Task Group 142 report: Quality assurance of medical acceleratorsa)

Abstract

The task group ͑TG͒ for quality assurance of medical accelerators was constituted by the American Association of Physicists in Medicine's Science Council under the direction of the Radiation Therapy Committee and the Quality Assurance and Outcome Improvement Subcommittee. The task group ͑TG-142͒ had two main charges. First to update, as needed, recommendations of Table II of the AAPM TG-40 report on quality assurance and second, to add recommendations for asymmetric jaws, multileaf collimation ͑MLC͒, and dynamic/virtual wedges. The TG accomplished the update to TG-40, specifying new test and tolerances, and has added recommendations for not only the new ancillary delivery technologies but also for imaging devices that are part of the linear accelerator. The imaging devices include x-ray imaging, photon portal imaging, and cone-beam CT. The TG report was designed to account for the types of treatments delivered with the particular machine. For example, machines that are used for radiosurgery treatments or intensity-modulated radiotherapy ͑IMRT͒ require different tests and/or tolerances. There are specific recommendations for MLC quality assurance for machines performing IMRT. The report also gives recommendations as to action levels for the physicists to implement particular actions, whether they are inspection, scheduled action, or immediate and corrective action. The report is geared to be flexible for the physicist to customize the QA program depending on clinical utility. There are specific tables according to daily, monthly, and annual reviews, along with unique tables for wedge systems, MLC, and imaging checks. The report also gives specific recommendations regarding setup of a QA program by the physicist in regards to building a QA team, establishing procedures, training of personnel, documentation, and end-to-end system checks. been considerably expanded as compared with the original TG-40 report and the recommended tolerances accommodate differences in the intended use of the machine functionality ͑non-IMRT, IMRT, and stereotactic delivery͒.

Comparison between electromagnetic transponders and radiographic imaging for prostate localization: A pelvic phantom study with rotations and translations

“…This could be determined by performing the monthly quality assurance check described in the Methods section. When multiple localization systems are available in a department, there may be a need to consider tighter tolerances on each individual system than specified in the AAPM TG142 report 30. In the extreme case, two localization systems may each be within 1 mm of the megavoltage radiation isocenter and hence within the AAPM TG142 tolerance, but may differ by 2 mm from each other.…”

“…These are based on the recommendations of AAPM Task Group 14230 for a linear accelerator used for IMRT and SRS/SBRT. The Task Group 142 report does not give recommendations for QA of electromagnetic transponder systems.…”

Beam focal spot position: The forgotten linac QA parameter. An EPID‐based phantomless method for routine Stereotactic linac QA

“…Recommendations on tests required with frequencies and tolerances are described in specialized publications such as AAPM TG‐1421 and IPEMB81 2. Modern linear accelerators have improved accuracy and precision in treatment delivery and allowed clinical implementation of advanced treatment modalities such as frameless Cranial Stereotactic Radiosurgery (CSRS) and Stereotactic Body Radiotherapy (SBRT).…”

Time‐resolved beam symmetry measurement for VMAT commissioning and quality assurance

“…The International Electrotechnical Commission (IEC) defines beam symmetry as the maximum ratio of the higher to lower absorbed dose at any two positions symmetrical to the radiation beam axis and inside the flattened area (3) . The recommendation of AAPM Task Group 142 (4) is that, at annual QA testing, the X‐ray symmetry change from baseline be within $\pm 1\%$.…”