用于神经细胞实验研究的低频交变磁场发生器的研制

本文介绍了一种用于神经细胞实验研究的低频磁场波形发生器。目的：为低频磁场辐照与肿瘤实验提供工具。材料与方法：采用单片机控制，用户手动选择参数。输出一定波形，强度和占空比的信号，经功放电路放大后得到低频磁场。本文将详细讨论仪器中波形发生的部分。结果：本仪器磁场强度最高可达100mT，频率0-500Hz。结论：仪器完全满足实验需要。     

感应式磁声成像正问题数学模型及仿真

就感应式磁声成像的正问题,探讨该新型功能成像方法的可行性.建立了感应式磁声成像正问题的数学模型,并利用有限元软件Comsol Multiphysics3.4进行仿真实验,得到不同电导率分布的导体内部的感应电流分布及声压分布;同时,研究了线圈与物体相对位置参数α对感应电流的影响.仿真结果表明,感应电流密度在中心位置处为零,在电导率边界处变化较大;声压分布在中心位置处为零,在边界处变化较大.仿真结果与理论推导相符,进一步说明可由声信号重建物体内部的电导率分布方法的可行性.     

基于声学不均匀特性的磁感应磁声成像声压解析

目的 依据人体声学参数,探索磁声耦合成像声信号在声学非均匀媒介中的传播对检测结果的影响.方法 参考人体组织声学特性建立仿真模型,借助有限元分析工具进行电磁场仿真,采用时域有限差分方法求解磁声信号在仿真模型中的传播,并在自由空间采集声压信号.最后,对比研究磁声信号在声学均匀模型和声学非均匀模型中的传播过程.结果 在两个声学模型中声源分布相同,声学非均匀模型中采集的声压信号峰值数量多于声源边界,且声压峰值间的时间间隔与声源边界之间的距离不匹配.结论 初步揭示了声学非均匀特性对磁感应磁声成像的影响,为声学非均匀媒介的重建算法研究奠定了一定基础.     

应用PVDF压电传感器测量诊断超声在宫腔内的辐照量和腹部软组织声衰减的方法

在超声诊断已成为妇产科和计划生育查孕查环查病的常规首选方法的情况下，其安全性问题更为世人关注。本文叙述应用一个安装在产科器械内的ＰＶＤＦ压电超声传感器测定了两种不同类型的Ｂ超仪在宫腔内产生的声场中的最大正、负声压及其典型声压波形，对５１例测量结果进行了分析。宫内测得的最大正、负瞬时声压值分别达到１．５ｘ１０５Ｐａ和－１．２５ｘ１０５Ｐａ；空间峰值时间峰值声强（Ｉｓｐｔｐ）达１．３２Ｗ／ｃｍ２；最大声强（Ｉｍ）达０．４４Ｗ／ｃｍ２．空间峰值脉冲平均声强（Ｉｓｐｐａ）达０．３１Ｗ／ｃｍ２；空间峰值时间平均声强（Ｉｓｐｔａ）达０．７４ｍＷ／ｃｍ２。１６例测量声压与Ｂ超仪在自由场中测得值相比较，可计算出超声所经过的软组织中的综合平均衰减为１．２４±０．１９ｄＢｃｍ－１ＭＨｚ－１。采用宫腔内直接测量方法获得的诊断超声剂量参数和衰减系数对妇产科超声诊断安全性的研究具有重要参考价值。     

HIFU治疗中媒质特性对声聚焦影响的研究

目的:研究声衰减系数、声速、温度等媒质参数对声聚焦的影响。方法:用瑞利积分对凹球面自聚焦超声换能器进行声场模拟。结果及结论:媒质的特性参数不同,聚焦表现不同的特点。声衰减系数增大,焦斑向声源靠近,且焦斑缩短;声速越大,焦距越小,但焦区最大声压升高,焦斑的面积增大;温度变化不大时对声聚焦的影响不明显。     

