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Cardiovascular

2019;():V001T01A001. doi:10.1115/DMD2019-3223.

Acute Myocardial Infarction (AMI) is the leading cause of worldwide death and disability, and approximately 720,000 Americans will experience an AMI in 2018. Studies have shown that rapid hypothermia therapy (< 35°C) before reperfusion in patients with AMI can reduce infarct size by 37%. Localized therapeutic hypothermia has proven the potential to cool heart tissue rapidly following AMI, 3°C in 5 minutes. Using digital imaging software and the finite volume method we analyzed temperature distributions in six patient-specific LCX artery models. A mock circulatory loop was used to determine the exiting temperatures of a standard 7 Fr catheter with flow rates ranging from 9.1 ml/min to 88.9 ml/min for input into our model. The said flow rates were fed into our model using 0.45 W and 128.4 W of cooling, respectively. Our work showed typical exit temperatures were between 35.8°C and 36.9°C using a 29.2 ml/min catheter infusion flow rate in all six heart models. Additionally, results of this study indicate that biovariability in patient-specific vascular structures significantly impacts Therapeutic Hypothermia (TH) treatment methods. These results indicate that further research is needed to examine more accurate physiological effects, such as pulsatile flow. Future models will be used to provide insight to guide more efficient TH device designs and operational parameters to optimize patient outcomes following AMI.

Commentary by Dr. Valentin Fuster
2019;():V001T01A002. doi:10.1115/DMD2019-3247.

Air embolism occurs when an air bubble enters the arterial system through the catheters. This can happen due to different reasons such as lack of attention, connection failure, or inexperience. This situation results in tissue damage in vital organs such as the heart and brain which may lead to death. To our knowledge, there is no technology preventing an air embolus from happening. Doctors try to prevent this complication with their attention and catheter control. In this project, a new air-trap device that prevents air embolus was tested in-vitro in air embolism model. Experimental results with a prototype showed that the new design was successful. Air embolism was blocked at various pressure-speed ranges. Air Trap device can be used to prevent air embolism by cardiologists, interventional radiologists and cardiovascular surgeons that perform a percutaneous intervention.

Commentary by Dr. Valentin Fuster
2019;():V001T01A003. doi:10.1115/DMD2019-3253.

Robot assisted surgery has been widely accepted by the medical community. Surgeons utilize robots in many different procedures worldwide. However, cardiothoracic surgeons do not regularly use robotic tools to aid them in performing even simple, catheter based procedures such as cardiac ablation or mapping. Some cardiac Monophasic Action Potentials (MAPs) and ablation catheters require a specific window of force to either effectively characterize or scar cardiac tissue. This is challenging to maintain through the cardiac cycle, so the application of a constant force is not a trivial task for surgeons. Robotic assistance to control the force applied to a catheter through ablation and mapping procedures is needed to improve the outcome for patients. The purpose of this work is to develop a single degree of freedom robot that controls the force applied to a beating swine heart. Rather than trying to predict the motion and timing of the heartbeat, or tracking its movement this robot senses and reacts to the force produced by the myocardium. Through the cardiac cycle, the robot applies a constant force to the surface of a beating heart. The kinematics of the cardiac tissue were characterized by utilizing piezoelectric transducers. Hardware to control the catheter motion was designed to fit most commercially available devices. The controller was designed by first building a mathematical model using measured data, and then a control law was implemented considering the heartbeat as disturbances to the system. Finally, testing was completed with dry runs, and in situ and ex-vivo testing in the Visible Heart® Laboratory.

Commentary by Dr. Valentin Fuster
2019;():V001T01A004. doi:10.1115/DMD2019-3259.

Medical device designers must develop catheters that avoid harming the vascular pathway during therapy delivery. To better characterize the necessary design features to minimize damage to central and peripheral vessels, the vascular pathway used for femoral delivery of a cardiac device is studied through high resolution, computed tomography images of fresh, human cadavers. Comparisons of the amount and location of vessel calcification are made between specified anatomical sections. Though the potential complications may be less fatal, the descending aorta and iliac regions were found to be most susceptible to embolism in our analysis.

Commentary by Dr. Valentin Fuster
2019;():V001T01A005. doi:10.1115/DMD2019-3282.

Recent advancements in deep learning have led to the possibility of increased performance in computer vision tools. A major development has been the usage of Convolutional Neural Networks (CNN) for automatically detecting features within a given image. Architectures such as YOLO1 have obtained incredibly high performances for the real-time detection of every-day objects within images. However to date, there have been few reports of deep learning applied to detect anatomical features within CT scans; especially those within the cardiovascular space. We propose here an automatic anatomical feature detection pipeline for identifying the features of the left atrium using a CNN. Slices of CT scans were fed into a single neural network which predicted the four bounding box coordinates that encapsulate the left atrium. The network can be optimized end-to-end and generate predictions at great speed, achieving a validation smooth L1 loss of 11.95 when predicting the left atrial bounding boxes.

Commentary by Dr. Valentin Fuster
2019;():V001T01A006. doi:10.1115/DMD2019-3292.

Coronary artery disease is a major cause of mortality worldwide. Plaque buildup within an individual’s coronary arteries can lead reduced flows, local ischemia, angina, and even result in a myocardial infarction (heart attack). In the past two decades, coronary stents have become one of the ‘gold standards’ for treating such plaque buildups. Stents are designed to push the plaque up against the vessel walls, so to expand the vessels to its original dimensions; ie., keeping the lumen patent allowing for laminar blood flow. Using the Visible Heart® Laboratories (1) capabilities, we have implanted coronary stents using various clinical protocols in porcine hearts. These hearts were subsequently scanned with a micro-CT, so they could be modeled and rendered in various 3D programs as well as fluid simulations. The ability to render fluid simulations through coronaries which had stenting procedures performed within, may allow clinicians to prescribe which bifurcation technique may be best suited for a given patient’s specific anatomy.

Commentary by Dr. Valentin Fuster
2019;():V001T01A007. doi:10.1115/DMD2019-3298.

As the prevalence of mitral and tricuspid valvular disease continues to grow with the aging population [1,2], there is a growing critical need to treat high mortality risk patients using minimally invasive and/or non-surgical percutaneous procedures. However, these transcatheter procedures, especially those aimed at repairing or replacing the mitral and tricuspid valves, are mostly still in development and/or early clinical testing. Catheter delivery, prosthesis fixation, and/or demonstrating device efficacy are major challenges currently being addressed [3,4]. Although in situ animal models can assess catheter systems with clinical imaging, direct visualization of tissue-device interactions in real human heart anatomies are desired. In vitro delivery and implantations of valvular prototypes in human heart specimens can be instrumental for accurate device testing and gaining important design insights. Such investigations can be performed on a pulsatile flow apparatus, utilizing perfusion fixed human hearts with mitral and/or tricuspid valves eliciting coaptation and relative function. The employment of endoscopic cameras provides direct visualization and can be coupled with echocardiography, providing novel insights relative to these transcatheter devices in a dynamic environment. However, these investigative approaches require appropriately fixed human heart specimens that will allow for dynamic valve movement. This study discusses the design, construction, and implementation of a novel fixation apparatus to promote the coaptation of the mitral and tricuspid valves in swine and fresh human heart specimen.

Topics: Testing , Valves
Commentary by Dr. Valentin Fuster
2019;():V001T01A008. doi:10.1115/DMD2019-3301.

Phonocardiogram (PCG) signals contain very important information regarding the heart condition. Recently, several automatic detection algorithms have been explored to profile the characteristics of heart sounds to aid in disease diagnosis. However, many of these methods has been demonstrated only on clean signals with limited test data and variety of PCG signals that can accurately provide information of diagnostic importance with higher sensitivity and specificity. In this work, we propose to characterize the multiscale frequency state of the normal PCG signals that can aid in accurate profiling of PCG to discriminate from pathological conditions.

Commentary by Dr. Valentin Fuster
2019;():V001T01A009. doi:10.1115/DMD2019-3321.

The use of computational modeling and 3D printing to assist in the procedural planning process for the correction of complex congenital heart malformations is becoming the standard of care. However, the use of this technology in planning the placement of ventricular support devices in pediatric patients with non-compaction has been significantly less common. We present the use of a series of models to help guide the sizing and positioning of both the inflow and outflow cannulae in a patient with left ventricular failure as an example of how these technologies can help improve patient outcomes and reduce procedural times.

Commentary by Dr. Valentin Fuster

Neuroengineering

2019;():V001T02A001. doi:10.1115/DMD2019-3219.

Spasmodic dysphonia (SD) is a voice disorder that leads to strained or choked speech. SD is unresponsive to speech therapy. There is no cure for SD. Preliminary work from our group showed that voice quality in SD improves when vibro-tactile stimulation (VTS) is applied over the larynx as a non-invasive form of neuromodulation. The goal of this paper is to describe the design and development of a non-invasive wearable device, which applies VTS to laryngeal muscles with the aim to improve voice quality of individuals with SD. This paper provides preliminary data about the effectiveness of this wearable device for treating the voice symptoms associated with SD.

Commentary by Dr. Valentin Fuster
2019;():V001T02A002. doi:10.1115/DMD2019-3224.

