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Poster — Thur Eve — 47: Automatic Comparison of Portal Images for the Detection of Radiotherapy Treatment Delivery Errors
Author(s) -
Lee R,
Tran M,
McCurdy B,
Pistorius S
Publication year - 2010
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 - 10.1118/1.3476152
Subject(s) - imaging phantom , rotation (mathematics) , image guided radiation therapy , perpendicular , artificial intelligence , plane (geometry) , computer science , computer vision , displacement (psychology) , set (abstract data type) , angle of rotation , physics , medical imaging , nuclear medicine , optics , mathematics , geometry , medicine , psychology , psychotherapist , programming language
The goal of this project is to develop a real‐time automatic comparison tool to detect portal dose image errors and has two logical parts: 1. A mechanism to detect the presence of a significant discrepancy. 2. A set of components to identify the probable cause(s) of the discrepancy including geometrical positioning errors as well as machine specific delivery errors. Initially, we have only considered in‐plane rotations and translations. A total of ∼700 portal images of an anthropomorphic pelvic phantom were obtained using a Varian aS1000 EPID. The images contained combinations of three types of geometrical patient set‐up errors. The angle of rotation (about the axis perpendicular to the EPID) was varied from [−5, +5] degrees and the translational distance was varied from [−10, +10] mm. The majority of the images were acquired from the AP direction however ∼130 images were of a lateral view. The system was found to be sensitive to in‐plane rotations down to ∼ 2°, out of plane rotations greater than ∼4° and displacements 3mm. For the lateral views, the calculated rotation was correct to within 1/2° and translations to within 5mm 53% of the time. Considering only translations, the accuracy increases to ∼82%. The results are much better for the AP views. The in‐plane rotation was within ±1/2deg; for all cases and the displacement error was greater than 1.5 mm in only 1 case. The system was able to analyze an image pair in ∼10s, however, no effort was put toward optimization of the system.