115/IMECE2018-87042.

Patellofemoral pain syndrome (PFPS) is a musculoskeletal condition characterized by anterior knee pain. The symptoms associated with PFPS can be further aggravated through activities that increase patellofemoral compressive forces. Despite the number of mechanisms that are considered to contribute to this disorder, there is no consensus about its etiology, causing difficulty in prescribing the appropriate treatment or physical therapy. To properly evaluate PFPS, the influences of various muscles and their geometries on knee joint reaction forces for a human subject during a normal gait cycle were observed by conducting parametric analysis using OpenSim. The muscles that were seen to be most critical and have a potential effect in reducing the pain experienced at the knee joint are the soleus, iliopsoas, and gastrocnemius muscles. It was observed that individually increasing the length of the soleus and iliopsoas muscles from 75% to 125% of their default lengths resulted in decrease in knee joint reaction forces of up to 400 N (57%) in the x-direction and 600 N (40%) in the y-direction for the soleus and 550 N (38%) in the x-direction and 1000 N (29%) in the y-direction for the iliopsoas. It was also seen that by indirectly reducing the cross-sectional area of the gastrocnemius muscles from 125% to 75% of their default value resulted in decreases in knee joint reaction forces of up to 250 N (50%) in the x-direction and 500 N (42%) in the y-direction. Therefore, exercises should be advised to specifically stretch or strengthen the soleus and iliopsoas, and the gastrocnemius muscles should be rested. Pain and recovery time may be substantially reduced with the utilization of a targeted physiotherapy treatment plan. It can be coupled with longterm physiotherapy program for improving muscle fitness.

Commentary by Dr. Valentin Fuster
2018;():V003T04A051. doi:10.1115/IMECE2018-87199.

Because the fracture behaviors of soft materials are complex, high-precision technology is needed to perform the detailed analysis necessary to produce more effective materials. Indentation methods exist to characterize the fracture behavior of soft materials, with fractures varying in accordance with the shape of the indenter. Thus, it is important to clarify the relationship between indenter shape and the fracture behaviors of soft materials, and necessary to consider the complicated deformation patterns induced by the mechanical nonlinearity of the materials. To this end, various needle-like indenter shapes are modeled via a finite element method (FEM). In this study, we employ a cone-shaped reference needle. Then, the shape is changed to have the tip form a curvilinear indentation, resembling a steep mountain ridgeline. In addition, shear strain is set as the fracture criterion for soft material in the FE analysis since the shear force resulting from penetration primarily damages the soft materials. Regarding the force applied to the needle, there is a tendency for the force to become smaller as it more resembles a cone shape. There are three fracture types: holing, opening, and slitting. Holing is generated by the cone needle, and the fracture of soft material appears along the shape of the needle. Opening fractures are generated by the needle with a curvilinearly spreading tip, forming a small slit on the surface of the soft material. Lastly, slitting fractures are also generated by the needle with a curvilinearly spreading tip, but the resulting slit is deepened without damaging the tissue surrounding the needling. These fracture types can also be classified according to the fracture area of the soft material surface, with slitting resulting in the smallest fracture area.

Commentary by Dr. Valentin Fuster
2018;():V003T04A052. doi:10.1115/IMECE2018-87680.

As it has been shown previously, the blood flow in the heart and the main vessels is a self-organizing tornado-like flow of a viscous fluid, exhaustively described by the particular solution of nonstationary hydrodynamic equations coined in 1986. This solution is implemented in a local dynamic cylindrical coordinate system, which origin moves with the flow. Streamlines of these flows are characterized with an axial symmetry and determine certain restrictions to the geometry of the flow channels. It has been proved, that the experimentally measured orientations of intraventricular trabeculae and dynamic geometric characteristics of the aortic flow channel during the cardiac cycle satisfy the conditions for the self-organization of tornado-like blood flow. This enables to obtain relative estimates of the flow parameters using the geometric characteristics of the flow channel. For this, a set of experimentally measured quasi-invariant anatomical marks was used, which static and dynamic parameters are utterly determined by the structure of the dominant blood jet. Such marks are the position of the embouchures of pulmonary veins and the left atrium auricle, the directions of the trabecular profile on the left ventricle streamlined surface, the dynamic geometry of the mitral and aortic valves, the length and radial elasticity of the aorta, etc. These marks allow a formal localization of the dynamic coordinate system position of a swirling blood flow in the investigated part of the cardiovascular channel and more accurate estimation of the jet structural parameters evolution.

Basing on these parameters, a consistent theory of the initiation and evolution of swirling blood jet in the flow channel beginning from the left atrium to the aorta and its main branches has been proposed. The result of the study is a concept, integrating the measured characteristics of the heart and the aorta flow channel (dynamic dimensions, elasticity) and the structural parameters of swirling blood flow. It was shown that flow channel pathological changes significantly affect the flow structure.

Commentary by Dr. Valentin Fuster
2018;():V003T04A053. doi:10.1115/IMECE2018-87683.

Nearly everyone, throughout their life, is at risk of being involved in a serious traumatic event, such as motor vehicle accidents, sports and occupational injuries, or natural disaster related injuries. Twenty-eight percent of trauma patients precipitously develop abnormalities in their blood coagulation system. These coagulopathies increase their mortality rate by 5fold. The current coagulopathy diagnosis protocol collects basic patient information, vital signs, and performs traditional lab and point-of-care (POC) blood testing. A high-stakes decision must then be made by the trauma surgeon, using their intuition, training, and the results from the blood drawn at least 15 minutes prior, to determine the requirement for a resuscitation treatment through coagulation inhibitors or activators. Computational modeling and system analysis of the human blood coagulation are integral to developing superior decision support tools for trauma surgeons. In short, the coagulation system consists of the following functional subsystems: 1) blood flow, 2) platelet function, 3) diffusion, 4) advection, and 5) biochemical kinetics. We utilize a combined approach of both 0-D and 3-D model development with the overarching goal of developing a validated, near real-time decision support system. The biochemical kinetics of the coagulation system is implemented in the 0-D model with a set of 113 nonlinear, coupled ordinary differential equations (ODEs), describing the time rate of change of the numerous chemical concentrations and their interaction with one another. 0-D models provide a fast, efficient means of simulating the coagulation biochemical kinetics, but these ODEs lack the ability to describe the global effects of fluid flow, advection, and diffusion. Hence, the set of 113 ODEs are modeled as source terms and combined with the Navier-Stokes and chemical advection/diffusion equations in a three-dimensional finite volume computational domain, providing a global coagulation model. Model validation studies employ parallel experimental POC blood testing and 3-D computational modeling. Results from the 0-D model are consistent with testimonials from expert trauma surgeons, whom verify the model provides appropriate reasoning for their difficulties in predicting patient outcome. Thus, validated computational models have potential as a hypothesis generator used for developing new approaches for providing trauma surgeons with sufficient information to make better informed clinical decisions, “the decision support tool,” leading to decreased mortality.

Commentary by Dr. Valentin Fuster
2018;():V003T04A054. doi:10.1115/IMECE2018-87793.

