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.
Duzenli
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Department of Medical Physics, Cross Cancer Institute Edmonton, Alberta, Canada.
McClean
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Field
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D006801:Humans; D010315:Particle Accelerators; D011874:Radiometry / Q000379:methods*; D011882:Radiotherapy, High-Energy; D012542:Scattering, Radiation