A comparative study on the accuracy of an automated multi-parameter high-dose-rate brachytherapy quality assurance system

This study aims to explore the measuring accuracy of an automated high-dose-rate brachytherapy (HDR BT) quality assurance system (hereinafter referred to as OriQA system) that could provide simultaneous measurements of dwell position, dwell time and source strength in a single test. Elekta-Flexitron was selected as the HDR BT afterloader, and measured the farthest transmission distance by source position simulator. Within the effective distance, we set dwell positions in two groups, specifically, plan_1 with an interval of 2.00 cm: 106.00 cm, 108.00 cm, 110.00 cm, 102.00 cm, 104.00 cm, 106.00 cm, 108.00 cm, and plan_2 with an interval of 0.20 cm: 111.40 cm, 111.60 cm, 111.80 cm, 112.00 cm, 112.20 cm, 112.40 cm, 112.60 cm. The measured values collected from OriQA device were compared with the data from traditional HDR BT QA tool (source position check ruler). Three groups of dwell time were set, specifically, plan_1: with fixed dwell time 2.00 s, plan_3 with interval 0.10 s: 3.70 s, 3.80 s, 3.90 s, 4.00 s, 4.10 s, 4.20 s, 4.30 s, and plan_4: fixed dwell time 5.00 s. Source strength was also measured continuously for a period of 10 weeks, and compared with the data collected from the well-chamber. The OriQA system showed reliable performance in the evaluation of measuring accuracy. The adjusted farthest transmission distance was 119.33 cm. And according to the time-position graph, the maximum deviation of dwell position between the measured and planned data was 0.34 mm, which was smaller than that between the ruler and planed data (0.75 mm). The maximum deviation of dwell time between the measured and planned data was 0.05 s. Fitting analysis revealed linear relationship between source strength Sk and the intensity detector response, with R2 = 0.9877, and intensity deviation fluctuated between 1.14% and 2.19%. Compared with the traditional QA tool, the OriQA device provided improved measuring accuracy and efficiency QA procedure for HDR BT.