共查询到20条相似文献，搜索用时 515 毫秒
1.
超声波的特性及在医学诊断中的应用 总被引：1，自引：0，他引：1
刘凤兰 《邢台职业技术学院学报》2008,25(3):101-103
本文用声学理论论述了声源辐射的能量与频率的关系、声传播的集柬性与频率的关系。谈了声波的衰减、在不均匀介质中传播时的性质、声源相对介质运动时的多普勒效应及应用。概述了利用超声波来携带或传递生物组织内部信息的原理,介绍了超声显像及其发展。 相似文献
2.
3.
4.
目的：探讨实时动态四维超声在胎儿畸形产前诊断的应用价值。方法：应用E8、VOLUSON730四维超声对38679例妊娠18～37周胎儿进行常规二维和实时四维超声检查。结果：38679例胎儿中共检出胎儿畸形235例,其中胎儿神经系统畸形65例,颜面部畸形28例,颈部（颈部淋巴水囊瘤）畸形14例,心脏畸形39例,胸部畸形14例,膈疝10例;腹部畸形12例,泌尿系统畸形17例,四肢骨骼畸形36例。结论：四维超声成像较二维超声能提供更丰富的诊断信息,全面直观地显示胎儿畸形,提高了产前诊断胎儿畸形的准确率,具有重要的应用价值。 相似文献
5.
利用Microsoft.net作为开发平台,完成超声相控阵无损检测自动成像系统的开发和设计。该系统可以通过USB接口控制相控阵电路硬件系统阵元发射,完成数据实时采集和数据实时成像任务。系统同时支持A扫、B扫和S扫等多种超声相控阵扫查方式,同时成像参数、成像方式可以通过界面参数进行选择,并能实现图像放大缩小、光标定位、图像标尺标定和实时系统参数校正,采集到的数据可根据不同的扫查方式,实现3种格式的文件存储。通过自主开发超声线控阵无损检测自动成像系统节约了成本并拥有独立的知识产权。该系统方便灵活,加深了对超声相控阵信号成像的直观理解,有助于推动相控超声技术在无损检测中的应用。该系统也可以植入便携式设备,方便检测人员的使用。 相似文献
6.
吴中享 《初中生世界(初三物理版)》2011,(Z1)
一、内容概述本讲学习内容由声现象和光现象的重点部分组成.在声现象部分,通过相关实验,初步认识声音产生和传播的条件;了解乐音的特性;了解现代技术与声现象有关的应用;认识噪声的危害及防治.在光现象部分,通过实验探究,了解光在同种均匀介质中直线传播的特点;了解光的反射定律和折射规律;了解平面镜成像的特点,知道凸透镜成像的规律,并了解凸透镜成像的应用等.二、考点解读 相似文献
7.
8.
9.
为了提高包含有交界面的三维复杂流动问题的求解精度，将二维坐标系中的Youngs算法公式推广到三维坐标系应用，根据流体体积分数的定义，在二维直角坐标系Youngs算法的基础上，把介质分界面近似为平面，通过引入修正系数，实现了Youngs算法在三维坐标系中的应用，给出计算方法，并编写程序进行算例验证，数值模拟了具有复杂边界的空中爆炸形成冲击波的形成和传播过程，通过数值试验，证明了Youngs算法在三维坐标系中成功的应用． 相似文献
10.
用光纤迈克尔逊干涉仪方法,建立了一种相干门层析成像实验装置,并用该装置测量了金属丝样品在奶粉溶液和土豆片两种混沌介质的一维和二维成像信号,给出了由OCT信号重建的灰度图.并对系统性能和结果做了分析. 相似文献
11.
FAN Bing WANG Xiao-ying LI Miao ZHANG Yu-dong ZHANG Bao-cui LUO Jian 《重庆大学学报(英文版)》2013,12(4):147-154
The aim of this study was to compare differences in imaging quality at different injection rates of gadobutrol(Gadovist? 1.0M) for dynamic supra-aortic imaging by contrast-enhanced magnetic resonance angiography(CEM RA). In 6 healthy volunteers,dynamic CEM RA examinations were performed twice at a 7 d interval with a gadobutrol dose of 0.1 mmol given to 1 kg body mass. For the two examinations,the contrast medium was injected at rates of 1.5 mL/s and 2.0 mL/s,followed by 20 mL normal saline injected at the same rate. Using a GE Signa 3.0T M R apparatus and the time-resolved imaging of contrast kinetics(TRICKS) technique,scanning was performed continuously for 15 phases at a time resolution of about 2.4 s. Vascular reconstruction was undertaken by multiplane reconstruction and maximum intensity projection techniques. Two radiologists experienced in CEM RA diagnosis subjectively evaluated the contrast effect,vascular detail,and pseudo-shadow of all images,and graded them via a 5-point scale. With the two drug injection rates,the image quality,peak signal-to-noise ratio(SNR) and contrast-to-noise ratio(CNR) were compared for imaging of the infra-aortic arch,brachiocephalic trunk,subclavian artery(left/right),common carotid artery(left/right),internal carotid artery(left/right),and external carotid artery(left/right). Characteristics of the time-signal-intensity(T-S-I) curves were also analyzed at the two injection rates. All studies were performed successfully,without any complications. There was good image quality with both gadobutrol injection rates of 1.5 mL/s and 2.0 mL/s,and subjective scores for image quality,SNR and CNR were not significantly different between the two rates(P 0.05). The time-to-peak(TTP) from the hand dorsal vein injection site to the carotid artery ranged from 16.0 s to 27.1 s(mean 21.7 s ±3.4 s) in the 6 subjects,and was also not significantly different between the two drug injection rates(P 0.05). We conclude that dynamic CEM RA examination of the supra-aortic arch with gadobutrol injection at a rate of 1.5 mL/s was feasible,and satisfactorily reflected vascular shape and dynamic blood flow information. 相似文献
12.
