Abstract：
:We present a finite element based simulation and analysis method to describe the spatial extent of stimulation and the effects of electrode-tissue interactions in subretinal prostheses. In particular, we estimate the threshold stimulation current needed to depolarise and evoke action potentials in the ganglion cells to be stimulated at a particular distance from the electrode. This is achieved through the application of a threshold electric field to a spherical neuronal soma model of a retinal ganglion cell under consideration. Threshold stimulation currents and the lateral extent of the stimulation zone were computed for disc microelectrodes in subretinal stimulation mode. Recent evidence indicates a decrease in threshold charge with time following subretinal implantation. Consequently, to explain the variation in threshold stimulation currents, we propose a hypothesis based on an electrode-tissue gap. Threshold stimulation currents and impedances for different electrode-tissue gaps were computed. We validate the hypothesis with our simulation results that the changes in impedance observed with time in vivo can be mainly attributed to the varying distance of the ganglion cells from electrodes due to changes in electrode-tissue gap. Our simulation framework proposes a convenient and practical method applicable for studying different electrode geometries used for retinal stimulation.
journal_name
Med Eng Physjournal_title
Medical engineering & physicsauthors
Kasi H,Bertsch A,Guyomard JL,Kolomiets B,Picaud S,Pelizzone M,Renaud Pdoi
10.1016/j.medengphy.2011.01.015subject
Has Abstractpub_date
2011-07-01 00:00:00pages
755-63issue
6eissn
1350-4533issn
1873-4030pii
S1350-4533(11)00019-1journal_volume
33pub_type
杂志文章abstract：:Recent approaches to the in vitro experimental study of cardiac fluid mechanics involve the use of whole biological structures to investigate in the lab novel therapeutic approaches for the treatment of heart pathologies. To enhance reliability and repeatability, the influence of the actuation strategy of the experime...
journal_title：Medical engineering & physics
pub_type： 杂志文章
doi：10.1016/j.medengphy.2016.01.007
更新日期：2016-04-01 00:00:00
abstract：:Results of a comparative analysis between Heart Rate (HR) patterns occurring before the onset of Paroxysmal Ventricular Tachycardia (PVT) and from healthy subjects are shown. Two study groups were made after electrocardiographic dynamical monitoring (Holter) of volunteers. The first group includes 100h from 27 healthy...
journal_title：Medical engineering & physics
pub_type： 杂志文章
doi：10.1016/j.medengphy.2010.08.004
更新日期：2010-12-01 00:00:00
abstract：:To better understand the mechanisms underlying distal radius fracture we have developed finite element models to predict radius bone strain and fracture strength under loading conditions simulating a fall. This study compares experimental surface strains and fracture loads of the distal radius with specimen-specific f...
journal_title：Medical engineering & physics
pub_type： 杂志文章
doi：10.1016/j.medengphy.2011.07.016
更新日期：2012-04-01 00:00:00
abstract：:Stent implantation has become a widely accepted endovascular intervention for the treatment of stenosed arteries. This minimally invasive technique has shown excellent results in unbranched arteries. However, stenting bifurcation lesions remains a challenge in coronary intervention as it is associated with a lower suc...
journal_title：Medical engineering & physics
pub_type： 杂志文章
doi：10.1016/j.medengphy.2008.11.013
更新日期：2009-05-01 00:00:00
abstract：:In order to assess the actual load on front teeth and tooth supportive tissue during brass instrument playing, a measuring system was developed permitting simultaneous recordings of mouthpiece forces and incisor deflections. By the application of strain gauges, the mouthpiece itself was converted into an extra-oral fo...
journal_title：Medical engineering & physics
pub_type： 杂志文章
doi：10.1016/1350-4533(95)00006-9
更新日期：1995-12-01 00:00:00
abstract：BACKGROUND AND AIMS OF THE STUDY:Mechanical heart valves (MHV) are widely used to replace dysfunctional and failed heart valves. The bileaflet MHV design is very popular due to its superior hemodynamics. Since their introduction in 1977, the hemodynamics of bileaflet prostheses has been extensively studied. In this stu...
journal_title：Medical engineering & physics
pub_type： 杂志文章
doi：10.1016/j.medengphy.2005.03.013
更新日期：2006-03-01 00:00:00
abstract：:The liquid ventilation (LV) technique was previously demonstrated to be a valuable alternative to ordinary gas ventilation, particularly for newborn patients with severely distressed lungs. This work describes a mathematical model of gas transfer phenomena occurring within the lungs of a preterm newborn baby ventilate...
journal_title：Medical engineering & physics
pub_type： 杂志文章
doi：10.1016/s1350-4533(96)00041-0
更新日期：1997-03-01 00:00:00
abstract：:Post-myocardial infarction remodeling process is known to alter the mechanical properties of the heart. Biomechanical parameters, such as tissue stiffness and contractility, would be useful for clinicians to better assess the severity of the diseased heart. However, these parameters are difficult to obtain in the curr...