The paper proposes a numerical approach for the analysis of the blood flow in human aorta under real operating conditions. An ad-hoc procedure is developed for importing the aorta geometry from magnetic resonance imaging in order to have a patient based analysis. The aortic flow is simulated accounting for the dynamic behavior of the flow resulting from the heart pulse and for the non-Newtonian properties of blood. Fluid – structure analysis is carried out to address the mutual influence of the flow transient nature and the aorta walls’ deformation on the pressure flow field and tissue’s stresses. Finite element method approach is used for the structural analysis of the aorta walls which are assumed as a linear elastic isotropic material; nevertheless, different regions are introduced to account for the Young modulus variation from the ascending aorta to the common iliac arteries. Mesh morphing techniques are adopted to simulate the wall deformation and a two equation turbulence model is adopted to include the turbulence effects.

The proposed numerical approach is validated against the measurements carried out on magnetic resonance imaging scanner and a good agreement is found in terms of aorta wall maximum and minimum deformation during the cardiac cycle. Therefore, the fluid-structure analysis can provide an important tool to extend the insight of the aortic system from magnetic resonance imaging techniques and improve the understanding of arteriosclerosis and the related phenomena as well as their dependence on flow structure and tissue stresses.

Commentary by Dr. Valentin Fuster
2018;():V003T04A055. doi:10.1115/IMECE2018-87868.

Background: Knot tying is considered a basic surgical skill, however, there is no consensus on the best technique. Suture breakage and slippage are failure modes during surgical repair and are related to stress concentrations which cannot be easily established with physical testing. Few computational models exist that describe the effect of knot topology on the failure mechanism. The purpose of this study was to implement the finite element method to analyze the mechanical behavior of surgical sutures according to number of throws and to validate the model against experiments.

Methods: Experiments and models of monofilament and multifilament sutures were conducted. Multiple throw knots were tested to failure in a laboratory setting and with corresponding finite element models. Gross loads were compared when the knot reached a localized material yield stress in the model or when failure occurred in laboratory tests that have the same suture topology.

Results: The results of laboratory tests and corresponding finite element models of single throw knots were compared and found to be well correlated and consistent with existing literature in strength prediction and failure location. Moreover, single throw knots have reduced failure strengths relative to non-knotted suture approximately by 120 N for both monofilament and multifilament sutures, respectively.

Clinical Relevance: This paper describes a model which can describe the initial failure process leading to knot failure. In addition, the model can evaluate the effect of knot topology on the mechanics of surgical suture. Numerically, no assessment has been completed of knot security (i.e., how likely the knot is to untie), therefore, clinical recommendations are premature. In the future, the results may provide a framework for choosing the suture and knot types for soft tissue repairs.

Commentary by Dr. Valentin Fuster
2018;():V003T04A056. doi:10.1115/IMECE2018-87869.

Background: Although trabecular bone is highly porous heterogeneous composite, most studies use homogenized continuum finite element (FE) approaches to model trabecular bone. Such models neglect the porous nature of the tissue. When microstructural models are desired, the use of continuum elements may require costly CT/MRI imaging and detailed meshing. The purpose of this study is to demonstrate an approach that simulates trabecular bone with less dependency on medical images while capturing of porosity.

Methods: A stochastic structural FE model was created representing the trabecular micro-architecture as beam elements. Beam orientation, length and connectivity were stochastically determined by random placement of nodes and meshing the resulting Voronoi diagram. Boundary conditions were applied on the structure to attain normalized axial and shear strain. Also, apparent mechanical properties, apparent densities and anisotropy ratio’s were calculated from the model output.

Results: The number of generated nodes within the model and cross sectional area of the random beams were observed as parameters that affect model outcome. Trabecular bone apparent density was found highly correlated to beams cross sectional area rather than the generated number of nodes. Similarly, Young’s moduli and shear moduli were dependent on beams cross sectional area. For example, a (0.015 mm2) increase in beam cross section area can produce (175 MPa, 30 MPa and 0.55 g/cm3) increases in Young’s moduli, shear moduli and apparent density, respectively.

Clinical Relevance: The proposed finite element technique provides a stochastically accurate structural representation of trabecular tissue and its reaction to applied loads. It incorporates several advantages of high fidelity methods but at lower cost and requiring only clinical imaging. Therefore, the approach may be useful for patient specific musculo-skeletal biomechanical models (e.g. osteoporosis, osteoarthritis, joint replacement and implants interface).

Commentary by Dr. Valentin Fuster
2018;():V003T04A057. doi:10.1115/IMECE2018-88036.

Modeling human thermal behavior is important for applications involving medical device design, non-ionizing radiation dosimetry, and human comfort. Most thermal models use the finite element method (FEM) to represent the complicated domain structure. With the FEM, challenges in mesh and equation derivation limit rapid implementation. Finite difference (FDM) and finite volume (FVM) methods are alternatives to the FEM but have their own limitations. The FDM faces challenges in discontinuous domains at the boundaries. The FVM provides a possible solution to problems faced with FDM and FEM use.

In a computational human phantom generated from medical imaging data, the finite volume structure is readily available in the form of two-dimensional pixels and three-dimensional voxels. However, geometric characteristics of rectangular prisms prevent acceptable surface-area convergence for curved surfaces, introducing an error that substantially impacts boundaries between regions such as a convection interface.

The present work focuses on developing surface-area corrections for a domain generated from computed tomography scans. These geometric corrections are coupled with an FVM heat-transfer solution on a structured mesh. Solutions are demonstrated for thermoregulation in a domain similar to a section of the human forearm. The ultimate goal of this work is to evaluate human body temperature distributions under the influence of external stimuli and internal heat generation.

Topics: Heat , Modeling
Commentary by Dr. Valentin Fuster
2018;():V003T04A058. doi:10.1115/IMECE2018-88113.

With the increasing application of improvised explosive devices, the ratio of traumatic ocular injury significantly increased in the past decades, which has become the fourth most happened injury to military deployment. The ocular injury treatment is costly and has been less effective, which influences the military service and life experience of the soldiers. With years of research on the traumatic ocular injury through experiment or computational simulations, the primary blast wave related overpressure was found to induce macular damage, globe rupture. While the influence of the primary blast wave on the posterior part of the eyeball was poorly understood, such as the optic nerve. In this work, we developed a three-dimensional computation model, which included lamina cribrosa (LC), optic nerve and cerebrospinal fluid (CSF). The strain evaluated in optic nerve was found to exceed neural tissue’s physiological loading range, which might explain the vision loss after the blast.

Topics: Waves
Commentary by Dr. Valentin Fuster
2018;():V003T04A059. doi:10.1115/IMECE2018-88116.

In this work, a computational model of PLLA (Poly L-lactic acid) stent was constructed to study the degradation behavior of the bioabsorbable stent in terms of the loss of mechanical integrity. A degradation model was improved based on experimental data from the literature, as well as a finite element (FE) model was constructed based on the model of the degradation behavior of PLLA material. The results showed that the degradation of the PLLA would switch the material property of stent from a uniform model to a heterogeneous model due to the decline of Young’s modulus locally at each location of the stent. Loss of mechanical integrity of the stent showed a bilinear behavior due to the decline of the Young’s modulus and the locale failure of the structure, respectively. The breakdown pieces of stent will stay a relative longer time in lesion after the loss of the mechanical integrity of the stent due to the nonlinear response of the degradation degree to the degradation time and strain in the material.

