SU‐E‐T‐412: Evaluation of Tungsten‐Based Functional Paper for Attenuation Device in Intraoperative Radiotherapy for Breast Cancer

Abstract

Purpose:Intraoperative radiotherapy (IORT) with an electron beam is one of the accelerated partial breast irradiation methods that have recently been used in early‐stage breast cancer. A protective acrylic resin‐copper disk is inserted between the breast tissue and the pectoralis muscle to minimize the dose received by the posterior structures. However, a problem with this protective disk is that the surgical incision must be larger than the field size because the disk is manufactured from stiff and unyielding materials. The purpose of this study was to assess the applicability of a new tungsten‐based functional paper (TFP) as an alternative to the existing protective disk in IORT.Methods:The newly introduced TFP (Toppan Printing Co., Ltd., Tokyo, JP) is anticipated to become a useful device that is lead‐free, light, flexible, and easily processed. The radiation shielding performance of TFP was verified by experimental measurements and Monte Carlo (MC) simulations using PHITS code. The doses transmitted through the protective disk or TFP were measured on a Mobetron mobile accelerator. The same geometries were then reproduced, and the dose distributions were simulated by the MC method.Results:The percentages of transmitted dose relative to the absence of the existing protective disk were lower than 2% in both the measurements and MC simulations. In the experimental measurements, the percentages of transmitted dose for a 9 MeV electron beam were 48.1, 2.3, and 0.6% with TFP thicknesses of 1.9, 3.7, and 7.4 mm, respectively. The percentages for a 12 MeV were 76.0, 49.3, 20.0, and 5.5% with TFP thicknesses of 1.9, 3.7, 7.4, and 14.8 mm, respectively. The results of the MC simulation showed a slight dose increase at the incident surface of the TFP caused by backscattered radiation.Conclusion:The results indicate that a small‐incision procedure may be possible by the use of TFP.