【作者】 徐辉；

【导师】 岳保荣；

【作者基本信息】 中国疾病预防控制中心 ， 放射医学， 2010， 硕士

【摘要】 目的比较数字乳腺摄影中手动曝光控制与常用自动曝光控制(AEC)在影像质量方面的差异,探讨能否通过图像后处理方法提高影像质量和降低病人剂量,并达到以下目的：(1)验证乳腺数字摄影系统在现有临床诊断条件下能否降低病人剂量；(2)探讨在不同乳腺厚度时,图像后处理对影像质量的改善程度；(3)探讨对不同乳腺病变细节,图像后处理对影像质量的改善程度；方法分别选用CDMAM 3.4模体和TORMAM模体,在一套乳腺CR系统中进行5个不同厚度的曝光,每一个厚度分别进行4次不同剂量的曝光。分别为1次AEC全自动曝光和三次手动曝光,手动曝光的剂量分别为AEC曝光剂量的80%,60%,和40%。由三名观察者对模体影像进行两次评分,一次不改动显示器设置,直接对原始图像评分；一次可以任意调节显示设置至最佳显示条件。比较降低剂量后的图像结果与AEC曝光剂量的影像质量之间的差异。结果通过图像后处理能够改善影像质量。对于不同厚度的模体,通过图像后处理降低的病人剂量程度不一样。当等效模体厚度较低时(30,35mm),可以减少约20%-40%的剂量；当等效模体厚度增至40,45,50mm时,通过图像后处理可减少病人剂量约40%-60%。不同病变中,对于纤维丝细节,通过图像后处理可以降低20%以内的剂量；图像后处理对圆形细节的显示改善明显,剂量可降低60%；然而对于颗粒群细节,图像后处理作用不明显。结论(1)通过图像后处理,可以改善乳腺数字摄影中图像显示效果。(2)通过手动曝光降低曝光剂量,并对图像进行后处理,对于不同厚度乳房可以降低病人剂量20%-60%；(3)图像后处理对于不同类型的模拟细节,所起的作用不同。对于圆形细节,影像质量改善显著；对于纤维丝细节,影像质量有所改善；而对于颗粒群细节,通过图像后处理未看到影像质量的改善。更多还原

【Abstract】 ObjectiveThis study aimed to investigate the difference of image quality between manual exposure and automatice exposure control (AEC) in a digital mammography, and the effect of image post-processing on improvement of image quality. To confirm the possibility of reducing patient dose through the methods of maunual exposure and image post-processing in digital mammography.MethodCDMAM 3.4 phantom and TORMAM phantom were selected and exposured in a CR system in 5 different phantom thickness. Under each thickness there are 4 dose levels. These corresponded to 100%,80%,60% and 40% dose. Three observers interpreted the all image. Each image was scored twice:unprocessed images and post-processed image. The differences of image quality were compared between three lower dose images and 100% dose image.ResultsThe image quality can be improved through image post-processing. The patient dose could be reduced from 20% to 40% through image poss-processing when the equivalent breast thickness is 30 and 35mm. When the equivalent breast thickness up to 40,45, and 50mm, the dose can be reduced from 40% to 60%. For filament details, the dose can be reduced 20% after image post-processing.For the circular details, the effects of image post-processing appear to significant and the dose can be reduced by 60%. However for the partical details, the effect of image post-processing on image quality is not obvious.ConclusionsThe image quality can be improved through image post-processing. For different equivalent breast thickness, the patient dose can be reduced from 20% to 60% through manual exposure and image post-processing. The effects of image post-processing are different on different phantom details.For filament details and circular details, the improvement of image quality is significant.The dose can be decreased by within 20% and 60% separately. However for the partical details, the effect of image post-processing on image quality is not obvious.更多还原