磁共振成像前列腺射频线圈的研制

介绍一种经直肠的射频线圈，通过减小线圈到前列腺的距离，增加线圈的填充系数以及提高线圈的品质因子的办法提高成像的信噪比。为了验证设计的效果．用网络分析仪对线圈的射频特性进行了分析。应用体模对线圈进行了模拟人体环境的成像，并与商用的TORSO线圈成像数据进行了比较分析．结果显示所设计线圈图像的信噪比要高出三倍．且其它参数都达到了设计的要求。     

植入式单穴位电刺激系统研究

目的：为实现对目前危害人类健康和造成不良社会影响的一些慢性疾病的长期、有效治疗,提出了植入式单穴位电刺激方法,并设计了仪器。方法：整个系统分为体外发射端和植入体内的接收刺激端。在能量发射端利用三极管的旁路电容和发射电感组成半串联谐振。针对无线能量供电的应用,通过实验分析能量供应的效率。实验中．选择合适的无线传输参数,20匝直径为35mm的空心线圈作为发射线圈,传输频率为150～200kHz．接收端使用100匝直径为10mm的空心线圈。结果：完成了整个系统的样机,在接收端间隔5mm时能获得5～10mA电流．已经满足应用的要求。结论：样机可用于各种单穴位刺激实验。     

一种简单的沙门氏菌培养修改方法——可提高检出尿中致突变物质的灵敏度

此文介绍了一种修改的沙门氏短期生物学试验液体培养方法。本法在原来液体培养法的基础上稍加改进后,可以大大提高人尿中致突变物质检出的灵敏度。本实验用沙门氏标准菌株TA 98,吸烟者尿中提取的复杂混合物作为模型研究其致突变作用,证实该法比Ames推荐的标准平皿渗入法灵敏度高20倍,比以前的液体培养法灵敏度高13倍。用苯并芘试验的结果灵敏度提高了14倍。回变菌株从原来标准渗入法的70个/ng苯并芘提高到994个/ng苯并芘,而自发回变数未见增加。可见该法有利于人尿中致突变活性的研究。对于估计人在     

新型功率可调MIT激励源设计及其磁场分析

目的：设计输出功率可调的MIT激励源和3种类型的激励线圈,以提高MIT相位检测的精度。方法：通过选取PA19放大器芯片,设计200 kHz工作频率下可调输出的功率放大电路;通过计算,设计制作了螺线管线圈和2种聚焦线圈;最终测试比较各激励线圈的磁场分布,并在不同激励线圈的磁场下对圆柱形铁块进行相位测试。结果：激励源输出峰值电流大于1 A,圆形螺旋聚焦线圈的磁场由线圈轴线向两边衰减斜率最大,约为0.06 T/cm,且在该激励线圈磁场中,对铁块的相位检测结果最大。结论：该激励源输出功率可调范围大,采用圆形螺旋聚焦线圈磁场聚焦效果最佳、相位检测效果最好。     

基于ACR体模的磁共振射频线圈性能的对比

目的探讨不同射频线圈在磁共振成像中的性能特点。方法根据美国放射学院(ACR)推荐的射频线圈检测标准,基于ACR体模,通过Siemens 3.0T Verio磁共振仪测定12单元头颅矩阵线圈、12单元腹部线圈及大体线圈的图像信噪比、图像均匀度及信号伪影比。结果 12单元头颅矩阵线圈及12单元腹部线圈的信噪比在SE-T1WI序列中分别是大体线圈的16.41倍和14.1倍,在double SE-T2WI序列中分别是大体线圈的6.31倍和5.35倍。大体线圈的均匀度最好,12单元头颅矩阵线圈和12单元腹部线圈稍差,其中12单元头颅矩阵线圈的均匀度未达到标准要求。在信号伪影比检测中,12单元头颅矩阵线圈的信号伪影比最低,12单元腹部线圈和大体线圈次之,但均达到了头线圈的标准要求。结论 3种线圈的性能各有优势,需根据不同情况进行应用。     

关于出版物上数字的用法

1数字的增减要注意下列用词和概念1.1增加为过去的二倍 ,即过去为一 ,现在为二。1.2增加到过去的二倍 ,即过去为一 ,现在为二。1.3增加二倍 ,即过去为一 ,现在为三。1.4增加了二倍 ,即过去为一 ,现在为三。1.5超额百分之八十 ,即定额为一百 ,实数为一百八十。1.6降低了百分之八十 ,即原来是一百 ,现在是二十。1.7降低到百分之八十 ,即原来是一百 ,现在是八十。2不能用“降低×倍”或“减少×倍”的提法 ,只能用“降低百分之几”或“减少百分之几”。3计算超产数字不能用“完成了×年任务”或“跨进了二0××年”的提法。4不能随便增加或删掉…     

