MRI of late microstructural and metabolic alterations in radiation-induced brain injuries.
OBJECTIVE
To evaluate the late effects of radiation-induced damages in the rat brain by means of in vivo multiparametric MRI.


METHODS
The right hemibrains of seven Sprague-Dawley rats were irradiated with a highly collimated 6 MV photon beam at a single dose of approximately 28 Gy. Diffusion tensor imaging (DTI), proton MR spectroscopy ((1)H-MRS), T2-weighted imaging, and T1-weighted imaging were performed to the same animals 12 months after radiation treatment.


RESULTS
Compared with the contralateral side, a significantly higher percentage decrease in fractional anisotropy was observed in the ipsilateral fimbria of hippocampus (29%) than the external capsule (8%) in DTI, indicating the selective vulnerability of fimbria to radiation treatment. Furthermore, in (1)H-MRS, significantly higher choline, glutamate, lactate, and taurine peaks by 24%, 25%, 87%, and 58%, respectively, were observed relative to creatine in the ipsilateral brain. Postmortem histology confirmed these white matter degradations as well as glial fibrillary acidic protein and glutamine synthetase immunoreactivity increase in the ipsilateral brain.


CONCLUSIONS
The microstructural and metabolic changes in late radiation-induced brain injuries were documented in vivo. These multiparametric MRI measurements may help understand the white matter changes and neurotoxicity upon radiation treatment in a single setting.
Chan
Kevin C
KC
Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong SAR, China.
Khong
Pek-Lan
PL
Cheung
Matthew M
MM
Wang
Silun
S
Cai
Ke-Xia
KX
Wu
Ed X
EX
D000818:Animals; D001921:Brain / Q000378:metabolism* / Q000473:pathology* / Q000528:radiation effects; D001930:Brain Injuries / Q000209:etiology / Q000378:metabolism* / Q000473:pathology*; D005786:Gene Expression Regulation / Q000528:radiation effects; D008279:Magnetic Resonance Imaging / Q000379:methods; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D018377:Neurotransmitter Agents / Q000032:analysis*; D011832:Radiation Injuries / Q000378:metabolism* / Q000473:pathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014018:Tissue Distribution
D018377:Neurotransmitter Agents