Szulc M, Judy P F
Med Phys. 1979 Nov-Dec;6(6):479-86. doi: 10.1118/1.594609.
X-ray source filtration as a means to reduce patient dose while maintaining image quality was investigated for CT scanners. The CT values, their variances for various materials, and the surface dose to a cylindrical phantom were calculated for different filter thicknesses and composition as well as for different tube potentials. Thermoluminescent dosimetry indicated that the maximum dose could be predicted by calculation with an accuracy of 10% (+/- 2 s.d.). The product of the variance of the CT values times surface dose was used to establish the appropriate thickness and composition of the filter, a figure of merit that was independent of dose and noise when the sole source of noise was Poisson statistics. This analysis indicated that source filter materials with an atomic number from 29 to 40 are optimum, and if aluminum is used, the minimum thickness, at 120 kVp, should be 4 mm.
针对CT扫描仪，研究了X射线源过滤作为在保持图像质量的同时降低患者剂量的一种手段。针对不同的滤过器厚度和成分以及不同的管电压，计算了各种材料的CT值、其方差以及圆柱形体模的表面剂量。热释光剂量测定表明，通过计算可以以10%（±2标准差）的精度预测最大剂量。CT值方差与表面剂量的乘积用于确定滤过器的合适厚度和成分，当唯一的噪声源是泊松统计时，该品质因数与剂量和噪声无关。该分析表明，原子序数为29至40的源过滤材料是最佳的，如果使用铝，在120 kVp时的最小厚度应为4毫米。
