Slone R M, Van Metter R, Senol E, Muka E, Pilgram T K
Electronic Radiology Laboratory, Mallinckrodt Institute of Radiology, Barnes-Jewish Hospital, St. Louis, MO 63110, USA.
Radiology. 1996 May;199(2):497-504. doi: 10.1148/radiology.199.2.8668802.
To study the effects of exposure error on the clinical utility of chest radiographs.
Under- and overexposed screen-film images were simulated by adding exposure offsets to the normalized CR log(10) exposure data from a computed radiography (CR) system and printed by using the sensitometric response of a medium-latitude system. The clinical utility of the overall image, lung, and soft tissue in 48 images were independently graded by eight radiologists.
Most variability in image scores was due to differences in exposure. About 95% of the lung regions and 75% of the soft-tissue regions were rated as having good or ideal clinical utility at the nominal exposure. About 80% of the overall images were rated as good or better for exposures within 40% [0.15 log(10) exposure] of the nominal. The overall image scores were heavily influenced by the lung region, and reader tolerance for exposure error was greater for soft tissue than for lung. The optimal exposure for soft tissue was about 60% [0.25 log(10) exposure] greater than for lung; therefore, no single exposure was optimal for the entire image.
Conventional medium-latitude screen-film systems have intrinsic limitations for capturing and displaying the wide transmittance differences in the thorax. The clinical utility of chest radiographs may be improved by developing better image capture and display techniques.
研究曝光误差对胸部X线片临床效用的影响。
通过对计算机X线摄影（CR）系统的归一化CR log(10)曝光数据添加曝光偏移量，模拟曝光不足和过度曝光的屏-片图像，并利用中纬度系统的感光响应进行打印。由八位放射科医生对48幅图像中的整体图像、肺部和软组织的临床效用进行独立评分。
图像评分的最大差异源于曝光不同。在标称曝光量时，约95%的肺部区域和75%的软组织区域被评为具有良好或理想的临床效用。对于在标称曝光量40%[0.15 log(10)曝光量]范围内的曝光，约80%的整体图像被评为良好或更好。整体图像评分受肺部区域影响很大，且读者对软组织曝光误差的耐受性高于肺部。软组织的最佳曝光量比肺部约高60%[0.25 log(10)曝光量]；因此，对于整个图像而言，不存在单一的最佳曝光量。
传统的中纬度屏-片系统在捕捉和显示胸部广泛的透光率差异方面存在固有局限性。通过开发更好的图像采集和显示技术，可能会提高胸部X线片的临床效用。
