Sensitivity study of an automated system for daily patient QA using EPID exit dose images

Abstract

The dosimetric consequences of errors in patient setup or beam delivery and anatomical changes are not readily known. A new product, PerFRACTION (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 PerFRACTION 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. PerFRACTION 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. PerFRACTION 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 PerFRACTION detected dose deviations up to 8% and 3% in open field and VMAT field delivery, respectively. PerFRACTION 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 PerFRACTION, using integrated EPID image, is sensitive enough to identify positional, angular, and dosimetric errors.

Analyses of integrated EPID images for on‐treatment quality assurance to account for interfractional variations in volumetric modulated arc therapy

“…In addition, intrafractional motion may have occurred, because the shoulder could not be immobilized with the thermoplastic shell. Zhuang et al reported that a setup error as small as 1 mm and 0.5° could be detected using an anthropomorphic phantom with the PerFRACTION software . As described above, the lack of a setup error evaluation was a limitation of our study.…”

Validation of three-dimensional electronic portal imaging device-based PerFRACTION™ software for patient-specific quality assurance

“…PerFRACTION™ reliably identified experimentally introduced errors and estimated their impact. With this initial validation result and recent publications,[11121314] we have introduced PerFRACTION™ into daily clinical practice to further validate this software program using clinical data.…”

Effect of collimator angle on HyperArc stereotactic radiosurgery planning for single and multiple brain metastases

“…reported that EPID based measurements using Per-FRACTION software could detect setup errors as small as 1 mm. 10 A number of investigators have shown a linear relation between EPID response and dose, and the EPID measurements have been increasingly introduced for daily pretreatment verifications owing to its simple procedure (without need for setting detectors). [18][19][20] However, the presence of the support arm may affect the EPID measurements because the backscattered radiation dose can be occurred from the metallic parts in the support arm.…”

“…The detector has an active area of 400 mm × 400 mm with a small pixel size of 0.34 mm, and the integrated dose images were acquired for each arc beam at the source to detector distance of 170 cm without any obstructions. The acquired images were automatically retrieved to a commercial dose verification software (PerFRACTION version 2.0.4, Sun Nuclear Corporation, Melborne, FL) 10,11 and were compared with the corresponding expected dose maps, which was generated from the DICOM files of treatment plan from the TPS.…”