Open AccessSensitivity study of an automated system for daily patient QA using EPID exit dose images
Author(s) -
Zhuang Audrey H.,
Olch Arthur J.
Publication year - 2018
Publication title -
journal of applied clinical medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.83
H-Index - 48
ISSN - 1526-9914
DOI - 10.1002/acm2.12303
Subject(s) - multileaf collimator , imaging phantom , collimated light , collimator , fraction (chemistry) , rotation (mathematics) , nuclear medicine , image guided radiation therapy , sensitivity (control systems) , computer science , position (finance) , beam (structure) , physics , optics , medicine , linear particle accelerator , medical imaging , artificial intelligence , engineering , laser , chemistry , organic chemistry , finance , electronic engineering , economics
Abstract The dosimetric consequences of errors in patient setup or beam delivery and anatomical changes are not readily known. A new product, Per FRACTION (Sun Nuclear Corporation), is designed to identify these errors by comparing the exit dose image measured on an electronic portal imaging device ( EPID ) from each field of each fraction to those from baseline fraction images. This work investigates the sensitivity of Per FRACTION to detect the deviation caused by these errors in a variety of realistic scenarios. Integrated EPID images were acquired in clinical mode and saved in ARIA . Per FRACTION automatically pulled the images into its database and performed the user‐defined comparison. We induced errors of 1 mm and greater in jaw, multileaf collimator ( MLC ), and couch position, 1° and greater in collimation rotation (patient yaw), 0.5–1.5% in machine output, rail position, and setup errors of 1–2 mm shifts and 0.5–1° roll rotation. The planning techniques included static, intensity modulated radiation therapy ( IMRT ) and VMAT fields. Rectangular solid water phantom or anthropomorphic head phantom were used in the beam path in the delivery of some fields. Per FRACTION detected position errors of the jaws, MLC , and couch with an accuracy of better than 0.4 mm, and 0.5° for collimator rotation error and detected the machine output error within 0.2%. The rail position error resulted in Per FRACTION detected dose deviations up to 8% and 3% in open field and VMAT field delivery, respectively. Per FRACTION detected induced errors in IMRT fields within 2.2% of the gamma passing rate using an independent conventional analysis. Using an anthropomorphic phantom, setup errors as small as 1 mm and 0.5° were detected. Our work demonstrates that Per FRACTION , using integrated EPID image, is sensitive enough to identify positional, angular, and dosimetric errors.