journal_title：Medical engineering & physics
pub_type： 杂志文章
doi：10.1016/j.medengphy.2020.09.003
更新日期：2020-11-01 00:00:00
abstract：:The results from studies of wave propagation in large arteries carried out over the last 25 years have shown that there is a good agreement among values of the imaginary part of the complex propagation coefficient, as expressed by pressure or flow-rate wave propagation velocity. However, there is considerable disparit...
journal_title：Medical engineering & physics
pub_type： 杂志文章
doi：10.1016/s1350-4533(96)00073-2
更新日期：1997-04-01 00:00:00
abstract：:Heart rate variability (HRV) is a non-invasive alternative to analyze the role of the autonomic nervous system (ANS) on heart functioning. Many tools have been developed to analyze collected cardiac data. Among them, the Central Tendency Measure (CTM) is a quantitative method for variability analysis of RR intervals. ...
journal_title：Medical engineering & physics
pub_type： 杂志文章
doi：10.1016/j.medengphy.2019.09.024
更新日期：2019-12-01 00:00:00
abstract：OBJECTIVE:A novel methodology has been developed to evaluate regional alterations in arterial wall material properties with induced atheroma in an animal model. METHODS:Atheromatous lesions (fatty, fibro-fatty, and fibrous) were induced in the carotid arteries of a Yucatan miniswine model by endothelial cell denudatio...
journal_title：Medical engineering & physics
pub_type： 杂志文章
doi：10.1016/j.medengphy.2004.09.014
更新日期：2005-03-01 00:00:00
abstract：:Segmentation of medical images is very important for clinical research and diagnosis, leading to a requirement for robust automatic methods. This paper reports on the combined use of a neural network (a multilayer perceptron, MLP) and active contour model ('snake') to segment structures in magnetic resonance (MR) imag...
journal_title：Medical engineering & physics
pub_type： 临床试验,杂志文章
doi：10.1016/s1350-4533(03)00137-1
更新日期：2004-01-01 00:00:00
abstract：:The paper described a limited part of the coagulation pathway, and in particular the inhibitory effects of activated protein C in the context of thrombin production. This is a computational modeling study with various assumption made of kinetic rates laws and their summation. The level of complexity and assumed parame...
journal_title：Medical engineering & physics
pub_type： 杂志文章
doi：10.1016/j.medengphy.2004.01.003
更新日期：2004-05-01 00:00:00
abstract：:This study employed a noncontact resonance frequency (RF) detection technique that was developed by our group to evaluate the interfacial bone in in vitro implant-bone models. Based on our method, the implant-bone structure was excited by the acoustic energy of a loudspeaker, and its vibration response was acquired wi...
journal_title：Medical engineering & physics
pub_type： 杂志文章
doi：10.1016/j.medengphy.2013.05.006
更新日期：2013-12-01 00:00:00
abstract：:Patients affected by motor disorders of the hand and having residual voluntary movements of fingers or wrist can benefit from self-rehabilitation exercises performed with so-called dynamic hand splints. These systems consist of orthoses equipped with elastic cords or springs, which either provide a sustained stretch o...
journal_title：Medical engineering & physics
pub_type： 杂志文章
doi：10.1016/j.medengphy.2013.10.015
更新日期：2014-02-01 00:00:00
abstract：OBJECTIVE:To illustrate (a) whether a statistical shape model (SSM) augmented with anatomical landmark set(s) performs better fitting and provides improved clinical relevance over non-augmented SSM and (b) which anatomical landmark set provides the best augmentation strategy for predicting the glenoid region of the sca...
journal_title：Medical engineering & physics
pub_type： 杂志文章
doi：10.1016/j.medengphy.2019.11.007
更新日期：2020-02-01 00:00:00
abstract：:The aim of this study was to evaluate comparatively five methods for automating mesh generation (AMG) when used to mesh a human femur. The five AMG methods considered were: mapped mesh, which provides hexahedral elements through a direct mapping of the element onto the geometry; tetra mesh, which generates tetrahedral...
journal_title：Medical engineering & physics
pub_type： 杂志文章
doi：10.1016/s1350-4533(97)00049-0
更新日期：1998-01-01 00:00:00
abstract：:Biomechanical movement analysis in 3D requires estimation of joint centres in the lower extremities and this estimation is based on extrapolation from markers placed on anatomical landmarks. The purpose of the present study was to quantify the accuracy of three established set of equations and provide new improved equ...
journal_title：Medical engineering & physics
pub_type： 杂志文章
doi：10.1016/j.medengphy.2015.07.001
更新日期：2015-10-01 00:00:00
abstract：AIMS:This study investigated the feasibility of automated differentiation between essential tissue types encountered during laparoscopic colorectal surgery using spectral analysis. METHODS:Wide band (440-1830 nm) spectra were collected using an optical fiber probe and spectrometer from freshly explanted, ex vivo, huma...
