Automating linear accelerator quality assurance Tobias Eckhause Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan 48109-5010 Hania Al-Hallaq Department of Radiation Oncology and Cellular Oncology, The University of Chicago, Chicago, Illinois 60637 Timothy Ritter Ann Arbor VA Medical Center, Ann Arbor, Michigan 48109 John DeMarco Department of Radiation Oncology, Cedars-Sinai Medical Center, Los Angeles, California, 90048 Karl Farrey Department of Radiation Oncology and Cellular Oncology, The University of Chicago, Chicago, Illinois 60637 Todd Pawlicki and Gwe-Ya Kim UCSD Medical Center, La Jolla, California 92093 Richard Popple Department of Radiation Oncology, University of Alabama Birmingham, Birmingham, Alabama 35249 Vijeshwar Sharma Karmanos Cancer Institute, McLaren-Flint, Flint, Michigan 48532 Mario Perez Royal North Shore Hospital, Sydney, NSW 2065, Australia SungYong Park Karmanos Cancer Institute, McLaren-Flint, Flint, Michigan 48532 Jeremy T. Booth Royal North Shore Hospital, Sydney, NSW 2065, Australia Ryan Thorwarth and Jean M. Moran a) Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan 48109-5010 (Received 17 May 2015; revised 5 September 2015; accepted for publication 9 September 2015; published 25 September 2015) Purpose: The purpose of this study was 2-fold. One purpose was to develop an automated, stream- lined quality assurance (QA) program for use by multiple centers. The second purpose was to evaluate machine performance over time for multiple centers using linear accelerator (Linac) log files and electronic portal images. The authors sought to evaluate variations in Linac performance to establish as a reference for other centers. Methods: The authors developed analytical software tools for a QA program using both log files and electronic portal imaging device (EPID) measurements. The first tool is a general analysis tool which can read and visually represent data in the log file. This tool, which can be used to automatically analyze patient treatment or QA log files, examines the files for Linac deviations which exceed thresholds. The second set of tools consists of a test suite of QA fields, a standard phantom, and software to collect information from the log files on deviations from the expected values. The test suite was designed to focus on the mechanical tests of the Linac to include jaw, MLC, and collimator positions during static, IMRT, and volumetric modulated arc therapy delivery. A consortium of eight institutions delivered the test suite at monthly or weekly intervals on each Linac using a standard phantom. The behavior of various components was analyzed for eight TrueBeam Linacs. Results: For the EPID and trajectory log file analysis, all observed deviations which exceeded established thresholds for Linac behavior resulted in a beam hold off. In the absence of an interlock- triggering event, the maximum observed log file deviations between the expected and actual compo- nent positions (such as MLC leaves) varied from less than 1% to 26% of published tolerance thresh- olds. The maximum and standard deviations of the variations due to gantry sag, collimator angle, jaw position, and MLC positions are presented. Gantry sag among Linacs was 0.336 ± 0.072 mm. The standard deviation in MLC position, as determined by EPID measurements, across the consortium was 0.33 mm for IMRT fields. With respect to the log files, the deviations between expected and actual positions for parameters were small (<0.12 mm) for all Linacs. Considering both log files 6074 Med. Phys. 42 (10), October 2015 0094-2405/2015/42(10)/6074/10/$30.00 © 2015 Am. Assoc. Phys. Med. 6074