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Feasibility of a Novel Evaluation Method for Deformable Image Registration-Based Dose Accumulation for HDR Brachytherapy with a 3D-Printed Deformable Phantom

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K Abe

K Abe1*, N Kadoya1 , S Hashimoto2 , Y Miyasaka1 , Y Nakajima1,2 , K Ito1 , K Sato3 , K Takeda1 , K Jingu1 , (1) Tohoku University Graduate School of Medicine, Sendai, Japan, (2) Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital, Bunkyo, Japan, (3)Tohoku University Hospital, Sendai, Japan,


SU-H3-GePD-J(B)-6 (Sunday, July 30, 2017) 4:00 PM - 4:30 PM Room: Joint Imaging-Therapy ePoster Lounge - B

Purpose: We developed a novel evaluation method for deformable image registration (DIR)-based dose accumulation for HDR brachytherapy (HDR-BT) with a 3D-printed deformable phantom and evaluated its feasibility.

Methods: To evaluate DIR-based dose accumulation, the dose at the same position before and after deformation should be measured using a deformable phantom. Therefore, we developed a 3D-printed deformable pelvis phantom to simulate organ deformation. Dose was measured using radiophotoluminescent glass dosimeter (GD-302M, Chiyoda Technol). We evaluated whether it’s possible to measure the dose at the same position and accuracy of the measured dose by comparing it with a Monte Carlo (MC) simulation dose (EGSnrc). The prescribed dose was 6 Gy at point A using the TG-43 method implemented in the Oncentra treatment planning system (TPS). Additionally, because DIR-based dose accumulation was performed using the TPS dose, we compared the measured dose with the TPS dose to understand its calculation accuracy.

Results: Upon visual inspection, the phantom seemed to deform naturally while maintaining the dosimeter's position. Because the dosimeter’s holders were set on the phantom, our method could measure the dose at the same position for each fraction of HDR-BT and external beam just by removal and insertion of the dosimeters in the holders. Dose differences between the measured and the MC dose for the uterus (12 dosimeters) and bladder (8 dosimeters) were 4.1 ± 2.8% and 2.8 ± 2.4% respectively, suggesting that our method can accurately measure the dose. Conversely, there were moderate differences between measurement and TPS dose (uterus: 15.2 ± 6.8%, bladder: 17.9 ± 8.0%) because of the lack of inhomogeneity correction.

Conclusion: Our results revealed that the described method using a 3D-printerd phantom can measure the dose at the same position before and after deformation with accurately, suggesting that this method is useful for DIR-based dose accumulation for HDR-BT.

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