Three hurdles that exist in selecting materials for the development of new medical devices for neurological treatment are creating a bond between substrates, developing a simple and feasible manufacturing process, and selecting materials that follow regulatory trends to meet possible future requirements. The Elkem team has assessed the adhesion and ideal surface preparation of various grades of thermoplastic polyurethane, metals, and silicone susbstrates with a novel, monocomponent, tin free adhesive that cures in ambient conditions. The surfaces of the substrates were treated via plasma, primer, or a combination of the two. Adhesion was evaluated by determining if the failure mode was adhesive or cohesive. Each of the substrates were successfully bonded using a surface preparation method that yielded cohesive failure. Manufactures now have an option for a fast and relatively simple processing set up that requires less energy than using silicone adhesives currently on the market which opens the door to a wider range of material options.

Commentary by Dr. Valentin Fuster
2019;():V001T02A003. doi:10.1115/DMD2019-3291.

Cerebrospinal fluid shunts for the treatment of hydrocephalus fail at a rate of 40% within the first year. The importance of this problem is supported by one institution’s analysis of neurosurgical 30-day readmissions with CSF shunt failure only second to brain tumor readmissions. Hospital shunt related costs have been estimated at $1.4 to $2 billion annually. The majority of these costs are attributable to shunt failures based on the number of revisions out of the total numbers of annual shunt procedures.

The technical innovation of this project is a low cost, low risk and easy to implement CSF shunt design change compatible with current protocols. The proposed product is an innovative distal catheter to minimize the need for revision surgery due to obstruction (also referred to as occlusion). This is accomplished with a dual lumen catheter (current distal catheters are single lumen) consisting of a primary lumen and a secondary lumen providing redundant functionality in the event ofprimary lumen occlusion thereby eliminating the need for surgical shunt revision.

40% of shunts fail within the year after implant and distal catheter obstruction accounts for up to 24% of failures. Though less prevalent than proximal catheter occlusion, incidence of distal catheter occlusion is significant and improved reliability would reduce costs and improve patient outcomes by lowering the number of revisions.

Commentary by Dr. Valentin Fuster
2019;():V001T02A004. doi:10.1115/DMD2019-3312.

The degree to which deep brain stimulation (DBS) therapy can effectively treat various brain disorders depends on how well one can selectively stimulate one or more axonal pathways within the brain. There is rapidly growing clinical interest in DBS lead implant designs with electrode arrangements that can better target axonal pathways of interest, especially in cases where the optimal target is immediately adjacent to a pathway that when stimulated will elicit adverse side effects. Numerical modeling has demonstrated that DBS leads with four radially segmented electrodes provide the best balance of directional targeting capability while minimizing the overall number of electrode contacts [1]. Here, we present a novel 4×4 DBS lead (16-channel electrode array) with the same form factor and materials as current 4 or 8-channel FDA-approved DBS leads. Electrode impedance spectroscopy was performed for three of these 4×4 DBS leads showing reliable electrode impedances before and after implantation within the brain.

Topics: Brain
Commentary by Dr. Valentin Fuster

Orthopedics and Rehabilitation

2019;():V001T03A001. doi:10.1115/DMD2019-3211.

Pressure ulcers remain a significant secondary complication for many wheelchair users, having significant adverse impacts on the health, function and independence of wheelchair users. Research suggests that both the magnitude and duration of loading on tissues can lead to tissue necrosis. This motivated research to measure the in-seat movement of wheelchair users as a means to characterize time of loading. During these research activities, the consistent finding was that persons were not adhering to their weight shift regimens as taught during rehabilitation. This served as motivation to develop a consumer product to inform users of their activities. The transition from a research tool to a consumer product is endowed with challenges. This paper describes the technology as well as the activities required to make this transition. Specific design challenges included attention to usability and device engagement and the need for near real-time data management and analysis to inform users of their in-seat movements.

Topics: Wheelchairs
Commentary by Dr. Valentin Fuster
2019;():V001T03A002. doi:10.1115/DMD2019-3218.

In this study, we focus on validating the accuracy of the previously developed software, which reconstructs thoracic rib cage and thoracic volume in 3D. This software is applied in spine deformity patients to help doctors monitor and follow spine curvature and the thoracic volume variation. Five users were recruited to perform usability testing for the developed software. The usability testing shows that the performance of the thoracic volume reconstruction via our software meets the criterion set by the American Thoracic Society, which recommends an acceptable error of ±3% for the respiratory measurement. In addition, the user operation results were analyzed through a two-way analysis of variance (ANOVA), without replication, statistical method. The outcome indicates the reconstruction accuracy of the software is satisfactory. In the reproducibility study, the result shows that the performance of the developed software is superior to previous literature and the reconstruction is clinically relevant.

Commentary by Dr. Valentin Fuster
2019;():V001T03A003. doi:10.1115/DMD2019-3227.

This project was seeking to improve on a previously completed manual wheelchair with an ergonomic drive system. The goals for improvement were decreasing weight and using a folding frame for increased accessibility. The new design was completed by using a frame from a commercially available wheelchair and adapting it to house an ergonomic drive system. During the design process, customer preference feedback was gathered from veterans to inform the design. The finished prototype is currently in the process of being licensed by a manufacturing partner.

Topics: Design , Wheelchairs
Commentary by Dr. Valentin Fuster
2019;():V001T03A004. doi:10.1115/DMD2019-3231.

Many children have an upper extremity disability leaving them unable to explore the environment around them. Hard exoskeletons can provide support to lift a child’s arms up against gravity, but these devices are generally large and obtrusive leading to low adherence. Children often prefer to have limited arm function rather than wearing such a device. Our lab has previously designed a passive soft exoskeleton to lift children’s arms, but this did not allow for user control and was limited in the length and weight of arm it could support. Building off of this research, we have created the preliminary design for a user-controlled pneumatic soft exoskeleton that may allow users to independently raise and lower their arms.

Commentary by Dr. Valentin Fuster
2019;():V001T03A005. doi:10.1115/DMD2019-3237.

As technological innovation is fused into the rehabilitation process, it gives conventional therapy a new direction with the products of interactive nature and easy to measure techniques. In the recent years, virtual reality based game therapy has turned out to be a promising option for post-stroke patients since it engages patients with fun based exercises during rehabilitation process. It also triggers their neuro-motor functions and accelerates the recovery process. Nevertheless it is necessary to extract some valuable information from the joint movements to measure the recovery condition of patients. Most of the designed games have introduced features to make them interesting as well as challenging for patients, however, only a few measure the joint parameters. We have designed a Kinect based game in Unity3D platform where patients can play game by moving their joints which results in different orthopaedic lessons required for rehabilitation therapy. In contrast to many Kinect based games where only joint movements are considered for playing the game, we have also introduced voice control through speech recognition and feedback provided in terms of audio-visual command to enhance patient’s engagement. Different joint parameters such as trajectory, range of motion, joint velocity, acceleration, reaching time and joint torque are also measured to help quantify the heath condition.

Commentary by Dr. Valentin Fuster
2019;():V001T03A006. doi:10.1115/DMD2019-3238.

A novel ankle-foot prosthesis with adjustable range-of-motion limits was developed to support implementation of gradual training protocols in the physical therapy of new amputees. Stakeholder interviews drove design requirements that guided the development. Our first prototype did not pass structural strength testing, but with minor revisions to some components, our second prototype was able to pass structural strength testing to the P6 load level (125kg user) of the ISO 10328 standard for prosthetic feet. The system is ready for laboratory testing with prosthesis users and clinicians to generate further insight for future design iterations.

Commentary by Dr. Valentin Fuster
2019;():V001T03A007. doi:10.1115/DMD2019-3242.

Grasping and manipulation are critical for many activities of daily living. However, current approaches to grasp rehabilitation do not measure coordination of fingertip forces nor provide metrics for feedback to the user as an aid in regaining fingertip coordination. This paper presents a low-cost mechatronic approach to design and develop a portable and commercially viable grasp rehabilitation device. The performance of the newly developed grasp rehabilitator is compared with an existing research-grade grasping device on a grip and lift task. The results suggest that the newly developed grasp rehabilitator can provide key force measurements that are equivalent to the ones provided by the research-grade grasping device, indicating its validity and potential viability for rehabilitation.

Commentary by Dr. Valentin Fuster
2019;():V001T03A008. doi:10.1115/DMD2019-3260.

Cartilage plays an important role in reducing mechanical stress and assist with smooth limb movement. Osteoarthritis is the degeneration of articular cartilage and bone. This osteochondral region is difficult to heal because of its dissimilar healing capability, so osteochondral transplantation is the most common method to resolve this issue. Post-traumatic osteoarthritis develops after a joint injury and can damage the cartilage and accelerate its wear and tear. Mosaicplasty is the most widely used method involving transplantation of small cylindrical bone cartilage plugs to fill up the affected region. The success of harvesting a larger and complex shaped graft to replace the damaged osteochondral area lies in effective extraction of the cartilage-bone graft from the donor site. Currently, no method exists to perform this procedure for autologous transplantation due to the complexity involved to extract graft without damaging the donor site. In this paper, we propose a novel graft removal mechanism to harvest a personalized autologous graft of virtually any shape and size. Our method involves drilling a profile similar to the effected region on the donor site and slicing off the desired cartilage-bone graft from its root to harvest it. We developed a new graft removal mechanism capable of inserting a flexible saw parallel to the transverse plane and slice the graft parallel to the coronal plane to extract a donor graft for autografting procedures.

Commentary by Dr. Valentin Fuster
2019;():V001T03A009. doi:10.1115/DMD2019-3315.