journal_title：Medical engineering & physics
pub_type： 杂志文章
doi：10.1016/j.medengphy.2013.01.004
更新日期：2013-07-01 00:00:00
abstract：:We developed a device for an objective measurement of non-nutritive sucking (NNS). NNS is newborns' spontaneous action that is a predictor of their neural system development and can be adopted as an intervention to train oral feeding skills in preterms. Two miniaturized digital pressure sensors were embedded into a co...
journal_title：Medical engineering & physics
pub_type： 杂志文章
doi：10.1016/j.medengphy.2015.12.013
更新日期：2016-04-01 00:00:00
abstract：:The definition of spinal instability is still controversial. For this reason, it is essential to better understand the difference in biomechanical behaviour between healthy and degenerated human spinal segments in vivo. A novel computer-assisted instrument was developed with the objective to characterize the biomechan...
journal_title：Medical engineering & physics
pub_type： 杂志文章
doi：10.1016/j.medengphy.2009.07.002
更新日期：2009-11-01 00:00:00
abstract：OBJECTIVE:Joint space narrowing is an important feature of progressive joint damage and functional impairment in rheumatoid arthritis (RA). Methods to provide a continuous measurement of joint space width have not been adopted in research or clinical settings. High-resolution peripheral quantitative computed tomography...
journal_title：Medical engineering & physics
pub_type： 杂志文章
doi：10.1016/j.medengphy.2013.04.003
更新日期：2013-10-01 00:00:00
abstract：:The purpose of the present study was to compare the passive angle-torque curves and the passive stiffness (PS, N m °(-)(1)) values recorded simultaneously from a load cell versus an isokinetic dynamometer during dorsiflexion stretch tolerance assessments in vivo. Nine healthy men (mean ± SD age = 21.4 ± 1.6 years) com...
journal_title：Medical engineering & physics
pub_type： 杂志文章
doi：10.1016/j.medengphy.2015.02.010
更新日期：2015-05-01 00:00:00
abstract：:Pulse transit time (PTT) has emerged over the recent decades as a simple and non-invasive measure to quantify inspiratory effort changes in adults with sleep disordered breathing (SDB). Hence, this shows promise to be an effective screening tool for the paediatrics. However, little is known about its utility and suita...
journal_title：Medical engineering & physics
pub_type： 杂志文章,评审
doi：10.1016/j.medengphy.2006.01.006
更新日期：2007-01-01 00:00:00
abstract：:T2 mapping is a powerful noninvasive technique providing quantitative biological information of the inherent tissue properties. However, its clinical usage is limited due to the relative long scanning time. This paper proposed a novel model-based method to address this problem. Typically, we directly estimated the rel...
journal_title：Medical engineering & physics
pub_type： 杂志文章
doi：10.1016/j.medengphy.2014.06.002
更新日期：2014-11-01 00:00:00
abstract：:Extensive research is ongoing in the field of orthoses/exoskeleton design for efficient lower limbs assistance. However, despite wearable devices reported to improve lower limb mobility, their structural impacts on whole-body vertical dynamics have not been investigated. This study introduced a model identification ap...
journal_title：Medical engineering & physics
pub_type： 杂志文章
doi：10.1016/j.medengphy.2020.04.005
更新日期：2020-06-01 00:00:00
abstract：:In stark contrast to the inspiring functionality of the natural hand, limitations of current upper limb prostheses stemming from marginal feedback control, challenges of mechanical design, and lack of sensory capacity, are well-established. This paper provides a critical review of current sensory systems and the poten...
journal_title：Medical engineering & physics
pub_type： 杂志文章
doi：10.1016/j.medengphy.2005.09.009
更新日期：2006-07-01 00:00:00
abstract：:An 'instantaneous' optimal filter is presented for improving the signal-to-noise ratio in averaged electrocardiograms (ECGs). The filter design is based on a simple model that accounts for correlation across the ensemble of beats but ignores correlation in time. Another property of the model is that the noise level is...
journal_title：Medical engineering & physics
pub_type： 杂志文章
doi：10.1016/s1350-4533(96)00069-0
更新日期：1997-04-01 00:00:00
abstract：:An inertial measurement unit (IMU) allows kinematic evaluation of human motion with fewer operational constraints than a gold standard optoelectronic motion capture (MOCAP) system. The study's aim was to compare IMU and MOCAP measurements of dynamic pelvic orientation angles during different activities of daily life (...
journal_title：Medical engineering & physics
pub_type： 杂志文章
doi：10.1016/j.medengphy.2015.11.009
更新日期：2016-03-01 00:00:00
abstract：:We developed an analytical biomechanical model for leg-extension equipment and the associated knee-extension/flexion exercises. The shear component, phi(t), of the tibiofemoral joint load was calculated taking into account all the fundamental elements of the equipment mechanics (resistance pad placement, cam/pulley sy...
journal_title：Medical engineering & physics
pub_type： 杂志文章
doi：10.1016/j.medengphy.2007.12.012
更新日期：2008-10-01 00:00:00
