Cohen G
J Comput Assist Tomogr. 1979 Apr;3(2):197-203. doi: 10.1097/00004728-197904000-00010.
Low-contrast visibility of various rotate-translate, rotating detector, and stationary detector computed tomogrphy (CT) scanners is measured at contrasts ranging from 0.3 to 3% using a phantom based on the partial volume of water and polystyrene. The results are plotted on log-log curves, as a function of entrance dose, to provide a family of contrast (C)--detail (d)--dose (D) visibility curves. The transition region, approximately 1 to 10% contrast, depends on modulation transfer function (MTF), contrast, and the dose (noise), while the noise region, less than or equal to 1% contrast, is independent of MTF. The slopes of the curves in the noise region are consistent with a value of -1, as opposed to a theoretically expected value of -3/2 for ideal CT noise. Relative dose efficiency of various scanners is examined by plotting CdD(1/2) versus contrast for both peak dose (Dp) and summation dose (D sigma). The rotating detector systems are shown to be, on the average (at 0.5% contrast), 3.4 (Dp) and 4 (D sigma) times more dose efficient than the stationary array system examined, and 2.4 (Dp) and 3.2 (D sigma) times more efficient than the rotate-translate units examined.
使用基于水和聚苯乙烯部分体积的体模，在0.3%至3%的对比度范围内，测量各种旋转平移、旋转探测器和平板探测器计算机断层扫描（CT）扫描仪的低对比度可见度。结果绘制在对数-对数曲线上，作为入射剂量的函数，以提供一系列对比度（C）-细节（d）-剂量（D）可见度曲线。过渡区域，对比度约为1%至10%，取决于调制传递函数（MTF）、对比度和剂量（噪声），而噪声区域，对比度小于或等于1%，与MTF无关。噪声区域曲线的斜率与-1的值一致，而理想CT噪声的理论预期值为-3/2。通过绘制CdD(1/2)与对比度的关系曲线，研究了各种扫描仪的相对剂量效率，包括峰值剂量（Dp）和总和剂量（D sigma）。结果表明，旋转探测器系统平均（在0.5%对比度下）的剂量效率比所研究的平板阵列系统高3.4倍（Dp）和4倍（D sigma），比所研究的旋转平移装置高2.4倍（Dp）和3.2倍（D sigma）。