The ankle mechanical impedance of healthy subjects was estimated during the standing pose while they co-contracted their lower-leg muscles. Subsequently, the impedance parameters were modeled as a function of the level of co-contraction using machine learning regression methods. From the experimental results, the average ankle stiffness coefficients in dorsi-plantar flexion (DP) showed more dependence to the muscle contraction than stiffness in inversion-eversion (IE): 4.6 Nm/rad per %MVC (percent of the maximum voluntary contraction) and 1.1 Nm/rad per %MVC, respectively. To accurately estimate the ankle impedance parameters as a function of the electromyography (EMG) signals, multiple EMG feature selection methods, regression models, and types of models were evaluated. Using a 1-vs-All model validation approach, the best regression model to fit the stiffness and damping in DP was the Least Square method with Regularization, and the best IE stiffness was the Gaussian Process Regression. No model was able to estimate the IE damping well, possibly because this parameter is not modulated with a changing co-contraction of the lower-leg muscles.

Commentary by Dr. Valentin Fuster

MEMS and Nano

2019;():V001T04A001. doi:10.1115/DMD2019-3225.

According to the CDC, 795,000 Americans are diagnosed with a stroke each year. Out of the all of the technology used to track the gait of a stroke patient, the Inertial Measurement Unit (IMU) is growing in recognition and use. These are often used as wearable sensors for rehabilitation, with their small size and cost effectiveness. The purpose of this research is to detail the innovation of an android application with the ability to receive IMU data and present it through medically significant visual displays. The data from a device is received via bluetooth, and is transmitted in terms of angles roll (x axis), pitch (y axis) and yaw (z axis). The application displays this data to allow the user to track the position of the IMU in live time. The medical professional has the ability to input a desired set of angles, and track the proximity of a connected device to the target position. The data is presented visually through the coronal, transverse & sagittal plane. When roll and pitch angles from the app were compared to angular values measured on a protractor, the average difference was +/− 0.366° and +/− 0.436°, in roll and pitch respectively. Along with the average accuracy being less than a 0.5° difference, the application has the ability to connect and track 3 IMU devices simultaneously. The data can be stored and exported. The greatest limitation is angular presentation latency. This creation has the potential to catalyze creation of an app that can track a high number of devices simultaneously, with high accuracy and low signal latency. The ability to track and position wearable IMU sensors using a smartphone or tablet offers an exciting future in rehabilitation, especially for recovering stroke patients.

Topics: Humanoid robots
Commentary by Dr. Valentin Fuster
2019;():V001T04A002. doi:10.1115/DMD2019-3263.

Femtosecond laser ablation is a powerful tool for the fabrication of medical devices, especially with materials commonly used in implantable micro devices as these materials are often incompatible with traditional machining techniques. Laser machining quality is highly dependent not only on the laser parameters, but also on the material that is being machined and so the process must be characterized for each material of interest. In this work, process characterization is presented for two materials commonly used in implantable micro devices — polyimide and silicon. The ablation threshold and etch rate were determined for femtosecond laser machining with a UV wavelength.

Topics: Laser ablation
Commentary by Dr. Valentin Fuster
2019;():V001T04A003. doi:10.1115/DMD2019-3264.

In this work, we developed giant magnetoresistive (GMR) based handheld biosensing systems that serve as platform for detecting human NT-proBNP. This assay takes advantages of high sensitivity and real-time signal readout of GMR biosensor. The limit of detection was estimated to be less than 0.01ng/mL, and detection range covered from 0.01 ng/mL to 5 ng/mL was obtained. The assay can be completed within 20 min, which is very important for further development of point-of-care testing. The proposed GMR handheld system is also successfully used for the detection of real NT-proBNP human samples. It can be foreseen that this handheld detection system could become a robust contender in the applications of in vitro biomarker diagnostics.

Topics: Testing , Biosensors , Signals
Commentary by Dr. Valentin Fuster

Sensors

2019;():V001T05A001. doi:10.1115/DMD2019-3267.

This paper presents the design and fabrication of a textile-based soft Electromyography (EMG) sensor and machine-learning-based methods to detect muscle spasticity. The textile EMG sensor is flexible, foldable, stretchable, washable for multiple times, and easily customizable to meet the heterogeneous needs of SCI individuals. The machine learning algorithms that can estimate the muscle status and the performance of functional ADLs by classification of function ADLs and the detection of muscle spasticity. The soft textronic sensors, its intelligent machine learning algorithms, and biofeedback-based rehabilitation has the potential to enable home-based rehabilitation and encourage more manipulation for function ADLs and independence in SCI and stroke individuals.

Commentary by Dr. Valentin Fuster
2019;():V001T05A002. doi:10.1115/DMD2019-3311.

Over the past two decades, there has been more of an emphasis by practitioners for mothers to perform skin-to-skin holding, known as Kangaroo Care (KC) due to the many benefits, such as decreased illness early in life, increased breastmilk production, and decreased chance of long term obesity for mother and child. Kangaroo Care is difficult in the NICU due to the health of the child and mother and numerous leads, IVs or breathing tubes attached to the child. With these problems, it is hard for mothers to follow best practices for performing KC, namely holding for a minimum of one hour and first hold within 24 hours of birth. Not following best practices lessens the benefits of KC for mother and child. Tracking of the duration of KC is often not measured by anyone including hospital staff so whether best practices are followed is difficult to know. Also, mothers may not have clothing that facilitates KC and there are few wearables specifically designed for mothers wanting to perform KC in the NICU. This project focuses on one part of designing a wearable that facilitates mothers performing KC while their child is in the NICU. To understand the effectiveness of said wearable, measuring how long the mothers are performing KC is needed. To accomplish this, a pressure sensor, incorporating Carbon Nanotube Fabric (CNT), was constructed to measure changes in pressure to track the number and duration of KC holds. As for the sensor, when a pressure is first applied or removed, the resistance changes rapidly but remains relatively constant with constant pressure. The average time difference between manually recording time and the sensor measurement was 4.06 seconds for a single event, such as applying a pressure to the sensor, and 6.66 seconds for a double event, such as the duration between when the pressure was applied to when it was removed. These results show that the sensor is accurate enough to measure the duration of KC for any period of time it is performed.

Commentary by Dr. Valentin Fuster

Surgical Tools

2019;():V001T06A001. doi:10.1115/DMD2019-3214.

Endoscopic radiofrequency ablation has gained interest for treating abdominal tumors. The radiofrequency ablation electrode geometry largely determines the size and shape of the ablation zone. Mismatch between the ablation zone and tumor shapes leads to reoccurrence of the cancer. Recently, work has been published regarding a novel deployable multi-tine electrode for endoscopic radiofrequency ablation. The prior work developed a thermal ablation model to predict the ablation zone surrounding an electrode and a systematic optimization of the electrode shape to treat a specific tumor shape. The purpose of this work is to validate the thermal ablation model through experiments in a tissue phantom that changes color at ablation temperatures. The experiments highlight the importance of thermal tissue damage in finite element modeling. Thermal induced changes in tissue properties, if not accounted for in finite element modeling, can lead to significant overprediction of the expected ablation zone surrounding an electrode.

Commentary by Dr. Valentin Fuster
2019;():V001T06A002. doi:10.1115/DMD2019-3244.

Intra-abdominal organ and vascular injuries during laparoscopic trocar placement remain a significant cause for surgical complications during laparoscopic procedures. These complications can arise if the surgeon deviates from the proper placement axis, requiring additional applied force to obliquely traverse the abdominal wall. This increase in force application increases the risk of internal vessel and organ damage immediately after entrance to the peritoneal cavity. To mitigate this risk, our group designed a trocar that provides real-time feedback of deviation from the proper insertion axis, applied force, and position of the trocar tip within the tissue. This was performed using an accelerometer, load cell, and electrical impedance measurement. Our device was tested in a surgical simulation laboratory by medical students using a porcine abdominal wall model. Results establish our device as an effective training tool for educating surgeons on trocar placement in laparoscopic surgery.

Topics: Surgery
Commentary by Dr. Valentin Fuster
2019;():V001T06A003. doi:10.1115/DMD2019-3249.

Image-guided, minimally-invasive cochlear implant surgery is a novel “keyhole” surgical approach for placing a cochlear implant electrode array eliminating the need for a wide-field mastoidectomy approach. Image guidance is used for path planning which is followed by the construction of a customized micro-stereotactic frame to drill a narrow channel from the skull surface to the cochlea. Herein, we present an insertion tool that uses roller wheels to advance the electrode array through the narrow tunnel and into the cochlea. Testing in a phantom revealed that when compared to insertions with surgical forceps, the new insertion tool was on average 26s faster, produced complete insertions more often (i.e. in 6/6 trials, vs. 1/6), and reduced array buckling (0/6 trials vs. 5/6). The tool provides a viable solution to complete the last step of this novel, minimally-invasive procedure. It also provides the advantage over previously developed manual insertion tools of enabling the surgeon to blindly actuate the roller wheel tool to advance the electrode into the tunnel. This allows the surgeon to visualize and guide insertion into the cochlea from a more advantageous visual perspective.

Commentary by Dr. Valentin Fuster
2019;():V001T06A004. doi:10.1115/DMD2019-3251.

Treatment of glaucoma involves lowering intraocular pressure, which can be achieved through several methods (e.g. topical medication, oral medication, surgery). This paper studies the use of stent implantations for pressure regulation, and proposes a direct illumination method to facilitate the insertion procedure. A proof-of-concept is demonstrated on a cadaver eye.

Topics: stents
Commentary by Dr. Valentin Fuster
2019;():V001T06A005. doi:10.1115/DMD2019-3271.

