Segmentation of iodine brachytherapy implants in fluoroscopy

Purpose In prostate brachytherapy, intraoperative dosimetry would allow for evaluation of the implant quality while the patient is still in treatment position. Such amechanism, however, requires 3-D visualization of the deposited seeds relative to the prostate. It follows that accurate and robust seed segmentation is of critical importance in achieving intraoperative dosimetry. Methods Implanted iodine brachytherapy seeds are segmented via a region-based implicit active contour model. Overlapping seed groups are then resolved using a templatebased declustering technique. Results Ground truth seed coordinates were obtained through manual segmentation. A total of 57 clinical C-arm images from 10 patients were used to validate the proposed algorithm. This resulted in two failed images and a 96.0% automatic detection rate with a corresponding 2.2% falsepositive rate in the remaining 55 images. The mean centroid error between the manual and automatic segmentations was 1.2 pixels. Conclusions Robust and accurate iodine seed segmentation can be achieved through the proposed segmentation workflow.