岛津SCT-100N-2S型CT机中几种高压元件故障的修复方法

<正> 一、高压发生电路中调压器的修复调压器的工作频率是在机器每扫描一个断层就工作一次(即调压器输出轮由电机带动,从调压器低端自动调到高端,X线曝光结束后又自动回到低端),总是满负荷运行,平均每天都要工作几百次以上,因而故障率较高,为此我们在实践中探索到如下修理方法:(1)调压器线圈局部烧焦的修理针对这样的故障,我们采取了烧坏几匝线圈更换几匝线圈的修理方法.具体做法是:先将烧坏的线圈从烧得历害处剪断,沿着两头向两端拆,直到将烧坏的线圈全部拆除,再用同样的漆包线接好,按原样绕上(一般只绕1-2圈)并与另一端接好.接头处下面垫好绝缘纸,上面用环氧树脂封注,然后在后缠的线圈上涂一     

基于定量对比方法的磁共振射频线圈的MatLAB图形化性能研究

目的为了验证磁共振成像中不同类型射频线圈的临床性能．我们以表面线圈．收发兼用型鸟笼线圈和八通道相控阵线圈为研究对象．分别测量了这三种线圈在Philips3．0T磁共振成像系统中的信噪比和图像均匀度。材料和方法在AAPM（美国医学物理师学会）推荐的方案测量信噪比和均匀度的基础上,增加对最终图像的MatLAB图形化分析,分别得到其两个互相垂直方向和整个平面上的信噪比空间分布。结果在体模中心的感兴趣区（ROI）中,收发兼用型鸟笼线圈和八通道相控阵线圈的信噪比分别是表面线圈信噪比的7倍和12倍以上．均匀度也都高于表面线圈的均匀度。结论收发兼用型鸟笼线圈和相控阵线圈在成像效果上均优于表面线圈;相控阵线圈能获得最好的信噪比．而收发兼用型鸟笼线圈则具有最好的均匀度。     

高场磁共振全身扩散成像图像质量评估与优化研究

目的通过比较不同扫描参数的图像质量,探讨全身背景抑制磁共振扩散成像（DWIBS）的最佳扫描技术。方法 15位健康志愿者、21例患者接受了DWIBS成像,通过ADC值、质量指数、SNR及AppCNR来评价不同扫描技术：体线圈和体部表面线圈扫描;SPAIR-EPI与STIR-EPI的比较。最后评价高分辨率MPR及MIP图像的可行性。结果体部表面线圈扫描的质量指数、SNR及AppCNR高于体线圈扫描（P〈0.01）,在b=800s/mm2时图像质量指数及AppCNR时最高（P=0.000）;STIR-EPI质量指数较高（P〈0.05）;STIR-EPI的AppCNR优于SPAIR-EPI（P〈0.05）。结论采用体部表面线圈,b=800s/mm2,层厚5mm,STIR脂肪抑制技术以及TR值在6000ms以上可以获得高质量的DWIBS图像。     

高频脉冲磁场动态检测技术研究

目的：为解决目前通用的经颅磁刺激设备不具有对磁场实时动态检测功能这一问题,基于法拉第电磁感应法,开展对10 kHz～1 MHz脉冲磁场动态检测技术的研究.方法：设计一种磁场动态测量与标定装置,选用正弦脉冲施加于磁场发生线圈,采集检测装置线圈上的感应电动势,通过信号处理电路完成所采集信号的求差、放大、滤波和积分处理,从而得到脉冲磁场参数.结果：该技术实现了对频率在10 kHz～1 MHz之间、强度为μΤ量级磁场的准确测量,测量结果通过标定,与真实值的相对误差小于2.5％,显示出较好的稳定性和一致性.结论：该技术能够对脉冲磁场进行较准确的测量和标定,可通过进一步的研究投入实际应用.     

Experimental studies of vibratory trauma of Corti's organ. I: Electrophysiological measurements

