Improved prostate delineation in prostate HDR brachytherapy with TRUS‐CT deformable registration technology: A pilot study with MRI validation

Accurate prostate delineation is essential to ensure proper target coverage and normal‐tissue sparing in prostate HDR brachytherapy. We have developed a prostate HDR brachytherapy technology that integrates intraoperative TRUS‐based prostate contour into HDR treatment planning through TRUS‐CT deformable registration (TCDR) to improve prostate contour accuracy. In a perspective study of 16 patients, we investigated the clinical feasibility as well as the performance of this TCDR‐based HDR approach. We compared the performance of the TCDR‐based approach with the conventional CT‐based HDR in terms of prostate contour accuracy using MRI as the gold standard. For all patients, the average Dice prostate volume overlap was 91.1 ± 2.3% between the TCDR‐based and the MRI‐defined prostate volumes. In a subset of eight patients, inter and intro‐observer reliability study was conducted among three experienced physicians (two radiation oncologists and one radiologist) for the TCDR‐based HDR approach. Overall, a 10 to 40% improvement in prostate volume accuracy can be achieved with the TCDR‐based approach as compared with the conventional CT‐based prostate volumes. The TCDR‐based prostate volumes match closely to the MRI‐defined prostate volumes for all 3 observers (mean volume difference: 0.5 ± 7.2%, 1.8 ± 7.2%, and 3.5 ± 5.1%); while CT‐based contours overestimated prostate volumes by 10.9 ± 28.7%, 13.7 ± 20.1%, and 44.7 ± 32.1%. This study has shown that the TCDR‐based HDR brachytherapy is clinically feasible and can significantly improve prostate contour accuracy over the conventional CT‐based prostate contour. We also demonstrated the reliability of the TCDR‐based prostate delineation. This TCDR‐based HDR approach has the potential to enable accurate dose planning and delivery, and potentially enhance prostate HDR treatment outcome.