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Medical Engineering & Physics

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https://www.readbyqxmd.com/read/28826857/3d-reconstruction-of-human-bones-based-on-dictionary-learning
#1
Binkai Zhang, Xiang Wang, Xiao Liang, Jinjin Zheng
An effective method for reconstructing a 3D model of human bones from computed tomography (CT) image data based on dictionary learning is proposed. In this study, the dictionary comprises the vertices of triangular meshes, and the sparse coefficient matrix indicates the connectivity information. For better reconstruction performance, we proposed a balance coefficient between the approximation and regularisation terms and a method for optimisation. Moreover, we applied a local updating strategy and a mesh-optimisation method to update the dictionary and the sparse matrix, respectively...
August 18, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28826570/effect-of-longitudinal-anatomical-mismatch-of-stenting-on-the-mechanical-environment-in-human-carotid-artery-with-atherosclerotic-plaques
#2
Zhenmin Fan, Xiao Liu, Anqiang Sun, Nan Zhang, Zhanming Fan, Yubo Fan, Xiaoyan Deng
Longitudinal anatomic mismatch (LAM) of stenting (i.e., a stenotic artery segment is not fully covered by a deployed stent) worsens the mechanical environment in the treated artery, which most likely is the cause for the associated high risks of restenosis, myocardial infarction and stent thrombosis. To probe the possibility, we constructed a patient-specific carotid model with two components of plaques (lipid and calcified plaque) based on MRI images; we numerically compared three different stenting scenarios in terms of von Mises stress (VMS) distribution in the treated arteries, namely, the short stenting (LAM), the medium stenting and the long stenting...
August 17, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28807513/second-generation-prototype-of-a-variable-stiffness-transverse-plane-adapter-for-a-lower-limb-prosthesis
#3
Corey Pew, Glenn K Klute
The prescription and fitting of a traditional lower limb prosthesis often focuses on straight walking, neglecting maneuvers such as turning and pivoting that require flexibility in the transverse plane. Current devices that allow transverse plane movement only offer a fixed stiffness and are incapable of adapting to varying daily activities. Pilot testing of a first-generation variable stiffness torsion adapter (VSTA I) showed a benefit for individuals with lower limb amputation by reducing peak transverse plane moments at the residual limb which could lead to increased comfort, but testing was limited due to excessive device height and mass...
August 11, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28807512/non-linear-finite-element-model-to-assess-the-effect-of-tendon-forces-on-the-foot-ankle-complex
#4
Enrique Morales-Orcajo, Thales R Souza, Javier Bayod, Estevam Barbosa de Las Casas
A three-dimensional foot finite element model with actual geometry and non-linear behavior of tendons is presented. The model is intended for analysis of the lower limb tendon forces effect in the inner foot structure. The geometry of the model was obtained from computational tomographies and magnetic resonance images. Tendon tissue was characterized with the first order Ogden material model based on experimental data from human foot tendons. Kinetic data was employed to set the load conditions. After model validation, a force sensitivity study of the five major foot extrinsic tendons was conducted to evaluate the function of each tendon...
August 11, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28802780/herringbone-like-hydrodynamic-structures-in-microchannels-a-cfd-model-to-evaluate-the-enhancement-of-surface-binding
#5
Elena Bianchi, Monica Piergiovanni, Chiara Arrigoni, Junji Fukuda, Alfonso Gautieri, Matteo Moretti, Gabriele Dubini
Selected adsorption efficiency of a molecule in solution in a microchannel is strongly influenced by the convective/diffusive mass transport phenomena that supply the target molecule to the adsorption surface. In a standard microchannel with a rectangular cross section, laminar flow regime limits the fluid mixing, thus suggesting that mass transport conditions can be improved by the introduction of herringbone-like structures. Tuning of these geometrical patterns increases the concentration gradient of the target molecule at the adsorption surface...
August 9, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28801142/synergistic-experimental-and-numerical-characterization-of-a-dry-heat-fluid-warming-device
#6
Winston Tan, Eph M Sparrow, John M Gorman, Jungwon Ahn
Fluids that are infused into the human body must be at a temperature that is compatible with the internal thermal state of the body. Since infusants are typically stored at temperatures that are too low for compatibility, a heating means is required to achieve the appropriate infusion temperature. This paper sets forth a synergistic investigation involving coupled experimentation and numerical simulation of the characteristics of one of the main categories of body-fluid heating means. The methodology developed here serves equally well as a design optimization tool...
August 8, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28778565/image-based-immersed-boundary-model-of-the-aortic-root
#7
Ali Hasan, Ebrahim M Kolahdouz, Andinet Enquobahrie, Thomas G Caranasos, John P Vavalle, Boyce E Griffith
Each year, approximately 300,000 heart valve repair or replacement procedures are performed worldwide, including approximately 70,000 aortic valve replacement surgeries in the United States alone. Computational platforms for simulating cardiovascular devices such as prosthetic heart valves promise to improve device design and assist in treatment planning, including patient-specific device selection. This paper describes progress in constructing anatomically and physiologically realistic immersed boundary (IB) models of the dynamics of the aortic root and ascending aorta...
