Quality Control in Brachytherapy

Brachytherapy is applied in 19 radiotherapy institutions in The Netherlands and in 20 institutions in Belgium. Each institution has its own Quality Assurance (QA) programme to ensure safe and accurate dose delivery to the patient. Because of the various guidelines employed and differences in individual interpretation, a large variety of test frequencies, test methods and accuracy criteria of the QA tests are applied.

To investigate the QA protocols for HDR, PDR and LDR brachytherapy, a questionnaire was sent to all radiotherapy institutions in The Netherlands and Belgium. The questions concerned test frequencies, methods, time required for the tests, and action levels of safety systems and irradiation parameters in brachytherapy. The answers to the questions showed large variations in test frequencies and test methods, and smaller variations in accuracy criteria. Furthermore, there were large variations in time spent on QA, mainly due to differences in QC resources available.

In addition to the questionnaire, the accuracy of implant reconstruction and dose delivery was determined during site visits of 33 institutions and by performing measurements with dedicated phantoms. The average reconstruction accuracy was -0.07 mm (±0.4 mm, 1 SD) for 41 localizers. The average deviation of the measured dos from the prescribed dose was ±0.9% (±1.3%, 1 SD) for 21 HDR afterloading systems, 1.0% (± 2.3%, 1 SD0) for 12 PDR afterloaders, and 1.8% (± 2.5%, 1 SD) for 15 LDR afterloaders.

The data gathered from the responses of the questionnaires were compared with existing recommendations on QA of brachytherapy. From this information, a set of minimum requirements on QA-procedures of HDR, PDR and LDR brachytherapy has been formulated, suitable for the situation in The Netherlands and Belgium. The recommendations include test frequencies, action levels and test methods for safety systems and physical parameters.

The use of radionuclides has increased rapidly in the field of endovascular brachytherapy to reduce the occurrence of restenosis in patients who are treated for vascular stenosis. Because of this tendency, it was decided to include a number of basic recommendations for the field of endovascular brachytherapy in this report. Furthermore, QA aspects of the treatment planning specific to brachytherapy are described, such as brachytherapy sources, implant entry, dose calculation models and the data transfer.

Note that this report is partially superseded by NCS 30.

https://doi.org/10.25030/ncs-013