In the present-day environment, vibration concomitant with noise is most frequently observed, but even though it is regarded as only a weak, additional traumatic factor affecting the organ of hearing. This opinion is contrary to a number of reports on the damage of the hearing organ caused by vibration in workers of various branches of industry. As experiments on humans are rather difficult, the harmful effect of vibration is usually examined on laboratory animals. In the majority of studies dealing with this problem the presence of noise (purposely or casually) was found in most cases. The aim of this study was to determine the effect of isolated long-term whole-body vibration and vertical sinusoidal shaking (10 Hz frequency, 5 mm amplitude, and 2 g acceleration) on Corti's organ. The study was carried out on young guinea pigs of both sexes. Eighty four animals (30 control and 54 experimental) with Preyer's reflex and without otoscopically detectable changes were used. A group of 18 animals was subjected to vibration in noiseless shaking apparatus for 30, 90 and 180 days. After a one-month rest, cochlear microphonics were performed under urethane anaesthesia. Our modification of the phase-sensitive detection method was used. Cochlear microphonics at frequencies of 260 Hz, 500 Hz, 1 kHz and 2 kHz was recorded from the apex of the cochlea and for 4 kHz and 8 kHz from the region of the round window. As the cochlear microphonics values showed significant individual differences, all experimental samples were examined by means of non-parametric tests. The outcome of the study demonstrated a gradual but considerable cochlear microphonics voltage decrease in the range to 2 kHz. This result pointed to the generation of vibration-induced damage in outer hair cells of the fourth and third turnings of the cochlea in the guinea pigs under study.     

Influence of sonic noise on human stereoscopic depth perception.

Scientific establishment of the no-effect response to finite levels of exposure to a physical or chemical agent is indeed a rigorous exercise and is frequently controversial. In earlier research by Slutsky under direction of the senior author, a statistically significant increase in stereoscopic depth perception error was noted among 24 test subjects exposed to high intensity noise. Additional extensive research reported in this paper indicates that error in stereoscopic depth perception is not significantly altered by exposure to continuous white noise of short duration at levels ranging from 70 to 115 dBA. Furthernore, exposure of humans for periods of a few minutes to white noise in octave bands centered on 250 Hz, 1000 Hz, 4 kHz and 16 kHz at 115 dB does not affect their depth perception measured by the Howard-Dolman test. A comprehensive analysis of depth perception errors measured under noise exposure conditions (n = 4040) in comparison with those obtained under control conditions (n = 1430) produced a mean change in error of -0.38 mm, a statistically insignificant difference (p = 0.17). Even if such an error were attributable to high level noise, it should be noted that minus sign designates an improvement of depth perception in noise and that it is difficult to imagine visual tasks in which change in error of +/-0.38 mm at a distance of 6.0 meters is meaningful.     

太原市社区老年人听力损失影响因素研究

目的 了解太原市社区老年人听力损失人群分布特征,分析听力损失影响冈素.方法 采用多级抽样方法,在太原市官地、朝阳两社区选取60岁以上社区老年人384名,进行听力损失的一般问卷调查.采集5 ml晨起空腹血进行血糖、甘油三酯和胆固醇检测.采用GVSLN-TC-GK2000型听觉评估仪分别测两耳0.5、1、2、3、4、8 kHz听阈,取听力较好耳平均听阈(0.5、1、2 kHz听阈平均值),3、4、8 kHz听阈作为应变量;社会人口学资料、环境因素、生化指标为自变量,采用SPSS 13.0软件进行t检验、方差分析及累加logistic回归进行听力损失影响因素分析.结果 老年人听力损失90.9%,听力残疾为78.6%,其中1.3%配带助听器.单因素分析结果显示:平均听阈及3、4、8 kHz听阈值在不同年龄、性别、文化程度、血糖、胆周醇组间的差异均有统计学意义(P<0.01).累加logistic回归显示:除血糖仅纳人中低频组外,年龄、性别、文化程度、胆同醇均纳入各频段构建累加logistic回归模型.老年男性、高龄、高血糖、高胆固醇是听力损失危险因素,高文化程度是保护因素.结论 听力损失在老年人群具有较高发生率.年龄、性别、文化程度、血糖、胆同醇与听力损失存在关联,预防高血糖、高血脂的发生对延缓听力损失有益.     

On using multiple-jet nozzles to suppress industrial jet noise

This work investigates the efficacy of multiple-jet nozzles in reducing exposure to noise radiated from high-speed jet flows that are frequently used for cleaning and other purposes. A single-jet nozzle is replaced by one with multiple and smaller outlets with the same combined exit area. Noise generated by multiple-jet nozzles will shift to higher frequencies due to the smaller openings; thus, a portion of the sound energy is moved to the ultrasonic range and the audible noise levels will be reduced. In this study, nozzle outlet sizes of 2.2 mm, 2 mm, 1 mm, and 0.7 mm are tested at various flow rates. Results show that the noise-abating effect of using smaller outlets is significant. Although industrial jet flows, in general, have multiple noise-generating mechanisms, the multiple-jet approach is effective for flows ranging from the subsonic to the highly choked. Noise spectra show that the reduction of noise level in the audible range is related to frequency shifting. The comparison of overall sound pressure levels generated by 1-mm and 0.7-mm outlets shows that even a raise of frequency by 40% can have a notable effect. As for the concern that the multiple-jet nozzles may suffer a drop in thrust, as long as the total exit area is fixed, thrust loss generally is not serious. One potential hazard of the multiple-jet nozzle is that posed by noise at frequencies higher than 10 kHz or ultrasound. More investigations in this field are suggested.     