Commentary by Dr. Valentin Fuster
2018;():V003T04A060. doi:10.1115/IMECE2018-88511.

There is a need for better 3-D model representations of cerebrovasculature particularly on the order of arterioles. Such a model would have many applications and could be a useful tool for those conducting studies involving the brain and its function. The load bearing effects of the vasculature can be better studied with such a model, such as in the case of large strains. In addition, by having a continuous hollow structure, studies involving flow properties can be conducted at a whole scale rather than in a segmented view. Such studies are critical to the advancement of knowledge about the brain and its mechanics which can lead to advancements in preventative and curative care, as well as preventative safety measures. The model developed in this paper could serve as a tool in such studies. A fractal L-system is used to define the branching nature of the model. As such a growing tree structure is developed and characterized by its bifurcation at the end of a vessel segment. The index of bifurcation, α, is a parameter that controls the behavior of the two generated daughter vessels. The model presented here grows from a single parent branch into a bifurcation each of which then bifurcates as many times as specified. The length and diameter of the two daughter vessels will be a function of the respective parent’s length and diameter as well as a value α. The branching angle of the two daughter vessels will be entirely controlled by α. The hollow continuous nature of the model allows for it to be used as a representation of the arteriole structures in the brain. There is also use for such a model in other areas of the body, however, this study will focus on the representation of the cerebrovasculature. The end result is a branching tree model generated in Abaqus which is continuous, hollow and capable of extensive generation with uses in modeling complex cerebrovascular mechanics.

Topics: Fractals
Commentary by Dr. Valentin Fuster
2018;():V003T04A061. doi:10.1115/IMECE2018-88583.

In this study, we aim to create and validate a Finite Element (FE) model to estimate the bone temperature after cement injection and compare the simulation temperature results with experimental data in three key locations of the proximal femur. Simulation results suggest that the maximum temperature-rise measured at the bone surface is 10°C which occurs about 12 minutes after the injection. Temperature profiles measured during the experiment showed an agreement with those of the simulation with an average error of 1.73 °C Although additional experiments are required to further validate the model, results of this pilot study suggest that this model is a promising tool for bone augmentation planning to lower the risk of thermal necrosis.

Commentary by Dr. Valentin Fuster
2018;():V003T04A062. doi:10.1115/IMECE2018-88588.

The present in vitro study aims at comparing the ablation volume obtained with commercially available RITA’s StarBurst® XL (dry type) and StarBurst® Xli-e (wet type) multi-tine electrodes during radiofrequency ablation (RFA) procedure. The experiments have been conducted on polyacrylamide based tissue-mimicking phantom gel whose thermo-electric properties are similar to that of the soft tissues. A temperature-controlled RFA has been performed utilizing AngioDynamics RITA 1500X® radiofrequency generator. The maximal longitudinal and maximal transverse dimensions of the coagulated phantom gels have been measured from which the derived ablation volume has been calculated. Further, the temperature distribution and power delivered with the dry type and wet type electrodes have been compared. The in vitro study revealed that the efficacy of wet type electrode is more pronounced as compared to the dry type electrode. Moreover, it has been found that both the electrodes are capable enough of producing ablation volume up to 5 cm in diameter.

Commentary by Dr. Valentin Fuster

Biomedical and Biotechnology Engineering: Damage Biomechanics

2018;():V003T04A063. doi:10.1115/IMECE2018-87689.

Current understanding of blast wave transmission and mechanism of primary traumatic brain injury (TBI) and the role of helmet is incomplete thus limiting the development of protection and therapeutic measures. Combat helmets are usually designed based on costly and time consuming laboratory tests, firing range, and forensic data. Until now advanced medical imaging and computational modeling tools have not been adequately utilized in the design and optimization of combat helmets. The goal of this work is to develop high fidelity computational tools, representative virtual human head and combat helmet models that could help in the design of next generation helmets with improved blast and ballistic protection.

We explore different helmet configurations to investigate blast induced brain biomechanics and understand the protection role of helmet by utilizing an integrated experimental and computational method. By employing the coupled Eulerian-Lagrangian fluid structure interaction (FSI) approach we solved the dynamic problem of helmet and head under the blast exposure. Experimental shock tube tests of the head surrogate provide benchmark quality data and were used for the validation of computational models. The full-scale computational NRL head-neck model with a combat helmet provides physical quantities such as acceleration, pressure, strain, and energy to blast loads thus provides a more complete understanding of the conditions that may contribute to TBI. This paper discusses possible pathways of blast energy transmission to the brain and the effectiveness of helmet systems at blast loads. The existing high-fidelity image-based finite element (FE) head model was applied to investigate the influence of helmet configuration, suspension pads, and shell material stiffness. The two-phase flow model was developed to simulate the helium-air shock wave interaction with the helmeted head in the shock tube.

The main contribution was the elucidation of blast wave brain injury pathways, including wave focusing in ocular cavities and the back of head under the helmet, the effect of neck, and the frequency spectrum entering the brain through the helmet and head. The suspension material was seen to significantly affect the ICP results and energy transmission. These findings can be used to design next generation helmets including helmet shape, suspension system, and eye protection.

Commentary by Dr. Valentin Fuster
2018;():V003T04A064. doi:10.1115/IMECE2018-88007.

Determination of human tolerance to impact-induced damage or injury is needed to assess and improve safety in military, automotive, and sport environments. Impact biomechanics experiments using post mortem human surrogates (PMHS) are routinely used to this objective. Risk curves representing the damage of the tested components of the PMHS are developed using the metrics gathered from the experimental process. To determine the metric that best explains the underlying response to the observed damage, statistical analysis is required of all the output response metrics (such as peak force to injury) along with the examination of potential covariates. This is conducted by parametric survival analysis. The objective of this study is to present a robust statistical methodology that can be effectively used to achieve these goals by choosing the best metric explaining injury and provide a ranking of the metrics. Previously published data from foot-ankle-lower leg experiments were used with two possible forms of censoring: right and left censoring or right and exact censoring, representing the no injury and injury data points in a different manner. The statistical process and scoring scheme were based on the predictive ability assessed by the Brier Score Metric (BSM) which was used to rank the metrics. Response metrics were force, time to peak, and rate. The analysis showed that BSM is effective in incorporating different covariates: age, posture, stature, device used to deliver the impact load, and the personal protective equipment (PPE), i.e., military boot. The BSM-based analysis indicated that the peak force was the highest ranked metric for the exact censoring scheme and the age was a significant covariate, and that peak force was also the highest ranked metric for the left censored scheme and the PPE covariate was statistically significant. IRCs are presented for the best metric.

Topics: Biomechanics , Damage
Commentary by Dr. Valentin Fuster
2018;():V003T04A065. doi:10.1115/IMECE2018-88026.

Mild traumatic brain injury (TBI) is a very common injury to service members in recent conflicts. Computational models can offer insights in understanding the underlying mechanism of brain injury, which can aid in the development of effective personal protective equipment. This paper attempts to correlate simulation results with clinical data from advanced techniques such as magnetic resonance imaging (MRI), diffusion tensor imaging (DTI), functional MRI (fMRI), MR spectroscopy and susceptibility weighted imaging (SWI), to identify TBI related subtle alterations in brain morphology, function and metabolism.

