Oda N, Nakata H, Murakami S, Terada K, Nakamura K, Yoshida A
Department of Radiology, University Hospital of Occupational and Environmental Health, Kitakyushu-shi, Japan.
Invest Radiol. 1996 Mar;31(3):126-31. doi: 10.1097/00004424-199603000-00002.
Optimal x-ray beam quality for chest computed radiography (CR) has not been determined. To investigate the optimal beam quality for chest CR, the authors measured the radiographic contrasts and compared the image quality of chest CR and screen-film (SF) radiographs using various x-ray tube voltages.
Chest CR and SF radiographs were obtained on a phantom lung and human volunteers with or without a variety of simulated lung opacities using various x-ray tube voltage levels. Exposures were set to maintain identical patient exposure doses for all images. The contrast between peripheral lung and rib or heart was measured on these images and the differences were compared. The quality of the images of each simulated opacity was evaluated by five radiologists using a five-point grading scale.
Contrast between peripheral lung and rib or heart increased on CR images obtained by lowering the tube voltage from 140 to 80 kV, but the degree of increase was less than half the increase on SF images. The CR images of the simulated opacities obtained using a lower tube voltage were judged to be superior to those obtained with a higher tube voltage. Scattered radiation was reduced on CR images with a lower tube voltage.
The image quality of chest CR was improved by using a lower tube voltage than that used for conventional SF chest radiography. Considering the problem of tube loading in clinical applications, a tube voltage of 100 kV is recommended for chest CR.
胸部计算机X线摄影（CR）的最佳X线光束质量尚未确定。为了研究胸部CR的最佳光束质量，作者测量了射线照相对比度，并使用不同的X线管电压比较了胸部CR和屏-片（SF）X线照片的图像质量。
使用不同的X线管电压水平，在模拟肺部模型和有或无各种模拟肺部混浊的人类志愿者身上获取胸部CR和SF X线照片。设置曝光量以确保所有图像的患者曝光剂量相同。在这些图像上测量外周肺与肋骨或心脏之间的对比度，并比较差异。由五名放射科医生使用五点分级量表对每个模拟混浊的图像质量进行评估。
通过将管电压从140 kV降低到80 kV获得的CR图像上，外周肺与肋骨或心脏之间的对比度增加，但增加程度不到SF图像上增加程度的一半。使用较低管电压获得的模拟混浊的CR图像被判定优于使用较高管电压获得的图像。较低管电压的CR图像上散射线减少。
与传统的SF胸部X线摄影相比，使用较低的管电压可提高胸部CR的图像质量。考虑到临床应用中的管负载问题，建议胸部CR的管电压为100 kV。
