基于直接数字合成技术用于心内膜三维标测的激励源设计

背景：低频电场定位方式下的心内膜三维标测技术中,激励源的设计是探测导管位置的前提。 目的：旨在设计一种结构简单、集成度高、专用于心内膜三维标测的激励源,并通过动物实验对激励源性能进行测试分析。 方法：基于直接数字合成技术,采用模块化设计,以单片机STC89C52控制三块直接数字合成芯片AD9851为核心,生成三路频率分别为28,30,32 kHz的1 mA正弦恒流信号。施加三路信号于动物体,采集并处理右心房内的定位信号数据,对激励源性能进行评价和分析。 结果与结论：动物实验结果表明,三路信号的电流值均可稳定于1 mA,其频率误差分别为0.054%,0.097%及0.056%,同时标测导管采集数据正常,能够分离出3个方向的电压信号。激励源恒流特性好、频率误差小,可满足心内膜三维标测的使用要求。     

心内膜三维电生理标准设备关键技术分析

首先介绍心内膜标测应用的现状和意义,其后从工程的角度分析该项技术需要完成的关键功能:定位和电标测.紧接着对比目前已经产品化的各个心内膜三维标测技术的关键技术和对软件功能的需求,最后介绍笔者目前研究的进展.     

128道心外膜电位标测系统的设计

心外膜电位标测是一种重要的心脏电生理研究方法,特别适用于房颤等复杂心律失常电生理机制的研究.128道心外膜电位标测系统由柔性电极、放大器、数据采集卡以及相应的软件组成,可用于心外膜实时标测.通过对标测结果的分析可以确定心律失常的起源部位和传导路径,为临床诊断、治疗提供重要依据.     

128道心外膜电位标测系统的前置放大模块的设计

心电标测是心脏电生理机理研究的主要方法,也是临床精密诊断和对心律失常病灶进行精确定位的重要手段,特别适用于房颤等复杂心律失常电生理机制的研究。该文主要介绍了心外膜电位标测系统中的前置放大模块的设计,并根据实际需要,增加了右腿驱动电路。通过人体与动物实验检测,应用右腿驱动电路后均能得到清楚的心电波形。     

八道计算机心外膜等时标测系统的建立及实验应用

为了研究致命性心律失常的机理,指导实验和临床探查并消除异位兴奋灶或异常传导路径,我们建立了八道计算机心外膜等时标测系统。系统的硬件由电极、前置放大级、量化级,计算机及输出显示四个部分组成。软件包括前置处理模块、峰值检测模块、时间计算模块、输出显示模块。应用此系统可探查出乌头碱诱发的室速病灶,并指导激光消除病变心肌,转复为窦性心律。     

心房颤动的心外膜标测表征方法初探

心房颤动（简称房颤）是临床上最常见的复杂心律失常。由于其电生理机制尚未完全阐明,临床上治疗效果仍不甚明显。我们采用复旦大学研制的64-176道心外膜标测系统,通过对心房外膜电活动的记录和分析,对房颤的最佳表征方法进行了初步研究。实验结果表明波动图和矢量图能反映房颤的不规则电活动。统计分析揭示一定时间内的激动频率和相关性统计中窦性心律和房颤出现较大的差异,间期变异范围二者也有区别。本组结果初步表明,可用波动图和矢量图对房颤进行动态观测,通过统计图可得知激动规律,这可为临床上房颤的精密诊断和治疗提供应用基础。     

标测导管定位信号处理及仿真分析中呼吸与心跳运动的干扰

背景：在采用电场定位原理的心内膜三维标测系统中,标测导管在胸腔内的位置信号受到呼吸与心跳运动的干扰,使其定位精度受到极大影响。 目的：找到在标测导管定位信号中人工加入和检出呼吸与心跳运动干扰项的仿真分析和信号处理方法。 方法：首先根据标测原理推导了包含呼吸与心跳运动干扰的定位信号数学模型,分析和确定了信号的调理、检波和提取方法;然后利用Matlab仿真软件进行信号处理过程的理论仿真计算,以验证数学模型的正确性;最后以满足手术过程中高速实时定位要求为前提,设计出与理论模型相对应的硬件电路,并用Multisim电路设计软件做仿真实验以验证所提方法在实际工作过程中实现的可行性。 结果与结论：仿真实验结果表明无论是数值模拟还是电路仿真都可以很好地仿真出包含呼吸与心跳运动干扰的导管定位信号,所给出的理论分析方法及实际电路系统都能将呼吸与心跳干扰项顺利提取出来。     

Signal processing in the vestibular system during active versus passive head movements