Dynamics of high-frequency hearing loss of operators of industrial ultrasonic devices

Summary This investigation was aimed at elucidating the dynamics of hearing loss in the range of 500 Hz to 20kHz of 26 Ultrasonic (Uls)-operators exposed to high-frequency noise exceeding known hygienic limits. Results of audiometric tests performed twice, before and after a period of three years, were compared. The determined hearing-threshold-shift in the range of 500Hz to 13 kHz could be explained as the effect of aging, whereas in the range of 13 to 17 kHz the stated mean threshold elevation of 2–5 dB, beyond the hearing loss connected with aging within three years, is the consequence of high-frequency noise exposure. On this basis the dynamics of high-frequency hearing loss of 1 dB/year in the case of continued exposure to high-frequency noise could be calculated. Apart from the observed threshold elevation, the fraction of ears responding to acoustic stimuli at the highest frequencies decreases by about 10% with frequency increase of 1 kHz in the range of 13 to 19 kHz. This indicates that the hearing organ is more susceptible to high-frequency noise at the highest hearing frequencies.     

噪声环境下传导性听力损失对骨导的保护作用分析

目的探讨噪声环境下传导性听力损失对骨导是否存在保护作用。方法 2009—2011年在广州开发区医院进行噪声危害职业健康监护的所检人员中选出48例存在单耳传导性听力损失的健康检查者,对其骨导听力进行对比分析。结果所选健康检查人员中,6 kHz频段有34人双耳骨导差大于10 dB,其中最大相差50 dB;4 kHz频段有28人双耳骨导差大于10 dB,即在4 kHz(t=33.830)及6 kHz(t=48.471)频段,双耳骨导阈值差异有统计学意义(均P0.05)。结论噪声环境下存在传导性听力损失对高频段听力,尤其是4 kHz和6 kHz频段的骨导具有保护作用。     

兔脑缺氧对脑阻抗影响的实验研究

目的：研究家兔脑缺氧时脑阻抗的定性变化,并优选最佳的电阻抗测量频率特性。方法：采用第四军医大学医学电子工程教研室研制的阻抗监护仪,将激励电流的幅度设为1．25mA,频率分别设为1、5、10、50、100和150kHZ,对兔短时缺氧和恢复供氧过程的脑部电阻抗变化过程进行监测。结果：兔脑短时缺氧过程中,脑阻抗明显升高,恢复供氧后．阻抗恢复初始状态。相同实验条件、不同激励频率的测量结果表明：在5kHz频率点,这一过程的阻抗值变化率最大（1．7％）,具有显著性差异（P〈0．001）,有统计学意义。结论：采用电阻抗成像技术对脑缺氧进行监测是可行的,同时采用不同的测量频率会得到不同的脑部电阻抗变化量,在所选测量频率点中．5kHZ时可以获得最高的脑缺氧灵敏度。     

Follow-up of hearing thresholds among forge hammering workers

Hearing threshold was reexamined in a group of forge hammering workers investigated 8 years ago with consideration of the age effect and of auditory symptoms. Workers were exposed to impact noise that ranged from 112 to 139 dB(A)—at an irregular rate of 20 to 50 drop/minute—and a continuous background noise that ranged from 90 to 94 dB(A). Similar to what was observed 8 years ago, the present permanent threshold shift (PTS) showed a maximum notch at the frequency of 6 kHz and considerable elevations at the frequencies of 0.25–1 kHz. The age-corrected PTS and the postexposure hearing threshold were significantly higher than the corresponding previous values at the frequencies 0.25, 0.5, 1, and 8 kHz only. The rise was more evident at the low than at the high frequencies. Temporary threshold shift (TTS) values were significantly less than those 8 years ago. Contrary to the previous TTS, the present TTS were higher at low than at high frequencies. Although progression of PTS at the frequencies 0.25 and 0.5 kHz was continuous throughout the observed durations of exposure, progression at higher frequencies occurred essentially in the first 10 to 15 years of exposure. Thereafter, it followed a much slower rate. Tinnitus was significantly associated with difficulty in hearing the human voice and with elevation of PTS at all the tested frequencies, while acoustic after-image was significantly associated with increment of PTS at the frequencies 0.25–2 kHz. No relation between PTS and smoking was found. PTS at low frequencies may provide an indication of progression of hearing damage when the sensitivity at 6 and 4 kHz diminishes after prolonged years of exposure. Tinnitus and acoustic after-image are related to the auditory effect of forge hammering noise.