Emma Dyce
Prince of Wales Hospital, University of Wollongong
ROMP registrar

Simon Downes
Chief Physicist
Prince of Wales Hospital

Background and Purpose

An Elekta Flexitron HDR unit was purchased and installed at a new brachytherapy suite at Prince of Wales Hospital in August 2016. Following operational training, a full commissioning of the brachytherapy suite, Flexitron system and several gynaecological applicators was carried out prior to clinical implementation.

Methods

Acceptance testing of the treatment suite and HDR system was performed in conjunction with the relevant service engineers. Using ESTRO Booklet 8[1] as a guide, safety system tests including radiation surveys, functionality of interlocks, warning lights and doors, power loss performance, channel locking, interrupt and emergency stop systems were done. Once a safe working environment was established, further commissioning tests including physical parameters, dosimetry and applicator checks were undertaken. All existing applicators were re-commissioned for use with the Flexitron with annual maintenance performed at the same time. New sharp and round-end 6F needles, 100 mm green and 294 mm gold marker wires, and multi-channel vaginal applicators were also commissioned. Treatment differences between the MicroSelectron and Flexitron were evaluated for gynaecology treatments. All planning was performed with Oncentra version 4.5.2. New quality assurance procedures were developed for daily and post- source exchange testing.

Results

Each brachytherapy acceptance and commissioning test passed within accepted tolerances. All applicators were approved for use with the Flexitron system. Several important workflow changes were established to accommodate the changes between HDR systems. The major differences included the change off all transfer tube lengths to 100 cm, reference point and first dwell position at the connector end of the tube (rather than the distal applicator end), a new fixed step size of 1mm, mandatory channel-mapping for gynaecological applicators and the introduction of a treatment control panel touch screen display in addition to the treatment control console.

Conclusions

Following full end-to-end tests, the Flexitron is now in clinical use using the existing applicators for intracavitary vaginal and cervical treatments. The workflow changes between the MicroSelectron and Flexitron have been documented with all relevant protocols updated.

References

1. ESTRO European Guidelines for Quality Assurance in Radiotherapy Booklet No. 8, “A practical guide to quality control of brachytherapy equipment”, ISBN 90-804532-8, 2004


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