Imaging and Anatomic Interaction

2008;():1-2. doi:10.1115/BioMed2008-38100.

We present a wide-field, near infrared spectral imaging modality called modulated imaging (MI) that shows great promise for quantitatively imaging superficial (1–5 mm depth) tissues. We have applied this method to a dorsal pedicle skin flap model to determine in-vivo local concentrations of oxy- and deoxy-hemoglobin and water.

Commentary by Dr. Valentin Fuster
2008;():3-4. doi:10.1115/BioMed2008-38107.

Computed Tomography (CT) is a widely used 3-D imaging technique. A 3-D volumetric grid is obtained from 2-D cross-sectional images. In order to be useful as a diagnostic tool, voxel-based numerical values that represent X-ray absorption in each voxel must be interpreted and combined to form an image that depicts tissue composition at a particular location. Transfer functions are used to translate measured X-ray absorption data into Hounsfield units, and Hounsfield units into intensities, colors and transparency values. Gradient-based transfer functions are used to highlight material boundaries and interfaces between different tissues. Multi-dimensional transfer functions combine the advantages of regular and gradientbased transfer functions, facilitating a wide spectrum of visual representations. Transfer functions are usually under user control and often difficult to find. Improper transfer functions can create misleading visualizations and may lead to erroneous diagnoses. This article discusses how multi-dimensional transfer functions can be derived that are clinically relevant and meaningful.

Commentary by Dr. Valentin Fuster
2008;():5-6. doi:10.1115/BioMed2008-38108.

Diffuse optical tomography (DOT) is a recently emerging technique that uses arrays of sources and detectors to obtain spatially dependent optical parameters of tissue. DOT techniques have been applied for a wide range of applications, especially for breast and head as well as animal imaging. We have developed an integrated dynamic MR/DOT imaging system. This combined system can acquire MR and optical data simultaneously with a high temporal resolution. Hence, the enhancement kinetics of multiple MR and optical contrast agents can be monitored independently.

Topics: Imaging
Commentary by Dr. Valentin Fuster

Simulation and Modeling

2008;():7-8. doi:10.1115/BioMed2008-38033.

Human total joint replacement has become a common place procedure in the past decade, principally to eliminate pain in patients affected by osteoarthritis of the knee, hips, shoulder and spine. While in the past, this was done mostly for older patients with reduced mobility, more recently these replacements are being done for much younger, much more active people. As a result, the artificial joints need larger ranges of motion and are subject to much higher loads, while being required to last longer in place.

Commentary by Dr. Valentin Fuster
2008;():9-10. doi:10.1115/BioMed2008-38051.

Computational modeling was performed to study how loss of compliance of the eye and abnormally high pressures result in changes in stresses and strains that may impact the optic nerve in diseases such as glaucoma. Hemispherical finite element models of the eye were created in which scleral thickness varied from the equatorial region to the optic nerve head (ONH). Nonhomogeneous material properties were used to model the ONH as a continuous region softer than the adjacent sclera. The ONH and an adjacent buffer zone in the sclera were modeled with enough detail that the size of the ONH could be changed to account for variations observed in humans. The model was provided with appropriate dimensions typical of patients and nonlinear material properties with decreased compliance. Models with different ONH sizes were inflated in small steps to 55 mmHg (7.33 kPa), providing deformed configurations at intermediate pressures of 15, 30 and 45 mmHg, respectively. Color-coded maps of stress and strain components were rendered directly on deformed configurations of the eye model; and animations were produced that show both spatial and temporal variations of stresses and strains as internal pressure increases. Three-dimensional stresses and accompanying finite strains were similar for ONH sizes ranging form 1.5 to 2.5 mm in diameter. Stress and strain differences were estimated as pressure was increased from 15 to 25 mmHg, 30 to 40 mmHg, and 45 to 55 mmHg. Substantial changes occurred in stress and strain differences as the pressure range was varied with large changes occurring in the lowest pressure range for strain components and moderate increases in stress differences as pressures increase.

Commentary by Dr. Valentin Fuster
2008;():11-12. doi:10.1115/BioMed2008-38066.

Lack of detailed stent artery interactions is responsible for rampant stent fracture in the human SFA or popliteal arteries. Armed with recent research work quantifying dynamic changes of the SFA and popliteal vessels, we investigated stent deformations under various modes of dynamic physiological conditions and their interactions using realistic artery constitutive models. Fatigue strains were calculated using finite element analysis and were compared with material’s endurance limit data obtained using a special V-shape sample. A linear damage accumulation formula (Minor’s rule) was employed to predict safety factors for the stent.

Topics: Durability , stents
Commentary by Dr. Valentin Fuster
2008;():13-14. doi:10.1115/BioMed2008-38069.

