Backscatter into the beam monitor chamber: implications for dosimetry of asymmetric collimators.
Backscatter from the asymmetric collimators of a linac into the beam monitor chamber (BMC) has been investigated for two accelerators having different BMC configurations. The effect has been quantified as a function of field size and collimator jaw position for 6 and 18 MV beams. The results indicate a maximum 2.5% (6 MV) and 4% (18 MV) decrease in output in one case and a negligible effect in the other case. The experiments indicate that the difference can be attributed to the different construction of the BMC's for the two accelerators.
Department of Medical Physics, Cross Cancer Institute Edmonton, Alberta, Canada.
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Duzenli
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McClean
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Field
D006801:Humans; D010315:Particle Accelerators; D011874:Radiometry / Q000379:methods*; D011882:Radiotherapy, High-Energy; D012542:Scattering, Radiation