High-resolution image data were obtained from the MRI scan of a young adult male, from a concussive head injury caused by a road traffic accident. The falling accident of human was modeled by combing high-resolution human head model with an articulated human body model. This mixed, multi-fidelity computational modeling approach can efficiently investigate such accident-related TBI. A high-fidelity computational head model was used to accurately reproduce the complex structures of the head. For most soft materials, the hyper-viscoelastic model was used to captures the strain rate dependence and finite strain nonlinearity. Stiffer materials, such as bony structure were simulated using an elasto-plastic material model to capture the permanent deformation. We used the enhanced linear tetrahedral elements to remove the parasitic locking problem in modeling such incompressible biological tissues. The bio-fidelity of human head model was validated from human cadaver tests.

The accidental fall was reconstructed using such multi-fidelity models. The localized large deformation in the head was simulated and compared with the MRI images. The shear stress and shear strain were used to correlate with the post-accident medical images with respect to the injury location and severity in the brain. The correspondence between model results and MRI findings further validates the human head models and enhances our understanding of the mechanism, extent and impact of TBI.

Commentary by Dr. Valentin Fuster
2018;():V003T04A066. doi:10.1115/IMECE2018-88284.

Numerical models were conducted to study the load/momentum/energy transfer to the clay and the clay response when it was used as backing behind hard and soft armor during ballistic experiments. Tie-break contacts were used to explicitly model the delamination in the composite panels. Yarn level models accounting for woven structures were used to model the soft armor. A rate-dependent material model with different responses under compression and tension, developed previously from impact tests, was used to model the clay. The clay indent depth was correlated to the momentum and kinetic energy transferred to the clay for with and without soft armor between the hard armor and clay backing.

Topics: Ceramics , Armor
Commentary by Dr. Valentin Fuster
2018;():V003T04A067. doi:10.1115/IMECE2018-88300.

Accurate material properties of the brain and skull are needed to examine the biomechanics of head injury during highly dynamic loads such as blunt impact or blast. In this paper, a validated Finite Element Model (FEM) of a human head is used to study the biomechanics of the head in impact and blast leading to traumatic brain injuries (TBI). We simulate the head under various direction and velocity of impacts, as well as helmeted and un-helmeted head under blast waves. It is shown that the strain rates for the brain at impacts and blast scenarios are usually in the range of 36 to 241 s−1. The skull was found to experience a rate in the range of 14 to 182 s−1 under typical impact and blast cases. Results show for impact incidents the strain rates of brain and skull are approximately 1.9 and 0.7 times of the head acceleration. Also, this ratio of strain rate to head acceleration for the brain and skull was found to be 0.86 and 0.43 under blast loadings. These findings provide a good insight into measuring the brain tissue and cranial bone, and selecting material properties in advance for FEM of TBI.

Commentary by Dr. Valentin Fuster
2018;():V003T04A068. doi:10.1115/IMECE2018-88382.

Recent research on behind-armor blunt trauma (BABT) has focused on the personal protection offered by lightweight armor. A finite element analysis was performed to improve the biofidelity of the US Army Research Laboratory (ARL) human torso model to prepare for simulating blunt chest impacts and BABT. The overly stiff linear elastic material models for the torso were replaced with material characterizations drawn from current literature. FE torso biofidelity was determined by comparing peak force, force-compression, peak compression, and energy absorption data with cadaver responses to a 23.5 kg pendulum impacting at the sternum at 6.7 m/s. Nonlinear foam, viscous foam, soft rubbers, fibrous hyperelastic rubbers, and low moduli elastic material were considered as material models for the flesh, organs, and bones. Simulations modifying one tissue type revealed that the flesh characterization was most crucial for predicting compression and force, followed closely by the organs characterizations. Combining multiple tissue modifications allowed the FE torso to mimic the cadaveric torsos by reducing peak force and increasing chest compression and energy absorption. Limitations imposed by the Lagrangian finite element approach are discussed with potential workarounds described. Proposed future work is split between considering additional impact scenarios accounting for position and biomaterial variability.

Commentary by Dr. Valentin Fuster
2018;():V003T04A069. doi:10.1115/IMECE2018-88419.

The aim of this study was to develop a test method to characterize the material behavior of bovine brain samples in large shear deformations and high strain rates relevant to blast-induced neurotrauma (BINT) and evaluate tissue damage. A novel shear test setup was designed and built capable of applying strain rates ranging from 300 to 1000 s−1. Based on the shear force time history and propagation of shear waves, it was found that the instantaneous shear modulus (about 6 kPa) was more than 3 times higher than the values previously reported in the literature. The shear wave velocity was found to be strain path dependent which is an indication of tissue damage at strains greater than 10%. The results of this study can help in improving finite element models of the brain for simulating tissue injury during BINT.

Commentary by Dr. Valentin Fuster
2018;():V003T04A070. doi:10.1115/IMECE2018-88447.

Finite element (FE) computational human body models (HBMs) have gained popularity over the past several decades as human surrogates for use in blunt injury research. FE HBMs are critical for the analysis of local injury mechanisms. These metrics are challenging to measure experimentally and demonstrate an important advantage of HBMs. The objective of this study is to evaluate the injury risk predictive power of localized metrics to predict the risk of pelvic fracture in a FE HBM.

The Global Human Body Models Consortium (GHBMC) 50th percentile detailed male model (v4.3) was used for this study. Cross-sectional and cortical bone surface instrumentation was implemented in the GHBMC pelvis. Lateral impact FE simulations were performed using input data from tests performed on post mortem human subjects (PMHS). Predictive power of the FE force and strain outputs on localized fracture risk was evaluated using the receiver operator characteristic (ROC) curve analysis.

The ROC curve analysis showed moderate predictive power for the superior pubic ramus and sacrum. Additionally, cross-sectional force was compared to a range of percentile outputs of maximum principal, minimum principal, and effective cortical element strains. From this analysis it was determined that cross-sectional force was the best predictor of localized pelvic fracture.

Commentary by Dr. Valentin Fuster

Biomedical and Biotechnology Engineering: Dynamics and Control of Biomechanical Systems

2018;():V003T04A071. doi:10.1115/IMECE2018-86779.

During walking, human lower limbs accelerate and decelerate alternately, during which period the human body does positive and negative work, respectively. Muscles provide power to all motions and cost metabolic energy both in accelerating and decelerating the lower limbs. In this work, the lower-limb biomechanics of walking was analyzed and it revealed that if the negative work performed during deceleration can be harnessed using some assisting device to then assist the acceleration movement of the lower limb, the total metabolic cost of the human body during walking can be reduced. A flexible lower-limb exoskeleton was then proposed; it is worn in parallel to the lower limbs to assist human walking without consuming external power. The flexible exoskeleton consists of elastic and damping components that are similar to physiological structure of a human lower limb. When worn on the lower limb, the exoskeleton can partly replace the function of the lower limb muscles and scavenge kinetic energy during lower limb deceleration to assist the acceleration movement. Besides, the generator in the exoskeleton, serving as a damping component, can harvest kinetic energy to produce electricity. A prototype of the flexible exoskeleton was developed, and experiments were carried out to validate the analysis. The experiments showed that the exoskeleton could reduce the metabolic cost by 3.12% at the walking speed of 4.5 km/h.

