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Improved the Accuracy of Prostate Delineation for Ultrasound-Guided CT-Based Treatment Planning in Prostate HDR Brachytherapy: A Pilot Study with MRI Validation

X Yang*, P Rossi, T Ogunleye, W Curran, T Liu, Emory University, Atlanta, GA

WE-C-WAB-11 Wednesday 10:30AM - 12:30PM Room: Wabash Ballroom

Purpose: In CT-based prostate High-Dose-Rate (HDR) brachytherapy, catheter (needle) placement is commonly performed under the guidance of intra-operative transrectal ultrasound (TRUS), while treatment planning is based on post-operative CT images. The main challenge for CT-based treatment planning is to accurately define target (prostate) volume in CT images due to the poor soft-tissue contrast. To overcome this limitation, we propose a novel approach that integrates intra-operative ultrasound-based prostate volume into treatment planning through TRUS-CT fusion based on the catheter locations.

Methods: Our approach requires acquisition of 3D TRUS prostate images in the operating room right after the HDR catheters are inserted, which takes 1-3 minutes. These TRUS images are then used to create prostate contours. The HDR catheters are reconstructed from the intra-operative TRUS and post-operative CT images, and subsequently used as landmarks for the TRUS-CT image fusion using a fuzzy-to-deterministic algorithm. After TRUS-CT fusion, the TRUS-based prostate volume is deformed to the CT images for treatment planning. This technique was evaluated through two studies: a prostate-phantom study and a pilot study with 9 patients undergoing HDR treatment for prostate cancer. The accuracy of our approach is assessed through the locations of 3 implanted fudicial (gold) markers, as well as previous T2-weighted MR images of patients.

Results: For the phantom study, the mean gold-marker displacement was 0.41±0.11 mm. For the 9 patients, the mean gold-marker displacement of was 1.09±0.25mm; the prostate volume difference between our approach and the MRI-based volume was 6.99±0.68%, and the prostate volume Dice Overlap Coefficient was 92.66±1.17%.

Conclusion:We have developed a novel approach to improve prostate contours utilizing intra-operative TRUS-based prostate volume in CT-based prostate HDR treatment planning, demonstrated its clinical feasibility, and validated its accuracy with MRIs. This technique will improve prostate delineation, enable accurate dose planning and delivery, and potentially enhance prostate HDR treatment outcome.

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