Author: Shira Abraham, Eric Aliotta, Michalis Aristophanous, Laura I. Cervino, Yu-Chi Hu, Phillip G. Lichtenwalner, Chuan Zeng, Pengpeng Zhang 👨🔬
Affiliation: Department of Medical Physics, Memorial Sloan Kettering Cancer Center, Memorial Sloan Kettering Cancer Center 🌍
Purpose:
We have developed a tool that uses deformable image registrations to perform deformable dose accumulation. In this work we evaluate use of this tool for adaptive head and neck dose accumulation.
Methods: Fifteen adaptive head and neck patients were analyzed using an in house developed Eclipse plug in, Radiotherapy Dose Accumulation Routine (RADAR), to accumulate initial and adaptive phase doses into a plan sum. Due to anatomical and tumor changes between the initial and adaptive planning scans, deformable registrations were clinically performed in MIM for offline adaptive planning. RADAR was used to deform initial phase doses to the adaptive planning scan. Deformed dose values were compared to initial phase dose values on the original planning CT as a quality assurance step. Accumulated dose values from RADAR were compared to numeric dose summations for each organ at risk (OAR) following our clinical standards.
Results: Comparing deformed initial phase doses on the adaptive scan to initial phase OAR doses, RADAR doses deviated on average by 4.8%±7.91%/6.1%±12.94%/ and -0.5%±3.86%/-0.3%±3.11%, for Lt/Rt parotid and Lt/Rt submandibular Dmean values with average deviations of 0.3%±3.1%/-0.2%±2.79% and 0.6%±2.36%, for Lt/Rt brachial plexus and cord Dmax values. Comparing RADAR dose summations over the entire course of treatment to clinical summation values, RADAR doses deviated on average by 55.7 cGy±80.4cGy/61.1cGy±115.1cGy and 44.7cGy±114.4cGy/12.5cGy±66.8cGy for Lt/Rt parotid, and Lt/Rt submandibular Dmean values, with maximum deviations of 260 cGy/391 cGy, -340.2 cGy/-201.1cGy. Dmax values to the Lt/Rt brachial plexus, and cord had average deviations of -89.8±168.1cGy/-159±201cGy and -101.1±84.9cGy, with maximum deviations of 377.6 cGy/411cGy, and -249.8cGy.
Conclusion: RADAR provides an efficient process performing dose summation for plan evaluation in the setting of offline adaptive head and neck radiotherapy. While Dmean values were similar between methods, accumulated Dmax values were generally lower than numeric dose summations, which is an inherently conservative approach.