Preliminary Study On Early Radiation-induced Brain Injury In Rats By Using Magnetic Resonance Imaging (MRI)

Part I MRI features of rat brainObjective: To investigate MRI features of rat brain using3Tesla MR machine andprovide the basis for early radiation-induced brain injury.Material and Methods: After anesthesia, Wistar rats were scanned with fast spinecho (FSE) T2WI, DWI, DTI, ASL and MRS sequences. All images were processedand region of interests (ROIs) were placed on bilateral parietal lobe to measure ADCvalues. FA values were detected on genu of the corpus callosum. CBF values ofbilateral basal ganglia were measured. MRS of whole rat brain was checked to obtainspectral line of metabolite.Results: The mean ADC values of bilateral parietal lobe were0.784±0.091(×10-3mm2/s)(left) and0.788±0.083(×10-3mm2/s)(right),respectively. Mean FAvalues of corpus callosum were0.296±0.046. The mean CBF values of left basalganglia were (29.85±9.58)ml100g-1min-1and the right side was (31.18±10.14)ml100g-1min-1. There were no statistically significant difference between bilateralADC (t=-0.160,p=0.874) and CBF values (t=-1.195,p=0.247). MRS of rat brain wassimilar with human brain.Conclusion:Images of rat brain were clear and stable using3.0tesla MR machine,and it can provide basis information for early radiation brain injury. Objective: Early radiation-induced brain injury model was established with gammaray radiation of the right lobe of rats. Using different MR sequences to detect earlyradiation-induced brain injury and compared the results with pathology.Material and Methods: After anesthesia, Wistar rats were irradiated with single doseof35Gy Gyro knife on right parietal lobe. All rats were scanned with FSE T2WI,DWI, DTI, ASL and MRS sequences at the end of1,2,4and6weeks. Parameterswere compared with normal group and the pathology of rat brain.Results:Mean ADC values of bilateral parietal lobe decreased gradually. At the endof the6th week, they were (0.686±0.148)×10-3mm2/s (left) and(0.690±0.164)×10-3mm2/s (right), respectively. Mean FA values of the genu ofcorpus callosum decreased from the first week. At the end of6th week mean FAvalues was0.219±0.032. Mean CBF values of bilateral basal ganglia were (21.13±9.39) ml100g-1min-1(left) and (20.40±8.98) ml100g-1min-1(right) respectively1week later and then increased. At the end of the4th week, they were (30.58±7.18)ml100g-1min-1(left) and (31.58±7.54) ml100g-1min-1(right), which was similarwith normal group and then decreased slightly with the left side being (28.70±12.80)ml100g-1min-1and the right side (29.32±12.56) ml100g-1min-1. MRS showed thatafter radiation, Cho/Cr increased gradually and NAA/Cr decreased.Conclusion:Parameters changed as early as the1st week after radiation. DWI, DTI,ASL and MRS were sensitive sequences, which can detect abnormal changes innormal appearing brain parenchyma.