August 1, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28774686/does-stabilization-of-the-degenerative-lumbar-spine-itself-produce-multifidus-atrophy
#8
Young Eun Kim, Hae Won Choi
The effect of stabilization of the degenerative segment on changes in the pattern of paraspinal muscle activity was investigated using a previously developed musculoskeletal model. Muscle activity change depending on L4-L5 segment stabilization with and without taking into account the presence of multifidus atrophy according to direct invasion of the back muscle during surgery (MADIBM) was analysed in erect standing and 20° flexed postures. For the stabilization of the degenerative segment, a fusion or non-fusion stabilization with a pedicle-based dynamic stabilization system (PBDS) was applied...
July 31, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28774685/in-vitro-performance-of-a-shape-memory-polymer-foam-coated-coil-embolization-device
#9
Anthony J Boyle, Mark A Wierzbicki, Scott Herting, Andrew C Weems, Adam Nathan, Wonjun Hwang, Duncan J Maitland
Intracranial saccular aneurysm treatment using endovascular embolization devices are limited by aneurysm recurrence that can lead to aneurysm rupture. A shape memory polymer (SMP) foam-coated coil (FCC) embolization device was designed to increase packing density and improve tissue healing compared to current commercial devices. FCC devices were fabricated and tested using in vitro models to assess feasibility for clinical treatment of intracranial saccular aneurysms. FCC devices demonstrated smooth delivery through tortuous pathways similar to control devices as well as greater than 10 min working time for clinical repositioning during deployment...
July 31, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28764879/influence-of-design-features-of-tibial-stems-in-total-knee-arthroplasty-on-tibial-bone-remodeling-behaviors
#10
Zhengbin Jia, He Gong, Shimin Hu, Juan Fang, Ruoxun Fan
In total knee arthroplasty, the optimal length and material of tibial stem remain controversial. This study aimed to evaluate influences of lengths and materials of cementless stems on tibial remodeling behaviors. Three groups of lengths were investigated (i.e., 110, 60, and 30 mm), and four materials (i.e., titanium, flexible 'iso-elastic' material, and two functionally graded materials [FGMs]) were selected for each group. FGM is a kind of material whose composition gradually varies in space. In this study, the compositions of two FGMs were Ti and hydroxyapatite (FGM I), and Ti and bioglass (FGM II), respectively...
July 29, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28760407/development-of-an-acoustic-measurement-protocol-to-monitor-acetabular-implant-fixation-in-cementless-total-hip-arthroplasty-a-preliminary-study
#11
Quentin Goossens, Steven Leuridan, Petr Henyš, Jorg Roosen, Leonard Pastrav, Michiel Mulier, Wim Desmet, Kathleen Denis, Jos Vander Sloten
In cementless total hip arthroplasty (THA), the initial stability is obtained by press-fitting the implant in the bone to allow osseointegration for a long term secondary stability. However, finding the insertion endpoint that corresponds to a proper initial stability is currently based on the tactile and auditory experiences of the orthopedic surgeon, which can be challenging. This study presents a novel real-time method based on acoustic signals to monitor the acetabular implant fixation in cementless total hip arthroplasty...
July 28, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28760406/the-variation-in-frequency-locations-in-doppler-ultrasound-spectra-for-maximum-blood-flow-velocities-in-narrowed-vessels
#12
Yingyun Zhang, Yufeng Zhang, Lian Gao, Li Deng, Xiao Hu, Kexin Zhang, Haiyan Li
This study assessed the variation in the frequency locations in the Doppler ultrasound spectra for the maximum blood flow velocities of in vessels with different degrees of bilaterally axisymmetric stenosis. This was done by comparing the relationship between the velocity distributions and corresponding Doppler power spectra. First, a geometric vessel model with axisymmetric stenosis was established. This made it possible to obtain the blood flow velocity distributions for different degrees of stenosis from the solutions of the Navier-Stokes equations...
July 28, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28754368/what-are-the-six-degree-of-freedom-errors-of-a-robotically-machined-femoral-cavity-in-total-hip-arthroplasty-and-are-they-clinically-important-an-in-vitro-study
#13
Chih Ming Hsieh, Stephen M Howell, Maury L Hull
Errors during a robot-assisted THA may result in a femoral cavity with position and orientation different than planned. This can lead to a femoral component placement that inaccurately sets a patient's femoral anteversion (FA), femoral offset (FO), and vertical offset (VO). The objectives of this study were to determine the position and orientation errors of robotically-machined femoral cavities in six degrees of freedom and to determine how position and orientation errors translate into errors in the setting of FA, FO, and VO...