Surgical needles are commonly used by medical specialists to reach target locations inside of the body for disease diagnosis or other medical interventions, such as biopsy, brachytherapy, thermal ablation, and drug delivery. Insertion of the needle in human body parts with a larger needle often results in severe tissue damage. Tissue damage could potentially be reduced by decreasing the insertion force caused mainly by the friction on the interface of needle and tissues. Here we propose the use of polydopamine (PDA) coating to reduce the friction force. In addition to its excellent biocompatibility, polydopamine has desirable adhesion, lubrication, biodegradability and, thermal stability properties. Our preliminary results on some needle prototypes show that by coating the needle with polydopamine, the insertion force can be reduced by 20–25%.

Commentary by Dr. Valentin Fuster
2019;():V001T06A006. doi:10.1115/DMD2019-3274.

Lung cancer is the leading cause of cancer deaths worldwide. In order to determine if lung nodules are cancerous, a biopsy needs to be taken. There is a need to be able to perform more of these biopsies through a transbronchial approach in order to reduce the risk of pneumothorax that is associated with transthoracic biopsies. This is particularly the case at the periphery of the lung where the bronchioles become too small for a traditional bronchoscope. The proposed biopsy tool incorporates a compact coaxial camera and illumination configuration to make it more compact than a traditional bronchoscope. It also includes a new flexible needle design that allows a biopsy to be taken adjacent to a radial ultrasound transducer. The navigation and tissue biopsy capabilities of the proposed device are demonstrated through benchtop and animal testing.

Topics: Lung
Commentary by Dr. Valentin Fuster
2019;():V001T06A007. doi:10.1115/DMD2019-3276.

The study aims to design and develop an Adaptive Bone Fracture Fixation System for the purpose of enhancing the control over fracture fixation as well as to permit quick device installation. The external ring fixator was designed to employ the use of bolted-nut hinges and rapid-gradual lengthening longitudinal elements to allow for full assembly expansion and progressive or immediate shape adjustment. The ring fixator was stress tested via direct loading (compression and tension) to determine if it can support the average human body weight [max 3.5 kN]. The study had verified that the device possesses intricate designs that would enhance the functionality of the external ring fixator, however these designs would limit the structural integrity of the bone fracture fixation system.

Commentary by Dr. Valentin Fuster
2019;():V001T06A008. doi:10.1115/DMD2019-3278.

A study to determine the optimal insertion point of the latissimus dorsi muscle for treatment of rotator cuff tears using in-silico biomechanical models. A cadaver trial was used to validate the simulation results. The optimal area for insertion for improving glenohumeral rotation throughout a range of flexion was found to be the center of the greater tuberosity.

Commentary by Dr. Valentin Fuster
2019;():V001T06A009. doi:10.1115/DMD2019-3281.

Most of the existing MRI guided robotic needle guide systems have been limited to research purposes and have not progressed towards clinical applications due to complex and bulky structures. The ‘device-to-image’ registration step further complicates the operation and significantly increases the overall procedure time. To address limitations, we developed an MRI guided transperineal prostate biopsy guide system that uses the concept of a ‘fixed coordinate device’ to simplify the overall biopsy procedure and eliminate the registration step, making the procedure more clinically friendly. We performed proof-of-concept targeting experiments using an agar phantom under 3T MRI. The targeting results were analyzed, and initial results prove that the simplified intervention concept would well be feasible. We plan to extend the study further to identify error components.

Commentary by Dr. Valentin Fuster
2019;():V001T06A010. doi:10.1115/DMD2019-3293.

Many gastric motility disorders, including gastroparesis, are caused by dysrhythmias occurring in the stomach musculature. Microwave ablation (MWA) offers potential as a minimally invasive endoscopic approach for targeted thermal destruction of the gastric musculature to disrupt irregular electrical rhythm within the stomach wall. An experimental study was conducted in a gel phantom to analyze the transient heating profile of a water-cooled 2.45 GHz MWA antenna enclosed within a PET balloon. Fiber-optic temperature sensors were used to collect temperature data at distances 1.5–7.5 mm from the balloon surface. Ablation profiles were also characterized in ex vivo porcine skeletal muscle. With 20 W applied power and cooling water temperature of 5 °C, temperature measured at 3.5 mm from the balloon surface exceeded the temperature at 1.5 mm from the balloon surface by 3 °C. In ex vivo tissue, for 40 W applied power, tissue within 2 mm of the balloon surface remained unablated. With adequate cooling and power, it may be feasible to thermally spare tissue within 2 mm of the MWA balloon applicator.

Commentary by Dr. Valentin Fuster
2019;():V001T06A011. doi:10.1115/DMD2019-3294.

To detect and treat colorectal cancers endoscopes are commonly used to perform colonoscopies, with an estimated 15 million performed in America every year. Endoscope designs rely on physicians physically pushing the long device into position through the intestine thereupon applying potentially damaging forces to the intestinal wall. To improve endoscopic procedures this paper presents the novel concept of Inverted Tubular Element Locomotion (ITEL) to reduce interaction forces between the endoscope and the intestine wall. Experiments are performed that demonstrate functionality of the tubular design and less than 3.5 kPa to deploy. The tube material thickness has a linear relationship with the force required. This unique design has the potential to enhance patient safety and to improve procedural efficiency.

Topics: Design , Endoscopes
Commentary by Dr. Valentin Fuster
2019;():V001T06A012. doi:10.1115/DMD2019-3299.

Needle insertion is used in many percutaneous surgical procedures such as thermal ablation, biopsy and brachytherapy. Since accurate placement of the needle tip governs the success of these procedures, needle tip tracking is particularly important during the insertion. Many research groups use phantom materials to test their proposed needle insertion technique for either developmental or training purposes. This work suggests new methods to improve visualization of the needle tip inside the phantom materials and thereby an enhanced needle tip tracking. Needle insertion tests were performed in phantoms with different transparency, and the needle tip tracking was done via an ultrasound machine. Simple Linear Iterative Clustering (SLIC) was then used to track the needle tip in different phantoms. The proposed method improved the needle tip visualization in ultrasound needle tracking.

Commentary by Dr. Valentin Fuster
2019;():V001T06A013. doi:10.1115/DMD2019-3303.

Foreign body retrieval is potentially needed when a patient ingests foreign objects; while many of these will pass naturally, intervention may be required. The retrieval process can be done endoscopically or surgically. This paper covers the novel use of shape memory alloy to assist in endoscopic foreign body removal. Six closure methods were constructed and tested for percentage contraction. These ranged from linear actuation and memorized simple shapes to shape-set springs. Of these closure methods, a spring based architecture yielded the greatest percentage contraction but tangled during the contraction process. The design presented in this paper will enable faster and less invasive gastroenterological foreign body retrieval from the stomach.

Commentary by Dr. Valentin Fuster
2019;():V001T06A014. doi:10.1115/DMD2019-3305.

Laser interstitial thermal therapy (LITT) is a neurosurgical procedure that involves using heat treatment to ablate glioblastomas in the brain. Current methods for placing probes in LITT involve straight trajectory pathways. This limitation often requires surgeons to make multiple trajectories or leave undesired margins. There has been extensive work in steerable needles, concentric tube cannulas, and flexible surgical tools. In this work, we present an approach which focuses on providing steerability to tools that aren’t inherently steerable. To do this, we developed a curved port delivery system that leverages an active cannula for the deployment of a plastic, flexible port that delivers existing surgical tools. We present an initial prototype coupled with feasibility results illustrating that the port can be placed to steer probes to a desired location.

Commentary by Dr. Valentin Fuster
2019;():V001T06A015. doi:10.1115/DMD2019-3307.

Needle-based surgical procedures for diagnostic and therapeutic purposes such as biopsy and brachytherapy has significantly contributed in minimally invasive surgeries. Percutaneous interventions demand precise navigation of surgical needles in soft tissue. Active needle steering increases the target placement accuracy, and consequently improves the clinical outcome. In this work, a novel 3D steerable active surgical needle with three Shape Memory Alloy (SMA) actuators is proposed. The actuation capabilities of SMAs were used to realize a 3D motion at the needle tip. The feasibility of 3D steerability was demonstrated through active control of multiple SMA actuators.

Topics: Surgery , needles
Commentary by Dr. Valentin Fuster
2019;():V001T06A016. doi:10.1115/DMD2019-3308.

Catheter associated urinary tract infections (CAUTI) are among the most common nonpayment hospital acquired conditions. Inexperienced health care providers placing indwelling urinary catheters are associated with an increased risk of CAUTI. The creation of high-fidelity simulators may reduce CAUTI risk during critical early learning. As a first step toward the creation of accurate simulators our group set out to characterize the mechanical aspects of urethral catheterization. This work presents an inexpensive, yet practical means of acquiring motion and force data from urethral catheter insertion procedures using OpenCV ArUco markers. Evaluation of the video system’s accuracy was done to understand the performance characteristics within the boundaries of the procedure’s target workspace. The tracking accuracy was validated to be roughly ± 3 mm in the plane of the camera, and ± 10–25 mm along its axis depending on the distance. Feasibility of using this platform in a clinically relevant setting was demonstrated by capturing the force and motion data when performing urinary catheterization on cadaveric donors (N=2).

Topics: Catheters
Commentary by Dr. Valentin Fuster
2019;():V001T06A017. doi:10.1115/DMD2019-3309.

Office-based endoscopic procedures are becoming an increasingly attractive option for the treatment of laryngeal abnormalities, but their effectiveness is limited by the lack of articulation in currently available surgical instruments. In this paper, we propose the development of novel miniaturized steerable instruments aimed to overcome this limitation and extend a surgeon’s reach inside the larynx. To guide the designs of these new instruments, we report on a simulation study which uses image-based anatomical models to derive the kinematic requirements to operate inside the laryngeal cavity.

