COMP report: CPQR technical quality control guidelines for brachytherapy remote afterloaders

Abstract The Canadian Organization of Medical Physicists (COMP), in close partnership with the Canadian Partnership for Quality Radiotherapy (CPQR) has developed a series of Technical Quality Control (TQC) guidelines for radiation treatment equipment. These guidelines outline the performance objectives that equipment should meet in order to ensure an acceptable level of radiation treatment quality. The TQC guidelines have been rigorously reviewed and field tested in a variety of Canadian radiation treatment facilities. The development process enables rapid review and update to keep the guidelines current with changes in technology (the most updated version of this guideline can be found on the CPQR website). This particular TQC details recommended quality control testing of brachytherapy remote afterloaders.


| SYSTEM DE SCRIPTION
Brachytherapy is the placement of encapsulated radionuclides or a miniaturized x-ray tube in, or adjacent to, tissue which has been prescribed a radiation dose. 3-10 This practice offers unique advantages to the management of several treatment sites and has been used to complement or replace external beam radiation therapy since the onset of radiation oncology.
Remote afterloading equipment was developed to reduce, and in many cases eliminate, the radiation exposure to members of the staff.
With remote afterloading systems the user does not directly handle the radioactive source and the patient is irradiated in a shielded room with staff operating and monitoring the process remotely.
High dose rate (HDR) refers to treatment dose rates larger than 20 cGy/min. For all HDR remote afterloaders, a single and small (< 1 mm 9 5 mm) radioactive source (mostly iridium-192, rarely cobalt60), laser-welded to a metallic cable, is moved out of the safe by a motor-drive mechanism to step along the prescribed positions High-dose rate miniaturized x-ray tube remote devices, along with intravascular and cardiovascular brachytherapy remote afterloaders using beta emitting radioactive sources, are beyond the scope of this document.
Various recommendations for brachytherapy quality assurance have been reported in the literature. [11][12][13][14][15][16][17][18] "Per treatment" tests must be executed prior to each treatment. "Treatment day" tests must be scheduled before treating the first patient of the day. For PDR remote afterloaders where treatments may last several days, "treatment day" tests should be performed prior to the initiation of the treatment.

| RELATED TECHNICAL QUALITY CONTROL GUIDELINE S
In order to comprehensively assess brachytherapy remote afterloader performance, additional guideline tests, as outlined in related CPQR Technical Quality Control (TQC) guidelines, must also be completed and documented, as applicable. Related TQC guidelines, available at http://www.cpqr.ca/programs/technical-quality-control/, include:

Q2
The configuration of this test will depend on the design of the facility and equipment. Safety is the concern and tests should be designed accordingly.
The first objective is to verify that the equipment safely retracts the source wire after a power failure. The second objective is to verify that the equipment properly records treatment delivered before power failure and permits to resume the treatment after power recovery Q3 Verify functionality of remote afterloader interlocks related to source and dummy wires. This includes incorrect connection of applicator to transfer guide tube, incorrect connection of transfer guide tube to remote afterloader, and obstruction Q4 Verify accuracy of dummy drive mechanism positioning. The purpose is to assure proper obstruction detection by assuring no false positive or false negative obstruction. If dummy drive mechanism is used to measure catheter length for treatment planning, then the action level should be lowered to 1 mm Q5 Accuracy of source drive mechanism to be verified. Autoradiographs or ion-chamber measurements could be used.

4.D | Notes on annual tests ACKNOWLEDG MENTS
We thank the many people who participated in the production of  A10 Check x-ray markers positional accuracy if used clinically for source positioning. If markers are only used to draw the applicator path, then only the integrity should be checked A11 The configuration of this test will depend on the design of the facility and equipment, and local regulations. All staff should review the emergency procedures when a source fails to retract properly and remains outside the safe A12 To ensure redundancy and adequate monitoring, a second qualified medical physicist must independently verify the implementation, analysis, and interpretation of the quality control tests at least annually A13 For PDR only, verify pulse sequencing functionality according to manufacturer's recommendations