Commentary by Dr. Valentin Fuster
2018;():V003T04A072. doi:10.1115/IMECE2018-86883.

The pulsatile pressure in an artery is accompanied by the radial motion of the arterial wall. In this paper, the governing equation of the radial wall motion is first derived, indicating that longitudinal stretching of the arterial wall plays a critical role in the radial wall motion. Based on the derived equation and time-harmonic nature of its radial motion, the arterial wall is modeled as a second-order dynamic system. A microfluidic-based tactile sensor is used to acquire the arterial pulsatile pressure waveform, which is used to represent the radial displacement of the arterial wall. Consequently, the 1st-order and 2nd-order derivatives of the radial displacement are the wall velocity and wall acceleration. In the context of time-harmonic vibration, the key features in the radial displacement and its two derivatives are interpreted to obtain the elasticity and viscosity of the arterial wall: spring stiffness and damping coefficient in the circumferential direction. Pulse signals at radial artery (RA) and superficial temporal artery (STA) on seven healthy human subjects are measured and processed to estimate the two physical properties of the arterial wall. The measured difference in the physical properties between the two arteries and among the seven subjects validates the feasibility of the proposed dynamic modeling of the radial wall motion to capture the physical properties of the arterial wall, and at the same time demonstrates the necessity of subject-specific and artery-site-specific measurements.

Commentary by Dr. Valentin Fuster
2018;():V003T04A073. doi:10.1115/IMECE2018-87249.

Sleeping is one of the most important factors that influence the quality of human life, and this state of existence should be thoroughly investigated to improve the quality of the life. The mechanical design of bedding has great influence on the comfort of a mattress. Thus, objective and conventional techniques to evaluate the mechanics of mattress comfort could help improve the quality of sleep. In this report, an analysis technique for the assessment of the sleeping posture of humans is presented to facilitate the development of mattress design technology. Herein, an analytical model which imitates the human body has been formulated to determine the design parameters of a mass-spring-joint system on a soft underlay. The physical model is composed of five components that represent the head, chest, hip, femur, and calf, with each body part being represented by a simple ball model. The spring joint connecting the five parts reflects the neck, lumbar, hip, and knee joints. The specifications of the body model are determined by actual measurements and previous studies. In order to determine the physical properties of the mattress, two types of mattress urethane foam material are tested using the ball indenter method. The parameters include Young’s modulus, plateau stress, and other physical parameters. Variation due to the type of mattress has been observed in the laying test using a pressure distribution sensor sheet. In the analysis performed using the physical model, the variation in the lying posture and the extent of body sinking are observed to be the same during experiments. Both variations are compared using the change in force distribution in each body part. In conclusion, it was found that the observed changes in distribution are the same in the experimental and physical models. Therefore, the proposed model reliably reflects the design characteristics of the mattress.

Commentary by Dr. Valentin Fuster
2018;():V003T04A074. doi:10.1115/IMECE2018-87289.

In this paper, we propose to design, develop, and study a cyber-physical system that enables patients and therapists to virtually interact for rehabilitation activities with assistive robotic devices. The targeted users of this system are post-stroke patients. On the patient’s side, an assistive robotic device can generate the force that the therapist applies to the patient. On the therapist’s side, another robotic device can reproduce the responsive force generated by the patient. With this system, the interaction can be virtually established. In addition, by integrating real human trajectories, the proposed assistive robotic system can help patients to perform rehabilitation activities in their own pace. Such an assistive robotic system and virtual interacting scheme can minimize both patient’s and therapist’s traveling time. The assistive functions of this light weight design can also help patients to in their ADLs.

Topics: Robotics
Commentary by Dr. Valentin Fuster
2018;():V003T04A075. doi:10.1115/IMECE2018-87585.

Balance control naturally deteriorates with age, so it comes as no surprise that nearly 30% of the elderly population in the United States report stability problems that lead to difficulty performing daily activities or even falling. Postural stability is an integral task to daily living which is reliant upon the control of the ankle and hip. To this end, the estimation of ankle and hip parameters in quiet standing can be a useful tool when analyzing compensatory actions aimed at maintaining postural stability.

Using an analytical approach, this work builds upon the results obtained by the authors and expands it to a two degrees of freedom system where the first two modes of vibration of a standing human are considered. The physiological parameters a second-order Kelvin-Voigt model were estimated for the actuation of the ankle and hip. Estimates were obtained during quiet standing when healthy volunteers were subjected to a step-like perturbation.

This paper presents the analysis of a second-order nonlinear system of differential equations representing the control of lumped muscle-tendon units at the ankle and hip. This paper utilizes motion capture measurements to obtain the estimates of the control parameters of the system. The dynamic measurements are utilized to construct a simple time-dependent regression that allows calculating the time-varying estimates of the control and body segment parameters with a single perturbation.

This work represents a step forward in estimating the control parameters of human quiet standing where, usually, the analysis is either restricted to the first vibrational mode of an inverted pendulum model or the control parameters are assumed to be time-invariant. The proposed method allows for the analysis of hip related movement in the control of stability and highlights the importance of core muscle training.

Commentary by Dr. Valentin Fuster
2018;():V003T04A076. doi:10.1115/IMECE2018-87645.

Raster imaging is a low cost application for the tracing of movements for biomedical applications. While of the shelf cameras can nowadays provide pictures with high resolution, the optics used can generate unwanted distortions. We evaluated the positional error obtained using a set of GoPro® cameras in conjunction with a Linear Camera Space Manipulation (LCSM) calibration model. The positioning error was compared with a post-processing algorithm to compensate for the radial distortion of a fisheye lens. We found that using the correction algorithm, the error is statistically lower, but the decrease is negligible for practical use. This demonstrates the imperviousness of LCSM to systematic errors of non-Gaussian nature.

Commentary by Dr. Valentin Fuster
2018;():V003T04A077. doi:10.1115/IMECE2018-87742.

The focus of this paper is on the development of an open loop controller for type 1 diabetic patients which is robust to meal and initial condition uncertainties in the presence of hypo- and hyperglycemic constraints. Bernstein polynomials are used to parametrize the evolving uncertain blood-glucose. The unique bounding properties of these polynomials are then used to enforce the desired glycemic constraints. A convex optimization problem is posed in the perturbation space of the model and is solved repeatedly to sequentially converge on a sub-optimal solution. The proposed approach is demonstrated on the classic Bergman model for Type 1 diabetic patients.

Commentary by Dr. Valentin Fuster
2018;():V003T04A078. doi:10.1115/IMECE2018-87759.

The focus of this paper is on the development of a chance constrained controller for type 1 diabetic patients in the presence of model, meal and initial condition uncertainty. Since the chance constraints require the mean and variance of the evolving uncertain blood-glucose, a conjugate unscented transform based approach is used to estimate the blood-glucose statistics. The proposed approach is demonstrated on the classic Bergman model augmented with a gut dynamics model.

Commentary by Dr. Valentin Fuster
2018;():V003T04A079. doi:10.1115/IMECE2018-87806.

