kVp Values Used During Medical Physicist Survey Testing
The term "kVp normally used clinically" should be considered as synonymous with the terms "clinical kVp" or "typical kVp."
In cases where the kVp is selected by the operator, we have required the physicists to perform some tests at the kVp normally used clinically at the facility (except for surveys that are done before the facility has established that value, such as mammography equipment evaluations of new units). 21 C.F.R. 900.12(e)(5)(ii), (e)(9). The kVp used in the survey/mammography equipment evaluation tests of reproducibility (both for kVp and AEC performance), HVL, dose, and phantom image evaluation (i.e., for all inspection questions where "the kVp used clinically," appears.) must not exceed +/- 1 kVp from the clinical kVp. For example, if the clinical kVp was 26, the test could be done at 25 kVp, 26 kVp, or 27 kVp. Likewise, fractional kVp values could be rounded off to the nearest integer without citing a noncompliance.
Note: There may be cases where the technique factors that the facility was using at the time of the survey/mammography equipment evaluation are different from the ones in use at the time of the inspection. In such cases, the technique factors in use at the time of the survey/mammography equipment evaluation should be applied.
For the kVp accuracy test and the kVp tracking portion of the AEC performance test, only the values used clinically at the facility need to be tested, up to a maximum of 3 values. If only 1 or 2 kVp’s are used, only those kVp’s need to be tested). If three or more kVp's are used, only three of those used need to be tested.