Transrectal ultrasound (TRUS)-guided brachytherapy is a treatment option for localized prostate cancer, in which 125I or 103Pd radioactive seeds are implanted into the prostate. In this procedure, automated seed localization is important for intra-operative evaluation of dose delivery, which permits the identification of under-dosed regions and remedial seed placement, and ensures that the entire prostate receives the prescribed dose. In this paper, we describe the development of an automated seed segmentation method for use with 3D TRUS images. It is composed of five steps: 1) 3D needle segmentation; 2) volume cropping along the detected needle; 3) non-seed structure removal based on tri-bar model projection; 4) seed candidate recognition using 3D line segment detection; and 5) localization of seed positions. Experiments with the agar and chicken phantom images demonstrated that our method could segment 93% of the seeds in the 3D TRUS images with a mean distance error of 1.0 mm in an agar phantom and 1.7 mm in a chicken phantom, both with respect to manual segmented seed positions. The false positive rate was 7% while the segmentation time on a PC computer with dual AMD Athlon 1.8GHz processor was 280 seconds.
We have developed a robotic aided 3D transrectal ultrasound (TRUS) guided, intraoperative prostate brachytherapy. This system allows brachytherapy needles to be inserted into the prostate along various trajectories including oblique to avoid pubic arch interference. We unified the robotic coordinate system with the 3D TRUS image coordinate system. In addition, we also hdeveloped the method to automatically detect the needle in TRUS images for oblique insertion. We have evaluated our prototype system using prostate phantoms in terms of different needle insertion depths and the distances of the needle from the TRUS transducer. We have shown that our robotic aided 3D TRUS guided system was capable of placing the needle tip with approximately 0.74 mm ± 0.24 mm accuracy at a target identified in the 3D TRUS image. Brachytherapy accuracy was tested by dropping 0.8 mm beads into prostate phantoms via various angles up to ± 20°. Our results showed that the bead-dropping accuracy was 2.59 mm ± 0.76 mm with the error due to the needle deflection caused by the needle's bevel.