Temporal Evolution Of Diffusion Kurtosis Imaging In Early Hypoxic-ischemic Cerebral Edema

ObjectiveIn this study,based on the animal model of hypoxic-ischemic encephalopathy in newborn piglets,diffusion kurtosis imaging(DKI)was used to evaluate the diffusion changes of early hypoxic-ischemic cerebral edema.To provide a dynamic,noninvasive and more accurate diagnostic and evaluation method for neonatal hypoxic-ischemic encephalopathy.The main research contents are as follows:1.Whether DKI can dynamically,noninvasive and accurately evaluate early hypoxic-ischemic cerebral edema;2.Evaluation of DKI on the effect of leptin on early hypoxic-ischemic cerebral edemaMaterial and Methods1.A total of 20(10 males,10 females)newborn healthy Yorkshire piglets were randomly divided into two groups:HIE(n=15;8 males,7 females)and control(n=5;2males,3 females).Anesthesia was administered by inhaling isoflurane.The bilateral common carotid arteries were separated by a 3～5-cm longitudinal incision in the middle of the neck.In the HIE groups,the bilateral common carotid artery was ligated with 4-0fine silk.The incisions were then stitched together.The piglets were placed into a closed hypoxic chamber with a mixture of 4%oxygen and 96%nitrogen at a flow rate of 2 L/min for 30 min.Only the bilateral carotid artery dissection was performed in the control group.3,6,9,12,16 and 24 hours after setting up model,DKI scanning was performed in HIE group and control group respectively.After scanning,select swine from HIE group and control group respectively for pathological examinations(hematoxylin-eosin staining).2.A total of 35(19 males,16 females)newborn healthy Yorkshire piglets were randomly divided into two groups:HIE(n=15;8 males,7 females),leptin(n=15;8males,7 females)and control(n=5;3 males,2 females).HIE models were prepared in both HIE group and leptin group,and the preparation process was the same as above.After surgery,the leptin group was intraperitoneally injected with leptin.3,6,9,12,16and 24 hours after setting up model,DKI scanning was performed in each group respectively.The lesion areas(cm~2)were measured on the MK and MD maps at each time points.After scanning,select swine from each group respectively for pathological examinations(hematoxylin-eosin staining and TEM).3.The SPSS 19.0 software was used for all statistical analyses.All parameter values were tested for normality and homogeneity of variance,and the data were expressed as the mean±standard deviation.Differences in parameter values among the different time points and between groups were calculated using a repeated measures ANOVA,the percent changes of different metrics within and between groups were compared using t-test.Comparisons between the lesion areas of the HIE and leptin group were made using the independent-samples t-test.All multiple comparisons were performed using the post-hoc least significant difference method.P<0.05 was set as the statistical significance threshold.Results1.In the lesion areas,DKI-related parameters(MK,Kr,Ka)in the lesion area demonstrated inhomogeneous high signals,whereas DTI-related parameters(MD,Dr,Da)showed relative homogeneous low signals.The MK,Ka,Kr,MD,Da,and Dr values were significantly different between the HIE and the control group(P-value<0.05);In the HIE group,the percent changes in the DKI-related variables(MK,Ka and Kr)were significantly higher than those of the DTI-related variables(MD,Da and Dr)at different time points,the relative magnitude of changes in the axial metrics(Ka and Da)were significantly higher than those in the radial metrics(Kr and Dr)(P-value<0.05).In the HIE group,the MK,Ka,Kr,MD,Da,and Dr values gradually changed from 3 to 24 h in the lesion areas(P-value<0.05);Pathological sections in the HIE group showed neuron swelling,interstitial edema,infiltration of a large number of inflammatory cells,peripheral vascular dilatation and glial nodules.2.At each time point,MK,Ka,and Kr values in the leptin group were significantly lower than those in the HIE group,whereas MD,Da,and Dr values displayed the opposite relationship(P-value<0.05);In the HIE and leptin groups,the percent changes in the DKI-related variables(MK,Ka and Kr)were significantly higher than those of the DTI-related variables(MD,Da and Dr)at different time points,the percent changes of leptin group were lower than that of HIE group(P-value<0.05);In the HIE and leptin group,the MK,Ka,Kr,MD,Da,and Dr values gradually changed from 3 to 24 h in the lesion areas,however,the trend of change in the leptin group slowed down significantly(P-value<0.05);the lesion areas of leptin group were smaller than those of HIE group at each time point,regardless of MK or MD maps(P-value<0.05).The pathological results showed that less cell and organelle injury occurred in the leptin group.ConclusionsIn conclusion,the advantages of DKI were the production of multiple b-value and multi-parameter images and more realistic imaging model,which can provide a more detailed information than conventional MRI techniques in describing the hypoxic-ischemic brain damage,and accurately,dynamically and noninvasive to evaluate the change trend and treatment effect of hypoxic-ischemic cerebral edema.Therefore,DKI can be potentially used in neonatal HIE.