Law J
Edinburgh University, Department of Medical Physics and Medical Engineering, Western General Hospital, UK.
Br J Radiol. 1996 Feb;69(818):143-7. doi: 10.1259/0007-1285-69-818-143.
Quality control procedures in relation to speed and contrast in X-ray film processors, both in X-ray departments and breast screening centres, are based on the use of film sensitometers. Calibrations of these instruments, or simple checks of their constancy with time, are not readily available. A procedure is described in which a reference sensitometer is compared on a 3-monthly basis with the local sensitometer in seven breast screening centres (13 processors) in a region. This demonstrated long-term stability of speed and contrast in both sensitometers and processors. The results may also be used to compare speed and contrast between processors in centres using film of a single type. Standard deviations for single measurements are estimated to be approximately 1% for step density on a single sensitometer, less than 3% for comparison of two sensitometers, about 6% for comparison of processor speed, and between 4 and 5% for processor contrast.
在X射线科室和乳腺筛查中心，X射线胶片冲洗机的速度和对比度相关的质量控制程序是基于胶片感光计的使用。这些仪器的校准，或者简单检查其随时间的稳定性，都不容易做到。本文描述了一种程序，即一个地区的七个乳腺筛查中心（13台冲洗机）每三个月将一台参考感光计与当地的感光计进行比较。这证明了感光计和冲洗机的速度和对比度具有长期稳定性。这些结果还可用于比较使用单一类型胶片的各中心冲洗机之间的速度和对比度。单次测量的标准偏差估计为：单台感光计上梯级密度约为1%，两台感光计比较时小于3%，冲洗机速度比较时约为6%，冲洗机对比度比较时为4%至5%。