X(γ)刀输出吸收剂量的测量与验证

目的：目前，国内X（γ）刀的国家检定规程正在起草之中，本文的目的是为X（γ）刀剂量测量提供合理的设备与吸收剂量计算方法。材料与方法：利用德国PTW-UNIDOS剂量仅与有效体积为0．015cc的针尖电离室及自制的小体积半导体探测器相匹配，在160mm直径的有机玻璃球形模体内测量X（γ）刀的输出吸收剂量，并验证其治疗计划的实际输出剂量，得到较满意的结果。结论：为了保证剂量的准确度，X（γ）刀治疗计划系统的实际输出剂量应定期在现场测量与验证，所用探测器的直径应小于射野直径的1／2，小灵敏体积的半导体探测器适宜X（γ）刀小野(如：Ф4mm)的测量。     

三维放射治疗计划系统临床物理数据的测量和验证

目的：探讨三维治疗计划系统测量的方法，分析拟合数据参数的计算方法，并且利用测量设备验证计算数据和拟合参数的准确性。方法：利用PTW和IBA三维水箱模体对多套三维计划系统进行所需的临床物理数据进行测量，对一种治疗计划系统依据测量数据进行拟合公式得到的线性系数进行分析，得到治疗计划时所需的计算数据，并且利用测量设备对计算数据进行验证。结果：利用测试数据得到的拟合数据及计算模型相关系数输入到TPS后得到相应的计算数据。通过测试设备验证：拟合数据PDD与测量PDD一致性比较好，误差小于±1％；Profiles数据在半影区域，小射野一致性误差最大可达到3％。对TPS的数据验证，单野PDD剂量点和Profiles数据点均能在±3％以内。结论：了解三维治疗计划系统的计算模型和参与物理数据的测试对TPS的质量保证和质量控制具有积极意义。     

基于滤波反投影算法的血管内光声图像重建

将目前在光声断层（PAT）成像中得到广泛应用的滤波反投影（FBP）重建算法应用到血管内光声（IVPA）成像中,提出一种简单快速的二维图像重建方法。首先,对组织产生的光声信号进行滤波、逆卷积和时域一阶求导的预处理;然后,针对IVPA在血管腔内封闭成像的特殊性,采用权重法将预处理后的光声信号数据对导管以外的成像区域沿弧线进行反投影,得到成像平面内每个网格点处的初始光声压。最后,得到反映血管壁组织结构形态的横截面灰阶图像。对仿真血管模型的实验表明,采用所提出的方法重建IVPA图像的结构,相似性指标（SSIM）可达到 0.571 7。合理选择滤波函数、滤波截止频率以及测量位置数,可以提高IVPA重建图像的质量;对光声信号进行时域一阶求导处理,能有效地突出重建图像中的组织结构信息。该方法为后续图像重建算法的优化奠定基础。     

宫外宫缩波的信号成分分析

目的：研制智能型的分娩监控分析仪器，实现胎儿监护与助产控制一体化。方法：用分娩监护分析系统对18例分娩的产妇作宫外信号临床数据测量，并进行了信号分析。通过分娩监护分析系统的人工选点截波程序，从临床数据中截取55个波次的宫缩波和90个波次的胎动、腹肌波。用STATISTCA统计软件分析。结果：得到识别波形时间参数、幅值参数的判别参考阈值，较规则的宫缩时距均值为75s，下限值为55s。识别胎动和腹肌的下限幅值为1．33kPa(10mmHg)，时距上限值为10s。此四个阈值可用于宫外宫缩波的信号识别。     

