Abstract
PURPOSE: Head-and-neck (HN) contouring presents significant challenges due to the complex anatomy of the region and the proximity of organs-at-risk (OARs) to the target. Manual contouring is time-consuming, labor-intensive, and prone to inter- and intra-observer variability. Additionally, contours delineated prior to treatment may not accurately reflect the patient's anatomy over the extended treatment course. This study explores the feasibility of using auto-generated OAR contours in HN planning. METHODS: A retrospective study was conducted on 20 patients, each with a planning CT and 35 CBCT images. OARs were manually delineated and automatically generated using atlas-based segmentation algorithms on planning CTs. Treatment plans were created via a novel two-step optimization process, incorporating a knowledge-based planning solution for both auto-generated (aOAR-plan) and manual OARs (mOAR-plan). The accuracy of auto-generated contours was quantified using the overlap index (OI) and dose similarity coefficient (DSC). Planning dose comparisons were performed between aOAR- and mOAR-plans. Additionally, planning doses were transferred from CT to CBCTs based on clinical shifts, and contour-based deformable registration was employed to calculate cumulative doses. Cumulative dose evaluations were performed for serial organs and parallel organs that can be fully imaged within the CBCT field. RESULTS: For OARs located farther from the target, even though atlas-based segmentation could not accurately reproduce patient anatomy, excellent agreement in planning doses was observed between the aOAR- and mOAR-plans. The average OI/DSC between manual and auto-generated contours were 85.0% ± 5.4%/87.4% ± 2.6% for the larynx, 76.0% ± 9.3%/77.0% ± 5.8% for the pharynx, 89.9% ± 4.0%/87.8% ± 2.5% for the oral cavity, 81.5% ± 10.5%/78.2% ± 5.9% and 83.2% ± 10.6%/77.8% ± 7.5% for the left and right parotid, respectively. The cumulative dose differences for OARs between aOAR- and mOAR-plans were within 2 Gy for 90% of patients studied. CONCLUSION: Automated-contouring tools offer improvement in contour consistency, provide acceptable doses compared with manually drawn contours in HN radiotherapy.