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Dosimetry of asymmetric x‐ray collimators
Author(s) -
Khan Faiz M.,
Gerbi Bruce J.,
Deibel Firmin C.
Publication year - 1986
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.595822
Subject(s) - dosimetry , medical physics , physics , optics , nuclear medicine , medical imaging , medicine , radiology
We have studied the dosimetry of an independent jaw system (provided with the Varian Clinac 2500) using ionometric measurements performed both in air and in a water phantom. Our study shows that the effect of the independent jaw on the dose distribution is similar to that of secondary blocking except for changes produced in the collimator scatter. A system of dose calculation was developed which takes into account the changes in the collimator scatter as well as in the isodose distribution. A method is described to correctly generate isodose curves for fields shaped by an independent jaw using a modified AECL TP11 treatment planning system. The primary modification in the program consists of correcting the zero‐area tissue–maximum ratios for the off‐axis variation in beam quality.