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A Pre-Clinical Study of Radiation-Induced Lung Toxicity When Treating in a Strong Magnetic Field

A Rubinstein

A Rubinstein*, C Peterson , C Kingsley , J Pollard , R Tailor , D Followill , A Melancon , L Court , The University of Texas MD Anderson Cancer Center, Houston, TX


MO-AB-FS4-2 (Monday, July 31, 2017) 7:30 AM - 9:30 AM Room: Four Seasons 4

Purpose: To assess the effect of a strong, transverse magnetic field on the severity of radiation-induced lung damage in mice. This data will be used to support the implementation of MRI-guided radiation therapy systems.

Methods: Monte Carlo simulations and EBT3 film measurements were used to determine the appropriate beam energy and magnetic field strength needed to produce magnetic-field-induced dose effects in mice comparable to those seen in human simulations. C57L/J mice were irradiated in a 3D printed holder to the whole thorax using parallel-opposed Co-60 beams (9.0, 10.0, 10.5, 11.0, 12.0, or 13.0 Gy). The mice were irradiated between the poles of an electromagnet in a 1.5T field (n=60) or 0T field (n=60). Twenty control mice did not receive radiation. Survival curves were compared using a log-rank test. Monthly respiratory rate and CBCT measurements (lung density and healthy lung volume) were made up to 8 months post-irradiation to assess the severity of radiation-induced pneumonitis. Differences between median effective dose (ED50) values were compared using an extra sum-of-squares F-test.

Results: Monte Carlo and film measurements showed that a 1.5T field and a Co-60 beam would produce dose perturbations in mice comparable to those seen in human simulations. The magnetic field had no significant impact on survival for mice in any dose group. For respiratory rate, lung density, and healthy lung volume measurements, the difference in the ED50 at 5 months between mice irradiated with and without a magnetic field present was small (2.4%, 1.6%, 2.2%, respectively), but significant (p<0.05).

Conclusion: This study showed that applying a strong transverse magnetic field during mouse lung irradiation had no impact on survival. However, the magnetic field did have an effect on respiratory rate and the appearance of lung in CBCT images. These results warrant a further investigation of biological consequences of magnetic-field-induced dose perturbations.

Funding Support, Disclosures, and Conflict of Interest: This work was partially funded by Elekta.

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