视皮层假体研究进展

视皮层假体作为最早开始研究的视觉假体,其发展已历经了半个多世纪。视皮层被最早定位于人工视觉修复的入路,有其自身的解剖、生理特点和优势,但同时也因为其高层面的视觉信息处理水平,研发面临重重困难。本文回顾、梳理视皮层假体发展历程,希望从中总结经验和发现未来研究的突破点。     

基于稀疏性与同步性的视皮质假体图像处理策略

背景:视觉系统是人类获知外部世界的重要感觉系统,因各种疾病或其他损伤导致视觉丧失的盲人数量与日俱增,视皮质假体的研究有望为盲人提供一条复明的途径.视皮质假体虽然经过多年的研究,在某些方面取得了一定的进展和成果,但仍存在很多问题和挑战.目的:针对置入视皮质的刺激电极数量有限这一问题,提出一种基于稀疏性和同步性的视皮质假体图像处理策略.方法:该策略借鉴视觉皮质的生理特性,首先采用基于稀疏性的拓扑独立成分分析方法提取自然图像的基函数及神经元的响应,然后采用基于同步性的脉冲耦合神经网络方法对响应系数进行筛选,获取最佳神经元响应,最后利用最佳神经元响应刺激相应的神经元达到恢复自然图像的目的.结果与结论:实验结果表明,该策略理论上可以利用较少的神经元表征自然图像中的重要信息,应用于视皮质假体可有效减少置入刺激电极的数量,达到更好的信息传递效果.     

视皮质假体中多路信号的无线传输

背景:信号无线传输系统担任着视皮质假体体内外信息交互的任务,为了使假体能够对刺激区域进行多靶位的有效刺激,需要从体外传输进来多个不同的刺激信号.目的:提出一种多路信号无线传输系统的设计方案.方法:利用频分复用技术,能够在单一通道上完成多路信号的传输,整个系统设计分体外发射电路和体内接收电路两部分,且接收电路采用无源设计,减少了供能给植入体带来的危害.在给出具体设计电路的同时,对影响系统传输效率的因素做了进一步分析,通过Multisim仿真实验验证其可行性.结果与结论:该多路信号无线传输系统可以扩展应用到各类植入式假体的信号传输部分,并日采用体内无源设计,避免了为电路供能给人体带来的伤害,通过初步的仿真实验证明该系统具有可行性,具有广泛的应用前景.     

基于整数小波变换和零树编码算法的医学图像压缩研究

现代医疗成象设备产生了大量高价值的医学图像,如何对信息的进行有效的存储、查询以及网络传输是一个亟待解决的问题.本文利用整数小波变换和零树编码算法对医学图像进行了压缩研究,试验表明,同传统JPEG标准相比,相同压缩比下本算法的峰值信噪比有明显的提高,同时本算法具有逐渐显现的特性,能够满足医学图像存储、查询以及网络传输的需求.     

小波变换医学DICOM图像压缩的研究

目的　利用小波变换实现对医学DICOM图像压缩。方法　分析小波变换技术特点及医学DICOM标准的数据结构 ,确定DICOM图像压缩的小波变换算法及编码方法。结果　用VC 实现基于小波技术的DICOM图像压缩。结论　该方法具备无损压缩、低比特速率有损压缩及渐进传输的优点 ,对我国远程医学和图像建档及通信系统的发展具有深远的意义     

鼠视皮质由神经钙蛋白对经验依赖可塑性的可逆性阻滞

研究证明,许多蛋白激酶对鼠视皮质的可塑性有影响,但丝氨酸苏氨酸蛋白磷酸酶的作用还不明了.神经钙蛋白突触--大脑中唯一已知的由钙离子/钙调蛋白活化的蛋白磷酸酶,在海马突触可塑性和记忆中乃是一种分子抑制物.在前脑神经元中诱导神经钙蛋白过度表达的转基因小鼠中,神经钙蛋白同样在眼优势的可塑性中发挥作用.研究发现,小鼠在单目视觉剥夺后,神经钙蛋白活动性一过性升高可以预防皮质反应的变化,并且其效应是可逆的.这些结果表明,鼠视皮质可塑性中蛋白激酶和磷酸酶的平衡非常关键.     

医学图像的零树小波编码

背景:医学数字图像必须是高质量的、高分辨率,所以数据量很大,如此巨大的数据量不利于图像存档与传输系统的运行和数字化医院、远程医疗的实现.因此,图像压缩成为图像存档与传输系统要解决的重要问题.目的:分析零树小波变编码算法原理并编程实现对医学数字图像的压缩,使之能够满足医学图像的传输和诊断要求.方法:应用嵌入式零树小波编码算法,探讨小波基和小波变换层数的选择,编程实现对医学数字图像的压缩.结果与结论:选择双正交小波基对医学图像进行4层小波变换实现压缩,获得了较高的峰值信噪比,取得了较好的压缩效果.     