The mechanical and biologic factors that drive bone fusion can be better understood. This is evident in the fact that of the approximately 200,000 spine fusion procedures performed each year failure to achieve a bony union can occur in as many as 40% of the cases (Boden 2002). Advances in computational methods and mathematical modeling of bone fusion make it advantageous to use numerical methods such as the finite element method, to better understand bone remodeling mechanics.

Topics: Bone
Commentary by Dr. Valentin Fuster
2008;():15-16. doi:10.1115/BioMed2008-38083.

We analyzed the kinematics of two rotating platform total knee replacement designs using KneeSIM, a commercially available computer code (LifeModeler, San Clemente, CA) in which we could manipulate the location of the axis of rotation of the rotating bearing.

Commentary by Dr. Valentin Fuster
2008;():17-18. doi:10.1115/BioMed2008-38093.

Shock wave lithotripsy (SWL) has been used to treat kidney stones for decades. However, there is growing recognition that shock waves induces trauma to kidney tissue [1, 2]. The poor understanding of stone comminution mechanisms means that the design of new lithotripters is principally a practice of empiricism [3]. A mechanistic understanding of stone comminution would provide a criterion to develop new lithotripsy systems. In this work, a three-dimensional finite-difference time-domain (FDTD) solution to the linear elastic equations was employed [4] to investigate the stress and displacement fields of kidney stones subject to lithotripsy shock waves. The kidney stone models were obtained from micro-computed tomography images (resolution of 20 μm) and have diameters from 2 mm to 5 mm.

Commentary by Dr. Valentin Fuster
2008;():19-20. doi:10.1115/BioMed2008-38096.

The ability to control mixing of reagents in MEMS systems is crucial for many biological and chemical analysis applications. However mixing in these microfluidic devices is a challenge because the flows are laminar corresponding to very low Reynolds number. In this paper mixing of such reagents in simple microchannel geometries is investigated computationally. A novel concept of “split flow design” is applied to these simple microchannel configurations. Significant improvement in mixing is seen by employing the split flow design technique.

Commentary by Dr. Valentin Fuster

Device Testing

2008;():21-22. doi:10.1115/BioMed2008-38064.

It has been well supported in the literature that using compression screws is the preferred method to achieve fixation of an arthrodesis [1, 2]. Indications for isolated subtalar arthrodesis include trauma, arthritis, talocalcaneal coalition, adult acquired flatfoot, posterior tibial tendon dysfunction, and Charcot neuroarthropathy [3, 4]. With the increase in bone screw shapes and designs, there is a desire to achieve the best compression generated by a type of screw so as to promote excellent bone healing and outcome for the patient; this will also allow the stability of the construct achieved by the screw and its placement to be determined. As indicated by Wheeler, et. al.[5] screw choice, compression, stability and loading can be very important when it comes to healing of fractures in small bones.

Topics: Screws , Compression
Commentary by Dr. Valentin Fuster
2008;():23-24. doi:10.1115/BioMed2008-38074.

This study aims to establish the construct validity of new Laparoscopic Training Simulator (LTS) developed at UCLA. The system was developed due to the increasing demand for Minimally Invasive Surgery (MIS) coupled with the difficulty associated in training surgeons in the use of MIS techniques with traditional apprenticeship models. In addition to training issues, there exists an immediate need for an objective assessment of Minimally Invasive Surgery (MIS) skills and techniques required to ensure safe and high quality treatment as previously established [1]. While currently available training systems have been used they are slow in educating new surgeons and they do not provide an objective assessment. The new system developed UCLA-LTS [2] addresses these very issues by combining the simplicity of the traditional training box with the advances in computer simulation technology to both train and to assess skill level.

Commentary by Dr. Valentin Fuster
2008;():25-26. doi:10.1115/BioMed2008-38092.

One of the shortcomings of the current endoscopic graspers is the lack of tactile sensing. We are reporting the results of the first stage of a research project to rectify the tactile sensing in endoscopic tools. This paper introduces a smart endoscopic grasper equipped with sensors for measuring the applied force and the angle of the grasper tip. It is shown that using this method, the softness of the grasped object can be estimated. The next phase of this research would be devising an appropriate method to feedback the measured date.

Commentary by Dr. Valentin Fuster

Device Design and Development

2008;():27-28. doi:10.1115/BioMed2008-38050.

This paper reports production of 4.5 μm-diameter monodisperse water droplets using silicon-based one MHz ultrasonic nozzles of a novel design. The novel design of multiple Fourier horns in resonance facilitates pure capillary wave mechanism atomization. The measured drop diameters are in very good agreement with those predicted by the capillary wave atomization mechanism. Due to the resonance effect, the power and voltage requirements for atomization were as low as 15 mW and 6.5 V at atomization rate as high as 300 μl/min. The droplet diameter was reduced to 4.1 μm when the surface tension of the liquid was reduced from 70 dyne/cm (water) to 50 dyne/cm (0.25% Triton X-100 surfactant solution). Such small diameter drops with GSD (geometrical standard deviation) as small as 1.1 was achieved in ultrasonic atomization for the first time. Note that the fraction of all particles smaller than 5.8 μm in diameter represents the inhaleable fine particle fraction and GSD of 1.3 or smaller is commonly accepted as the standard for monodispersity. Therefore, the MEMS-based MHz ultrasonic nozzle should have very significant impacts on targeted delivery of reproducible doses of medicine to the respiratory system.

