The Design of an Audit Test for (60)Co Brachytherapy Treatment Planning System

BACKGROUND: Auditing the treatment planning system (TPS) software for a radiotherapy unit is of paramount importance in any radiation therapy department. A Plexiglas phantom was proposed to measure the ionization of (60)Co high dose rate (HDR) source and compare dose points in the planning system for auditing and verifying TPS. METHODS: Auditing was performed using a Plexiglas phantom in an end-to-end test, and relative dose points were detected by a farmer-type ionization chamber and compared with the relative dose of similar points in TPS. The audit results were determined as pass optimal level (<3.3%), pass action level (between 3.3% and 5%), and out of tolerance (>5%). RESULTS: The comparison of the collected data revealed that 80% of the measured values were ≤5% in the pass level, and 20% of the points were out of tolerance (between 5% and 6.99%). CONCLUSION: This study documented the appropriateness of the dosimetry audit test and this phantom design for the HDR brachytherapy TPS.