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Title: SU-F-T-451: Doses to Organs-At-Risk in the Presence and Absence of a 1.5 T Magnetic Field for NSCLC Patients Undergoing SABR

Abstract

Purpose: To determine whether the electron return effect (ERE) has deleterious effects on lung SABR plans optimized in the presence of an orthogonal 1.5 T magnetic field. Methods: Data from five NSCLC-SABR patients were used. The Dose was modeled with a 2.5 mm dose grid in the presence and absence of a magnetic field using the Monaco (Elekta) TPS with the Monte Carlo GPUMCD (v5.1) algorithm. For each patient, two plans were generated, one using our conventional Elekta Agility linac beam model and another using the Elekta MRI Linac (MRL) model. Both plans were generated on the average CT using similar dose constraints and a 5 mm PTV. The optimization was performed using our clinic’s planning criteria, with normalization of the targets such that their V99% was equal to 99%. The OAR DVHs were compared for each patient. Results: The DVH plots revealed that there were limited differences when optimizing plans in the presence or absence of the magnetic field. The mean of the absolute differences, between the two planning types, in the equivalent uniform doses (EUDs) for the OARs were: 0.3 Gy (range of 0.0 - 1.0 Gy) for the esophagus, 0.6 Gy (range of 0.1 – 1.9 Gy)more » for the heart, 0.5 Gy (range of 0.2 – 0.8 Gy) for the lungs, and 0.6 Gy (range of 0.2 – 1.5 Gy) for the spinal canal. Regarding the maximum doses to the serial organs, the mean of the differences were 3.0 Gy (esophagus) and 0.9 Gy (spinal canal). No trends in the differences were observed. Conclusion: This study has demonstrated that there were no major differences between plans optimized using a conventional linac and those optimized using an MRI linac with an orthogonal 1.5 T magnetic field. This is attributed to the consideration of the ERE in the optimization. This project was made possible with the financial support of Elekta.« less

Authors:
; ; ; ; ; ;  [1]
  1. Sunnybrook Health Sciences Centre, Toronto, Ontario (Canada)
Publication Date:
OSTI Identifier:
22649042
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; GY RANGE 01-10; LINEAR ACCELERATORS; MAGNETIC FIELDS; MONTE CARLO METHOD; NMR IMAGING; OPTIMIZATION; PATIENTS; PLANNING

Citation Formats

Al-Ward, S, Kim, A, McCann, C, Ruschin, M, Cheung, P, Sahgal, A, and Keller, B. SU-F-T-451: Doses to Organs-At-Risk in the Presence and Absence of a 1.5 T Magnetic Field for NSCLC Patients Undergoing SABR. United States: N. p., 2016. Web. doi:10.1118/1.4956636.
Al-Ward, S, Kim, A, McCann, C, Ruschin, M, Cheung, P, Sahgal, A, & Keller, B. SU-F-T-451: Doses to Organs-At-Risk in the Presence and Absence of a 1.5 T Magnetic Field for NSCLC Patients Undergoing SABR. United States. doi:10.1118/1.4956636.
Al-Ward, S, Kim, A, McCann, C, Ruschin, M, Cheung, P, Sahgal, A, and Keller, B. Wed . "SU-F-T-451: Doses to Organs-At-Risk in the Presence and Absence of a 1.5 T Magnetic Field for NSCLC Patients Undergoing SABR". United States. doi:10.1118/1.4956636.
@article{osti_22649042,
title = {SU-F-T-451: Doses to Organs-At-Risk in the Presence and Absence of a 1.5 T Magnetic Field for NSCLC Patients Undergoing SABR},
author = {Al-Ward, S and Kim, A and McCann, C and Ruschin, M and Cheung, P and Sahgal, A and Keller, B},
abstractNote = {Purpose: To determine whether the electron return effect (ERE) has deleterious effects on lung SABR plans optimized in the presence of an orthogonal 1.5 T magnetic field. Methods: Data from five NSCLC-SABR patients were used. The Dose was modeled with a 2.5 mm dose grid in the presence and absence of a magnetic field using the Monaco (Elekta) TPS with the Monte Carlo GPUMCD (v5.1) algorithm. For each patient, two plans were generated, one using our conventional Elekta Agility linac beam model and another using the Elekta MRI Linac (MRL) model. Both plans were generated on the average CT using similar dose constraints and a 5 mm PTV. The optimization was performed using our clinic’s planning criteria, with normalization of the targets such that their V99% was equal to 99%. The OAR DVHs were compared for each patient. Results: The DVH plots revealed that there were limited differences when optimizing plans in the presence or absence of the magnetic field. The mean of the absolute differences, between the two planning types, in the equivalent uniform doses (EUDs) for the OARs were: 0.3 Gy (range of 0.0 - 1.0 Gy) for the esophagus, 0.6 Gy (range of 0.1 – 1.9 Gy) for the heart, 0.5 Gy (range of 0.2 – 0.8 Gy) for the lungs, and 0.6 Gy (range of 0.2 – 1.5 Gy) for the spinal canal. Regarding the maximum doses to the serial organs, the mean of the differences were 3.0 Gy (esophagus) and 0.9 Gy (spinal canal). No trends in the differences were observed. Conclusion: This study has demonstrated that there were no major differences between plans optimized using a conventional linac and those optimized using an MRI linac with an orthogonal 1.5 T magnetic field. This is attributed to the consideration of the ERE in the optimization. This project was made possible with the financial support of Elekta.},
doi = {10.1118/1.4956636},
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}
}