Commentary by Dr. Valentin Fuster

Computer Modeling and Simulation

2019;():V001T07A001. doi:10.1115/DMD2019-3210.

The increasing complexity of the medical regulatory environment and the inherent complexity of medical devices, especially due to the increased use of connected devices and embedded control software, impose adoption of new methods and tools for the system design, safety and security analyses. In this paper, we propose a method and an associated toolchain to couple model-based system engineering and safety/security analyses at the design phase of medical devices. The method is compliant with ANSI/AAMI/ISO TIR57 safety and security guidance, and compatible with INCOSE Biomedical-Healthcare Model-Based Systems Engineering works. The toolchain is based on a system architecture modelling tool and supports medical device domain specific reference architecture, as well as tools for safety and security risk analyses. The proposed method and toolchain are illustrated by considering a RGB’s TOF-CUFF monitor device analyzed in the scope of the AQUAS project as a medical device use case.

Commentary by Dr. Valentin Fuster
2019;():V001T07A002. doi:10.1115/DMD2019-3222.

In this study, a commercially available computational fluid dynamics (CFD) program was used to simulate coil embolization techniques, standard coiling (SC) and stent-assisted coiling (SAC), in simplified vessels that are representative of vessels found in the brain. The test models included a curved vessel, ranging from 3mm to 4mm in diameter. The vessel was afflicted with a spherical aneurysm, ranging from 8mm to 16mm in diameter. The four test cases were simulated without treatment, with SC treatment, and with SAC treatment, for a total of twelve simulations. The parameters of interest were blood volume flow into aneurysm, fluid velocity, wall shear stress (WSS), and vorticity. Results of the simulations indicate, on average, SC and SAC reduced volume flow into the aneurysm by 50% and to over 60%, respectively. Both SC and SAC appeared to reduce distal neck WSS. Both treatments reduced average overall dome WSS by approximately 76%. Average aneurysm neck velocity was reduced by both treatments; SC reduced neck velocity by 69% and SAC reduced neck velocity by 75%. Information on SC and SAC efficacy in idealized scenarios could assist medical professionals determining viable approaches for patient-specific cases and lays foundation for future CFD studies exploring coil embolization treatments.

Commentary by Dr. Valentin Fuster
2019;():V001T07A003. doi:10.1115/DMD2019-3246.

Current chemotherapy delivery methods and CSF sampling in leukemia pediatric patients represents a challenge with multiple associated risks creating the need for a more efficient technique. The proposed design of a novel intrathecal device was submitted to computer simulation analysis finding promising results regarding the fluid behavior inside the port and the structural performance of the components.

Commentary by Dr. Valentin Fuster
2019;():V001T07A004. doi:10.1115/DMD2019-3275.

Scapular dyskinesis is a common occurrence in overhead athletes, i.e. athletes who participate in any sport where the upper arm and shoulder is used above the athlete’s head. However, no consensus has been reached on how to evaluate scapular dyskinesis quantitatively. This article describes the development of a measurement technique that can be used to evaluate certain key clinical parameters specific to scapular dyskinesis. The technique employs a 3D structured light computer vision approach to create a surface map of the soft-tissue across the scapula. This surface map is then analyzed using a surface curvature analysis to identify the key clinical parameters associated with scapular dyskinesis. The main advantage of this method is that it provides a marker-less 3D approach. This may aid with diagnosis and monitoring of scapular dyskinesis by allowing measurement data to be collected both before and after treatment and rehabilitation. We expect that this technique will make the monitoring of treatment effectiveness easier while contributing to diagnostic computer vision.

Commentary by Dr. Valentin Fuster
2019;():V001T07A005. doi:10.1115/DMD2019-3288.

Legg-Calvé-Perthes disease (LCPD) is a painful pediatric hip condition caused by an idiopathic disruption of blood flow to the femoral head. The bone subsequently becomes necrotic and fragile. This can result in significant femoral head deformity, leading to pain and early degeneration of the hip. Severity of avascular involvement of the femoral head correlates with long-term outcomes, including hip arthritis and replacement. Preclinical models present extreme cases of the disease and do not represent the spectrum of LCPD seen clinically. A virtual model was developed to explore advancing the preclinical model through new methods of visualizing the data. Overall, three opportunities to advance the preclinical model and our understanding of LCPD are presented.

Commentary by Dr. Valentin Fuster
2019;():V001T07A006. doi:10.1115/DMD2019-3319.

The number of young people getting total hip arthroplasty surgery is on the rise and studies have shown that the average number of perfect health years after such surgery is being reduced to about 9 years; this is because of complications which can lead to the failure of such implants. Consequently, such failures cause the implant not to last as long as required. The uncertainty in design parameters, loading, and even the manufacturing process of femoral stems, makes it important to consider uncertainty quantification and probabilistic modeling approaches instead of the traditional deterministic approach when designing femoral stems. This paper proposes a probabilistic analysis method which considers uncertainties in the design parameters of femoral implants to determine its effect on the implant stiffness. Accordingly, this method can be used to improve the design reliability of femoral stems. A simplified finite element model of a femoral stem was considered and analyzed both deterministically and probabilistically using Monte Carlo simulation. The results showed that uncertainties in design parameters can significantly affect the resulting stiffness of the stem. This paper proposes an approach that can be considered a potential solution for improving, in general, the reliability of hip implants and the predicted stiffness values for the femoral stems so as to better mitigate the stress shielding phenomenon.

Topics: Design , Uncertainty , Risk
Commentary by Dr. Valentin Fuster

Human Factors

2019;():V001T08A001. doi:10.1115/DMD2019-3204.

Laparoscopic surgery offers multiple clinical advantages over open surgical procedures. The rise in adoption of laparoscopic surgery brings with it unique human factors challenges for surgeons and device developers. The design of laparoscopic surgical tools requires specialized human factors analysis and ergonomic considerations to overcome these challenges. Often, this necessary ergonomic design refinement is a secondary effort after proof-of-concept engineering prototypes demonstrate technological feasibility.

In this paper, the evaluation and redesign of an engineering proof-of-concept multimodal hand tool, is presented. The baseline design, a three-in-one laparoscopic hand tool for liver resection, merged three distinct devices into one integrated solution for dissection, vessel sealing, and tissue cautery. The work described herein evolves the initial prototype using a multifaceted human factors analysis and design process. This included the use of operating room and laboratory contextual inquiry, simulated use studies, anthropometric underlays, an iterative design process, and expert reviews. The revised design reduced ulnar deviation based on directed hand position via design, provided dual grip options, added over-molded interaction points, incorporated end-effector rotation, and implemented a new handle and controls layout based on anthropometric underlays. The outcome reinforces the notion that human factors and industrial design principles are required elements of a successful user centered design process.

Commentary by Dr. Valentin Fuster
2019;():V001T08A002. doi:10.1115/DMD2019-3310.

Fine and gross motor skills of the hand are essential to complete the work of surgery. During examinations and surgery, the hand becomes a surgeon and a medical professional’s first point of contact with a patient, as they use their hands to perform tasks with various tools while wearing gloves. The anthropometry of hands and the interaction of the tool can affect the probability of developing a musculoskeletal injury [3]. Tools for healthcare professionals are typically designed using male anthropometric data taken from only one position using tape measures and calipers. The problem with this approach is that humans are rarely in these positions when carrying out everyday tasks and hand measurements and form change with movement. This paper discusses a new method of capturing dynamic hand anthropometry through the use of 3D scanners, to address traditional anthropometric hand data’s limitation. Based on an initial assessment of surgical instruments, six functional hand grasps were selected and compared to traditional hand anthropometric poses. Using these poses, a pilot study with one male was conducted. In total 65 measurements were gathered through 8 poses. The positions with the largest range of measurement change were: Total Hand Length-Palmar with 48 mm, Total Hand Length-Dorsal with 39 mm, and the tip of the first digit through webspace to the tip of digit 2 (Web) with 26 mm. Understanding dimensional change in select areas of the hand is essential to developing more ergonomic, better fitting products for surgeons and medical professionals. A 26–48 mm dimensional change can have a significant impact on the positioning of surgical tool properties, as well as the functionality of the tool and precision of work for surgeons and medical professionals with different hand sizes. This pilot study demonstrated the feasibility of using functional hand grasps as a basis for collecting hand anthropometric data using a 3D scanner.

Topics: Biomedicine
Commentary by Dr. Valentin Fuster

Wearables

2019;():V001T09A001. doi:10.1115/DMD2019-3205.

The ability to investigate sleep is of scientific and clinical interest. Polysomnography (PSG) has long been considered the gold standard assessment for sleep physiology; however, its cost and inconvenience have spurred the development of consumer devices capable of evaluating sleep outside the laboratory. The development of dedicated consumer sleep monitoring devices, e.g., the Zeo Personal Sleep Manager, smart bands, e.g., the Microsoft Band 2 (MB2), and activity trackers, e.g., the Fitbit Charge 2 (FC2), with the ability to automatically distinguish between sleep and wakefulness has important implications for sleep research and medicine.1–3

Topics: Sleep
Commentary by Dr. Valentin Fuster
2019;():V001T09A002. doi:10.1115/DMD2019-3206.