Commentary by Dr. Valentin Fuster
2008;():29-30. doi:10.1115/BioMed2008-38076.

This research highlights the design, fabrication and experimental validation of a Shape Memory Alloy (SMA) actuated robotic catheter. The prototype consists of four SMA tendons that actuate a central tubular substructure in two orthogonal directions. The experimental shape memory characteristics are used to optimize the design. Joule heating is used to generate tip deflections and the experimental bending characteristics are obtained using a dual camera imaging system. These measurements reveal important nonlinearities and hysteretic characteristics of the system. A dynamic model of the system is developed to describe the SMA-effected bending mechanics, and simulation results are compared to experimental measurements for model validation. The applicability of this technology to cardiovascular procedures, like atrial ablation, is demonstrated through precise tracking of trajectories using PID control.

Commentary by Dr. Valentin Fuster
2008;():31-32. doi:10.1115/BioMed2008-38078.

Tactile sensors are the interfaces to detect the physical properties of objects and have extensive applications in robotic sensing, biomechanics, minimally invasive surgery and human prosthetics [1]. For human prosthetics applications, the current prosthetic hand can offer only the manipulation function. With the sensing being part of the prosthetic hand, the user can get feedback from the prosthetic. This feeling can help users decrease their dependency on visual information and have better body control on weight balancing and signal limb stance.

Commentary by Dr. Valentin Fuster
2008;():33-34. doi:10.1115/BioMed2008-38085.

Mitral valve regurgitation [1] (MVR) is a functional heart disease in which the valve does not close completely and causes blood to leak back into the left atrium. This condition increases the workload on the heart, and if left untreated, can lead to irreversible heart damage, cardiac arrhythmia, and congestive heart failure. Annually, in the United States, more than 50 000 patients undergo mitral valve repair. The causes of MR can be either primary, due to an anatomical change of the valve apparatus, or secondary to ischemic heart disease and idiopathic cardiomyopathy. Currently, the intervention requires an open heart surgery with cardiopulmonary bypass. Under such conditions, the patient is subjected to intra and post-operative trauma that can result in a mortality increase and that can prevent high risk individuals from undergoing the repair. A non-invasive percutaneous method would greatly reduce risks associated with a conventional surgery while increasing the potential candidates for repair. Introduced in this paper is a concept for a novel procedure that relies on a robotically-guided compliant catheter, fitted with an anchoring mechanism, intended to reshape the mitral-valve annulus to dimensions suitable for the effective support of the valve leaflets.

Topics: Maintenance , Valves
Commentary by Dr. Valentin Fuster
2008;():35-36. doi:10.1115/BioMed2008-38086.

An implantable, single-use miniature infusion pump (MIP) was designed to allow radiotracer injection and functional neuroimaging in freely moving mice. The pump comprises a pressurized reservoir, and a parylene electrothermal valve, which opens to inject tracer through an intravenous catheter into the circulation. A 3-layer 300 μl elastomeric reservoir was built by molding silicone in two-part metal casts. The valve was powered by inductive power transfer from an external 20 cm diameter primary coil to an implanted miniature 8-turn, 1.6 cm diameter Litz-wire secondary coil capable of generating 150 mW at the frequency of 2 MHz.

Commentary by Dr. Valentin Fuster
2008;():37-38. doi:10.1115/BioMed2008-38101.

Premature infants receive enteral feedings well before the time they would have if they remained in utero. The alimentary system may or may not be receptive to nutrition. Neonatal caretakers must decide whether it is safe to feed the patient. Possible etiologies of bowel dysfunction include bowel obstruction, functional or anatomic which may be reflected as an abnormality or lack of peristalsis. This peristalsis may be monitored acoustically to determine the health of the patient’s digestive tract.

Topics: Acoustics
Commentary by Dr. Valentin Fuster
2008;():39-40. doi:10.1115/BioMed2008-38105.

An apnea event is defined as the cessation of breathing for 10 to 20 seconds, generally accompanied by bradycardia (decrease in heart rate), cyanosis, or both. Unlike apnea in adults, which is usually caused by an obstruction in the airway, central apnea events appear in premature babies because the autonomic nervous system is not yet fully developed.

Topics: Nervous system
Commentary by Dr. Valentin Fuster

Device Technology and Innovation

2008;():41-42. doi:10.1115/BioMed2008-38046.

