Must medical physicists test all AEC detectors for AEC performance in mammography units with multiple AEC detectors and can the testing procedures be modified if the detectors are in the same cassette holder (bucky)?
The general principle is that all AEC detectors must be tested. What is considered adequate testing will depend on the arrangement of the AEC detectors in the mammography unit.
1. Where a mammography unit has different AEC detectors in the different size cassette holders (buckys), each detector must be tested separately as described above in questions #3 or #4.
2. Where a mammography unit has more than one AEC detector in a single cassette holder (bucky), the physicist must test all the individually selectable AEC detectors and may test the detectors using either of the following methods:
i. All detectors as described above in questions #3 or #4, OR;
ii. One detector as described above in questions #3 or #4 AND comparing the OD obtained at 4 cm from each of the other detectors to the MOD obtained from the first detector. When results across different detectors are compared, the medical physicist may use the action limit of +/- 0.30 OD
3. Where a mammography unit has multiple AEC detectors that are not individually selectable by the operator, the AEC can be tested as if it was a single detector. An example of such a system is one with three fixed detectors in which the system automatically chooses which detector will be active during the exposure. Similarly, a large field detector that automatically selects its active area needs to be tested only as a single detector. However, a system with three fixed detectors, each of which can be selected individually by the operator, needs to have all three detectors tested as described in section #2 above. Please note that a detector that can be moved to different positions by the operator is still considered a single detector and needs to be tested at only one of those positions.