Abstract
AAPM Task Group 119 has produced quantitative confidence limits as baseline expectation values for IMRT commissioning. A set of test cases was developed to assess the overall accuracy of planning and delivery of IMRT treatments. Each test uses contours of targets and avoidance structures drawn within rectangular phantoms. These tests were planned, delivered, measured, and analyzed by nine facilities using a variety of IMRT planning and delivery systems. Each facility had passed the Radiological Physics Center credentialing tests for IMRT. The agreement between the planned and measured doses was determined using ion chamber dosimetry in high and low dose regions, film dosimetry on coronal planes in the phantom with all fields delivered, and planar dosimetry for each field measured perpendicular to the central axis. The planar dose distributions were assessed using gamma criteria of 3%/3 mm. The mean values and standard deviations were used to develop confidence limits for the test results using the concept confidence limit = /mean/ + 1.96sigma. Other facilities can use the test protocol and results as a basis for comparison to this group. Locally derived confidence limits that substantially exceed these baseline values may indicate the need for improved IMRT commissioning.
Highlights
The head and neck case has a PTV volume that is relatively large, such as for a postoperative treatment, while clinical cases often have multiple targets prescribed to different doses
None of the test cases represent the broad targets found in pelvic cases in which lymph node chains are targeted and bowel is to be spared
Facilities should create mock clinical cases that reasonably represent the types of cases that they see in clinical practice, including tests of other energies if used
Summary
Ezzell Department of Radiation Oncology, Mayo Clinic Scottsdale, 5777 East Mayo Boulevard, MCSB Concourse, Phoenix, Arizona 89054. Burmeister Wayne State University School of Medicine, Karmanos Cancer Center, 4100 John R Street, Detroit, Michigan 48201. Mechalakos Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, New York 10065. Dimitris Mihailidis Department of Radiation Oncology and Medical Physics, Charleston Radiation Therapy Cons, 3100 MacCorkle Avenue Southeast, Charleston, West Virginia 25304. Palta Department of Radiation Oncology, University of Florida Health Science Center, 2000 Archer Road, Gainesville, Florida 32610–0385
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