An analysis of discrepancies encountered by the AAPM radiological physics center.

The AAPM Radiological Physics Center has reviewed 188 institutions and has evaluated such parameters as coincidence of radiation field and light field, timer error (end effect), beam flatness and symmetry, transmission through blocking trays, wedges and compensators, and central-axis depth-dose data. In previous papers these data had been presented in combination as they resulted in discrepancies in tumor dose. The individual sources of discrepancies were listed only as frequency and maximum deviation. A detailed analysis is now presented which may help define criteria of recommended practice.