Recommendations for an independent verification of the initial output calibration of megavoltage radiotherapy unit

Whenever a megavoltage radiotherapy unit is installed, it is necessary that the physicist performs a complete commission of the therapy unit to characterize the radiation parameters of the beam. Also, the physicist should have in place a comprehensive quality assurance program to assure that the machine performance remains within acceptable levels during the life of the unit. There was a general consensus to recommend that the initial output calibration be immediately verified by an independent measurement. This is essential to assure that no clinically significant dosimetry error has been made. This paper contains the some recommended criteria for this process