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A Novel 3D Printer Based Patient Specific Intensity Modulated High-Dose-Rate (HDR) Brachytherapy: Proof-Of-Concept

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H Zhang

H Zhang1*, J Jung2 , S Olberg3 , H Li4 , R Khan5 , J Kim6 , S Mutic7 , J Park8 , (1) Washington University School of Medicine in St. louis, Saint Louis, MO, (2) University of Florida, Gainesville, FL, (3) Missouri University of Science and Technology, Rolla, Missouri, (4) Washington University School of Medicine, St. Louis, MO, (5) Washington University School of Medicine, St Louis, MO, (6) Yonsei University College of Medicine, Yonsei Cancer Center, Seoul, ,(7) Washington University in St Louis, St Louis, MO, (8) Washington University in St. Louis, St. Louis, MO


SU-E-205-3 (Sunday, July 30, 2017) 1:00 PM - 1:55 PM Room: 205

Purpose: In this study, we demonstrate a novel method for automatically designing a 3D printed, patient specific applicator for intensity modulated High-Dose-Rate (HDR) brachytherapy using the inverse plan optimization model.

Methods: The external shape of the HDR applicator resembles the conventional brachytherapy applicator. However, at each dwell position of the HDR source, the shielding wall is divided into six equiangular sections with varying thicknesses. To determine the optimal thickness of the shielding, we developed a mathematical model to simultaneously optimize the shielding and the dwell time according to the anatomical information of the patient and the dose prescribed by the physician. In the model, we considered the transmission rates of the shield on the brachytherapy applicator and the dwell time of the source as variables to be calculated in order to achieve the best possible target coverage. The model, which is a bi-convex optimization problem, is solved using alternating minimization. Finally, the applicator design parameters were input into 3D modeling software for 3D printing. The applicator has been tested on both a numerical phantom and clinically treated cervical cancer patient.

Results: The proposed approach exhibited substantial improvements of HR_CTV coverage over the conventional method. For the phantom case, 99.18% of the HR_CTV was covered by the prescribed dose using the proposed method, compared to only 58.32% coverage achieved by the conventional method. For the patient case, the proposed method increased the coverage of the HR_CTV from 56.21% to 99.92%. In each case, both methods satisfied the treatment constraints for neighboring organs at risk (OARs).

Conclusion: The present study demonstrates the concept of inverse plan-based HDR brachytherapy using a 3D printed applicator. The total treatment time for the patient was within approximately 24 minutes.

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