In case of direction-dependent viscoelasticity, a simplified formulation of the three-dimensional quasi-linear viscoelasticity has been obtained manipulating the original Fung equation. The experimental characterization of the static hyperelastic behaviour, the relaxation, the dynamic modulus and the loss factor of woven Dacron from a commercial aortic prosthesis has been performed. An 11 % difference of the reduced relaxation (after infinite time) between axial and circumferential directions has been observed for the woven Dacron. A very large increase in stiffness is obtained in case of harmonic loading with respect to the static loading. These findings are particularly relevant for dynamic modelling of currently used aortic grafts.

Topics: Viscoelasticity
Commentary by Dr. Valentin Fuster
2018;():V003T04A080. doi:10.1115/IMECE2018-88123.

A 2-dimensional anatomical knee model was developed for aligning knee joint related bone structures with experimental kinematic data. The experimental data was collected using motion capture cameras, which recorded the position of reflective markers placed on the human subject. Velocities were calculated by numerically differentiating the marker position with respect to time. Joints, such as the hip, knee, and ankle, were represented by axes of rotation. These axes were determined by calculating the relative instantaneous center of rotation of a body segment with respect to the adjacent body segment. Body-fixed coordinate systems were set for both thigh and shin. Anatomical bone structures were obtained from an x-ray and represented mathematically as polynomials. The femoral bone surface was aligned with the experimental data by superimposing the center of rotation of the shin with respect to thigh with the geometric center of the femoral condyle. The tibial surface was aligned with the experimental data by aligning the bones at minimum flexion and then superimposing the tibia with a shared point between femur and tibia. Ligaments were modeled as non-linear elastic springs. Cruciate ligaments were divided into a posterior and anterior ligament fiber bundle. Cruciate ligament forces were calculated for the squatting exercise for five different femoral geometric centers. Geometric centers were determined using a nonlinear least squares optimization technique. Cruciate ligament forces are discussed in this paper.

Commentary by Dr. Valentin Fuster
2018;():V003T04A081. doi:10.1115/IMECE2018-88612.

Animal skeletal muscle exhibits very interesting behavior at near-stall forces (when the muscle is loaded so strongly that it can barely contract). Near this physical limit, the actinmyosin cross bridges do more work than their energy releasing molecules, Adenosine TriPhosphate (ATP) suggest they can. It has been shown that the advantageous utilization of thermal agitation is a likely source for this increased capacity. Here, we propose a spatially two-dimensional mechanical model to illustrate how thermal agitation can be harvested for useful mechanical work in molecular machinery without rate functions or empirically-inspired spatial potential functions. Additionally, the model accommodates variable lattice spacing, and it paves the way for a full three dimensional model of cross-bridge interactions where myosin II may be azimuthally misaligned with actin binding sites. With potential energy sources based entirely on realizable components, this model lends itself to the design of artificial, molecular-scale motors.

Commentary by Dr. Valentin Fuster

Biomedical and Biotechnology Engineering: Musculoskeletal and Sports Biomechanics

2018;():V003T04A082. doi:10.1115/IMECE2018-87129.

In recent years, interest has developed in Chronic Traumatic Encephalopathy (CTE) and the related concussions that occur in sports at both professional and amateur levels. Subsequently there is interest in developing new types of athletic helmets to both absorb energy to detect and reduce concussions. To test these helmets, an appropriate head form must be used that will fit the helmet and also exhibit the dynamic properties of the human head. While much effort has gone into creating biofidelic heads containing instrumentation for automotive crash testing, these heads can cost upwards of $10,000. The goal of this project is to create a head form for a few hundred dollars with the appropriate dynamic properties for testing linear and angular accelerations of a helmet.

The specific goals of this project are to create a head form with the following characteristics: 1) External size and shape that will properly fit a hockey helmet; 2) Weight representative of an adult head; 3) Robust enough to withstand a thousand impact tests. The manufacture of the head form and the verification that the design goals are described.

Commentary by Dr. Valentin Fuster
2018;():V003T04A083. doi:10.1115/IMECE2018-87304.

Recently, compression wear has become the preferred performance material for many athletes, where it has the effect of reducing the burden on the body by suppressing muscle vibrations and improves athletic performance by providing the body with suitable moderate pressure. This study concerns thigh sleeves formed of compression wear. The optimal level of compression is studied in order to improve athletic performance and reduce muscular strain. Subsequently, the mechanics of the thigh compression sleeve are discussed. Here, the optimal tensile rigidity of the sleeve, which is calculated using the Young’s modulus of the sleeve in the circumferential direction, is discussed with the aim of reducing muscular strain. The finite element method model is adopted to represent the thigh, which commonly experiences muscle strain during running. The model is constructed using a semi-circular shape, which represents the thigh cut in the transverse plane. The model consists of two solid components, which reflect the muscle (outer) and femur (inner), as well as a shell that covers the thigh. The model generates sinusoidal vibrations, which reflect human behavior when running in a uniaxial direction. The maximum shear strain is approximately half of the tensile rigidity of the sleeve. Indeed, the muscle is sufficiently soft that the tensile rigidity of the sleeve is generally smaller when there is little shear strain on the muscle. From these results, it is concluded that the maximum shear strain of the muscle decreases by almost half when covered by the thigh compression sleeve compared to when no thigh compression sleeve is worn. Furthermore, the shear strain of the muscle can be reduced by varying the tensile rigidity of the sleeve when the human is running. Finally, the tensile rigidity of the sleeve can be decreased to reduce the shear strain of the muscle as it softens.

Commentary by Dr. Valentin Fuster
2018;():V003T04A084. doi:10.1115/IMECE2018-87670.

The paper focuses on the gait analysis for the investigation of the typical events occurring in human movements and validate its use as a method for musculoskeletal disease evaluation and for the improvement of athletic training. In the present research the motion capture system is combined with an in-house developed prototype of uniaxial force plates for the measurement of the vertical component of ground reaction forces during movement.

While similar techniques are implemented for gait, this equipment can be employed to investigate running, thus, covering a larger number of possible applications and providing a deeper insight either of the athlete performance or the disease analysis.

For the prevention and the treatment of those events occurring during running, a thorough understanding of its mechanisms is critical; therefore, a method for evaluating both the kinematic behavior of the human body and the ground reaction forces combined to a model for determining the muscle forces is proposed.

An infrared motion capture technique is adopted for measuring accurately the body motion and a multiple force-plate system is used to calculate the force exerted by the ground and sub-divided in the three components by an ad-hoc developed routine.

Moreover, the data are used as input parameters for the OpenSim software to derive muscles forces. Finally, the potential of the proposed protocol is determined by an experimental campaign on healthy subjects and a significant database of muscle forces is constructed for different running speeds.

Topics: Gait analysis
Commentary by Dr. Valentin Fuster
2018;():V003T04A085. doi:10.1115/IMECE2018-88347.

The goal of this research is to evaluate the extent of damage to the brain in regard to concussions when female soccer players head the ball to pass, defend, and score goals. It is reported that female soccer players have higher concussion rates than male players, which is why they will be the focus of this study. The anatomy of the female body seems to be structured in a way that increases the risk of concussions, but that has not been verified yet.

While many clinical studies document post-concussion results, our research evaluates the impact of the soccer ball during active play both computationally and experimentally. The force from the ball hitting the head and the resulting acceleration of the brain are analyzed. First, the head accelerations and corresponding HIC (Head Injury Criterion) values are obtained using computational programming. Then, a newly developed experimental framework is used to track the head acceleration using an accelerometer. The velocity and angle at which the ball makes contact with the head are measured using a projectile motion and time-lapse imaging technique. The results of heading the ball in different kick scenarios are compared with the threshold HIC values for concussions.