多参数经皮神经肌肉电刺激仪的设计

目的：电刺激仪器是通过电流作用于目标组织，使目标组织产生相应的功能变化。刺激方式、刺激电流、波形等均会影响治疗效果。市面上现有的神经肌肉电刺激仪一般只有单一的治疗模式，局限性很大。为了有针对性地治疗不同肌肉疾病，我们设计了一个能够方便准确地控制刺激电流的多参数经皮神经肌肉电刺激仪系统：方法：设计了一个以STC12C5410AD单片机为核心控制芯片的多参数经皮神经肌肉电刺激仪系统，采用串口实现上下位机的通讯，通过软件编程，上位机发送波形、频率、脉宽、间隙时间、最大刺激电流等各项参数指令，由单片机控制D／A转换芯片DAC8532输出指定波形，经过高压开关保护电路加入恒流源电路，产生恒定的电流对目标组织进行刺激。系统加入多项安全控制措施，有效地避免了实际操作过程中的安全隐患；结果：通过对系统进行电阻测试，验证了系统为恒流型仪器，经过电阻的刺激电流由且仅由输入信号的各项参数确定，与电阻的大小无关。由临床试验证明了通过改变参数，可以改变刺激模式，并验证了该系统的安全性和有效性。结论：该系统能设置成临床上使用的经皮电神经刺激疗法的各种模式。安全有效，有利于临床实验和相关科研的开展。     

Use of a fibre-optic hydrophone in measuring acoustic parameters of high power hyperthermia transducers

A fibre-optic hydrophone consisting of a polarisation-maintaining fibre carrying light from a laser source has been used to measure the acoustic output parameters of a single focused hyperthermia transducer and a six-transducer assembly. Beam profiles of the transducers were measured using the fibre-optic hydrophone and the results compared with those obtained using a PVDF hydrophone. The acoustic power output from the hyperthermia transducer was measured using a radiation force balance. It was observed that the root mean square voltage of the fibre-optic hydrophone output is proportional to the square root of the acoustic power up to more than 80 W. It was also observed that, under continuous-wave operation, the fibre optic hydrophone can stand up to very high power (more than 200 W) without being damaged. As its sensing element is the fibre itself, whose diameter is considerably narrower than the width of the ultrasonic beam, it can provide resolution of about 80 microm in beam profile measurement. The fibre is a line sensor and a computer tomographic technique is used to recover the pressure profile from the hydrophone output voltage. In typical clinical operations, the six-transducer assembly is driven with less than 150 W of electrical power input. In such cases, each individual transducer receives less than 25 W of input power and non-linearity and generation of high frequency harmonics at the focus is not a significant problem.     

HS-OAE耳声发射检测系统的研制与开发

耳声发射(OAE)是产生于内耳耳蜗,经听骨链和鼓膜传导,释放到外耳道的音频能量,在临床中有广泛应用.本文详细介绍了HS-OAE耳声发射检测系统的研制.该系统基于个人计算机和多媒体声卡实现,能够检测TEOAE和DPOAE两种耳声发射信号.硬件方面,检测系统由声学传感器,前置处理器,多媒体声卡和计算机四部分组成;软件方面,除了能够检测两种耳声发射信号,系统还实现了对病案数据的管理,制作检测报告等辅助功能.检测系统的输出声学参量经过校准,符合有关要求.文章最后介绍了与同类检测设备ILO耳声发射检测仪进行的临床对照试验的情况.临床试验的结果表明,HS-OAE耳声发射检测系统已经具备临床应用水平.     

Automated gamma knife radiosurgery treatment planning with image registration, data-mining, and Nelder-Mead simplex optimization

Gamma knife treatments are usually planned manually, requiring much expertise and time. We describe a new, fully automatic method of treatment planning. The treatment volume to be planned is first compared with a database of past treatments to find volumes closely matching in size and shape. The treatment parameters of the closest matches are used as starting points for the new treatment plan. Further optimization is performed with the Nelder-Mead simplex method: the coordinates and weight of the isocenters are allowed to vary until a maximally conformal plan specific to the new treatment volume is found. The method was tested on a randomly selected set of 10 acoustic neuromas and 10 meningiomas. Typically, matching a new volume took under 30 seconds. The time for simplex optimization, on a 3 GHz Xeon processor, ranged from under a minute for small volumes (<1000 cubic mm, 2-3 isocenters), to several tens of hours for large volumes (>30,000 cubic mm, >20 isocenters). In 8/10 acoustic neuromas and 8/10 meningiomas, the automatic method found plans with conformation number equal or better than that of the manual plan. In 4/10 acoustic neuromas and 5/10 meningiomas, both overtreatment and undertreatment ratios were equal or better in automated plans. In conclusion, data-mining of past treatments can be used to derive starting parameters for treatment planning. These parameters can then be computer optimized to give good plans automatically.     

