权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Patient Exposure and Image Quality in Medical X-ray Imaging Including Scatter

医学 X 射线成像（包括散射）中的患者曝光和图像质量

基本信息

批准号：
62580182
负责人：
KANAMORI Hitoshi
金额：
$ 0.83万
依托单位：
Kyoto Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1987
资助国家：
日本
起止时间：
1987 至 1988
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-62580182/
关键词：
Medical x-ray imaging Scattered x-rays Patient exposure Image quality X線スペクトル

项目摘要

In order to measure X-ray spectra of scattered radiation together with primary beam by using a planar Ge detector, we have confirmed that the active area of a 10mm x 7mm detector is 7mm in diameter and the available incident angle is within 20 . We prepared conic Pb collimators of various maximum incident angles of up to 20 . Scatter rejection effects of the air-gap method and angular distributions of the scattered radiation were analyzed by experiments and computer simulation techniques. Variables were 70 kV of tube voltage, an object of 20-cm acrylic resin, 2-cm and 30-cm fields, and object-detector distances of 1 to 50 cm. The results show that scatter fractions do not decrease prominently by the air-gap method for the 30-cm field, but they decrease noticeably for the 2-cm field. For the 30-cm field we have obtained angular dependence relations by attaching beam stoppers of various diameters to the exit surface of the object. It was confirmed that the larger scatter angle yielded the lower mean energy and the lower exposure. These phenomena are caused by the Compton effect.The information spectrum given by us in 1984 is modified by the effect of scatter which decreases the contrast of radiographs. The modification is simply that the signal Wiener spectrum is multiplied by (1-s)^2, where s is the scatter rate. Also the effects of blurs due to object motion are inserted in the information spectrum, by inserting the MTF caused by the blur into the signal Wiener spectrum. Examples are demonstrated, where the detectability of low-contrast objects and resolution of highcontrast objects are successfully explained by information spectral values in low- and high-frequency ranges, respectively.The scatter degrades the image quality but decreases the patient dose. These two competitive effects should be investigated, and the best scatter ratio for each object should be found.

为了用平面Ge探测器测量散射辐射和主光束的X射线能谱，我们确定了10 mm×7 mm探测器的有效区域直径为7 mm，可用入射角在20以内。我们制备了各种最大入射角可达20度的圆锥形铅准直器。通过实验和计算机模拟技术，分析了气隙方法的散射抑制效应和散射辐射角分布。变量是70千伏的管电压，20厘米的丙烯酸树脂物体，2厘米和30厘米的磁场，以及1到50厘米的物体探测器距离。结果表明，气隙方法对30 cm场强的散射分量没有明显的减小作用，但对2 cm场强的散射分量有明显的减小作用。对于30厘米的光场，我们通过在物体出射表面附加不同直径的束阻止器，得到了角度依赖关系。结果表明，散射角越大，平均能量越低，曝光量越小。这些现象是由康普顿效应引起的。我们在1984年给出的信息谱被散射效应修正了，从而降低了射线照片的对比度。修改的方法简单地是将信号维纳谱乘以(1-S)^2，其中S是散射率。此外，通过将由模糊引起的MTF插入到信号维纳谱中，将由于对象运动引起的模糊的影响插入到信息谱中。实例表明，低对比度目标的可探测性和高对比度目标的分辨率分别可以用低频和高频范围的信息光谱值来解释。散射降低了图像质量，但降低了患者的剂量。应该研究这两种竞争效应，并找到每个对象的最佳散布比。