Commentary by Dr. Valentin Fuster
2018;():V003T04A086. doi:10.1115/IMECE2018-88363.

It has been shown that children are susceptible to many dangers in child safety seats that do not involve a car accident. One issue involves the hyperextension of the neck muscles when the child falls asleep in a slumped position. Another issue is positional asphyxia, which is a form of asphyxia where the child’s position prevents them from breathing adequately.

The present study designed a realistic model of the cervical spine and conducted a finite element analysis to observe if and where stress and strain concentrations existed. This analysis simulated the effects of a moving vehicle on the child while their head was slumped forward.

A car seat redesign was also undertaken to overcome the afore mentioned issues. This involved employing a motor and control system.

Commentary by Dr. Valentin Fuster

Biomedical and Biotechnology Engineering: Posters

2018;():V003T04A087. doi:10.1115/IMECE2018-86392.

Intravascular treatment is known as one of effective treatment methods for cerebral aneurysms. One problem of this therapy is that an intravascular treatment device unexpectedly moves and a tip of the device strongly contacts on a vessel wall. This unexpected movement of the device causes vascular injury. In actual treatment, 2D X-ray image is used. It is difficult for an operator to estimate 3D position of the device from the 2D X-ray image. In this study, we propose estimation methods for 3D position of devices using a X-ray image and a 3D blood vessel model.

At the first step of estimation procedure, a 3D position of X-ray image, a 3D blood vessel model and X-ray source (Xs) are determined by 2D/3D registration method. The actual 3D position of the device tip (P) is placed on the straight line between Xs and P. Moreover, its position is limited within the 3D vessel model. From characteristics, the 3D position of the device tip is estimated. In this study, two methods to estimate the 3D position of the device are proposed. First: A closest point to the straight line from the center line of the blood vessel model is defined as the position in 3D space of the guidewire (one-point estimation method). Second: A mean value of points on the straight line inside the blood vessel model is defined as the position in 3D space of the guidewire (average estimation method). The accuracy of estimation methods depends on angle of X-ray irradiation. In this study, the relationship between the accuracy of estimation methods and the angle of X-ray irradiation. The estimation accuracy was investigated using numerical calculation.

In the case of a simple blood vessel shape, the error of the estimation was proportional to the angular difference between an ideal and an actual. The errors of the estimated arc length parameter at the ideal angle of X-ray irradiation were 0.002 mm and 0.078 mm, respectively. This result shows that this method is effective for simple blood vessel shape. In future work, other factors to affect the accuracy are also investigated.

Commentary by Dr. Valentin Fuster
2018;():V003T04A088. doi:10.1115/IMECE2018-86689.

Magnetic Seizure therapy (MST) is emerging as a treatment for patients suffering from severe depression where an induced current due to an external electromagnetic field is employed. This procedure can only be considered effective when sufficient induced current activates the neurons in the prefrontal cortex. Computer simulation of MST is essential to provide better insight of this procedure and to supplement the clinical trials. To this end, an understanding of transmission of electric impulse through the nerve is considered essential. Stochastic impulse spike sequences are trigged when membrane potential crosses a threshold value. Quantitative numerical predictions employing a mathematical model and induced current defined via Ornstein Uhlenbeck (OU) process predict that both the linear steady-state and rectified models provide adequate threshold adaptation while the rectified model exhibits superior spiking behavior. The present study when combined with suitable numerical simulation of electromagnetic induction is envisaged to aid the MST clinical treatment.

Commentary by Dr. Valentin Fuster
2018;():V003T04A089. doi:10.1115/IMECE2018-86945.

Following head trauma caused by traffic accidents, many patients are unable to completely recover their social functions due to higher brain dysfunction although they are able to return home. To predict the onset and severity of post-traumatic higher brain dysfunction, the visualization of responsible injury is considered urgent. In this study, we focused on five patients with higher brain dysfunction following head trauma caused by traffic accidents to establish a method for quantitatively evaluating higher brain dysfunction. The injury conditions were reproduced on the basis of multibody dynamic and collision analyses using finite element (FE) modeling of the human head to determine mechanical responses inside the cranium of these patients. The strain on the frontal lobe generated by an injury condition was suggested to contribute to the onset of attention disturbance during the chronic phase of medical treatment. Reproduction analysis of the injury conditions using FE modeling of the head could predict the onset and severity of traumatic higher brain dysfunction.

Commentary by Dr. Valentin Fuster
2018;():V003T04A090. doi:10.1115/IMECE2018-88233.

This work aims at utilizing natural resources and recycling materials from aircraft industries to enable their usage in medical and purification applications. The main application for which the materials are tested is the adsorption of bilirubin toxin from the liver of end stage liver failure patients. The two materials of concern are date seeds and carbon fiber reinforced polymers (CFRP). Samples of the materials will be treated to produce activated carbon (AC). Following the preparation of the ACs and chitosan coated ACs, tests are carried out to compare uncoated ACs with chitosan coated ACs. FTIR spectroscopy, TGA, DSC and a Spectrophotometer are utilized in order to characterize the samples obtained. From the data acquired, it is concluded that the chitosan coated ACs have better adsorption than the uncoated ACs. The activated carbon fibers showed the highest efficiency for the adsorption of bilirubin toxin. At an adsorbent dose of 0.8 gm, findings show that 98.4% of bilirubin toxin is adsorbed in samples where ACF is used as the adsorbent while 96.5% remained in samples where DPAC was used as the adsorbent.

Commentary by Dr. Valentin Fuster

Biomedical and Biotechnology Engineering: Symposium on MechanoBiology

2018;():V003T04A091. doi:10.1115/IMECE2018-87650.

External mechanical forces can reach the cell nucleus causing changes in nuclear morphology, size and motility. A common explanation is that these forces are transmitted by surrounding cytoskeleton network through its linkage to nuclear envelope; shear stress causes reorganization of cytoskeleton, thus, the changes in nuclear shape. In this study, we measured nuclear shape and intracellular Ca2+ under fluid shear stress in MDCK cells using a parallel plate microfluidic chip. We show that fluid shear stress (1.1 dyn/cm2, 3 hrs) causes significant changes in nuclear shape in cells, from a flat disk shape having larger area to a thicker disk having smaller area. An increase in intracellular Ca2+ is required for shear induced nucleus deformation. Inhibiting Ca2+ influx with GsMTx4 and Gd3+ eliminated Ca2+ influx and abolished the nuclear deformation. The cytoskeleton reorganization occurred in parallel with Ca2+ rise in the cells. Increasing intracellular Ca2+ with thapsigargin that depletes the Ca2+ stores resumed the nuclear deformation. This suggests that shear induced nuclear deformation is a Ca2+ dependent process.

Commentary by Dr. Valentin Fuster

Biomedical and Biotechnology Engineering: Vibration and Acoustics in Biomedical Applications

2018;():V003T04A092. doi:10.1115/IMECE2018-86306.

