(P131) Improved Prostate Delineation in Prostate HDR Brachytherapy With TRUS-CT Deformable Registration Technology

Xiaofeng Yang, Peter Rossi, MD, Ashesh Jani, MD, Hui Mao, PhD, Tomi Ogunleye, Walter J. Curran, Tian Liu; Emory University

PURPOSE: The main challenge for computed tomography (CT)-based prostate high-dose-rate (HDR) treatment planning is to accurately define prostate volume in CT images due to the poor soft-tissue contrast. To address this issue, we have developed a novel approach that integrates intraoperative transrectal ultrasound (TRUS)-based prostate volume into HDR treatment planning through TRUS-CT deformable registration (TCDR) based on the catheters. This study’s purpose is to assess the clinical feasibility of the TCDR-based approach and compare its performance with the standard physician’s CT contours in the setting of HDR prostate brachytherapy.

METHODS: To improve prostate contour accuracy, the proposed TCDR-based approach utilizes two unique features in the HDR procedures: (1) Accurate prostate volume obtained from three-dimensional (3D) TRUS images-during HDR procedure, 3D TRUS images of the prostate are acquired with 1- or 2-mm step size right after the catheters are inserted. (2) Accurate TRUS-CT image registration using HDR catheters-both TRUS and CT images are obtained after the catheter insertions.

The catheters are reconstructed on the TRUS and CT images and subsequently used as landmarks for the TRUS-CT image registration using a fuzzy-to-deterministic algorithm. The intraoperative TRUS-based prostate volume is then deformed to the CT image to obtain the CT prostate volume, which is used for HDR treatment planning. In a pilot study, 16 prostate HDR brachytherapy procedures were evaluated retrospectively. CT-based prostate volumes were contoured by two experienced physicians. Both TCDR-based prostate volume and the standard CT-based prostate volumes are compared with the MRI-defined prostate contours (gold standard). A t-test was used to examine the significance of the difference between the two physicians’ CT-based contours, the TCDR-defined contours, and the MRI-defined prostate volumes.

RESULTS: A 20% to 40% improvement in prostate volume accuracy can be achieved with the TCDR-based approach as compared with the standard CT-based prostate volumes. TCDR-defined prostate volumes match closely to the MRI-defined prostate volumes (mean difference: 0.9 ± 7.3%; P = .54). CT-based contours assessed by the two physicians overestimated the size of the prostate gland by 7.3% (7.3 ± 18.7%) and 59.7% (59.7 ± 37.8%) and were associated with significant variability, even between these two experienced physicians (P < .01).

CONCLUSIONS: We have developed a novel TCDR-based approach to improve prostate delineation utilizing intraoperative TRUS-based prostate volume in prostate HDR brachytherapy and demonstrated its improvement in prostate volume accuracy over the standard CT-defined prostate volumes. Integration of TRUS into the HDR brachytherapy treatment planning workflow has the potential to enable accurate dose planning and delivery and enhance prostate HDR treatment outcome.

Proceedings of the 97th Annual Meeting of the American Radium Society - americanradiumsociety.org