title: An effective correction algorithm for off-axis portal dosimetry errors.
abstract: 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.
authors.affiliation: Department of Physics, State University of New York at Buffalo, Buffalo, New York 14260, USA.
authors.forename: Daniel W
authors.initials: DW
authors.lastname: Bailey
authors.forename: Lalith
authors.initials: L
authors.lastname: Kumaraswamy
authors.forename: Matthew B
authors.initials: MB
authors.lastname: Podgorsak
mesh_terms: D000465:Algorithms; D001921:Brain / Q000528:radiation effects; D001932:Brain Neoplasms / Q000532:radiotherapy; D001940:Breast / Q000528:radiation effects; D001943:Breast Neoplasms / Q000532:radiotherapy; D002138:Calibration; D005260:Female; D006258:Head and Neck Neoplasms / Q000532:radiotherapy; D006801:Humans; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*