According to statistical data, approximately 800,000 individuals across the United States have strokes each year [2]. A stroke event causes neurological and orthopedic deficits, such as weak muscles, decreased proprioception, and spasticity [6]. To regain function, increase motor skills, and retrain muscles, many stoke survivors utilize aquatic therapy as a form of rehabilitation [14]. Typically inside water, the lower body part of a person has to carry 75% less weight, This decreases the effect of gravity allowing increased joint range of motion [6], [13]. This also helps increase muscle strength as water offers about 600 more resistance than air [13]. The water temperature also helps decrease pain, spasticity, and rigidity [13]. The uniform pressure along with buoyancy contributes to an improved balance of the body [13].

Commentary by Dr. Valentin Fuster
2019;():V001T09A003. doi:10.1115/DMD2019-3207.

A method for the design and development of a feedback device for the treatment of focal dystonic symptoms of Parkinson’s patients is described in this work. This device utilizes haptic feedback produced via a soft pneumatic actuator incorporating zero-volume chambers and channels, to signal to the patient that they are falling into a dystonic pattern so that they themselves can manually break out of the pattern preserving and prolonging the use of the afflicted limb, in this case the hand. The system of detection for the dystonic symptoms is a conductive rubber stretch sensor that detects changes to the circumference of the forearm as the muscles begin to involuntarily contract. The signal from the sensor then feeds into a microcontroller that will activate the onboard pump that will in-turn pulse the soft pneumatic actuator producing a gentle but noticeable haptic sensation on the patient’s arm.

Topics: Haptics
Commentary by Dr. Valentin Fuster
2019;():V001T09A004. doi:10.1115/DMD2019-3208.

The soft actuated wearable deltoid assistance device presented in this paper aims at assisting patients with activities of daily living by dynamically producing flexion and abduction movements for them. By counteracting the force of gravity on the patient’s arm it allows them to move in the frontal plane to perform activities of daily living.

Topics: Gravity (Force)
Commentary by Dr. Valentin Fuster
2019;():V001T09A005. doi:10.1115/DMD2019-3213.

This paper proposes an adaptive sampling algorithm for a pair of smart shoes for patients to use as a daily health monitoring device. The main hardware of the smart shoes features four pneumatic pressure sensors that measure ground contact forces (GCFs) and a global positioning system (GPS) to track the location of the user. The sampling rate of the pressure sensors and the GPS are changed based on the activity, either walking or sitting, detected from the user’s GCFs. An outdoor test was conducted to validate the adaptive sampling algorithm. The result was a 95% reduction in data size compared to sampling with the highest settings from all components. Collected GPS information from a subject’s morning activities was displayed onto a map to demonstrate how it could be used as contextual data for daily monitoring.

Commentary by Dr. Valentin Fuster
2019;():V001T09A006. doi:10.1115/DMD2019-3221.

To promote eye contact learning and behavior in children with autism, there exist specialized environments as well as smartphone applications. However, few currently available techniques support the assessment of desired behavioral improvement during learning. In this paper, we describe recently developed wearable smart glasses instrumented with mechatronic sensors and controllers. The mechatronics glasses, worn by both an instructor and a child, quantitatively measure the eye contact behavior of the child. The instructor glasses connect with a smartphone application through Bluetooth low energy. A user interface is created and hosted on the smartphone to enable the instructor to customize the reward to the child based on improvements in eye contact behavior. Specifically, the smartphone application quantifies the eye contact duration, frequency, latency, and session time, allowing instructors, therapists, and clinicians to monitor and track the child’s progress in eye contact behavior. The results from preliminary user testing of the device with control subjects show that the device is capable of recording sessions details and supporting eye contact behavior assessment.

Topics: Glass
Commentary by Dr. Valentin Fuster
2019;():V001T09A007. doi:10.1115/DMD2019-3232.

Prosthetic sockets are static interfaces for dynamic residual limbs. As the user’s activity level increases, the volume of the residual limb can decrease by up to 11% and increase by as much as 7% after activity. Currently, volume fluctuation is addressed by adding/removing prosthetic socks to change the profile of the residual limb. However, this is impractical and time consuming. These painful/functional issues demand a prosthetic socket with an adjustable interface that can adapt to the user’s needs. This paper presents a prototype design for a dynamic soft robotic interface which addresses this need. The actuators are adjustable depending on the user’s activity level, and their structure provides targeted compression to the soft tissue which helps to limit movement of the bone relative to the socket. Testing of the prototype demonstrated promising potential for the design with further refinement. Work on embedded sensing and intelligent feedback control should be continued in future research in order to create a viable consumer product which can improve a lower limb amputee’s quality of life.

Commentary by Dr. Valentin Fuster
2019;():V001T09A008. doi:10.1115/DMD2019-3236.

Drowsiness, a transitional psychological state between alertness and sleepiness, is one of the leading reasons for the increased risk of accidents, particularly in commercial aviation. Though electroencephalography (EEG) is widely used for drowsiness assessment, it is impractical for unobtrusive airborne monitoring due to discomfort induced by the number of electrodes touching the scalp. In this work, we investigated the potential of pulse arrival time (PAT), and photoplethysmogram (PPG) features as indicators of drowsiness. Simultaneous vertical electrooculogram (EOG), ear PPG, and electrocardiogram (ECG) were recorded from 18 commercially-rated pilots from 02:00 AM to 04:30 AM. ECG R-peaks and PPG peaks were detected and used for calculation of PAT and heart rate to observe their changes during drowsiness. During the drowsy periods, the PAT and RR intervals increased (i.e., decrease in heart rate) significantly (p < 0.05) compared to baseline. Features based on only PPG also showed a significant increase during drowsiness. However, decrease in PAT/RR during drowsiness for most of the subjects indicates that increase in PAT is not linearly correlated to RR interval and might be reflecting changes in arterial stiffness. Hence, PAT and derived PPG based features with continuous heart rate monitoring can serve as useful indicators of early drowsiness detection.

Commentary by Dr. Valentin Fuster
2019;():V001T09A009. doi:10.1115/DMD2019-3245.

Preterm and critically ill infants are treated in neonatal intensive care units (NICUs), where human milk is increasingly recommended and prescribed to this population as a medical intervention [1]. However, due to the medical acuity and complex character of caring for preterm infants, sometimes feeding at the breast is not possible. When feeding at the breast is not possible medical devices or commercial products may influence a mothers’ decision to express human milk for her NICU infant. Feeding human milk to infants cared for in NICUs reduces rates of mortality by decreasing instances of necrotizing enterocolitis (NEC) especially for extremely low birthweight infants [2] and is implicated in reducing incidence and severity of retinopathy of prematurity [3].

Commentary by Dr. Valentin Fuster
2019;():V001T09A010. doi:10.1115/DMD2019-3266.

This paper presents a portable inertial measurement unit (IMU)-based motion sensing system and proposed an adaptive gait phase detection approach for non-steady state walking and multiple activities (walking, running, stair ascent, stair descent, squat) monitoring. The algorithm aims to overcome the limitation of existing gait detection methods that are time-domain thresholding based for steady-state motion and are not versatile to detect gait during different activities or different gait patterns of the same activity. The portable sensing suit is composed of three IMU sensors (wearable sensors for gait phase detection) and two footswitches (ground truth measurement and not needed for gait detection of the proposed algorithm). The acceleration, angular velocity, Euler angle, resultant acceleration, and resultant angular velocity from three IMUs are used as the input training data and the data of two footswitches used as the training label data (single support, double support, swing phase). Three methods 1) Logistic Regression (LR), 2) Random Forest Classifier (RF), and 3) Artificial Neural Network (NN) are used to build the gait phase detection models. The result shows our proposed gait phase detection with Random Forest Classifier can achieve 98.94% accuracy in walking, 98.45% in running, 99.15% in stair-ascent, 99.00% in stair-descent, and 99.63% in squatting. It demonstrates that our sensing suit can not only detect the gait status in any transient state but also generalize to multiple activities. Therefore, it can be implemented in real-time monitoring of human gait and control of assistive devices.

Commentary by Dr. Valentin Fuster
2019;():V001T09A011. doi:10.1115/DMD2019-3268.

Individuals with spinal cord injury (SCI) and stroke who is lack of manipulation capability have a particular need for robotic hand exoskeletons. Among assistive and rehabilitative medical exoskeletons, there exists a sharp trade-off between device power on the one hand and ergonomics and portability on other, devices that provide stronger grasping assistance do so at the cost of patient comfort. This paper proposes using fin-ray-inspired, cable-driven finger orthoses to generate high fingertip forces without the painful compressive and shear stresses commonly associated with conventional cable-drive exoskeletons. With combination cable-driven transmission and segmented-finger orthoses, the exoskeleton transmitted larger forces and applied torques discretely to the fingers, leading to strong fingertip forces. A prototype of the finger orthoses and associated cable transmission was fabricated, and force transmission tests of the prototype in the finger flexion mode demonstrated a 2:1 input-output ratio between cable tension and fingertip force, with a maximum fingertip force of 22 N. Moreover, the proposed design provides a comfortable experience for wearers thanks to its lightweight and conformal properties to the hands.

Commentary by Dr. Valentin Fuster
2019;():V001T09A012. doi:10.1115/DMD2019-3272.

Strategically-applied compression on the body has been shown to elicit positive affect by creating feelings of calmness/relaxation. Although compression-based therapies are widely used in Occupational Therapy as a clinical intervention, current compression garment solutions suffer from various functional and usability issues and the spatial distribution between different commercially-available solutions vary widely. Currently, little is known about the specific location(s), intensity, and duration of pressure on the body that should be targeted in order to improve physical or mental well-being. With the hopes of contributing to more empirically-based compression garment designs in the future, this work reports a pilot investigation of the subjective user experiences when compression is applied on varying body locations.

