乳腺计算机X射线摄影曝光条件的研究

目的通过比较乳腺摄影屏-片系统与计算机X射线摄影(CR)系统的曝光条件,以及不同曝光量对乳腺CR影像的影响,探讨乳腺CR摄影条件的优化原则。方法应用屏-片组合和CR,分别采用26、28、30 kV对fluke NA 18-220 乳腺模体采用自动曝光控制(AEC)模式进行摄影,并记录曝光量数值(mAs),对CR影像进行处理。同时CR采用上述相同kV、照射野,以及不同的曝光量对模体进行摄影,并对CR影像进行不同的处理。所获图像由4位放射医师进行双盲阅片,按照美国放射学会(ACR)的评分标准评价打分。结果采用自动曝光模式,乳腺CR摄影的曝光量明显高于传统屏-片组合的曝光量;乳腺CR摄影的曝光量降低到标准自动曝光模式的1/2~1/3时仍能满足诊断要求,此时的曝光量较屏-片组合采用自动曝光模式的曝光量低。结论乳腺CR摄影采用不经重新校正的自动曝光模式时,曝光量明显增加;符合诊断要求的乳腺CR摄影所需曝光量可低于屏-片组合,合理使用CR是降低乳腺CR摄影剂量的关键。

Exploration of the exposal condition of mammography with computed radiology

Objective To explore the optimal condition of mammography on computed radiology system (CRS) through comparing the exposal condition of mammography using radiology screen or film system (RSFS) and CRS,as well as the effect of different doses for CRS images.Methods The fluke NA18_220 mammographic phantom were photographed with 26, 28 and 30 kV X_ray in automatic exposure control (AEC) model. And the exposure doses were recorded, the CRS images were processed. Subsequently the same mammographic phantom were photographed with the same kV of X_ray and irradiation field as well as different exposure doses in same model, and the CRS images were processed again. The images of SFS and CRS were read by four independent radiologists under mixed condition. The images of calcification,nylon fibers and masses were assessed by the four experienced readers according to the criterion of American College of Radiology.Results On the AEC model, the exposed dose of CRS was higher than that of RSFS, but the exposure dose lowered to the 1/2_1/3 of the former, the image quality may satisfy the clinical demand, and the exposed dose was lower than SFS.Conclusions The exposed dose may rise distinctly if the image is taken on CRS with no calibration AEC, and the image may satisfy the clinical demand with lower exposed dose than RSFS. So how to use CRS reasonably plays a key role in mammography.