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Title: SU-F-T-374: Dosimetric Effects of Irradiation Through a Bilateral Hip Prosthesis in a MRI Linac

Abstract

Purpose: To evaluate the interface effects when irradiating through a hip prosthesis in the presence of an orthogonal 1.5 T magnetic field using Monte Carlo simulations. Methods: A 20×20×38 cm virtual phantom with two 5×5×5 cm sections of bilateral titanium hip prosthesis was created in GPU-based Monte Carlo (MC) algorithm (GPUMCD, Elekta AB, Stockholm Sweden). The lateral prosthesis spacing was based on a representative patient CT scan. A treatment SAD of 143.5 cm was chosen, corresponding to the Elekta AB MRI Linac and the beam energy distribution was sampled from a histogram representing the true MRI Linac spectrum. A magnetic field of 1.5 T was applied perpendicular to the plane of irradiation. Dose was calculated, in voxels of side 1 mm, for 2×2, 5×5, and 10×10 cm treatment field sizes with normal beam incidence (gantry at 90° or 270°) and at 5° and 10° from normal, representing the range of incidence through the bilateral prosthesis. Results: With magnetic field ON (B-On) and normal beam incidence the backscatter dose at the interfaces of proximal and distal implants is reduced for all the field sizes compared to the magnetic field OFF (B-Off) case. The absolute reduction in doses at the interface wasmore » in the range of 12.93% to 13.16% for the proximal implant and 13.57% to 16.12% for the distal implant. Similarly for the oblique incidences of 5o and 10o the dose in the plane adjacent to the prosthetic implants is lower when the magnetic field is ON. Conclusion: The dosimetric effects of irradiating through a hip prosthesis in the presence of a transverse magnetic field have been determined using MC simulation. The backscatter dose reduction translates into significantly lower hot spots at the prosthetic interfaces, which are otherwise substantially high in the absence of the magnetic field. This project was supported through funding provided by ElektaTM.« less

Authors:
; ; ;  [1];  [2];  [1]
  1. Sunnybrook Odette Cancer Center, Toronto (Canada)
  2. (Canada)
Publication Date:
OSTI Identifier:
22648972
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 43; Journal Issue: 6; Other Information: (c) 2016 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; 61 RADIATION PROTECTION AND DOSIMETRY; BEAMS; COMPUTERIZED SIMULATION; COMPUTERIZED TOMOGRAPHY; IMPLANTS; INTERFACES; IRRADIATION; LINEAR ACCELERATORS; MAGNETIC FIELDS; MONTE CARLO METHOD; NMR IMAGING; PROSTHESES; RADIATION DOSES

Citation Formats

Wronski, M, Sarfehnia, A, Sahgal, A, Keller, B, University of Toronto, Department of Radiation Oncology, Toronto, and Ahmad, S. SU-F-T-374: Dosimetric Effects of Irradiation Through a Bilateral Hip Prosthesis in a MRI Linac. United States: N. p., 2016. Web. doi:10.1118/1.4956559.
Wronski, M, Sarfehnia, A, Sahgal, A, Keller, B, University of Toronto, Department of Radiation Oncology, Toronto, & Ahmad, S. SU-F-T-374: Dosimetric Effects of Irradiation Through a Bilateral Hip Prosthesis in a MRI Linac. United States. doi:10.1118/1.4956559.
Wronski, M, Sarfehnia, A, Sahgal, A, Keller, B, University of Toronto, Department of Radiation Oncology, Toronto, and Ahmad, S. Wed . "SU-F-T-374: Dosimetric Effects of Irradiation Through a Bilateral Hip Prosthesis in a MRI Linac". United States. doi:10.1118/1.4956559.
@article{osti_22648972,
title = {SU-F-T-374: Dosimetric Effects of Irradiation Through a Bilateral Hip Prosthesis in a MRI Linac},
author = {Wronski, M and Sarfehnia, A and Sahgal, A and Keller, B and University of Toronto, Department of Radiation Oncology, Toronto and Ahmad, S},
abstractNote = {Purpose: To evaluate the interface effects when irradiating through a hip prosthesis in the presence of an orthogonal 1.5 T magnetic field using Monte Carlo simulations. Methods: A 20×20×38 cm virtual phantom with two 5×5×5 cm sections of bilateral titanium hip prosthesis was created in GPU-based Monte Carlo (MC) algorithm (GPUMCD, Elekta AB, Stockholm Sweden). The lateral prosthesis spacing was based on a representative patient CT scan. A treatment SAD of 143.5 cm was chosen, corresponding to the Elekta AB MRI Linac and the beam energy distribution was sampled from a histogram representing the true MRI Linac spectrum. A magnetic field of 1.5 T was applied perpendicular to the plane of irradiation. Dose was calculated, in voxels of side 1 mm, for 2×2, 5×5, and 10×10 cm treatment field sizes with normal beam incidence (gantry at 90° or 270°) and at 5° and 10° from normal, representing the range of incidence through the bilateral prosthesis. Results: With magnetic field ON (B-On) and normal beam incidence the backscatter dose at the interfaces of proximal and distal implants is reduced for all the field sizes compared to the magnetic field OFF (B-Off) case. The absolute reduction in doses at the interface was in the range of 12.93% to 13.16% for the proximal implant and 13.57% to 16.12% for the distal implant. Similarly for the oblique incidences of 5o and 10o the dose in the plane adjacent to the prosthetic implants is lower when the magnetic field is ON. Conclusion: The dosimetric effects of irradiating through a hip prosthesis in the presence of a transverse magnetic field have been determined using MC simulation. The backscatter dose reduction translates into significantly lower hot spots at the prosthetic interfaces, which are otherwise substantially high in the absence of the magnetic field. This project was supported through funding provided by ElektaTM.},
doi = {10.1118/1.4956559},
journal = {Medical Physics},
number = 6,
volume = 43,
place = {United States},
year = {Wed Jun 15 00:00:00 EDT 2016},
month = {Wed Jun 15 00:00:00 EDT 2016}
}