July 25, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28751011/a-coupled-mitral-valve-left-ventricle-model-with-fluid-structure-interaction
#14
Hao Gao, Liuyang Feng, Nan Qi, Colin Berry, Boyce E Griffith, Xiaoyu Luo
Understanding the interaction between the valves and walls of the heart is important in assessing and subsequently treating heart dysfunction. This study presents an integrated model of the mitral valve (MV) coupled to the left ventricle (LV), with the geometry derived from in vivo clinical magnetic resonance images. Numerical simulations using this coupled MV-LV model are developed using an immersed boundary/finite element method. The model incorporates detailed valvular features, left ventricular contraction, nonlinear soft tissue mechanics, and fluid-mediated interactions between the MV and LV wall...
July 24, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28734875/investigation-of-the-feasibility-of-non-invasive-optical-sensors-for-the-quantitative-assessment-of-dehydration
#15
Cobus Visser, Eduard Kieser, Kiran Dellimore, Dawie van den Heever, Johan Smith
This study explores the feasibility of prospectively assessing infant dehydration using four non-invasive, optical sensors based on the quantitative and objective measurement of various clinical markers of dehydration. The sensors were investigated to objectively and unobtrusively assess the hydration state of an infant based on the quantification of capillary refill time (CRT), skin recoil time (SRT), skin temperature profile (STP) and skin tissue hydration by means of infrared spectrometry (ISP). To evaluate the performance of the sensors a clinical study was conducted on a cohort of 10 infants (aged 6-36 months) with acute gastroenteritis...
July 19, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28734874/robotic-assistants-in-personal-care-a-scoping-review
#16
REVIEW
A Bilyea, N Seth, S Nesathurai, H A Abdullah
The aim of this study is to present an overview of the technological advances in the field of robotics developed for assistance with activities of daily living (ADL), and to present areas where further research is required. Four databases were searched for articles presenting either a novel design of one of these personal care robotic system or trial results relating to these systems. Articles presenting nine different robotic personal care systems were examined, six of which had been developed after 2005. These six also all have publications relating to their trials...
July 19, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28734872/modeling-the-cleavage-of-von-willebrand-factor-by-adamts13-protease-in-shear-flow
#17
Brooke Huisman, Masoud Hoore, Gerhard Gompper, Dmitry A Fedosov
Von Willebrand factor (VWF) is a key protein in hemostasis as it mediates adhesion of blood platelets to a site of vascular injury. A proper distribution of VWF lengths is important for normal functioning of hemostatic processes, because a diminished number of long VWF chains may significantly limit blood clotting and lead to bleeding, while an abundant number of long VWFs may result in undesired thrombotic events. VWF size distribution is controlled by ADAMTS13 protease, which can cleave VWF chains beyond a critical shear rate when the chains are stretched enough such that cleavage sites become accessible...
July 19, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28728867/finite-element-analysis-of-tavi-impact-of-native-aortic-root-computational-modeling-strategies-on-simulation-outcomes
#18
Alice Finotello, Simone Morganti, Ferdinando Auricchio
In the last few years, several studies, each with different aim and modeling detail, have been proposed to investigate transcatheter aortic valve implantation (TAVI) with finite elements. The present work focuses on the patient-specific finite element modeling of the aortic valve complex. In particular, we aim at investigating how different modeling strategies in terms of material models/properties and discretization procedures can impact analysis results. Four different choices both for the mesh size (from  20 k elements to  200 k elements) and for the material model (from rigid to hyperelastic anisotropic) are considered...
July 17, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28728866/deformability-and-size-based-microcapsule-sorting
#19
Doriane Vesperini, Oriane Chaput, Nadège Munier, Pauline Maire, Florence Edwards-Lévy, Anne-Virginie Salsac, Anne Le Goff
Biomedical applications often require to sort cells according to their physical properties, such as size, density or deformability. In recent years, microfluidics has provided a variety of tools to sort micro-objects. We present here a simple microfluidic device consisting of a channel containing a semi-cylindrical obstacle against which capsules are squeezed by the flow, followed by a diverging chamber where streamlines separate. We demonstrate that this basic system is capable of sorting elastic microcapsules according to their size at low flow strength, and according to the stiffness of their membrane at high flow strength...
July 17, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28728865/mass-spring-models-for-the-simulation-of-mitral-valve-function-looking-for-a-trade-off-between-reliability-and-time-efficiency
#20
O A Pappalardo, F Sturla, F Onorati, G Puppini, M Selmi, G B Luciani, G Faggian, A Redaelli, E Votta
Patient-specific finite element (FE) models can assess the impact of mitral valve (MV) repair on the complex MV anatomy and function. However, FE excessive time requirements hamper their use for surgical planning; mass-spring models (MSMs) represent a more approximate approach but can provide almost real-time simulations. On this basis, we implemented MSMs of three healthy MVs from cardiac magnetic resonance (cMR) imaging to simulate the systolic MV closure, including the in vivo papillary muscles and annular kinematics, and the anisotropic and non-linear mechanical response of MV tissues...
July 17, 2017: Medical Engineering & Physics
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