Pathological and radiological-control study of brain tissue radiation injury in normal rats: a comparative study

Abstract

Objective To study the imaging findings and pathologic changes of early radiation injury of normal brain tissue in rats with gamma ray irradiation. Methods Seventy adult SD rats were randomly divided into either a radiation group or a control group. Using the self-made rat stereotactic head frame, the right side of rat brain tissue was irradiated by 100 Gy doses. Each observation time point received 7.0 T head MRI and diffusion tensor imaging (DTI) at 1, 2, 3, 4, 5, 6, and 7 weeks after radiation. The values of apparent diffusion coefficient (ADC) and fractional anisotropy (FA) were statistically analyzed. Brain tissue samples were obtained for pathological observation at the same time. Results (1) The findings of DTI: There were significant differences in rADC values and rFA values from the 4th week between the radiation group and the control group (the ratios at the 4th, 5th, 6th, and 7th weeks were 1.27±0.06 vs. 0.98±0.04 and 0.75±0.05 vs. 1.04±0.05, 1.52±0.08 vs. 0.98±0.03 and 0.64±0.08 vs.1.04±0.05, 1.35±0.09 vs. 1.00±0.02 and 0.63±0.03 vs. 1.04±0.05, and 1.37±0.10 vs. 0.99±0.05 and 0.58±0.04 vs. 1.04±0.03, respectively; all P<0.01). (2) The pathological changes of brain tissue after radiation included two stages: Early microvascular peripheral edema and the structural integrity of blood-brain barrier structure; late target lesions changed significantly, including the decreased number of neurons and glial cells, vasodilatation and deformation, obviously damaged blood-brain barrier structure, and myelin disintegration. Conclusions Early change of rat brain tissue radioactivity is mainly vasogenic edema. The changes of neurons, glial cells, microvascular damage, and demyelination appear in late stage, and these significant changes are consistent with the findings of DTI, indicating the value of DTI in the studies of radiation damage. Key words: Radiosurgery; Gamm knife; Brain injuries; Radioactivity; Diffusion tensor imaging; Rats