From Contour to Ideally Desired Dose Distribution to High Quality Deliverable Larynx SBRT Plan
Abstract
Purpose
Stereotactic body radiation therapy (SBRT) has been shown effective in treating early-stage laryngeal cancer. However, treatment planning is challenging due to its demand of steep dose falloffs and strict dose constraints, which introduce lengthened planning time and increased inter-planner variability. Our study aims to develop an efficient treatment planning approach with minimal manual interventions to generate high quality SBRT plans for laryngeal cancer patients.
Methods
This novel planning approach starts with generating an ideally desired distribution based on contours of targets and nearby critical structures using an in-house developed script. The ideal dose distribution includes five dose levels in this study. The next step utilizes Fallback planning in RayStation to generate an initial deliverable plan mimicking the ideal dose. Then the plan is finalized by RayStation Fine-tune tool or adding a small number of optimization objectives to address any unmet dose-volume goals. This study includes four laryngeal cancer patients who were treated with SBRT using VMAT technique at our center. Dosimetric plan quality is compared between the dose mimicking-based plans and the manual clinical plans.
Results
The dose mimicking-based plans achieved equivalent plan quality compared to the clinical plans for all cases. The average PTV D0.01cc and V42.5Gy were 44.8 Gy and 95.2%, respectively, compared to 44.3 Gy and 96.6% of the clinical plans. The average D0.01cc for left/right carotid artery, spinal cord and esophagus were 9.5 Gy, 19.0 Gy, 4.9 Gy, and 12.2 Gy, respectively, compared to 9.5 Gy, 17.1 Gy, 5.0 Gy and 11.8 Gy of the clinical plans. The total planning time upon completing contouring for the proposed approach was within one hour for the four test cases.
Conclusion
This new dose mimicking-based planning approach was able to generate high quality SBRT larynx plans with high efficiency using a commercial treatment planning system.