原代培养大鼠视网膜与视皮质神经元的方法学特点(英文)

背景:神经元的原代培养是进行神经系统结构和功能研究的一种重要手段.如果能建立稳定良好的视网膜、视皮质神经细胞体外培养体系,对深入研究其各种细胞成分的生物学功能、病理改变过程与机制以及药物反应等十分重要.目的:对比观察原代培养新生大鼠视网膜及视皮质神经元的特点,探求最佳分离和培养方法.方法:分别采用机械分离及酶消化法分离新生大鼠视网膜及视皮质神经元,应用含体积分数为10%新牛牛血清、10%F-12 Nutrient Mixtures的DMEM培养基进行接种培养,含2%B-27 Serum-Free Supplements的Neurobasal Medium进行维持培养,利用尼氏染色进行神经元鉴定.结果与结论:培养的神经元生长良好,胞体饱满,突起长.尼氏染色示视网膜神经元比例大于90%,视皮质神经元比例大于50%.提示视网膜及视皮质神经元培养方法及生长特点存在不同,需采用不同的方法进行培养以获得高纯度的神经元.     

弱视视皮层可塑性的分子生物学机制研究进展

弱视是视觉发育敏感期异常视觉经验所导致的以空间视力损害为特征的一组视力不良综合症[1].视皮层在发育的过程中存在"敏感期",具有可塑性,而弱视治疗的依据就在于视觉发育敏感期内可塑性的存在[2],现在对弱视的视皮层可塑性机制研究已经上升到了分子水平,现将近10年视皮层可塑性的分子生物学研究文献综述如下.     

人工髋关节假体的分类及设计

背景:人工髋关节置换是指用生物相容性良好的材料制成的一种类似人体骨关节的假体,置换被疾病或损伤所破坏的关节或关节平面,缓解关节疼痛、矫正畸形假体、改善关节的活动功能。目的:对人工髋关节假体分类及设计研究文献的发展趋势进行多层次探讨分析。方法:以电子检索方式对CNKI数据库学术期刊2002-01/2011-12收录有关人工髋关节假体分类及设计研究的文献进行分析,采用检索词为"髋关节置换;人工假体;假体设计;假体类型",运用数据库的分析功能和Excel软件图表的功能分析数据特征。结果与结论:CNKI数据库学术期刊2002/2011收录人工髋关节假体分类及设计研究的文献135篇,从文献数量上看处于上升趋势。以外科学分类的文献为主。《中国组织工程研究与临床康复》杂志因设有医学植入物栏目,在人工髋关节假体分类及设计研究中发表文献数量最多为33篇。上海交通大学是人工髋关节假体分类及设计研究的重点单位,王成焘教授是从事此研究的重要核心作者。文献关键词显示人工髋关节假体设计和类型主要考虑髋关节、股骨的生物力学方面问题,以及人工髋关节假体有限元分析、翻修、假体无菌性松动等。     

An image overlay system for medical data visualization

Image Overlay is a computer display technique which superimposes computer images over the user's direct view of the real world. The images are transformed in real-time so they appear to the user to be an integral part of the surrounding environment. By using Image Overlay with three-dimensional medical images such as CT reconstructions, a surgeon can visualize the data 'in-vivo', exactly positioned within the patient's anatomy, and potentially enhance the surgeon's ability to perform a complex procedure. This paper describes prototype Image Overlay systems and initial experimental results from those systems.     

An on-board surgical tracking and video augmentation system for C-arm image guidance

Purpose

Conventional tracker configurations for surgical navigation carry a variety of limitations, including limited geometric accuracy, line-of-sight obstruction, and mismatch of the view angle with the surgeon??s-eye view. This paper presents the development and characterization of a novel tracker configuration (referred to as ??Tracker-on-C??) intended to address such limitations by incorporating the tracker directly on the gantry of a mobile C-arm for fluoroscopy and cone-beam CT (CBCT).

