tailieunhanh - Báo cáo hóa học: " Simulation of epiretinal prostheses - Evaluation of geometrical factors affecting stimulation thresholds"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Simulation of epiretinal prostheses - Evaluation of geometrical factors affecting stimulation thresholds | Kasi et al. Journal of NeuroEngineering and Rehabilitation 2011 8 44 http content 8 1 44 Iril JOURNAL OF NEUROENGINEERING NCR AND REHABILITATION RESEARCH Open Access Simulation of epiretinal prostheses - Evaluation of geometrical factors affecting stimulation thresholds Harsha Kasi1 Willyan Hasenkamp1 Gregoire Cosendai2 Arnaud Bertsch1 and Philippe Renaud1 Abstract Background An accurate understanding of the electrical interaction between retinal prostheses and retinal tissue is important to design effective devices. Previous studies have used modelling approaches to simulate electric fields generated by epiretinal prostheses in saline and to simulate retinal ganglion cell RGC activation using passive or and active biophysical models of the retina. These models have limited scope for studying an implanted human retinal prosthesis as they often do not account for real geometry and composition of the prosthesis-retina interface. This interface consists of real dimensions and location of stimulation and ground electrodes that are separated by the retinal tissue and surrounded by physiological fluids. Methods In this study we combined the prosthesis-retina interface elements into a framework to evaluate the geometrical factors affecting stimulation thresholds for epiretinal prostheses used in clinical human trials as described by Balthasar et al. in their Investigative Ophthalmology and Visual Science IOVS paper published in 2008 using the Argus I epiretinal implants. Finite element method FEM based computations were used to estimate threshold currents based on a threshold criterion employing a passive electric model of the retina. Results Threshold currents and impedances were estimated for different electrode-retina distances. The profiles and the values for thresholds and impedances obtained from our simulation framework are within the range of measured values in the only elaborate published clinical trial until now using Argus I epiretinal .