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Program Information

Changing Paradigms for Linac QA Using EPIDS


T Ritter

E Van Uytven

B Cai

T Pawlicki




T Ritter1*, E Van Uytven2*, B Cai3*, T Pawlicki4*, (1) Veterans Health Administration, Richmond, VA, (2) CancerCare Manitoba, Winnipeg, MB, (3) Washington University School of Medicine, St. Louis, MO, (4) UC San Diego, La Jolla, CA

Presentations

10:00 AM : Current state of EPID based linac QA - T Ritter, Presenting Author
10:30 AM : Use of EPIDs for routine linac QA - E Van Uytven, Presenting Author
11:00 AM : Use of EPIDs for non-routine linac QA - B Cai, Presenting Author
11:30 AM : Processes and tools for rethinking linac QA - T Pawlicki, Presenting Author

TH-CD-FS4-0 (Thursday, August 3, 2017) 10:00 AM - 12:00 PM Room: Four Seasons 4


With high spatial resolution, availability on most modern medical linear accelerators (linac), and great potential for test automation, Electronic Portal Imaging Devices (EPID) have drawn great attention for applications in linac mechanical and dosimetric QA and testing. From linac acceptance tests to TG142 based routine quality assurance (QA), EPID based measurements and associated image processing methodologies have been proposed and investigated by many medical physics groups. Most mechanical tests (EPID based Winston-Lutz test, MLC positional test, Jaw parallelism tests, etc.) and dosimetric tests (daily output constancy check, field flatness & symmetry tests, enhanced dynamic wedge measurement, etc.) have been successfully implemented with EPIDs by different groups. There are also several commercial solutions available for EPID based QA of linacs. Prior to implementation of EPID based linac QA, it is crucial that physicists understand the benefits and limitations of EPIDs in this setting. EPID based linac QA offers an unprecedented degree of automation and standardization of QA procedures but EPIDs also suffer from a multitude of technical constraints which can potentially lead to misinterpretation of QA results and to suboptimal linac performance. This presentation is aimed at highlighting the emerging trends in EPID based linac QA and describing the challenges which can be experienced in this process. We also hope to stimulated additional developments and research in this area.

Learning Objectives:
1. To provide a review of EPID based QA publications, trends in the field, and selected results from literature
2. To provide a practical example and experience on use of EPID for routine QA
3. To discuss the role and opportunities of EPIDs for linact acceptance testing and commissioning
4. To describe processes and tools for rethinking linac QA, including how to analyze the AAPM TG-142 model, leverage data for driving decisions towards new paradigms in QA, SPC, FMEA analysis of EPID based QA processes


Funding Support, Disclosures, and Conflict of Interest: Parts of research supported by Varian Medical Systems

Handouts


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