Beaman S A, Lillicrap S C
Phys Med Biol. 1982 Oct;27(10):1209-20. doi: 10.1088/0031-9155/27/10/001.
A number of authors have calculated x-ray energies for mammography using, as a criterion, the maximum signal-to-noise ratio (SNR) obtainable per unit dose to the breast or conversely the minimum exposure for constant SNR. The predicted optimum energy increases with increasing breast thickness. Tungsten anode x-ray spectra have been measured with and without various added filter materials to determine how close the resultant spectra can be brought to the predicted optimum energies without reducing the x-ray output to unacceptable levels. The proportion of the total number of x-rays in a measured spectrum lying within a narrow energy band centred on the predicted optimum has been used as an optimum energy index. The effect of various filter materials on the measured x-ray spectra has been investigated both experimentally and theoretically. The resulting spectra have been compared with molybdenum anode, molybdenum filtered x-ray spectra normally used for mammography. It is shown that filters with K-absorption edges close to the predicted optimum energies are the most effective at producing the desired spectral shape. The choices of filter thickness and Vp are also explored in relationship to their effect on the resultant x-ray spectral shape and intensity.
许多作者已计算出用于乳腺摄影的X射线能量，其标准是每单位乳房剂量可获得的最大信噪比（SNR），或者反过来，是恒定SNR下的最小曝光量。预测的最佳能量随乳房厚度的增加而增加。已测量了有和没有各种添加过滤材料时的钨阳极X射线光谱，以确定在不将X射线输出降低到不可接受水平的情况下，所得光谱能多接近预测的最佳能量。在以预测最佳能量为中心的窄能带内的测量光谱中，X射线总数的比例已被用作最佳能量指数。已通过实验和理论研究了各种过滤材料对测量的X射线光谱的影响。所得光谱已与通常用于乳腺摄影的钼阳极、钼过滤X射线光谱进行了比较。结果表明，K吸收边接近预测最佳能量的过滤器在产生所需光谱形状方面最有效。还探讨了过滤厚度和管电压对所得X射线光谱形状和强度的影响。