In this work, a new design method is proposed to intensify the focused acoustic field generated inside a circular cylindrical piezoelectric transducer. The proposed design incorporates a stepped-thickness piezoelectric transducer which has thickness variations along the length. The location of these steps are identified based on the mode shape analysis of a uniform-thickness tube. Once the step locations are identified, two cases are considered with internal and external steps. Acoustic radiation characteristics and mode shapes are compared with the uniform-thickness shell. All the investigations are performed using ANSYS. An increase in the sound pressure level is obtained utilizing the stepped-thickness tube at the same input power.

Commentary by Dr. Valentin Fuster
2018;():V003T04A093. doi:10.1115/IMECE2018-87133.

High-intensity focused ultrasound (HIFU) can be used for the ablation of tissue, such as in the case of prostate cancer. However, targeting tissue deeper inside the body remains challenging due to the increased attenuation and scattering of the ultrasonic waves. In this work, the partial and complete obstruction of the ultrasonic beam from a HIFU transducer at bones is investigated. Ultrasonic transmission and reflection under such conditions have scarcely been the focus of previous research. Thus, this work provides a reference based on numerical and experimental results. To this end, numerical simulations are conducted for various bone obstruction configurations. In addition, a diffraction-based shadowgraph technique is used for the ultrasound visualization in laboratory experiments. Imaging of focused ultrasonic waves is performed in water with no obstruction, varying partial obstruction, as well as with complete obstruction by bones phantoms. It is shown that there is reasonable agreement between the findings from experiments and simulations. While the field of view in experiments is limited, the entire pressure field in the area of interest can be investigated in numerical simulations. Overall, the results of this work provide a basis for future research in the field of therapeutic ultrasound.

Commentary by Dr. Valentin Fuster
2018;():V003T04A094. doi:10.1115/IMECE2018-87288.

In this study, we examined the suppression effect of brain cooling on the epileptic focus and surrounding area. An epileptic seizure was induced in rats to obtain electrocorticography (ECoG) data when brain cooling was performed on the epileptic focus and its surroundings. Then, the frequency response characteristics were calculated by applying fast Fourier transform (FFT) and band pass filter to the obtained multichannel brain wave data. At this time, the frequency band calculated by the band pass filter was α waves (8.0–13.0Hz) and β waves (13.0–30.0 Hz) which were remarkably observed in epileptic seizure in the previous study, the analysis window of FFT was 4.095 seconds, and the overlap was 75%. As a result of comparing the calculated frequency responses for each rat, it was found that at the site where epileptic seizures were observed, power was reduced by cooling and suppressing effect was observed, whereas at the same time, the power increased at the site a few millimeters adjacent to the seizure site. This result suggests that epileptic waves suppressed by brain cooling might propagate to the surrounding area by a few millimeters.

Topics: Cooling , Brain
Commentary by Dr. Valentin Fuster
2018;():V003T04A095. doi:10.1115/IMECE2018-87341.

Shirodhara is an ayurveda therapy treating subjects for stress (depression/anxiety/hypertension) insomnia, headache and several kinds of psychosis. When there is a fluid impact on a solid surface, a transient impact will be developed at the interface in short time duration as vibration on forehead. The fluid impact of the liquid falling from the beaker at controlled flow rate is measured using an integrated circuit piezoelectric (ICP) force sensor for various tapping condition. The time-dependent response of the sensor is acquired using data acquisition system which is connected to the computer. The force is determined by measuring the voltage output from the piezoelectric force sensor. The impact experiment is done for single droplet, intermittent flow of drops and continuous flow of liquid falling from a fixed height of 7.5 cm. From the results, we observe the impact force for each fluid have a subtle variation depending on the falling condition and impact velocity of the fluid falling from a height.

Topics: Fluids , Biomedicine
Commentary by Dr. Valentin Fuster
2018;():V003T04A096. doi:10.1115/IMECE2018-87364.

This paper describes a mechanism of cell proliferation promotion of cultured osteoblasts by mechanical vibration focusing on β-catenin. 12.5 Hz and 0.5 G mechanical vibration was reported to promote the cell proliferation of cultured osteoblasts in plane culture. That is because the mechanical vibration weakens cell-cell adhesion, promotes to pile up cells, and allows cells to form multilayer structure. However, it has not been clarified why cells continue cell division after their monolayer confluent state. Here we show that mechanical vibration not only weakens cell-cell adhesion bound by β-catenin but also promotes to move β-catenin from the cytoplasm to the nuclei, where β-catenin associates with DNA-binding members of the Tcf/LEF family and other associated transcription factors including cell division. After osteoblastic cells were cultured under 12.5 Hz and 0.5 G mechanical vibration, cells were fractionated into nuclear and cytoplasmic fractions using a centrifugation method. β-catenin in each fraction was detected by a western blot experiment. The protein bands from western blot films were quantified with an image processing and analysis software, ImageJ. As a result, the vibration group gave higher expression of β-catenin in nuclear fraction than the non-vibration group just after the vibration group reached the saturated cell density. It indicates that 12.5 Hz and 0.5 G mechanical vibration may promote to move β-catenin into the nuclei and the cell division.

Commentary by Dr. Valentin Fuster
2018;():V003T04A097. doi:10.1115/IMECE2018-88103.

Traumatic brain injury (TBI) may happen due to loads at high rates. Due to the limitations in experimental approaches, computational methods can simulate and quantify mechanical properties. The experiments show that the human skull has nonlinear mechanical behavior and is significantly strain rate dependent. In this study, we implement Mooney-Rivlin nonlinear hyper and linear-elastic constitutive models to the experimental tensile data at different strain rates; 0.005, 0.1, 10, and 150 1/sec. A dried human skull including frontal, parietal, and occipital bones, was modeled by the 3D laser scanner and discretized by HyperMesh software to perform modal analysis using LS-Dyna finite element software. Using a roving hammer experimental modal analysis scheme, the frequency response function (FRF) and the first three natural frequencies of the skull will be measured. We found these natural frequencies are 496.9 Hz, 560.9 HZ, and 1246 Hz. Performing numerical modal analysis on the skull with pre-assumed linear elastic properties at high strain rate showed close natural frequencies as obtained by experiments. This study provides a new insight into a better understanding of the nonlinearity dynamical behavior of the human skull.

Commentary by Dr. Valentin Fuster
2018;():V003T04A098. doi:10.1115/IMECE2018-88112.

The nonlinear analysis may help to reveal the complex behavior of the Electroencephalogram (EEG) signal. In order to analyze the EEG in real time, we have proposed an EEG analysis model using a nonlinear oscillator with one degree of freedom and minimum required parameters. Our method identifies EEG model parameters experimentally. The purpose of this study is to examine the specific characteristic of model parameters. Validation of the method and investigation of characteristic of model parameters were conducted based on alpha frequency EEG data in both relax state and stress state. The results of the parameter identification with the time sliding window for 1 second show almost all of the identified parameters have a normal distribution spread around the average. The model outputs can closely match the complicated experimental EEG data. The results also showed that the existence of nonlinear term in the EEG analysis is crucial and the linearity parameter shows a certain tendency as the nonlinearity increases. Furthermore, the activities of EEG become linear on the mathematical model when suddenly change from the relax state to the stress state. The results indicate that our method may provide useful information in various field including the quantification of human mental or psychological state, diagnosis of brain disease such as epilepsy and design of brain machine interface.

Commentary by Dr. Valentin Fuster

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