Topics: Compression
Commentary by Dr. Valentin Fuster
2019;():V001T09A013. doi:10.1115/DMD2019-3285.

This paper investigates the tradeoffs between design variables important for the development of a mobility support soft exoskeleton for horizontal shoulder adduction. The soft exoskeleton utilizes discreet shape memory alloy (SMA) spring actuators to generate the required torque to move the arm segment, while preserving the qualities of a soft, wearable garment solution. A pilot benchtop test involving varying power input, actuator anchor position, actuator orientation, and added weight, was investigated to evaluate their effects against the degree of motion the soft exoskeleton allows. The results show that the power input, actuator anchor position, and simulated limb weight each affect the ultimate horizontal adduction angle the exoskeleton is able to induce. Further, the project highlights a crucial point in regard to the tradeoffs between functionality and wearability: when actuator orientation was investigated, we found a decrement in functionality (as measured by maximum achievable horizontal adduction angle) when the actuators were constrained close to the body. This shows that when aiming to improve the hypothetical system’s wearability/usability, the effective torque that can be generated is reduced. Together these findings demonstrate important design considerations while developing a wearable, soft exoskeleton system that is capable of effectively supporting movement of the body while maintaining the comfort and discreetness of a regular garment.

Commentary by Dr. Valentin Fuster
2019;():V001T09A014. doi:10.1115/DMD2019-3287.

In the world of soft-robotic medical devices, there is a growing need for low profile, non-rigid, and lower power actuators for soft exoskeletons and dynamic compression garments. Advanced compression garments with integrated shape memory materials have been developed recently to alleviate the functional and usability limitations associated with traditional compression garments. These advanced garments use contractile shape memory alloy (SMA) coil actuators to produce dynamic compression on the body through selective heating of the SMA material. While these garments can create spatially- and temporally-controllable compression, typical SMA materials (e.g., 70°C Flexinol) consume considerable power and require considerable thermal insulation to protect the wearer during the heating phase of the SMA actuation. Alternative SMA materials (e.g., NiTi #8 by Fort Wayne Metals, Inc.) transform below room temperature and do so using no applied electrical power and generate no waste heat. However, these materials are challenging to dynamically control and require active refrigeration to reset to material. In theory, low-temperature SMA actuators made from materials like NiTi #8 may maintain additional dynamic actuation capacity once equilibrated to room temperature (i.e., the material may not fully transform), as the SMA phase transformation temperature window expands when the material experiences applied stress. This paper investigates this possibility: we manufactured and tested low-temperature NiTi coil actuators to determine the magnitude of the additional force that can be generated via Joule heating once the material has equilibrated to room temperature. SMA spring actuators made from NiTi #8 consumed 84% less power and stabilized at significantly lower temperatures (26.0°C vs. 41.2°C) than SMA springs made from 70°C Flexinol, when actuated at identically fixed displacements (100% nominal strain) and when driven to produce equal forces (∼3.35N). This demonstration of low-power, minimal-heat exposure SMA actuation holds promise for many future wearable actuation applications, including dynamic compression garments.

Commentary by Dr. Valentin Fuster
2019;():V001T09A015. doi:10.1115/DMD2019-3290.

Supplemental heating systems for the distal extremities often require a tradeoff between wearability and thermal comfort. Textile-based thermal actuation helps manage this tradeoff by increasing comfort of on-body systems. However, textile-based thermal actuation also presents important limitations in the form of current requirements, control structures, and thermal flux afforded. Further, on-body active thermal control is affected by three intersecting thermal systems: the environment, the human body, and the active heating system. Here, we present lessons learned from iterative development of textile-based wearable systems (V1, V2) designed to heat the distal extremities. Experimental characterization of textile actuator power/temperature relationships and limits; actuator performance in cool ambient temperatures and in on-body conditions; and efficacy of closed-loop duty cycle control of actuated skin temperature are presented, and implications of these characteristics for garment system design are discussed.

Commentary by Dr. Valentin Fuster

Special Devices

2019;():V001T10A001. doi:10.1115/DMD2019-3209.

A dental articulator is a mechanical device used to simulate the relative position and motion between the upper and lower jaw when testing dental work or dental treatments (implants or bridges). Typically, it can be adjusted to approximate patient-specific jaw kinematics. However, the use of dental articulators is essentially a trial-and-error method in order to fine-tune fit and function of the dental work. In this paper we propose a robotic articulator suitable for reproducing tracked movements of the patient’s jaw. Based on an asymmetric-leg parallel structure, dimensional synthesis is performed to optimize performance over the range of motion typical of the human jaw. The resulting robotic device is expected to improve workflow in the processing of dental implants. Fabrication and testing of a prototype robot is also presented.

Topics: Robots , Design
Commentary by Dr. Valentin Fuster
2019;():V001T10A002. doi:10.1115/DMD2019-3212.

This paper discusses the design and application of magnetic-based position tracking in surgical trainers. The utilization of magnetic-based position tracking in Laparoscopic Trainers provides a cost-effective solution to the next generation of medical education, training and evaluation. The utilization of 3D printed parts as well as off the shelf electronics allows us to maximize accuracy while minimizing design cost. Our current design costs less than $300.00 while providing results with an error of 1.474–14.265%.

Commentary by Dr. Valentin Fuster
2019;():V001T10A003. doi:10.1115/DMD2019-3215.

Blurring the line between the physical and digital environment, augmented reality (AR) is the next frontier for medical device design. It is particularly useful as a means for rapid concept visualization and iterative refinement. By selectively mixing AR and physical prototypes, designers can conduct haptic evaluation alongside visual assessment. The integration of AR and traditional tools during development continues the practice of advancing design methods in parallel with technology. This paper explains the design of a mobile medical device/workstation using an AR aided medical device design process from an industry perspective. This case study demonstrates the viability and benefits of an AR aided design process pairing off-the-shelf AR technology with physical models of increasing fidelity. AR aided medical device design helps design teams accelerate development, lower prototyping costs, assess scaled designs earlier, illustrate contextual constraints, and reduce development risk.

Commentary by Dr. Valentin Fuster
2019;():V001T10A004. doi:10.1115/DMD2019-3216.

Intranasal drug delivery is an attractive route to noninvasively achieve a rapid therapeutic effect, avoid first pass metabolism, and bypass the blood brain barrier. However, the types of drugs that can be administered by this route has been limited, in part, by device technology. Herein, we describe a pneumatic nasal spray device that is capable of mixing liquid and solid components of a drug formulation as part of the actuation process during dose administration. The ability to store a nasal spray drug formulation as two separate components can be leveraged to solve a variety of stability issues that would otherwise preclude intranasal administration. Examples of drugs that could be delivered intranasally by utilizing this two-part formulation strategy include biomolecules that are unstable in solution and low solubility drugs that can be rendered into metastable supersaturated solutions. A proof of concept nasal spray device prototype was constructed to demonstrate that a liquid and solid can be rapidly mixed and atomized into a spray in a single action. The primary breakup distance and angle of the spray cone were measured as a function of the function of the propellant gas pressure.

Topics: Sprays , Drugs
Commentary by Dr. Valentin Fuster
2019;():V001T10A005. doi:10.1115/DMD2019-3217.

Two different methods of attaching the current leads for segmental bioelectrical impedance analysis measurements were compared. The first method was leaving the current electrodes in place at the hand and foot for all measurements, while the second method involved moving the current electrodes to be adjacent to the voltage electrodes when measuring each segment. Each method was compared to a whole-body measurement performed at the same occasion as the segmental measurements. Slight deviation from the whole-body measurement was expected, as the electrode placements resulted in small gaps that were not measured between each of the arm, trunk, and leg segments. The second method, moving the current electrodes for each segment, was found to be the closer of the two methods for whole body measurements, with errors of 2% and 5.8% at R0 and R, respectively, while the first method had errors of 4.2% and 6% respectively.

Topics: Electrodes , Errors
Commentary by Dr. Valentin Fuster
2019;():V001T10A006. doi:10.1115/DMD2019-3226.

Congenital Tracheal Stenosis (CTS) is a rare birth defect requiring surgical interventions when it affects more than 30% of the trachea. Slide tracheoplasty, the current standard of care, is associated with reinterventions including the need for intraluminal stenting leading to increased airway infections. We propose a novel Bio-Synthetic Graft for long segment tracheal reconstructions in CTS patients. Preliminary bench performance testing, using lamb tracheas, shows that the Bio-Synthetic Graft reconstructed tracheas have comparable radial, axial and bending stiffness in hyperextension to healthy tracheas and resist collapse when subjected to bending in flexion. These results suggest that Bio-Synthetic Graft could be a promising alternative to existing solutions for long segment CTS.

Commentary by Dr. Valentin Fuster
2019;():V001T10A007. doi:10.1115/DMD2019-3233.

Tracheobronchomalacia (TBM) is a condition where the trachealis muscle is too weak to withstand the pressure difference between the outer and inner walls of the trachea. This causes the airway to narrow or collapse. Patients with TBM may have symptoms including coughing, wheezing, and/or difficulty in breathing. There are current treatments available but each one has their own limitations and complications. Such complications of current commercially available airway stents are migration, breakage, and mucus build-up. The team has developed a unique airway stent that potentially has fewer complications called the Low Profile Airway Stent. It is a thin, metal zig-zag shaped wire that will be anchored parallel to the trachealis muscle to prevent trachea narrowing and collapsing. The Low Profile Airway Stent will not fully cover the cilia in the trachea which reduces mucus build-up. The stent will also be anchored to the walls of the trachea which will prevent migration. The team is still in the process of developing an anchoring method and delivery device for the stent.

