Application Of DWI And DTI In The Diagnosis Of Minimal Hepatic Encephalopathy

Objective To analyze the brain function changes in patients with minimal hepatic encephalopathy(MHE)by using diffusion weighted imaging(DWI)and diffusion tensor imaging(DTI)techniques,and to investigate the correlation between changes in some brain regions and blood ammonia value,neuropsychological test score and child-pugh grade of liver function.So as to explore the application value of DWI and DTI to the MHE patients and provide clues to the pathogenesis of MHE.Materials and Methods Patients with hepatitis B cirrhosis diagnosed in the Department of Infectious Diseases of our hospital were selected as subjects.They were divided into MHE group and simple cirrhosis group by digital connection test-A(NCT-A)and digit symbol test(DST),and there were 20 cases in each group.At the same time,20 healthy volunteers of equal age and gender were recruited as healthy controls.Each participant underwent routine magnetic resonance imaging(MRI),DWI and DTI scan.The bilateral frontal and occipital white matter,centrum semiovale,genu of corpus callosum,splenium callosum,head of caudate nucleus,anterior limb of internal capsule,posterior limb of internal capsule,substantia nigra and red nucleus were outlined on apparent diffusion coefficient(ADC)and fractional anisotropy(FA)images,and the values of the corresponding regions were obtained.Single factor of analysis of ADC,FA values differences were used among three groups.Pearon correlation analysis was made between statistically significant target value with abnormal differences and blood ammonia value,NCT-A and DST score,and Spearman correlation analysis with Child-Pugh grade of liver function.Results1.The ADC values of bilateral frontal white matter,occipital white matter,genu of corpus callosum,splenium callosum were significantly different among the three groups(P<0.05).The ADC values increased successively from healthy control group,simple cirrhosis group to MHE group.The ADC values of bilateral posterior limb of internal capsule,head of caudate nucleus and bilateral substantia nigra in MHE group were higher than those in normal control group and simple cirrhosis group(P<0.05).There was no statistical difference in ADC values of other sites.(P>0.05).2.The FA value of the genu of corpus callosum was statistically significant(P<0.05)in the healthy control group,the simple cirrhosis group and the MHE group,and the FA value decreased in turn.There was no statistical difference in FA values of other sites.(P>0.05).3.The NCT-A finishing time was positively correlated with the ADC values of the white matter of the frontal part(r=0.590,P=0.000),the genu of the corpus callosum(r=0.532,P=0.000),the white matter of the occipital part(r=0.319,P=0.045)and the substantia nigra(r=0.527,P=0.000).The NCT-A finishing time was negatively correlated with the FA value of the genu of the corpus callosum(r=-0.528,P=0.000).The DST score was negatively correlated with the the ADC values of white matter of the frontal part(r=-0.550,P=0.000),the genu of the corpus callosum(r=-0.456,P=0.003),the occipital white matter(r=-0.325,P=0.040)and the substantia nigra(r=-0.430,P=0.006).The DST score was positively correlated with the FA value of the genu of corpus callosum(r=0.607,P=0.000).4.The level of blood ammonia was positively correlated with the ADC value of the head of caudate nucleus(r=0.356,P=0.024).The Child-Pugh grade of liver function was positively correlated with the ADC value of the posterior limb of the internal capsule(r=0.357,P=0.024),and negatively correlated with the FA value of the genu of the corpus callosum(r=-0.341,P=0.031).Conclusion1.The increase of ADC values in most brain regions of MHE patients suggests that there may be extensive low-grade brain edema of MHE.2.The decrease of FA value in the genu of corpus callosum in MHE patients suggests that the integrity of white matter fibers in the genu of corpus callosum may be impaired in MHE patients.3.The ADC values of bilateral frontalis,occipital lobe,nigra and corpus callosum knee tissue and FA values of corpus callosum knee were correlated with NCT-A and DST scores in patients with MHE.It is inferred that bilateral frontalis and occipital lobe of MHE patients.The brain edema of substantia nigra and corpus callosum knee and the destruction of white matter fiber structure in the knee of corpus callosum may lead to the decrease of cognitive function in patients with MHE.4.The level of blood ammonia was positively correlated with the ADC value of the head of caudate nucleus in patients with MHE,suggesting that the head of caudate nucleus might be one of the sensitive sites of high blood ammonia level.5.DWI combined with DTI may have the clinical value of potential diagnosis of MHE.