International Journal of Radiation Oncology*Biology*Physics
Oral Scientific SessionMulti b-value Diffusion Imaging of Radiation-Induced White Matter Damage
Section snippets
Purpose/Objective(s)
Radiotherapy for brain tumors is limited in part by collateral damage to white matter and its extra-axonal matrix, likely contributing to post-radiation neurocognitive decline. We utilized diffusion tensor imaging (DTI) with multiple b-values (diffusion weightings) to model the effects of radiation on intra-axonal and extra-axonal white matter.
Materials/Methods
Fifteen patients with high-grade glioma treated with radiotherapy and chemotherapy underwent MRI with DTI prior to, and 1, 4-6, and 9-11 months after radiotherapy. The diffusion tensor was modeled as high b-value (b = 0, 4000), standard b-value (b = 0, 500, 1500), and low b-value (b = 0, 500). Region of interest was all white matter. Maps of fractional anisotropy (FA) and mean diffusivity (MD), markers of white matter integrity, as well as axial diffusivity (AD) and radial diffusivity (RD),
Results
MD, AD, and RD increased with time and dose, with corresponding decrease in FA. RD increased more than AD. Changes were observed at all doses, with those at lower doses taking longer to detect. Greater changes were seen with lower b-value, except for FA. All time-dose interactions were statistically significant (Table 1). The difference in dose response between high and low b-values reached significance at 9-11 months for MD, AD, and RD (P < 0.001, P < 0.001, P = 0.005 respectively) as well as
Conclusion
We found dose-dependent progressive white matter changes across all dose bins and time points. Greater change in RD suggests demyelination as a predominant change. There were greater changes at low b-values, suggesting more prominent microstructural changes in the extracellular environment, possibly due to neuroinflammation and vascular permeability, a known factor in radiation injury. Imaging at different b-values with DTI helps characterize the evolution of white matter radiation injury.
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Author Disclosure: M. Connor: None. R. Karunamuni: None. C. McDonald: None. N. White: None. N. Pettersson: None. V. Moiseenko: Prior honorarium and travel fees from Varian Medical Systems for a talk outside the submitted work; Varian. T.M. Seibert: None. D.C. Marshall: None. L.I. Cervino: None. H. Bartsch: None. J. Kuperman: None. V. Murzin: None. A. Krishnan: None. N. Farid: None. A. Dale: Research Grant; GE Healthcare, Medtronic. Patent/License Fees/Copyright; CorTech Labs, Inc. J.A. Hattangadi: Research Grant; Varian.