In everyday life, vestibular receptors are activated by both self-generated and externally applied head movements. Traditionally, it has been assumed that the vestibular system reliably encodes head-in-space motion throughout our daily activities and that subsequent processing by upstream cerebellar and cortical pathways is required to transform this information into the reference frames required for voluntary behaviors. However, recent studies have radically changed the way we view the vestibular system. In particular, the results of recent single-unit studies in head-unrestrained monkeys have shown that the vestibular system provides the CNS with more than an estimate of head motion. This review first considers how head-in-space velocity is processed at the level of the vestibular afferents and vestibular nuclei during active versus passive head movements. While vestibular information appears to be similarly processed by vestibular afferents during passive and active motion, it is differentially processed at the level of the vestibular nuclei. For example, one class of neurons in vestibular nuclei, which receives direct inputs from semicircular canal afferents, is substantially less responsive to active head movements than to passively applied head rotations. The projection patterns of these neurons strongly suggest that they are involved in generating head-stabilization responses as well as shaping vestibular information for the computation of spatial orientation. In contrast, a second class of neurons in the vestibular nuclei that mediate the vestibuloocular reflex process vestibular information in a manner that depends principally on the subject's current gaze strategy rather than whether the head movement was self-generated or externally applied. The implications of these results are then discussed in relation to the status of vestibular reflexes (i.e., the vestibuloocular, vestibulocollic, and cervicoocular reflexes) and implications for higher-level processing of vestibular information during active head movements.     

全数字B超的信号处理

全数字B超是超声医疗仪器的发展方向,它的基本技术特点是用数字硬件电路来实现数据量极其庞大的超声信号的实时处理。概述了全数字B超的发展方向及主要的信号处理技术,包括动态滤波、对数放大、包络检波和二次采样,并详细介绍了国内外信号处理各阶段采用的方法。     

Signal processing in scanning thermoacoustic tomography in biological tissues

Microwave-induced thermoacoustic tomography was explored to image biological tissues. Short microwave pulses irradiated tissues to generate acoustic waves by thermoelastic expansion. The microwave-induced thermoacoustic waves were detected with a focused ultrasonic transducer to obtain two-dimensional tomographic images of biological tissues. The dependence of the axial and the lateral resolutions on the spectra of the signals was studied. A reshaping filter was applied to the temporal piezoelectric signals from the transducer to increase the weight of the high-frequency components, which improved the lateral resolution, and to broaden the spectrum of the signal, which enhanced the axial resolution. A numerical simulation validated our signal-processing approach.     

Signal transduction and information processing in mammalian taste buds

The molecular machinery for chemosensory transduction in taste buds has received considerable attention within the last decade. Consequently, we now know a great deal about sweet, bitter, and umami taste mechanisms and are gaining ground rapidly on salty and sour transduction. Sweet, bitter, and umami tastes are transduced by G-protein-coupled receptors. Salty taste may be transduced by epithelial Na channels similar to those found in renal tissues. Sour transduction appears to be initiated by intracellular acidification acting on acid-sensitive membrane proteins. Once a taste signal is generated in a taste cell, the subsequent steps involve secretion of neurotransmitters, including ATP and serotonin. It is now recognized that the cells responding to sweet, bitter, and umami taste stimuli do not possess synapses and instead secrete the neurotransmitter ATP via a novel mechanism not involving conventional vesicular exocytosis. ATP is believed to excite primary sensory afferent fibers that convey gustatory signals to the brain. In contrast, taste cells that do have synapses release serotonin in response to gustatory stimulation. The postsynaptic targets of serotonin have not yet been identified. Finally, ATP secreted from receptor cells also acts on neighboring taste cells to stimulate their release of serotonin. This suggests that there is important information processing and signal coding taking place in the mammalian taste bud after gustatory stimulation.     

Changes in endocardial cell morphology during development of the endocardial cushions

Summary This paper presents a scanning electron microscope study of the morphologic changes undergone by the endocardium during development of the atrioventricular (A-V) endocardial cushions. Prior to cell seeding into the cushions, endocardial cells show a regular, uniform morphology, many of them appearing to be oriented in the direction of the blood flow. Concomitant with the appearance of cells in the A-V cushions, endocardial cells lose their elongated appearance, become more flattened and adopt a variable morphology. Endocardial cells at this stage develop filopodia and lamellipodia, overlap each other and show a variable number of microvilli and different degrees of flattening. After completion of endocardial migration, the endocardial cells that remain in the plane of the endocardium become extremely flattened, the degree of overlapping decreases and the cells adopt a polygonal morphology. These changes in endocardial cell morphology appear to be related to endocardial cell activity. It is suggested that the whole endocardial cushion, not just the cells that migrate into the cushions, is involved in cushion development. The activity of the endocardial cells may be related to the maintenance of the integrity of the endocardium.