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Title: SU-F-T-432: Magnetic Field Dose Effects for Various Radiation Beam Geometries for Patients Treated with Hypofractionated Partial Breast Irradiation

Abstract

Purpose: Hypofractionated partial breast irradiation (HPBI) is being used at our clinic to treat inoperable breast cancer patients who have advanced disease. We are investigating how these patients could benefit from being treated in an MRI-linac, where real-time daily MRI tumor imaging and plan adaptation would be possible. As a first step, this study evaluates the dosimetric impact of the magnetic field for different radiation beam geometries on relevant OARs. Methods: Five patients previously treated using HPBI were selected. Six treatment plans were generated for each patient, evaluating three beam geometries (VMAT, IMRT, 3DCRT) with and without B{sub 0}=1.5 T. The Monaco TPS was used with the Elekta MRI-Linac beam model, where the magnetic field is orthogonal to the radiation beam. All plans were re-scaled to the same isocoverage with a prescription of 40Gy/5 to the PTV. Plans were evaluated for the effect of the magnetic field and beam modality on skin V{sub 3} {sub 0}, lung V{sub 2} {sub 0} and mean heart dose. Results: Averaged over all patients, skin V{sub 3} {sub 0}for 3DCRT was higher than VMAT and IMRT (by +22% and +21%, with B{sub 0}-ON). The magnetic field caused larger increases in skin V{sub 3} {submore » 0}for 3DCRT (+8%) than VMAT (+3%) and IMRT (+4%) compared with B{sub 0}-OFF. With B{sub 0}-ON, 3DCRT had a markedly lower mean heart dose than VMAT (by 538cGy) and IMRT (by 562cGy); for lung V{sub 2} {sub 0}, 3DCRT had a marginally lower dose than VMAT (by −2.2%) and IMRT (also −2.2%). The magnetic field had minimal effect on the mean heart dose and lung V{sub 2} {sub 0} for all geometries. Conclusion: The decreased skin dose in VMAT and IMRT can potentially mitigate the effects of skin reactions for HPBI in an MRI-linac. This study illustrated that more beam angles may result in lower skin toxicity and better tumor conformality, with the trade-off of elevated heart and lung doses. We are receiving funding support from Elekta.« less

Authors:
 [1];  [2]; ; ; ; ;  [1];  [2]
  1. Sunnybrook Odette Cancer Centre, Toronto (Canada)
  2. (Canada)
Publication Date:
OSTI Identifier:
22649025
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; BIOMEDICAL RADIOGRAPHY; GEOMETRY; HEART; IRRADIATION; LUNGS; MAGNETIC FIELDS; MAMMARY GLANDS; NEOPLASMS; NMR IMAGING; PATIENTS; RADIATION DOSES; RADIOTHERAPY; SKIN

Citation Formats

Lim-Reinders, S, University of Toronto, Department of Physics, Keller, B, McCann, C, Sahgal, A, Lee, J, Kim, A, and University of Toronto, Department of Radiation Oncology. SU-F-T-432: Magnetic Field Dose Effects for Various Radiation Beam Geometries for Patients Treated with Hypofractionated Partial Breast Irradiation. United States: N. p., 2016. Web. doi:10.1118/1.4956617.
Lim-Reinders, S, University of Toronto, Department of Physics, Keller, B, McCann, C, Sahgal, A, Lee, J, Kim, A, & University of Toronto, Department of Radiation Oncology. SU-F-T-432: Magnetic Field Dose Effects for Various Radiation Beam Geometries for Patients Treated with Hypofractionated Partial Breast Irradiation. United States. doi:10.1118/1.4956617.
Lim-Reinders, S, University of Toronto, Department of Physics, Keller, B, McCann, C, Sahgal, A, Lee, J, Kim, A, and University of Toronto, Department of Radiation Oncology. Wed . "SU-F-T-432: Magnetic Field Dose Effects for Various Radiation Beam Geometries for Patients Treated with Hypofractionated Partial Breast Irradiation". United States. doi:10.1118/1.4956617.
@article{osti_22649025,
title = {SU-F-T-432: Magnetic Field Dose Effects for Various Radiation Beam Geometries for Patients Treated with Hypofractionated Partial Breast Irradiation},
author = {Lim-Reinders, S and University of Toronto, Department of Physics and Keller, B and McCann, C and Sahgal, A and Lee, J and Kim, A and University of Toronto, Department of Radiation Oncology},
abstractNote = {Purpose: Hypofractionated partial breast irradiation (HPBI) is being used at our clinic to treat inoperable breast cancer patients who have advanced disease. We are investigating how these patients could benefit from being treated in an MRI-linac, where real-time daily MRI tumor imaging and plan adaptation would be possible. As a first step, this study evaluates the dosimetric impact of the magnetic field for different radiation beam geometries on relevant OARs. Methods: Five patients previously treated using HPBI were selected. Six treatment plans were generated for each patient, evaluating three beam geometries (VMAT, IMRT, 3DCRT) with and without B{sub 0}=1.5 T. The Monaco TPS was used with the Elekta MRI-Linac beam model, where the magnetic field is orthogonal to the radiation beam. All plans were re-scaled to the same isocoverage with a prescription of 40Gy/5 to the PTV. Plans were evaluated for the effect of the magnetic field and beam modality on skin V{sub 3} {sub 0}, lung V{sub 2} {sub 0} and mean heart dose. Results: Averaged over all patients, skin V{sub 3} {sub 0}for 3DCRT was higher than VMAT and IMRT (by +22% and +21%, with B{sub 0}-ON). The magnetic field caused larger increases in skin V{sub 3} {sub 0}for 3DCRT (+8%) than VMAT (+3%) and IMRT (+4%) compared with B{sub 0}-OFF. With B{sub 0}-ON, 3DCRT had a markedly lower mean heart dose than VMAT (by 538cGy) and IMRT (by 562cGy); for lung V{sub 2} {sub 0}, 3DCRT had a marginally lower dose than VMAT (by −2.2%) and IMRT (also −2.2%). The magnetic field had minimal effect on the mean heart dose and lung V{sub 2} {sub 0} for all geometries. Conclusion: The decreased skin dose in VMAT and IMRT can potentially mitigate the effects of skin reactions for HPBI in an MRI-linac. This study illustrated that more beam angles may result in lower skin toxicity and better tumor conformality, with the trade-off of elevated heart and lung doses. We are receiving funding support from Elekta.},
doi = {10.1118/1.4956617},
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}
}