Sabol J M, Tam K K, Plewes D B
Department of Medical Biophysics, University of Toronto, Sunnybrook Health Science Centre, Ontario, Canada.
Med Phys. 1994 Oct;21(10):1523-33. doi: 10.1118/1.597262.
The detection of cancer in the radiographically dense breast is problematic, since the breast will produce a range of exposure that exceeds the useful dynamic range of high contrast film-screen combinations. It has been shown previously that mammographic scanning equalization radiography (MSER) can be used to overcome the latitude limitations of film-screen mammography. However, the tube loading of MSER is orders of magnitude greater than conventional mammography. A new rotary geometry for equalization radiography is proposed, in which the image receptor is exposed by repeated scans of a modulated slot beam, oriented at a variety of scanning angles with respect to the object. The superposition of the exposure from appropriately modulated, rotated slot beams produces an entrance exposure that will effectively equalize the film exposure. The principle advantages of this geometry is its simplicity and reduced tube loading. To determine the effectiveness and feasibility of RSER the effect of conventional, MSER, and RSER have been numerically simulated on the appearance of clinical mammograms, the relative heat loading, and the fraction of the breast imaged with high contrast are calculated. It is found that RSER produces images that are free of artefacts, and exhibit a similar degree of equalization, as found in MSER images. RSER accomplishes this with only four scanning angles, and a beam that is approximately 4 cm wide. The resulting tube loading is only three times greater than that found in conventional imaging. Numerical simulations indicate that RSER is a simple, feasible means of overcoming the latitude limitations of film-screen mammography.
在乳腺组织致密的乳房中检测癌症存在问题，因为乳房产生的一系列曝光会超过高对比度胶片 - 屏片组合的有效动态范围。先前已表明，乳腺钼靶扫描均衡摄影（MSER）可用于克服胶片 - 屏片乳腺摄影的宽容度限制。然而，MSER的管负载比传统乳腺摄影大几个数量级。本文提出了一种用于均衡摄影的新型旋转几何结构，其中图像接收器通过对调制狭缝光束进行重复扫描来曝光，该光束相对于物体以各种扫描角度定向。来自适当调制、旋转的狭缝光束的曝光叠加产生一个入射曝光，该曝光将有效地均衡胶片曝光。这种几何结构的主要优点是其简单性和降低的管负载。为了确定旋转狭缝均衡摄影（RSER）的有效性和可行性，已对传统乳腺摄影、MSER和RSER在临床乳腺钼靶图像外观上的效果进行了数值模拟，计算了相对热负载以及乳腺高对比度成像部分的比例。结果发现，RSER产生的图像没有伪影，并且显示出与MSER图像相似的均衡程度。RSER仅通过四个扫描角度和大约4厘米宽的光束就能实现这一点。由此产生的管负载仅比传统成像中的管负载大三倍。数值模拟表明，RSER是克服胶片 - 屏片乳腺摄影宽容度限制的一种简单可行的方法。
