Young K C, Wallis M G, Ramsdale M L
Department of Medical Physics, St Luke's Hospital, Guildford.
Clin Radiol. 1994 Jul;49(7):461-5. doi: 10.1016/s0009-9260(05)81741-6.
From its inception, the UK National Breast Screening Programme (NHSBSP) has recognized that optimum image quality of the mammographic screening test is a key objective. The overall optical density of the mammography film is one of the factors expected to have a significant effect on the image quality of the mammogram with the potential to influence cancer detection. In a previous review of the performance of mammography equipment in the NHSBSP, it was observed that there was a very wide range in the mammographic film densities used at different breast screening centres. In this study a mammography test object was used to show experimentally that, for a typical mammography system, image quality increased substantially with increased film density. Summary data was therefore requested from radiologists in the NHSBSP on the rate of detection of small invasive cancers (diam. < or = 10 mm) and the typical film density used during that year. Proforma were completed for 61 annual sets of results from 31 screening centres involving over 500,000 women. Where centres reported using film densities of less than 1.2D the average small cancer detection rate was 0.12% +/- 0.01%, as compared to an average of 0.17% +/- 0.01% for centres using higher film densities. The results indicate that there is a need for national guidelines in the setting of film densities, and a range for target film densities of 1.4D to 1.8D has been suggested. Attention to optimizing image quality by increasing film density is of particular importance to any screening centre where film densities of less than 1.2D are used, as there may be the potential to increase the detection of small breast cancers by as much as 50%.
自成立以来，英国国家乳腺筛查计划（NHSBSP）就认识到乳腺钼靶筛查测试的最佳图像质量是一个关键目标。乳腺钼靶胶片的总体光学密度是预期会对乳腺钼靶图像质量产生重大影响的因素之一，有可能影响癌症检测。在之前对NHSBSP中乳腺钼靶设备性能的审查中，观察到不同乳腺筛查中心使用的乳腺钼靶胶片密度范围非常广泛。在本研究中，使用了一个乳腺钼靶测试物体来通过实验表明，对于典型的乳腺钼靶系统，图像质量会随着胶片密度的增加而显著提高。因此，向NHSBSP的放射科医生索取了关于小浸润性癌（直径≤10毫米）的检出率以及当年使用的典型胶片密度的汇总数据。为来自31个筛查中心的61组年度结果填写了表格，涉及超过50万名女性。在报告使用胶片密度低于1.2D的中心，小癌症的平均检出率为0.12%±0.01%，而使用较高胶片密度的中心平均为0.17%±0.01%。结果表明，需要制定关于胶片密度设定的国家指南，并建议目标胶片密度范围为1.4D至1.8D。对于任何使用胶片密度低于1.2D的筛查中心来说，通过提高胶片密度来优化图像质量尤为重要，因为这有可能将小乳腺癌的检出率提高多达50%。