核医学仪器科学中的电路仿真

目的：核电子学可应用到核医学诊断领域,为核医学研究提供硬件支持。提高核仪器的电路性能可从根本上促进核医学的发展。借助电路仿真,本文研究核电子学中一个重要的基本部件,电荷灵敏前置放大器。该前置放大器在高分辨率能谱测量系统中有着广泛的应用。方法：我们利用Pspice,orCAD电路仿真软件,对电荷灵敏前置放大器的基本电路,进行了温度效应、噪声效应和其他主要性能指标的仿真分析,并与理论值进行了比较。通过调节电路参数,可动态观察输出结果如输出电压波形,并可形象地观察工作温度的变化对输出信号和输出噪声的影响,从而了解电路指标的温度效应。结果：对变换增益和平均计数率等主要电路参数的仿真结果和理论一致。泄放电阻的使用可以释放累加的电荷信号,使放大器工作在线性范围。分布电容是产生前置放大器噪声的主要原因,减小噪声必须减小分布电容。输出噪声在正常的工作频率范围内,会随温度增加而增大。结论：在高分辨率能谱分析仪设计中,使探测器和前置放大器系统的信噪比最大化是至关重要的。充分考虑电路的温度和噪声等效应是设计高性能前置放大器的基础,有助设计低噪声的前置放大器。电路仿真具有实现快、输出结果形象、可将如噪声效应抽离进行分析等特点,在核电子学以及医学仪器设计方面有广泛的应用空间。     

A sensitivity analysis of a personalized pulse wave propagation model for arteriovenous fistula surgery. Part A: Identification of most influential model parameters

Previously, a pulse wave propagation model was developed that has potential in supporting decision-making in arteriovenous fistula (AVF) surgery for hemodialysis. To adapt the wave propagation model to personalized conditions, patient-specific input parameters should be available. In clinics, the number of measurable input parameters is limited which results in sparse datasets. In addition, patient data are compromised with uncertainty. These uncertain and incomplete input datasets will result in model output uncertainties. By means of a sensitivity analysis the propagation of input uncertainties into output uncertainty can be studied which can give directions for input measurement improvement. In this study, a computational framework has been developed to perform such a sensitivity analysis with a variance-based method and Monte Carlo simulations. The framework was used to determine the influential parameters of our pulse wave propagation model applied to AVF surgery, with respect to parameter prioritization and parameter fixing. With this we were able to determine the model parameters that have the largest influence on the predicted mean brachial flow and systolic radial artery pressure after AVF surgery. Of all 73 parameters 51 could be fixed within their measurement uncertainty interval without significantly influencing the output, while 16 parameters importantly influence the output uncertainty. Measurement accuracy improvement should thus focus on these 16 influential parameters. The most rewarding are measurement improvements of the following parameters: the mean aortic flow, the aortic windkessel resistance, the parameters associated with the smallest arterial or venous diameters of the AVF in- and outflow tract and the radial artery windkessel compliance.     

