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Effect of a Strong Magnetic Field On Select Radiation Dosimeters

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M Mathis

M Mathis*, Z Wen , R Tailor , G Sawakuchi , D Flint , S Beddar , G Ibbott , The University of Texas MD Anderson Cancer Center, Houston, TX


SU-E-T-368 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: To determine the effect of a strong magnetic field on TLD-100, OSLD (Al₂O₃:C), and PRESAGE dosimetry devices. This study will help to determine which types of dosimeters can be used for quality assurance and in-vivo dosimetry measurements in a magnetic resonance imaging-linear accelerator (MRI-linac) system.

Methods: The dosimeters were separated into two categories which were either exposed or not exposed to a strong magnetic field. In each category a set of dosimeters was irradiated with 0, 2, or 6 Gy. To expose the dosimeters to a magnetic field the samples in that category were place in a Bruker small animal magnetic resonance scanner at a field strength slightly greater than 2.5 T for at least 1 hour pre-irradiation and at least 1 hour post-irradiation. Irradiations were performed with a 6 MV x-ray beam from a Varian TrueBeam linac with 10x10 cm² field at a 600 MU/min dose rate. The samples that received no radiation dose were used as control detectors.

Results: The readouts of the dosimeters which were not exposed to a strong magnetic field were compared with the measurements of the dosimetry devices which were exposed to a magnetic field. No significant differences (less than 2% difference) in the performance of TLD, OSLD, or PRESAGE dosimeters due to exposure to a strong magnetic field were observed.

Conclusion: Exposure to a strong magnetic field before and after irradiation does not appear to change the dosimetric properties of TLD, OSLD, or PRESAGE which indicates that these dosimeters have potential for use in quality assurance and in-vivo dosimetry in a MRI-linac. We plan to further test the effect of magnetic fields on these devices by irradiating them in the presence of a magnetic fields similar to those produced by a MRI-linac system.

Funding Support, Disclosures, and Conflict of Interest: Elekta-MD Anderson Cancer Center Research Agreement

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