Methods

A video-based tracker (MicronTracker, Claron Technology Inc., Toronto, ON, Canada) was mounted on the gantry of a prototype mobile isocentric C-arm next to the flat-panel detector. To maintain registration within a dynamically moving reference frame (due to rotation of the C-arm), a reference marker consisting of 6 faces (referred to as a ??hex-face marker??) was developed to give visibility across the full range of C-arm rotation. Three primary functionalities were investigated: surgical tracking, generation of digitally reconstructed radiographs (DRRs) from the perspective of a tracked tool or the current C-arm angle, and augmentation of the tracker video scene with image, DRR, and planning data. Target registration error (TRE) was measured in comparison with the same tracker implemented in a conventional in-room configuration. Graphics processing unit (GPU)-accelerated DRRs were generated in real time as an assistant to C-arm positioning (i.e., positioning the C-arm such that target anatomy is in the field-of-view (FOV)), radiographic search (i.e., a virtual X-ray projection preview of target anatomy without X-ray exposure), and localization (i.e., visualizing the location of the surgical target or planning data). Video augmentation included superimposing tracker data, the X-ray FOV, DRRs, planning data, preoperative images, and/or intraoperative CBCT onto the video scene. Geometric accuracy was quantitatively evaluated in each case, and qualitative assessment of clinical feasibility was analyzed by an experienced and fellowship-trained orthopedic spine surgeon within a clinically realistic surgical setup of the Tracker-on-C.

Results

The Tracker-on-C configuration demonstrated improved TRE (0.87 ± 0.25)?mm in comparison with a conventional in-room tracker setup (1.92 ± 0.71)?mm (p Conclusions The proposed tracker configuration demonstrated sub-?mm TRE from the dynamic reference frame of a rotational C-arm through the use of the multi-face reference marker. Real-time DRRs and video augmentation from a natural perspective over the operating table assisted C-arm setup, simplified radiographic search and localization, and reduced fluoroscopy time. Incorporation of the proposed tracker configuration with C-arm CBCT guidance has the potential to simplify intraoperative registration, improve geometric accuracy, enhance visualization, and reduce radiation exposure.     

Verification of delay time and image compression thresholds for telesurgery

Introduction

Telerobotic surgery relies on communication lines, causing delays, and video information requires pre-transmission compression. Such delays and video degradation will continue to be unavoidable making communication conditions verification essential. Understanding the network specification values required for telerobotic surgery entails determining acceptable levels of delay and degradation due to the video compression and restoration processes during surgery.

Methods

The hinotori™ surgical robot from Medicaroid was used. Eight surgeons, skilled in robotic surgery, performed gastrectomy or rectal resection on pigs. Image compression (bitrate: 120, 60, 30, 20, 10 Mbps) was random, changing encoder settings during surgery, and delay times (30, 50, 100, 150 milliseconds) were pseudo-randomly inserted, changing emulator settings. Acceptable video levels were evaluated. Subjective evaluations by surgeons and evaluators regarding image degradation and operability, and objective evaluations of image degradation and operability were given five-point ratings.

Results

Regarding delay time, 30 and 50 millisecond periods garnered average ratings of 3.6 and 4.0, respectively, signifying that surgery was feasible. However, at 100 and 150 millisecond, average ratings were 2.9 and 2.3, respectively, indicating surgery was not feasible for the most part in these cases. The average rating for image compression was 4.0 or higher for bitrates of 20, 30, 60, and 120 Mbps, suggesting that surgery is possible even at bitrates as low as 10 Mbps, with an average rating of 4.0.

Conclusion

In remote robotic surgery using the hinotori™, image compression and delay time are largely acceptable, so surgery can be safely performed.     

Magnetic resonance imaging of the visual system in vivo: transsynaptic illumination of V1 and V2 visual cortex

Brain nuclei directly receiving retinal projections are readily labeled in magnetic resonance images following intraocular injection of manganese (Mn). To assess whether Mn in retinal ganglion cell axons can be transsynaptically delivered to visual cortex, mice that had previously received intraocular Mn injection were anesthetized with isoflurane, and T1-weighted data sets were acquired of the eyes and brain using a 7-T magnetic resonance imaging machine. Image intensity within contralateral brain structures was evaluated by assessing 1) signal-to-noise ratios, 2) mean image intensity, and 3) mean image intensity normalized to facial muscle intensity. Image intensity was increased throughout the visual pathway including within contralateral visual cortex areas V1 and V2L. Mean normalized image intensity was greater by 53% in the ipsilateral optic nerve and by 31% and 28% in the contralateral lateral geniculate nucleus and superior colliculus, respectively (N=5, P<0.02, paired t test). In contralateral visual cortex areas V1 and V2L, image intensity was increased by 7.5% and 6.8%, respectively (P<0.02 for both, paired t test). Power analysis of the different evaluation methods yielded evidence of superior sensitivity using the normalization method. Reconstruction of the visual system based upon threshold analysis allowed simultaneous visualization of all portions of the major retinal projections to the brain. These results support use of high magnetic field MRI imaging and data normalization for in vivo quantitative analysis of the mouse brain visual system including visual cortex.