Confidence-based automated tracking of small gold seeds in single frame amorphous silicon megavoltage images

Abstract

Listen

Translate article

Implant tracking in radiotherapy is dominated by classical implementations of the less than robust correlation template matching scheme, frequently using large gold seeds under idealised imaging conditions. Consequently, objective quantification of seed detection has attracted little attention. For dynamic, automated seed tracking to be adopted clinically, the reliability of small seed detection must be known for the most testing of imaging conditions. In this study, the authors report a robust, confidence-based development of correlation matching using a novel hybrid template, which is intended for use with small, linear gold seeds, similar to those used in prostate brachytherapy. For subsecond, single frame, 8 MV amorphous silicon imaging of randomly arranged test seeds, the hybrid approach produces separation between true and false seed distributions in both the anterior–posterior (AP) and lateral (LR) imaging directions through the bony pelvis. The AP detection rate is better than predicted at 85%, with effectively no false identifications. The LR rate of 29% is poor, as expected, with a high false identification rate. However, the LR results are three times better than predicted, even without a priori information. This suggests that minimal relative positional information for seeds has the potential to significantly boost performance.