Table 2.

Some of the discrepancies detected during RPC dosimetry review visits to 156 institutions in 2005–2011.

Errors regarding	Number of institutions (%)
Inadequacy of QA program	115 (74)
Photon field-size dependence (small fields)*	62 (40)
Wedge transmission factor*	50 (32)
Off-axis factors, beam symmetry	46 (29)
Electron calibration*	27 (17)
Photon depth dose*	25 (16)
Electron depth dose*	18 (11)
Photon calibration*	13 (8)

The parameters indicated by “*” are considered significant dosimetry parameters that influence the calculation of patient treatment meter settings. During this 6-year period, 70% of the visited institutions received one or more recommendations to address discrepancies in these dosimetry parameters.