鲁静 《湖北第二师范学院学报》2013,(8):53-55
水下环境中的介质和悬浮颗粒产生了光散射现象,导致水下激光图像存在严重的图像退化问题,大大降低了目标图像的信噪比。本文通过对水下连续激光成像光路图的分析,推导由于前向散射和后向散射而产生的图像退化模型。 相似文献
13.
INTRODUCTIONHarmonicimaging (HI)isoneofthemostimportantultrasoundimagingproceduresdevel opedrecently,differingfromfundamentalimag ing (FI)bytransmittingultrasoundatonefre quencyandreceivingitattwoormoretimesthetransmittedfrequency .Clinicalapplicationshad… 相似文献
14.
Objectives: To directly compare the quality of harmonic imaging (HI) and fundamental imaging (FI) in fetal echocardiography and to determine any differences in image quality between the two modalities. Methods: Fetal echocardiograms were performed with the use of FI and HI in 58 fetuses, image quality and visualization of left and right atria, left and right ventricles, mitral and tricuspid valves, aortic and pulmonary valves, left and right ventricular outflow tracts were evaluated and compared between FI and HI. Results: Mean HI scores were higher than mean FI scores (2.73±0.43 vs 2.16±0.69, P<0.001)for all the cardiovascular structures evaluated. Compared with FI, HI improved the image quality and visualization of fetal cardiac structures in subjects with both good (2.73±0.43 vs 2.88±0.32, P<0.001) and suboptimal (1.65±0.41 vs 2.58±0.47, P<0.001) echocardiographic windows. The interobserver correlation coefficient for the grading scores was 0.74 (P<0.001). Conclusions: harmonic imaging enhances and improves the image quality of fetal echocardiography; and has important potential role in cardiac imaging in the fetus. 相似文献
15.
16.
物体的成像规律及作图方法贯穿几何光学的始终,在折射或反射、特别是在光具组的成像过程中,往往会出现虚物的作图求像,而教材又没有具体阐明相应的内容,针对这种情况,在近轴条件下,用平行于主光轴的入射光线的性质阐明虚物在各光学元件中的成像规律,并对主光轴上虚物点的作用给出一般的方法。 相似文献
17.
Kulinder Pal Singh 《Resonance》2005,10(6):15-23
X-ray astronomy has benefited enormously with the deployment of imaging X-ray telescopes in space, leading to a veritable
revolution. Such telescopes require distortion free focusing of X-rays and the use of position sensitive X-ray detectors.
In this article I shall describe the importance of X-ray imaging, the optical principles behind the creation of images and
the instruments based on these principles. The various techniques used to fabricate such X-ray telescopes are described briefly.
The many types of detectors used in X-ray astronomy will be described in the second part of this article in a subsequent issue
ofResonance.
Kulinder Pal Singh is in the Department of Astronomy and Astrophysics of the Tata Institute of Fundamental Research, Mumbai.
His primary fields of research are X-ray studies of hot plasmas in stars, supernova remnants, galaxies, intergalactic medium
in clusters of galaxies, active galactic nuclei, cataclysmic variables and X-ray binaries. He is leading the development of
a soft X-ray imaging telescope for the ASTROSAT mission to be launched by India in 2007–2008. 相似文献
18.
19.
Kulinder Pal Singh 《Resonance》2005,10(7):8-20
The excellent X-ray images produced by X-ray telescopes require the use of detectors with imaging capability at the focal
plane of the telescopes. In this concluding part of the article on experimental techniques in X-ray astronomy, I describe
many X-ray detectors that have been used over the years. These can broadly be classified into two physical types: non-dispersive
and dispersive. Traditionally the simple non-dispersive types have been used extensively in X-ray astronomy. The advancement
of solid state technologies, cryogenics, and the quality of X-ray imaging has led to many new detectors of both types. Both
the traditional and the new types of detectors are described briefly here with emphasis on principles and some technical details.
Kulinder Pal Singh is in the Department of Astronomy and Astrophysics of the Tata Institute of Fundamental Research, Mumbai.
His primary fields of research are X-ray studies of hot plasmas in stars, supernova remnants, galaxies, intergalactic medium
in clusters of galaxies, active galactic nuclei, cataclysmic variables and X-ray binaries. He is leading the development of
a soft X-ray imaging telescope for the ASTROSAT mission to be launched by India in 2007–2008.
Part 1. Imaging Telescopes,Resonance, Vol. 10, No. 5, pp. 15–23, 2005. 相似文献
20.
Kavita Dorai 《Resonance》2005,10(12):203-216