Anastomotic leakage is the main, yet unsolved reason for mortality in abdominal surgery. Every year patients die because of anastomotic leakage after surgery. In the case of colorectal surgery, statistics show an incidence rate of 10–13% and a mortality rate of 32%. The aim of this work is to reduce the complications by improving the feedback to the surgeon during the operation and to minimise the fatalities by developing an early warning system. Currently, there are no peroperative methods to avoid anastomotic leakage or any validated early postoperative parameters for leakage detection. Therefore, an objective aid to detect leakage during surgery and recovery is of utmost importance.

Topics: Measurement , Leakage
Commentary by Dr. Valentin Fuster
2008;():43-44. doi:10.1115/BioMed2008-38053.

There is a need in medical and biological research to probe cells with high spatial resolution. We have developed a method for fabricating integrated carbon nanopipes with diameters ranging from 10’s to 100’s of nanometers to form carbon nanopipettes (CNPs) without the need for cumbersome assembly. CNPs are easily adapted to standard cell physiology equipment and simultaneously provide an accessible nanoscale channel for mass transport and a conductive pathway for electrical measurements. We present the fabrication method, the characterization of the device, and their ability to inject fluids into cells, specifically, calcium mobilizing second messengers.

Commentary by Dr. Valentin Fuster
2008;():45-46. doi:10.1115/BioMed2008-38091.

The widespread use of screening mammography has significantly altered the composition of breast cancer being diagnosed today. Cancers are being diagnosed earlier and the mortality rate from breast cancer is dropping, mostly attributable to the use of screening mammography [1]. At breast care centers, approximately 25% of new breast cancers are now being diagnosed when still in-situ (i.e. confined to the ducts). These are nearly 100% curable, generally with breast conserving surgery. The mammographic finding most commonly associated with in-situ cancer is mammographic calcification. Unfortunately, it is often difficult to differentiate malignant type calcification from those associated with a myriad of benign processes. As a result calcification lesions have a greater false-positive rate than mass lesions. Among biopsies of calcification lesions, over 80 percent are benign. In the U.S., the vast majority of mammograms are interpreted by general radiologists whose experience with mammographic calcifications is limited. As “delay in diagnosis of breast cancer” is the most common source of medical-legal lawsuits against diagnostic radiologists, the tendency is to practice defensively. We describe a computer aid that offers to reduce the false positive rate of calcification lesions and thereby to reduce the incidence of defensive reading of mammograms. The objective of this study is to evaluate the ability of a patented two-dimensional mapping of calcification lesions to help the radiologist-interpreter reduce the incidence of false positives in screening apparent calcifications for cancer. We refer to this mapping as a relational map. We introduced the relational map to the radiology community in June 2000 [2]. This paper reports on a recent test of the ability of the relational map to help reduce the numbers of falsely diagnosed suspicious cancers and unnecessary recalls associated with the analysis of calcification regions of interest (ROIs).

Commentary by Dr. Valentin Fuster

Bio-Sensors and Diagnostics

2008;():47-48. doi:10.1115/BioMed2008-38081.

We describe a high-throughput lensfree optical imaging system that can characterize numerous cell types found within a heterogeneous mixture. Here, we specifically discuss the effect of the refractive index of the substrate material on the performance of the proposed lensfree optical cell characterization platform. It is experimentally illustrated that the use of high index materials such as SrTiO3 significantly improves the signal-to-noise ratio of the acquired lensfree images, which is a significant step towards more robust high-throughput cell analysis and characterization. The imaging configuration of the reported high-index material based characterization scheme is massively parallel enabling a cell counting speed of >100,000 cells/sec over a field of view of ∼10 cm2 . This novel system can also form the basic building block of a simple and compact point-of-care cell counting technology that can be made as small as a regular cell-phone to rapidly measure the count of e.g., red blood cells or T-lymphocytes from whole blood samples. Such a powerful point-of-care platform may have a significant impact especially for global health related problems in the developing world.

Commentary by Dr. Valentin Fuster
2008;():49-50. doi:10.1115/BioMed2008-38094.

Anthrax is an acute and deadly disease caused by the bacterium Bacillus anthracis. Upon exposure, usually through inhalation, ingestion, or cutaneous contact, B. anthracis spores begin multiplying, creating a life-threatening situation. If not quickly detected and treated, humans can die within several days. With renewed bio-terrorism concerns, there is a need for a rapid and automated system capable of sample (respiratory or blood) to answer (positive infection) so that quarantine procedures and treatment can be administered immediately. Microfluidic platforms hold great promise of fulfilling these requirements.

Topics: Microfluidics , Blood
Commentary by Dr. Valentin Fuster

Therapeutic Devices

2008;():51-52. doi:10.1115/BioMed2008-38030.

