Implementation of GaN based real-time source position monitoring in HDR brachytherapy

•A simple brachytherapy QA phantom has been instrumented.•Dwell positions have been estimated according to measured dose rate by GaN probes.•Measured dose rate shows 1% average deviation from calculated results.•Determined dwell position precision and measureable range was studied.

For High Dose Rate (HDR) brachytherapy Quality Assurance (QA), we propose a seed position verification method by using two GaN dosimetric probes integrated in an instrumented phantom. As dose rate measured from one probe is related to the seed distance, seed position inside catheter can be determined. The proposed two-probe method extends measureable range and improves accuracy in comparison with the use of one single probe. One instrumented phantom implementing the method was designed, fabricated and tested in clinical conditions. The measureable range of the two-probe method is 105 mm compared to 36 mm using single probe. The validity of the method was experimentally verified.