全数字乳腺摄影机最佳曝光条件的探讨

目的 探讨并找出全数字乳腺摄影机(FFDM)的最佳曝光条件。方法 用全数字乳腺X 线摄影机对Fluke NA 18-220 乳腺模体进行自动曝光控制(AEC)摄影,记录曝光条件为29kV、40mAs,用手动调整不同的mAs值(24、28、32、36和45mAs)和kV (22、23、25、27和31kV)对模体曝光,由4位影像学家在相同条件下进行软阅读,并按照美国放射学会(ACR)的评分标准对模体中的钙化点、尼龙纤维、肿块灶进行打分,对所得数据进行方差分析(ANOVA)。结果 在相同的摄影电压29 kV下,手动曝光条件下32mAs和AEC的40mAs的影像信息的评价分值差异没有统计学意义(P>0.05),说明这2种摄影条件对乳腺摄影体模内容物的显示基本相同,但二者的辐射剂量确有明显的不同。在相同的摄影电流40mAs下,27kV和29kV的影像信息的评价分值没有统计学意义(P>0.05),说明这2种摄影条件对乳腺摄影体模内容物的显示基本相同,但二者的辐射剂量不相同。结论 在保证影像质量的前提下,自动曝光控制摄影条件初始设定水平的合理性应进行必要的检测来验证。

Optimization of exposure factor in full-field digital mammography

Objective To investigate and find out the optimization of exposure factors in full-field digital mammography.Methods The images of NA18-220 mammography phantom were taken at FFDM system with automatic exposure control and the exposure factors were recored. The phantom with FFDM system were exposed by varying mAs (24, 28, 32,36 and45mAs)with the same kV of AEC. The phantoms with FFDM system were exposed by varying kVs (22,23,25,27 and 31kV) with the same mAs of AEC. The exposure factors were recorded. The images on monitor with the best window width and window level were read by four independent radiologists. The image groups of specks,nylon fibers and masses were assessed by the four experienced readers according to the criteria of 1999 Mammography Quality Control Manual for American College of Radiology. Statistical analysis was performed using analysis of variance.Results The scorings of specks, nylon fibers and masses were not statistically significant(P>0.05) at the exposure factors between 29kV,40mAs and 29kV,32mAs. But their exposure doses were different.The imaging quality of the phantom was not significantly different (P>0.05) between 40mAs,29kV and 40mAs,27kV. But their exposure doses were different.Conclusions To ensure the imaging quality, the AEC of primitive set should be detected.