Spinal fusion is the latest application of electrical stimulation as a fracture healing. This exciting new application has been proven over 30 years of use, and the market is now poised for rapid growth. Patent activity shows an increased interest in this technology, and both start-up companies and orthopedic giants can thus benefit from introducing new products in this field.

Commentary by Dr. Valentin Fuster
2008;():53-54. doi:10.1115/BioMed2008-38042.

This paper describes a design process for a new pediatric ventricular assist device (VAD), the PediaFlow. The VAD is a magnetically levitated turbodynamic pump design for chronic support of infants and small children. The design entailed the consideration of multiple pump topologies, from which an axial mixed-flow configuration was chosen for further optimization via computation fluid dynamics. The magnetic design includes permanent-magnet (PM) passive bearings for radial support of the rotor, an actively controlled thrust actuator for axial support, and a brushless DC motor for rotation. These components are closely coupled both geometrically and magnetically, and were therefore optimized in parallel, using electromagnetic, rotordynamic and fluid models. Multiple design objectives were considered including efficiency, size, and margin between critical speed to operating speed. The former depends upon the radial and yaw stiffnesses of the PM bearings. Analytical expressions for the stiffnesses were derived and verified through FEA. A toroidally-wound motor was designed for high efficiency and minimal additional negative radial stiffness. The design process relies heavily on optimization at the component-level and system-level. The results of this preliminary design optimization yielded a pump design with an overall stability margin of 15 percent, based on a pressure rise of 100 mmHg at 0.5 lpm running at 16,000 RPM.

Commentary by Dr. Valentin Fuster
2008;():55-57. doi:10.1115/BioMed2008-38097.

This paper describes a polymer-based shear stress sensor built on catheter for in vivo measurements and potential application in atherosclerosis diagnosis. MEMS shear stress sensor with backside wire bonding has been used to address in vitro applications for micro-scale hemodynamics with high temporal and spatial resolution. However, to assess shear stress in the tortuous and dynamic arterial circulation, we had to develop a new generation of polymer- and catheter-based sensors that are both flexible and deployable. The individual sensor was packaged near the tip of a catheter for intravascular shear stress analysis. The wire bonding and electrode leads were insulated by a film of Parylene C and were connected to the external circuit along the guide-wire. The sensor was deployed through the catheter into the aorta of New Zealand White (NZW) rabbits by the femoral cut-down procedure. Based on the heat transfer principle, the device was able to detect small temperature perturbation in response to the pulsatile flow at ∼200 beats/minutes in the rabbits. The sensor was calibrated in the presence of rabbit blood flow at 37.8°C. We demonstrated the feasibility of translating a polymerbased device for dynamic intravascular measurement with a potential for clinical applications in detecting coronary artery disease and stroke.

Commentary by Dr. Valentin Fuster

Clinical and Regulatory

2008;():59-60. doi:10.1115/BioMed2008-38044.

2007 saw significant changes in patent law, and 2008 is promising additional significant developments. Those changes have significant effects on the value of patents and on how medical device developers and manufacturers should manage their patent strategy. The paper and discussion will detail those changes and provide practical guidance on what steps a medical device company can take to properly address those changes.

Commentary by Dr. Valentin Fuster
2008;():61-62. doi:10.1115/BioMed2008-38045.

Biomedical device development and (bio)material selection primarily for its casing go hand in hand. Traditionally “inert” materials were selected for surfaces in contact with tissue structures. Also a large number of surface treatment processes have been developed in order to increase the biocompatibility. With these technologies in hand, a broad range of materials can be selected.

Commentary by Dr. Valentin Fuster


2008;():63-64. doi:10.1115/BioMed2008-38032.

This paper presents an experimental and numerical method for investigating the biomechanics of soft tissue sutured tendons. The aim is to achieve a better understanding of the mechanics of a sutured tendon applicable to tendon injury.

Topics: Tendons
Commentary by Dr. Valentin Fuster
2008;():65-66. doi:10.1115/BioMed2008-38034.

A simple approach is presented to determine several critical parameters of a liquid needle-free injector. A jet injector system was developed based on the approach, and its jet characteristics were tested.

Topics: Ejectors , Testing , needles
Commentary by Dr. Valentin Fuster
2008;():67-68. doi:10.1115/BioMed2008-38035.

Modular endo-prostheses were introduced in 1980s with the intent of replacing custom made implants, which were criticized for lack of intra-operative flexibility, and high lead time and cost [1]. A typical modular prosthesis set may have as many as 200 components, making it difficult to select the right set of components in intra operative stage. An automated prosthesis selection methodology to limit the choice of prosthesis components with a qualitative tag such as: (1) ‘most suitable’, (2) ‘probably suitable’, and (3) ‘not suitable’, will greatly help the surgeons. This article describes a computer aided decision support system for selecting endo-prosthesis components driven by anatomical data of the patient. The methodology is explained with a case study of distal femur replacement.

