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Title: SU-G-JeP2-11: Polymer Gels as 3D QA Devices in Magnetic Resonance-Guided Radiation Therapy

Abstract

Purpose: To demonstrate the potential of polymer gels to serve as 3D QA devices in MR-guided radiotherapy. Methods: Custom-designed polymer gel dosimeters (MGS Research, Madison, CT) were centered on the penumbras of a radiation field, parallel to the magnetic field lines inside a 1.5 T MR scanner integrated with a 7 MV linac (MR-Linac). 15 Gy were delivered perpendicular to the magnetic field. Coronal MR images were acquired with a 2D balanced-Fast Field Echo (b-FFE) sequence in real-time during irradiation and with a 2D spin echo sequence at different times after irradiation. Signal intensities (SI) were measured inside and outside the radiation field on b-FFE images obtained during irradiation. Spin-spin relaxation rate (R2) maps were calculated from images after irradiation and penumbra widths were calculated from these maps. Results: A difference in SI between areas of the dosimeter inside and outside of the radiation field could be measured immediately after the beam was turned on. The difference in SI increased throughout the duration of the exposure. R2 values from immediately after irradiation were 83% of those measured 24h post-irradiation. At 1h after irradiation, the R2 values were 87% of those at 24h indicating that polymerization of the gel was stillmore » ongoing. At 24h postirradiation the width of the 80/20 penumbra on the left field edge measured 6.5 mm and on the right 5.6 mm. Conclusion: The MR-Linac allows for MR imaging during treatment and measurements of 3D dose distributions with steep dose gradients without having to transfer dosimeters for read-out. The results showed promise for polymer gels as relative 3D QA devices to verify radiation treatment plans delivered by an MR-Linac. To our knowledge, this was the first time that polymer gels were used for real-time image acquisition. Further investigations into the application of polymer gel dosimetry on MR-Linac are ongoing.« less

Authors:
 [1];  [2];  [3]; ;  [4];  [1]
  1. University of Houston, Houston, TX (United States)
  2. (United States)
  3. MR Therapy, Philips healthTech, Cleveland, OH (United States)
  4. UT MD Anderson Cancer Center, Houston, TX (United States)
Publication Date:
OSTI Identifier:
22649377
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; BIOMEDICAL RADIOGRAPHY; DOSEMETERS; IMAGES; IRRADIATION; LINEAR ACCELERATORS; MAGNETIC FIELDS; MAGNETS; POLYMER GEL DOSIMETRY; POLYMERIZATION; RADIATION DOSE DISTRIBUTIONS; RADIOTHERAPY

Citation Formats

Roed, Y, UT MD Anderson Cancer Center, Houston, TX, Kadbi, M, Wang, J, Ibbott, G, and Pinsky, L. SU-G-JeP2-11: Polymer Gels as 3D QA Devices in Magnetic Resonance-Guided Radiation Therapy. United States: N. p., 2016. Web. doi:10.1118/1.4957031.
Roed, Y, UT MD Anderson Cancer Center, Houston, TX, Kadbi, M, Wang, J, Ibbott, G, & Pinsky, L. SU-G-JeP2-11: Polymer Gels as 3D QA Devices in Magnetic Resonance-Guided Radiation Therapy. United States. doi:10.1118/1.4957031.
Roed, Y, UT MD Anderson Cancer Center, Houston, TX, Kadbi, M, Wang, J, Ibbott, G, and Pinsky, L. Wed . "SU-G-JeP2-11: Polymer Gels as 3D QA Devices in Magnetic Resonance-Guided Radiation Therapy". United States. doi:10.1118/1.4957031.
@article{osti_22649377,
title = {SU-G-JeP2-11: Polymer Gels as 3D QA Devices in Magnetic Resonance-Guided Radiation Therapy},
author = {Roed, Y and UT MD Anderson Cancer Center, Houston, TX and Kadbi, M and Wang, J and Ibbott, G and Pinsky, L},
abstractNote = {Purpose: To demonstrate the potential of polymer gels to serve as 3D QA devices in MR-guided radiotherapy. Methods: Custom-designed polymer gel dosimeters (MGS Research, Madison, CT) were centered on the penumbras of a radiation field, parallel to the magnetic field lines inside a 1.5 T MR scanner integrated with a 7 MV linac (MR-Linac). 15 Gy were delivered perpendicular to the magnetic field. Coronal MR images were acquired with a 2D balanced-Fast Field Echo (b-FFE) sequence in real-time during irradiation and with a 2D spin echo sequence at different times after irradiation. Signal intensities (SI) were measured inside and outside the radiation field on b-FFE images obtained during irradiation. Spin-spin relaxation rate (R2) maps were calculated from images after irradiation and penumbra widths were calculated from these maps. Results: A difference in SI between areas of the dosimeter inside and outside of the radiation field could be measured immediately after the beam was turned on. The difference in SI increased throughout the duration of the exposure. R2 values from immediately after irradiation were 83% of those measured 24h post-irradiation. At 1h after irradiation, the R2 values were 87% of those at 24h indicating that polymerization of the gel was still ongoing. At 24h postirradiation the width of the 80/20 penumbra on the left field edge measured 6.5 mm and on the right 5.6 mm. Conclusion: The MR-Linac allows for MR imaging during treatment and measurements of 3D dose distributions with steep dose gradients without having to transfer dosimeters for read-out. The results showed promise for polymer gels as relative 3D QA devices to verify radiation treatment plans delivered by an MR-Linac. To our knowledge, this was the first time that polymer gels were used for real-time image acquisition. Further investigations into the application of polymer gel dosimetry on MR-Linac are ongoing.},
doi = {10.1118/1.4957031},
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}
}