Evaluation of acoustic shock induced early hearing loss with audiometer and distortion product otoacoustic emissions

Background: Acoustic shock injury has been described as a permanent injury to the auditory system either due to daily noise dose of in excess of 85 decibels or very loud impulse sound reputed to be in excess of 120 decibels and acoustic incidents. This study was performed to compare the results of audiogram and the newer diagnostic method distortion product otoacoustic emissions (DPOAEs) parameters due to acoustic shock injury in call center professionals working in a noisy environment and prone to acoustic injury. Materials and Methods: Hearing functions of 340 subjects were first assessed with pure tone audiometry and then DPOAEs results were compared among acoustic shock exposed subjects with normal audiogram and those with abnormal audiogram. Results: Out of 340 acoustic shock exposed subjects 304 were normal on audiometric testing and 34 had abnormal audiograms. Subsequently on DPOAE testing out of 304 acoustic shock exposed subjects with normal audiogram 125 failed and 181 passed. Conclusions: This study showed that DPOAEs are more sensitive than audiometry to detect pre-symptomatic inner ear damage. It may play a role as screening and monitoring test for acoustic shock-exposed workers.     

Computer assisted optimization of an electromagnetic transducer design for implantable hearing aids

A simple, contactless electromagnetic transducer design for implantable hearing aids is investigated. It consists of a coil and a permanent magnet, both of which are intended for implantation in the middle ear. The transducer is modeled and optimized using computer simulations, followed by experimental verification. It is shown that the proposed transducer design can, because of its size and geometry, allow implantation through the external auditory canal, and provide a sufficiently high acoustic output corresponding to approximately 120 dB sound pressure level. It can be optimized to be tolerant of radial displacements between coil and magnet of up to 1 mm.     

Computerised analysis of auscultatory sounds associated with vascular patency of haemodialysis access

Vascular access for renal dialysis is a lifeline for about 120 000 individuals in the United States. Stethoscope auscultation of vascular sounds has some utility in the assessment of access patency, yet can be highly skill-dependent. The objective of the study was to identify acoustic parameters that are related to changes in vascular access patency. The underlying hypothesis is that stenoses of haemodialysis access vessels or grafts cause vascular sound changes that are detectable using computerised data acquisition and analysis. Eleven patients participated in the study. Their vascular sounds were recorded before and after angiography, which was accompanied by angioplasty in most patients. The sounds were acquired using two electronic stethoscopes and then digitised and analysed on a personal computer. Vessel stenosis changes were found to be associated with changes in acoustic amplitude and/or spectral energy distribution. Certain acoustic parameters correlated well (correlation coefficient=0.98, p<0.0001) with the change in the degree of stenosis, suggesting that stenosis severity may be predictable from these parameters. Parameters also appeared to be sensitive to modest diameter changes (>20%), (p<0.005, Wilcoxon rank sum test). These results suggest that computerised analysis of vascular sounds may be useful in vessel patency surveillance. Further testing using longitudinal studies may be warranted.     

HIFU在牛肝组织中的传播衰减研究

运用辐射压力法研究高强度聚焦超声在牛肝组织中的传播衰减。在室温 2 0℃下 ,利用 4种治疗超声换能器 ,在不同的换能器表面输出声功率下 ,分别测量 2 0、4 0、6 0、80 m m不同厚度新鲜离体牛肝在放入脱气水前后的声辐射力 F、F′,然后计算出声衰减。使用治疗超声换能器 4 ,对于不同辐照深度 ,以声强 ISATA=2 2 .0× 10 3W/cm2、辐照时间 5 s的超声剂量定点辐照新鲜离体牛肝 ,以断层方式剖开后测量凝固性坏死组织体积。研究结果表明 ,对于一个具体的治疗超声换能器 ,在牛肝厚度一定时 ,辐射力穿透率 F′/F法与换能器表面声强及样品近治疗超声换能器表面声窗面积无关。采用最小 F′/F法拟合得出辐射力穿透率随牛肝厚度增加呈指数规律递减 ,且与凝固性坏死组织体积随牛肝厚度 (辐照深度 )增加呈指数规律递减趋势一致。采用最小二乘法拟合得出高度聚集超声在牛肝组织中传播的声衰随频率近似线性增加且呈幂函数关系。这为进一步研究高强度聚焦超声治疗剂量学提供了实验依据