A facility is using more than one type of screen-film combination. Must it perform the QC tests separately for each combination used?
It depends. For the majority of the QC tests, the type of screen-film combination used in the test is irrelevant to the test outcome. However, for the following QC tests, the regulations spell out specific requirements:
- System Resolution - must be measured for each screen-film combination used at the facility with its corresponding unit(s).
- Phantom Image and Dose – each of these must be conducted for each screen-film combination clinically used for the standard breast. 21 C.F.R. 900.12(e)(2), 900.12(e)(5)(vi)
Note that the phantom image test applies to both the weekly QC and the annual test conducted by the medical physicist as part of the survey report. If only one combination is routinely used for the standard breast and the other combination is used for non-routine examinations of the standard breast, FDA recommends that the dose and phantom image QC tests also be conducted for the other combination, because the outcome of both tests is heavily influenced by the film-screen combination used.
Note that testing for the uniformity of screen speed must be conducted for all screens and cassettes respectively. Hence, by default, it includes all types of screens used, but this does not preclude performing this test with only one type of film. System artifacts must be performed for each cassette size.