Topics: Prostheses , Geometry , Tumors , Knee
Commentary by Dr. Valentin Fuster
2008;():69-70. doi:10.1115/BioMed2008-38037.

The aim of this study is to evaluate the surgical and prosthetic results of edentulous patients with highly atrophic mandibles using the Endo-Distraction technique.

Commentary by Dr. Valentin Fuster
2008;():71-72. doi:10.1115/BioMed2008-38038.

Based on the transient hot-wire method and well developed microfabrication techniques, a new thermal sensor, in which the microfabricated gold wire serves as both a heater and a thermometer, has been developed for measuring the thermal conductivities of semi-rigid materials. The intention that only one calibration constant is needed for an entire batch of sensors has been validated. Thermal conductivities of distilled water, ethylene glycol, dimethyl sulfoxide (DMSO), and apple at different temperatures have been obtained. Measurements are in agreement with suggested values. Complete results will be presented at the conference. The operating temperature of 0°C to 27°C has been tested and is anticipated to be −20°C to 60°C. In spite of conventional advantages, the presented sensor offers new exciting superior performance characteristics, such as reduced thermal resistivity and higher sensitivity, easier manufacturing for mass production, flexibility to reconfigure the sensor for samples with various sizes and shapes, and much reduced workload for system calibration.

Commentary by Dr. Valentin Fuster
2008;():73-74. doi:10.1115/BioMed2008-38039.

This paper aims to develop detection techniques and associated devices on irregular osseointegration during and after dental implant operations. More specifically, the study relates to the quantitative evaluation of an osseointegration between a dental implant and an alveolar bone through examining differences of dynamic characteristics of the dental implant and irregular bone defects. Developed techniques are able to inspect quantity, orientation and depth of bone defect. The associated device to this purpose is designed based upon the application of acoustic induced excitation and vibration response.

Commentary by Dr. Valentin Fuster
2008;():75-79. doi:10.1115/BioMed2008-38048.

Vertebral arteries are a system of two blood vessels through which blood is carried to the rear region of the brain. This region of the human body has to be very well supplied with blood, without any breaks or deficiencies in the blood flow. Blood is delivered to the brain through carotid arteries as well. All these arteries are connected to the circle of Willis, which has to fulfill all demands of the human brain as far as the blood flow is concerned. However, vertebral arteries due to their position and shape are a special kind of blood vessels. They originate at various distances from the aortic ostium, may branch off at different angles, have various length, inner diameter and spatial shape. Three different geometries of vertebral arteries, which most frequently occur in the human body structure, have been chosen, and for each twenty five various combinations of artery inner diameters have been used to generate 3D models of these arteries. For seventy five different models thus created, the numerical simulations have been performed. The results obtained have indicated explicitly that differences in the flow and instantaneous velocity values in vertebral arteries and in the point they join to form the basilar artery do not result from pathological changes in the artery system, but may follow from physical phenomena that occur in arteries as a consequence of the pulsating character of the flow and the unique geometry, which is related to the individual human anatomical structure.

Commentary by Dr. Valentin Fuster
2008;():81-82. doi:10.1115/BioMed2008-38058.

Rationally designed, individualized therapeutic strategies have long been a desired objective for breast cancer patients and clinicians as an estimated 178,480 new cases of invasive breast cancer will be diagnosed among women in the United States this year and over 40,000 women are expected to die from the disease. [1] The increasing appreciation of breast tumor cellular heterogeneity raises fundamental questions as to the relative contributions of cellular subsets to the biologic behavior of an individual patient’s tumor. [2] As such, it has become increasingly clear that in many cases, an individualized strategy for the treatment of breast cancer would be of great benefit, and that the ability to isolate relevant cellular subsets from the main tumor population is one of the critical limits to accomplishing this goal.

Topics: Tumors
Commentary by Dr. Valentin Fuster
2008;():83-84. doi:10.1115/BioMed2008-38060.

Colonoscopy is currently the gold standard for diagnosing colorectal cancer and inflammatory bowel disease. During a colonoscopy, a flexible endoscope is inserted into the patient’s colon to inspect the inner wall of the large intestine, from the rectum to the caecum. This procedure is very important for cancer screening and can yield early diagnosis. Colon cancer is 85–95% successfully treated if detected early; however, there is only a 30% compliance rate for the procedure in the United States. This low compliance rate for the examination is largely due to its uncomfortable nature, caused by difficulties in blind scope manipulation, and “looping” of the endoscope which can lead to stretching and perforation of the bowel [1] (Figure 1).

Commentary by Dr. Valentin Fuster
2008;():85-86. doi:10.1115/BioMed2008-38061.

Back pain is one of the most widespread sources of chronic pain in the human population. The etiology of back pain is nearly as diverse as the treatment measures used to alleviate the discomfort. However, when conservative options have been exhausted, without achieving adequate relief, the patient and physician often turn to surgical options to eliminate the source of pain.

