Radiation‐induced early changes in the brain and behavior: Serial diffusion tensor imaging and behavioral evaluation after graded doses of radiation

Abstract

The nuclear arsenal and the use of nuclear technologies have enhanced the likelihood of whole-body/partial-body radiation exposure. The central nervous system is highly susceptible to even low doses of radiation. With the aim of detecting and monitoring the pathologic changes of radiation-induced damage in brain parenchyma, we used serial diffusion tensor magnetic resonance imaging (DTI) with a 7T magnetic resonance unit and neurobehavioral assessments mice irradiated with 3-, 5-, and 8-Gy doses of radiation. Fractional anisotropy (FA) and mean diffusivity (MD) values at each time point (baseline, day 1, day 5, and day 10) were quantified from hippocampus, thalamus, hypothalamus, cudate-putamen, frontal cortex, sensorimotor cortex, corpus callosum, cingulum, and cerebral peduncle. Behavioral tests were performed at baseline, day 5, and day 10. A decrease in FA values with time was observed in all three groups. At day 10, dose-dependent decreases in FA and MD values were observed in all of the regions compared with baseline. Behavioral data obtained in this study correlate with FA values. Radiation-induced affective disorders were not radiation dose dependent, insofar as the anxiety-like symptoms at the lower dose (3 Gy) mimics to the symptoms with the higher dose (8 Gy) level but not with the moderate dose. However, there was a dose-dependent decline in cognitive function as well as FA values. Behavioral data support the DTI indices, so it is suggested that DTI may be a useful tool for noninvasive monitoring of radiation-induced brain injury.

Altered brain metabolism after whole body irradiation in mice: A preliminary in vivo1H MRS study

“…Recently, one study from our group observed memory defi cit, altered anxiety level and gross behavioural changes based on open fi eld test and novel object recognition test at day 5 and day 10 following whole body radiation exposure of 8 Gy. Th ese changes corresponded well with decreased fractional anisotropy and Int J Radiat Biol Downloaded from informahealthcare.com by Monash University on 09/20/13 reduced mean diff usivity in diff erent brain regions of mice post irradiation (Trivedi et al 2012). In our study, we have found reduced mI and tau levels in the hippocampus region in response to whole body radiation exposure.…”

Longitudinal changes in the DTI measures, anti-GFAP expression and levels of serum inflammatory cytokines following mild traumatic brain injury

“…The DTI data obtained for different timepoints was processed as described in detail elsewhere (Trivedi et al, 2012). Briefly, after image cropping and distortion corrections, the data was interpolated to attain isotropic voxels and decoded to obtain the tensor field for each voxel.…”

Radiation Injury to the Normal Brain Measured by 3D‐Echo‐Planar Spectroscopic Imaging and Diffusion Tensor Imaging: Initial Experience

“…Diffusion tensor imaging (DTI) is commonly used in the evaluation of brain tumors 21 and to evaluate radiation injury to the normal brain in pre-clinical models 22,23 as well as in clinical studies. [24][25][26][27] These studies reported alterations in mean diffusivity (MD) and fractional anisotropy (FA) from various regions of the normal brain.…”