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An effective correction algorithm for off‐axis portal dosimetry errors
Author(s) -
Bailey Daniel W.,
Kumaraswamy Lalith,
Podgorsak Matthew B.
Publication year - 2009
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 - 10.1118/1.3187785
Subject(s) - dosimetry , collimator , detector , radiation treatment planning , physics , nuclear medicine , medical imaging , algorithm , optics , computer science , mathematics , radiation therapy , medicine , artificial intelligence , radiology
Portal dosimetric images acquired for IMRT pretreatment verification show dose errors of up to 15% near the detector edges as compared to dose predictions calculated by a treatment planning system for these off‐axis regions. A method is proposed to account for these off‐axis effects by precisely correcting the off‐axis output factors, which calibrate the imager for absolute dose. Using this method, agreement between the predicted and the measured doses improves by up to 15% for fields near the detector edges, resulting in passing rate improvements of as much as 60% for gamma evaluation of 3 mm , 3% within the collimator jaws.