Correlation between venous blood phase values detected by enhanced gradient echo T2 star weighted angiography sequence and neurological severity scale scores in mild and severe traumatic brain injury models of rabbits

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. Key words: Brain injuries; Magnetic rsonance imaging; Models, animal