Johns P C, Drost D J, Yaffe M J, Fenster A
Med Phys. 1985 May-Jun;12(3):297-304. doi: 10.1118/1.595767.
Dual-energy x-ray techniques may be able to enhance the detectability of calcifications in mammographic examinations by removing the background "clutter" caused by contrast between adipose and glandular tissue. This hypothesis is examined experimentally by implementation of dual-energy imaging on a prototype digital scanned projection radiography system developed in our laboratory. A model of the propagation of signal and noise in dual-energy processing for a given radiation dose is validated by measurements from phantom images. The experimental imaging system has low spatial resolution and cannot be operated at dose-optimum energies; however, since both the single- and dual-energy images are subject to the same technical limitations, a comparison of such images allows an assessment of the benefits of dual energy. Experimental images of breast tissue specimens, showing improved detectability of calcifications when obscuring background clutter is removed, are presented. The dose required for a given signal-to-noise ratio can be reduced by smoothing the higher energy image prior to dual-energy processing. For practical implementation, it is reasonable to smooth the higher energy image such that its variance is reduced fourfold.
双能X射线技术或许能够通过去除由脂肪组织和腺体组织之间的对比度所导致的背景“干扰”，提高乳腺钼靶检查中钙化的可检测性。通过在我们实验室开发的原型数字扫描投影射线照相系统上实施双能成像，对这一假设进行了实验验证。通过体模图像测量，验证了给定辐射剂量下双能处理中信号和噪声传播的模型。实验成像系统空间分辨率较低，且无法在剂量最优能量下运行；然而，由于单能图像和双能图像都受到相同的技术限制，对这些图像进行比较可以评估双能的优势。展示了乳腺组织标本的实验图像，这些图像显示，去除模糊的背景干扰后，钙化的可检测性得到了改善。在双能处理之前，通过对高能图像进行平滑处理，可以降低给定信噪比所需的剂量。对于实际应用而言，合理的做法是对高能图像进行平滑处理，使其方差降低四倍。
