DOSIMETRIC CHARACTERIZATION OF AN ACCESSORY MOUNTED MINI-BEAM COLLIMATOR ACROSS MULTIPLE CLINICALLY BEAM-MATCHED MEDICAL LINEAR ACCELERATORS

摘要

A mini-beam collimator has been dosimetrically characterized on three clinically beam matched medical linear accelerators. Beam quality, peak-to-valley dose ratio, collimator factor, and relative output were obtained for mini-beam collimated 6 MV fields of various sizes on three Varian iX medical linear accelerators. Though the beam quality remained constant, discrepancies in peak-to-valley dose ratio, collimator factor, and relative output were observed across accelerators. Monte Carlo simulations of the mini-beam collimated fields revealed that these differences were related to the linac electron beam width.