Mammography systems with image receptor modalities other than screen-film must undergo periodic quality control tests following procedures that are recommended by the manufacturer of the mammographic modality. As is the case for screen-film QC, the facility must keep records of these tests and all applicable corrective actions for the longer of: last 12 months or since the last annual inspection which verifies compliance, or until the test has been done two additional times at the required frequency. 21 C.F.R. 900.12(d)(2). Regardless of the mammographic modality, the mean glandular dose delivered during a single cranio-caudal view of an FDA-accepted phantom must not exceed 3.0 milligray (mGy) (0.3 rad) per exposure. 21 C.F.R. 900.12(e)(5)(vi). If the test results exceed the action level, corrective action must be taken within the required time frames. 21 C.F.R. 900.12(e)(8).