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Diffusion MRI monitoring of specific structures in the irradiated rat brain
Author(s) -
Constanzo Julie,
Dumont Matthieu,
Lebel Réjean,
Tremblay Luc,
Whittingstall Kevin,
MassonCôté Laurence,
Geha Sameh,
Sarret Philippe,
Lepage Martin,
Paquette Benoit,
Descoteaux Maxime
Publication year - 2018
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.27112
Subject(s) - fractional anisotropy , white matter , diffusion mri , astrogliosis , corpus callosum , hippocampus , nuclear medicine , medicine , pathology , magnetic resonance imaging , central nervous system , radiology
Purpose The analysis of biological and mesoscopic structures properties by diffusion MRI (dMRI) in brain after radiation therapy remains challenging. In our study, we described the consequences associated with an unwanted dose to healthy tissue, assessing radiation‐induced brain alterations of living rats with dMRI compared to histopathology and behavioral assays. Methods The right primary motor cortex M 1 of the rat brain was targeted by stereotactic radiosurgery with a mean radiation dose of 41 Gy. Multidirectional single b‐value dMRI data of the whole brain were acquired with a 7T small‐animal scanner before irradiation until 110 days post‐irradiation. Diffusion tensor imaging metrics, such as fractional anisotropy (FA), mean diffusivity (MD), axial (AD), and radial diffusivity (RD) were compared to brain alterations detected by immunohistochemistry and motor performances measured by a behavioral test. Results Between days 90 and 110, radiation necrosis was observed into the white matter spreading into M 1 . Results showed a reduction of FA in the corpus callosum and in the striatum, which was driven by an increase in RD from 90 to 110 days post‐irradiation, whereas only RD increased in M 1 . Values of RD and AD increased in the irradiated hippocampus, while FA remained constant. Moreover, an increased MD, AD and RD was observed in the hippocampus that was probably related to inflammation as well as reactive astrogliosis after 110 days post‐irradiation. Finally, rats did not exhibit locomotor deficits. Conclusions dMRI metrics can assess brain damage; the sensitivity of dMRI metrics depends on the brain region.