Topics: Surgery
Commentary by Dr. Valentin Fuster
2008;():87-88. doi:10.1115/BioMed2008-38062.

Cooling rate is one of the most critical factors affecting the survival of cells during cryopreservation. A novel box-in-box device has been developed for use in the cryopreservation of human hematopoietic stem cells (HSCs). This work presents the comparison of experimentally observed thermal profiles for two different setups and, in the near future, cryopreservation survival rates of live cells accordingly. In experiments, using a simple protocol with a −80°C freezer, the box-in-box device is used to: (1) achieve an average cooling rate of −1°C/min with polyethylene insulation layers on both sides, and (2) achieve an average cooling rate of −2°C/min with a polyethylene insulation layer on one side and by having the other side directly contacted to the outermost aluminum case, both from room temperature to −40°C. The concept that utilizes thermal inertia of materials may be readily adapted to other cooling rates to support cryopreservation of a wide array of tissues and cells. It is concluded that the box-in-box system can be developed into a cost-effective, durable and reliable device for the cryopreservation of HCSs.

Commentary by Dr. Valentin Fuster
2008;():89-90. doi:10.1115/BioMed2008-38063.

Valvular heart disease results in approximately 275,000 valve replacement procedures performed annually worldwide. Structural deterioration, calcification, tissue overgrowth, and thromboembolism frequently lead to abnormal tissue stiffness levels that contribute to the failure of native heart valves. While many treatment alternatives exist, understanding the factors that regulate the activity of heart valve cells is critical for circumventing pathological heart valve fibrosis and engineering improved biologically active heart valve replacements.

Topics: Testing , Valves , Bioreactors
Commentary by Dr. Valentin Fuster
2008;():91-96. doi:10.1115/BioMed2008-38065.

The characterization of blood flow is important to establish links between the hemodynamics and the occurrence of cardiovascular diseases. This study describes the development of a 3-D computational model able to predict the blood flow along the abdominal aorta, including the renal and iliac branches. Upstream branches in the abdominal aorta lead to more complex flow patterns downstream, intensifying reverse and asymmetric flow patterns. The focus is on the occurrence of reverse flow and the perturbations in blood flow patterns originated by the branches. Results show regions of recirculation in the walls of the abdominal aorta, renal and iliac branches. It is concluded that, the renal branches induces perturbations in blood flow and result in asymmetric velocity profiles.

Commentary by Dr. Valentin Fuster
2008;():97-103. doi:10.1115/BioMed2008-38068.

The aim of the present study was to evaluate the performance of Ventilan® coupled to the Volumatic® spacer. An experimental study was conducted using the four stage Multistage Liquid Impinger (MSLI). This enabled the observation that half of the pharmacological dose is retained within the body of the spacer. Therefore, the air flow inside the spacer was studied, along the respiratory cycle, using Fluent™. Several recirculation regions were observed inside the spacer that may influence the aerosol flow and also the deposition of the drug.

Commentary by Dr. Valentin Fuster
2008;():105-106. doi:10.1115/BioMed2008-38070.

Light scanning device has many applications and is causing a lot of interest. Optical coherence tomography (OCT) is one example of its application in the field of biomedical imaging. With the trend of miniaturization of biomedical devices, miniaturized light scanning devices are desired for applications like compact OCT system [1].

Commentary by Dr. Valentin Fuster
2008;():107-108. doi:10.1115/BioMed2008-38073.

This study aims at the design, implementation, and verification of a near infrared (NIR) diffuse optical tomography (DOT) electro-optical imaging system based on a measuring instrument with scanning mechanism of synchronous multi-point detection and an image reconstruction scheme implemented on an off-line PC. The developed measurement instrument possesses a high degree of angular resolution and can be operated in a continuous-intensity or intensity modulation scheme to acquire output NIR radiance signals. Experimental trials are conducted using both homogeneous and heterogeneous phantoms made of high-scattering Intralipid. Promising results have been obtained with a superior spatial resolution, especially for absorption image, compared with the system with fixed number of detection channels.

Commentary by Dr. Valentin Fuster
2008;():109-110. doi:10.1115/BioMed2008-38075.

Shoulder joint biomechanics can be investigated using cadaveric testing setups. A novel system is described which uses a computer and graphical user interface to both control electronic actuators and record data from sensors. The algorithm of the custom software, programmed in the LabVIEW G language, is described. A desktop computer running the custom software and through National Instruments I/O hardware gives users full control over dynamic and static actuation and also collects, compiles, and records all data streams from disparate sensing modalities. Data gathered from a run to validate the system is also presented.

Commentary by Dr. Valentin Fuster
2008;():111-112. doi:10.1115/BioMed2008-38084.

