Evaluation of the spectral response of the Wisconsin Mammographic kVp Cassettes.

The spectral response of several Wisconsin Mammographic kVp cassettes was measured under various diagnostic conditions. The response for both unfiltered and externally filtered x-ray beams from tungsten and molybdenum target tubes with different tube voltage ripple was studied for single phase x-ray units. The response for a three phase generator with a molybdenum target tube was also measured. The maximum difference between these experimental response curves and the manufacturer's cassette calibration curve was 3.5 kVp for cassettes with Cu + Al step wedges and 6.0 kVp for cassettes with Cu + Ni step wedges under these widely different spectral conditions. The average difference between the experimental results and the manufacturer's calibration was +2 kVp for Cu + Al step wedge cassettes and +/- 3.5 kVp for Cu + Ni cassettes. kVp measurements were made with an NBS calibrated voltage divider.