Evaluation and routine testing in medical imaging departments - part 2 - 2 constancy tests - radiographic cassettes and film changers - film - screen contact and relative sensitivity of the screen - cassette assembly 医用成像部门的评价及例行试验第2 - 2部分:稳定性试验x射线摄影暗匣和换片器-屏-片接触和屏-匣组件相对灵敏度