Port wine stain (PWS) birthmarks are progressive vascular malformations that occur in ∼12,000 live births per year in the United States. The majority (∼90%) of PWS birthmarks occur on the head and neck regions, and thus are difficult to conceal. The psychosocial development of individuals with PWS birthmarks is adversely affected. Facial PWS lesions have been associated with increased incidence of glaucoma and seizures. The progressive nature of PWS skin may be due to lack of neuronal regulation of blood vessel size. Progressive development of the PWS results in a darker appearance, soft tissue hypertrophy, nodularity, and overall further disfigurement. Current treatment options have significant limitations in terms of efficacy and risk. With laser therapy, a reduction in size and degree of redness of PWS skin occurs in ∼60% of treated patients. After ten treatment sessions, complete disappearance of the PWS occurs in only ∼10% of treated patients. To reduce the financial burden and potential risks of repeated treatments under general anesthesia, there is a need for innovative, personalized methods to maximize the reduction in PWS redness per treatment session. Without addressing this need, the overall efficacy of PWS laser therapy will remain variable, because treatment protocols will remain based primarily on the subjective impression and overall experience of the treating surgeon. To address this need, we propose use of laser speckle imaging (LSI) to provide real-time, quantitative feedback during laser surgery.

Commentary by Dr. Valentin Fuster
2008;():113-114. doi:10.1115/BioMed2008-38087.

The use of external fixator for femoral shaft fixators in children has been a device of choice. The use though satisfactory, the occurrences of wire/ pin tract infections has been widely reported. Moreover, the use of Ilizarov external fixator in adults has been limited due to its bulk. Hence there is a need for improvement on the current external fixators for femoral fractures. The objective of the study is to design an external fixator for femoral fracture reduction with improved angulation and adjustability, reduced bulk, and comparative stiffness.

Commentary by Dr. Valentin Fuster
2008;():115-116. doi:10.1115/BioMed2008-38090.

A steady-state model coupling mass transfer across cell and fiber membranes is theoretically developed to investigate the removal process of cryoprotective agents (CPAs) from cryopreserved blood with hollow fiber modules, and then CPA concentration variation and cell volume response are studied.

Commentary by Dr. Valentin Fuster
2008;():117-118. doi:10.1115/BioMed2008-38095.

EONS modeling platform is a resourceful learning and research tool to study the mechanisms underlying the non-linear dynamics of synaptic transmission with the aid of mathematical models. Mathematical modeling of information processing in CNS pathways, in particular modeling of molecular events and synaptic dynamics, have not been extensively developed owing to the complex computations involved in integrating a multitude of parameters. In this paper, we discuss the development of a strategy to adapt the EONS synaptic modeling platform to a multi-node environment using a parallel computational framework to compute data intensive long simulations in a shorter time frame. We describe how this strategy can be applied to (i) determine the optimal values of the numerous parameters required for fitting experimental data, (ii) determine the impact of all parameters on various aspects of synaptic transmission (under normal conditions or conditions mimicking pathological conditions) and (iii) study the effects of exogenous molecules on both healthy and pathological synaptic models.

Topics: Modeling , Drugs , Mechanisms
Commentary by Dr. Valentin Fuster
2008;():119-120. doi:10.1115/BioMed2008-38098.

Early stage medical device development teams investigate many alternatives before selecting a final design proposal. The team must be able to retrace and reproduce successful designs and understand factors that underpin decisions that came before. This is especially important in a university setting due to the natural turnover on the team that is inherent in a successful research group. Effective design control provides this support to the design team.

Commentary by Dr. Valentin Fuster
2008;():121-122. doi:10.1115/BioMed2008-38106.

The availability of low-cost field programmable gate arrays (FPGAs) and wireless technologies provides new opportunities for the development of a wearable computing platform for human performance research. Our goal is a flexible research platform that is configurable for a number of sensor types, provides various options for information processing, and is useful in various simple protocols. This dynamic monitoring device will enable further investigations of the feasibility of use in clinical research and practice settings.

Commentary by Dr. Valentin Fuster
2008;():123-124. doi:10.1115/BioMed2008-38109.

The intra-articular contact characteristics of the diarthrodial joints have been measured by using Fuji pressure sensitive films and a Tekscan sensor system. Direct measurement can only provide resultant contact information. Indirect contact estimation methods, such as mathematical modeling or a stereophotogramametric method can be used to estimate contact kinematics on each articulating surface. However, indirect estimation methods are often based on simplified geometry due to limited accuracy or simplification, resulting in erroneous contact estimation. The objective of this study was to quantify the intra-articular contact area and shape of the glenohumeral joint determined by surface reconstruction. The results showed that the contact estimation method using surface reconstruction was in good agreement with the results of Tekscan measurement (accuracy ≤ 5.3% and repeatability ≤ 11.2%). The contact estimation method may provide a valuable avenue for understanding contact kinematics in human diarthrodial joints.

Topics: Geometry
Commentary by Dr. Valentin Fuster

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