ABSTRACT
Objective To investigate dynamic regulation of quantifying fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values in rotational brain injury models of rabbit using diffusion tensor imaging (DTI), and its correlation with β?amyloid precursor protein (β-APP). Methods Forty-two 6-month-old New Zealand rabbits were randomly divided into three groups, including control group (n=6), mild injured group (n=18) and severe injured group (n=18), and preformed on autonomous rapidly rotational brain injury device. The rotational angles of 45° for mild injured group and 90° for severe injured group were condemned, and MRI and pathology were conducted at 6 h, 12 h, 24 h, 48 h, 72 h and 1 week after injury (3 rabbits per subgroup). Routine sequences and DTI technique were performed on 3.0 T MRI. FA and ADC values in subcortical white matter, corpus callosum and brain stem were measured. Independent t?test was performed to evaluate the significance of the intergroup difference in FA and ADC values in mild and severe injured groups of verious brain regions by timing, one?way ANOVA was performed to evaluate its timing variation and its correlation with the number of the β-APP positive axons was analyzed by Pearson correlation analysis. Results FA and ADC values of the severe injured group were lower than that of the mild in most brain regions(P<0.05), and the difference in mild injured group was smaller than that in severe injured group. Both FA and ADC values in brain stem of the severe injured group were lower at 6 h after injury compared to mild injured group, which were sensitive to injury. Furthermore, FA and ADC values in each brain regions of mild and severe injured groups showed similar dynamic trends, namely gradually decreasing by time, and FA values were more sensitive to injury than ADC values. FA values in subcortical white matter and brain stem reduced in severe injured group at 6 h after injury compared with that before injury(P<0.05), and decreased in various brain area of both injured groups at 12 h after injury(P<0.05). Meanwhile, ADC values in all regions were declined in the severe injured group at 12 h after injury(P<0.05), and decreased in various regions in both injured groups at 24—48 h after injury(P<0.05)except for subcortical white matter in mild injured group. There were statistically negative correlations between FA and ADC values and the number of β-APP positive axons in 12—48 h after injury in most regions(P<0.05). Conclusions DTI can quantitatively detect and assess the pathological process in white matter and axons of TBI in earlier stage of the brain injury, and can be applied in evaluation and quantitative diagnose in these patients.
ABSTRACT
Objective To explore the change of venous blood phase values detected by enhanced gradient echo T2 star weighted angiography(ESWAN)sequence in mild and severe traumatic brain injury (TBI) models of rabbits in diverse phases and investigate their association with neurological severity scale (NSS) scores. Methods Fifty-one New Zealand rabbits, which were randomly divided into control group (n=3) ,mild injured group (n=24) , and severe injured group (n=24) by random digital table method, underwent routine MRI and ESWAN sequence at the time points of baseline, 1 h, 6 h, 12 h, 24 h, 48 h, 72 h, 1 week, and 2 weeks after injury(3 rabbits per subgroup)respectively. Blood phase values in veins of interest were recorded. Observation of behavior characteristics and abnormalities, followed by NSS, was executed post injury, and the correlation between venous blood phase values and NSS scores was statistically analyzed. Two independent-samples t-test was applied to compare venous blood phase values of diverse measured veins in each group separately at every time ponits. One-way ANOVA was used to analyze venous blood phase values varying over time of measured vessels in each injured group. Least significant difference t-test was applied to compare blood phase values within the subgroups with each other at each time point. NSS scores of mild and severe injured groups were compared by two independent-samples t-test. Correlations between venous blood phase values and NSS scores in each vein and group was analyzed with Spearman correlation analysis. Results Blood phase values in veins of interest presented an inclination of descending, which was more obvious in severe injured groups than in the mild. Change of venous blood phase values over time featured continuing reduction in earlier phases which reached to the minimum in 24-48h, and then increased gradually, especially in VMV, VLV, DSS, and MDVB (P<0.05). ICV and DCV also showed similar trend. Values of NSS scores in the two group were (15.5 ± 3.1) and (33.2 ± 6.5) respectively (t=3.543,P=0.001). Blood phase values in most of the measured veins correlated with NSS scores (P<0.05) after 6h post injury, especially significant during 24-72h among all the measured veins(P<0.05). Higher accuracy and sensitivity were presented in the supratentorial or superficial veins compared with subtentorial or profound veins. Conclusions It is feasible to evaluate oxygen saturation of veins after TBI by measuring venous blood phase values on ESWAN images. The method is effective in the assessment of the degree of injury and clinical status, indicating a favorable application prospect.