Topics: stents
Commentary by Dr. Valentin Fuster
2019;():V001T10A008. doi:10.1115/DMD2019-3240.

This paper presents a modular robot for assisting individuals with spinal cord injury with everyday tasks. The basic premise of modularity for task-variable environments is laid out, and the modular robot design is detailed including needs assessment, kinematics, and hardware. Early pilot testing of the robot is also described.

Topics: Robots , Wounds , Spinal cord
Commentary by Dr. Valentin Fuster
2019;():V001T10A009. doi:10.1115/DMD2019-3252.

It is widely known that hyperbilirubinemia (colloquially known as jaundice) is a common neonate ailment developed in about 50% of term and 80% of preterm neonates. This condition arises from bilirubin deposits in the skin and causes yellow coloring in newborns. [1] If left untreated, neonates are at risk of developing extreme hyperbilirubinemia which can lead to neurological impairment (bilirubin related encephalopathy). [2]

Topics: Skin , Nervous system , Risk
Commentary by Dr. Valentin Fuster
2019;():V001T10A010. doi:10.1115/DMD2019-3254.

We describe the formulation and manufacture of thermoplastic polyurethane (TPU)-based steroid-eluting components and the development of a versatile, material-agnostic analytical method for their rapid characterization. The impact of materials, formulation, and processing on controlled release behavior was characterized and compared to current industry standard components under physiologically relevant conditions. The combination of factors modulated drug release, offering new avenues for controlling the release of steroids from implantable medical devices.

Commentary by Dr. Valentin Fuster
2019;():V001T10A011. doi:10.1115/DMD2019-3265.

The purpose of this examination was to determine a) how bioimpedance scanning generates data about the human body and b) compare the Bodystat Multiscan 5000 and the Skulpt Chisel. The Bodystat Multiscan 5000 is bioelectrical impedance spectroscopy (BIS) device that performs a scan of 50 measurements, from 5 kHz to 1000 kHz. This scan generates a 2d Cole analysis plot that compares the resistance and reactance of the scanned muscle group. Higher frequencies measure the amount of intracellular fluid (ICF), and lower frequencies measure the amount of extracellular fluid (ECF). Lower values for the resistance and reactance relate to a greater level of fitness for the scanned area. The Skulpt Chisel is an electrical impedance myography (EIM) that performs a single 50 kHz measurement. This scan determines the muscle quality and percent body fat of the scanned muscle group. The test subject was scanned with each device. Each plane was scanned three times with the Bodystat Multiscan 5000, and scanned five times with the Skulpt Chisel. The data was recorded to Excel and analyzed using MATLAB. The Bodystat Multiscan measurements for the surfaces were examined at a frequency of 50 kHz to be comparable to the Skulpt Chisel data. The surfaces are recorded in descending order of magnitude for resistance: medial, 22.14 Ω; anterior, 20.31 Ω; posterior, 17.89 Ω; lateral, 12.6 Ω. The Cole Analysis for the right thigh at 45-degree intervals are recorded in descending order of magnitude for resistance: medial/posterior, 23.89 Ω; posterior/lateral, 23.06 Ω; anterior/medial, 21.09 Ω; lateral/anterior, 16.13 Ω. The Skulpt Chisel surfaces are recorded in an increasing order of magnitude, the first value being muscle quality and the second value being percent body fat: lateral, 81.12, 13.1%; posterior, 62.22, 16.46%; anterior, 50.88, 19.24%; medial, 42.16, 23.16%. The data display an inverse relationship between resistance/reactance and muscle quality, and a direct relationship between resistance/reactance and percent body fat. The larger the magnitude of the resistance/reactance recorded for a muscle group, the lower the level of muscle quality will be. This leads to a larger percent body fat value.

Commentary by Dr. Valentin Fuster
2019;():V001T10A012. doi:10.1115/DMD2019-3270.

This paper explores the ability to measure the impedance of a system consisting of the biological system of the patient combined with the mechanical system of the hot snare and, given a specified impedance threshold value, turn off the firing of an electrosurgical device before serious injury occurs. In electrosurgery, the tissue damage is caused by the thermal energy generated from the resistance in the cells. An impedance feedback control system is designed and tested to minimize the effects of too much thermal damage. This design is based on measuring the impedance of the system and implementing a microcontroller to coordinate the activity and to interrupt the electrosurgical device preventing further firing. The feedback control system was proven to automatically stop the electrosurgical device for three given impedance values of 500Ω, 750Ω, and 1000Ω with an accuracy of ±5Ω. The auto-stop system is able to measure and fire at 5.4 times a second with a duty cycle of 41%. This successfully minimizes the thermal injury sustained from electrosurgery.

Commentary by Dr. Valentin Fuster
2019;():V001T10A013. doi:10.1115/DMD2019-3273.

A novel reloadable autoinjectors (Zibipen) for intramuscular adrenaline injections were designed and developed. This novel AAI was performance tested against some of the leading commercially available autoinjector devices. The results were found to be encouraging to recommend further technological development of the novel autoinjector.

Topics: Ejectors , Testing
Commentary by Dr. Valentin Fuster
2019;():V001T10A014. doi:10.1115/DMD2019-3277.

The study focuses on developing a novel dosage counter system for a low-cost sleeve attachment device for enhancing the usability and functionality of any standard pressurised metered dosage inhaler (MDI). The paediatric metered dosage inhaler sleeve attachment’s (pMDI’s) primary function is to allow patients 5 years and older to safely use their inhalers, particularly in emergencies. Currently patients don’t know how many dosages are remaining in the MDIs, cant activate the devices and refuse to use their inhalers because of stigma, The dosage counter was a critical feature as it was discovered that patients are using empty inhalers, which leads to hospitalizations and increased mortality rates. A dosage counter was found to be a critical feature for the sleeve attachment, as all MDIs should have one.

Commentary by Dr. Valentin Fuster
2019;():V001T10A015. doi:10.1115/DMD2019-3297.

Stethoscopes are ubiquitous across the healthcare system. For the most part, stethoscopes do not represent a financial burden, mostly throughout the developed world. Further reducing the cost of stethoscopes has both humanitarian and prophylactic goals. The Glia project pioneered the concept of 3D printing stethoscopes for war or poverty-stricken regions of the world. Cross-contamination concerns have led researchers and manufacturers to develop single-use stethoscopes. Our aim is to develop a fully printed, multi-material, functional stethoscope to alleviate these concerns. Our team also seeks to establish a framework for the on-demand manufacturing of medical devices to reduce costs associated with shipping, distribution, and inventory.

Commentary by Dr. Valentin Fuster
2019;():V001T10A016. doi:10.1115/DMD2019-3300.

“No-option” patients have vasculature too tortuous for existing catheters to navigate. To treat these patients, new catheter technologies are needed that are easy to actuate and can be customized for each patient. We propose using fiber-reinforced elastomeric enclosures (FREEs), which have been shown to be capable of performing screwing, spiraling, twisting, extending, and other motions when the fiber wrap angles are adjusted. Here, we present and validate an automated system capable of manufacturing FREEs with wrap angles from 0–90 degrees. The prescribed fiber angles were within 5 percent error when manufactured.

Commentary by Dr. Valentin Fuster
2019;():V001T10A017. doi:10.1115/DMD2019-3302.

Bioprinting is a 3D fabrication technology used to accurately dispense cell-laden biomaterials for the fabrication of complex 3D functional living tissues. A syringe-based extrusion (SBE) deposition method comprising of multiple nozzles is integrated into the system. This allows for a wider selection of biomaterials that can be used for the formation of the extracellular matrix (ECM). The 3D bioprinting system presented in this paper aims to facilitate the process of 3D bioprinting through its ability to control the environmental parameters within an enclosed printing chamber. The primary objective of this research is to print viable 3D tissue constructs seeded with cells with high structural integrity and high resolution.

Commentary by Dr. Valentin Fuster
2019;():V001T10A018. doi:10.1115/DMD2019-3304.

Evidence of prosthetic use can be dated back to the second Punic War [1]. However, state-of-the-art devices have advanced very little, especially for individuals who need forearm and hand functionality, and have little financial support for high-end, custom robotic devices. This is particularly the case for military veterans. The prosthetics prescribed are thermally hot, heavy in weight, fit poorly, restrict mobility and are unattractive. This paper will review how the aforementioned design challenge was addressed through 3D body scanning and rapid prototyping technologies, for an undergraduate product design student’s capstone project.

Commentary by Dr. Valentin Fuster
2019;():V001T10A019. doi:10.1115/DMD2019-3313.

Palpation, or physical manipulation of tissue to assess mechanical properties is one of the most prevalent and valuable clinical evaluations. Because physical interaction is needed, historically palpation has been limited to easily accessible surface level tissues. Magnetic resonance elastography (MRE) combines non-invasive Magnetic Resonance Imaging (MRI) with mechanically induced shear waves, producing the ability to map elasticity of soft tissues in vivo. Actuator design has been a limiting factor in MRE advancements. In this study, a mechanical resonator with adjustable resonant frequency was designed to be used in MRE applications. The designed piezoelectric actuator was fully MRI compatible, and capable of dynamically adjusting its resonant frequency. The purpose was to keep the displacement amplitude sufficiently large over a wide actuation frequency range. The outer stage of the amplifier contained movable side masses for tuning resonance frequency.

Commentary by Dr. Valentin Fuster

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