MRI-Readable Radiation Dosimetry at Low Magnetic Field (64 mT)

Portable low-field magnetic resonance imaging (LF-MRI) is revolutionizing access to MRI. In addition to new possibilities for point-of-care diagnostics, LF-MRI may have applications beyond imaging patients. For example, the scanners may be used for on-demand 3D imaging of biomimetic objects. In this study, we explored the use of 64 mT LF-MRI for applications in MRI-readable radiation dosimetry, a technique that uses radiation-sensitive biomimetic objects to assess the accuracy of clinical radiation treatments. The use of LF-MRI is advantageous, as it requires less infrastructure than MRI at higher fields, potentially allowing the scanner to be located near radiation oncology units to provide rapid feedback. We developed dosimeters filled with radiation-sensitive MAGIC (Methacrylic and Ascorbic acid in Gelatin Initiated by Copper) gels [1] and exposed the samples to 6 MV photons using linear acceleration. LF-MRI at 64 mT was used to measure the radiation dose deposition in 3D via the longitudinal (T1) and transverse (T2) relaxation times, which changed as a function of radiation dose.  The dosimeter readout was also measured using 3 T MRI for comparison. Analysis suggests that LF-MRI readout for radiation dosimetry can be useful in some cases, but has tradeoffs compared to 3 T.

[1] P. M. Fong, D. C. Keil, M. D. Does, and J. C. Gore, Polymer gels for magnetic resonance imaging of radiation dose distributions at normal room atmosphere, Phys. Med. Biol. 46, 3105 (2001).