SU-G-TeP3-12: Retrospective Assessment of R2star Using Ultra-High Field MRI in a Rodent Model of Radiation Necrosis
- University of Western Ontario, London, ON (Canada)
- University of Western Ontario, London, Ontario (Canada)
Purpose: To establish a quantitative MRI method that would be capable of predicting radiation necrosis without using a contrast agent. Methods: Healthy male Fischer 344 rats were irradiated using an animal irradiator capable of delivering 2.3 Gy/min with a kVp of 225 V. A dose of 40 Gy was given to half the brain in a single session. Rats were scanned using a 9.4 T animal MRI before irradiation and every two weeks following radiation until either necrosis developed or they were sacrificed for health reasons. A multi-echo gradient-echo sequence was acquired at every time point and the apparent transverse relaxation rate R{sub 2}* was calculated based on the measured signal decay. At the last time point, an ROI mask with an R{sub 2}* value of greater than 45 s{sup −1} was applied in the area of the external and internal capsule where radiation necrosis was confirmed. A retrospective analysis was performed to determine whether R{sub 2}* values would be able to predict where radiation necrosis would occur. Results: Radiation necrosis was morphologically visible between weeks 22–24 following treatment. Gadolinium MRI and histology confirmed radiation necrosis in the area of MRI enhancement. Our data suggests that there is a trend towards significance in the lesion as early as 12 weeks prior to morphological changes on MRI with significance occurring 6 weeks prior (p≤0.05, p≤0.01 at week 24). Measurements of the R{sub 2}* in the hippocampus did not show any significant difference; however, there are areas of visible R{sub 2}* change within sub-hippocampal regions. Conclusion: R{sub 2}* is a promising method that could be able to predict an underlying disease process that occurs prior to radiation necrosis. The constant increase in R{sub 2}* values suggests a possible neuroinflammatory mechanism rather than an acute vascular event where R{sub 2}* would tend to decrease in the area.
- OSTI ID:
- 22649433
- Journal Information:
- Medical Physics, Vol. 43, Issue 6; Other Information: (c) 2016 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-2405
- Country of Publication:
- United States
- Language:
- English
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