Diffusion Kurtosis Imaging Study Of Brain Microstructure In Alzheimer’s Disease

Objective: To initially exploit the clinical application value of diffusion kurtosisimaging (DKI) on brain microstructure damage in Alzheimer’s disease (AD) bymeasuring the diffusion kurtosis data of white matter (WM) and gray nucleus.Materials and Methods: This prospective study was approved by the hospitalethics committee. The subjects were divided into two groups, AD group and healthycontrol (HC) group. Twenty three cases of AD clinically confirmed were participatedinto this study, including11males and12females. Twenty four healthy volunteerswhose age and gender matched with AD group were as control group (12males,12females). The clinical data of all the subjects was collected, and the mental status wasalso evaluated for every case through MMSE table by neurologist.All patients performed conventional MRI scan and DKI sequence. Bilateral MKvalues, Ka values, Kr values, MD values, Da values, Dr values and FA values of thefrontal lobe-WM, parietal lobe-WM, occipital lobe-WM, temporal lobe-WM, head ofcaudate nucleus, putamen, globus pallidus, splenium of the corpus callosum, genu of thecorpus callosum, trunk of the corpus callosum, thalamus, red nucleus, substantia nigra,anterior limb of the internal capsule, posterior limb of the internal capsule, externalcapsule, hippocampus, dentate nucleus, hemispherium cerebelli were measured. EveryROI was drawn manually three times, and the corresponding mean values of theparameters in each ROI were calculated.Using SPSS20.0statistic software for analysis, all measurement data are shown asmean value and standard deviation, all statistical results were P≤0.05as statistically significant. Two independent samples t-test was used to compare the mean values ofparameters in all brain regions between the AD and HC groups. Receiver operatingcharacteristic (ROC) test were used to assess the ability of regional diffusion measuresto discriminate differences between groups. The correlations between DKI parametersand MMSE score were tested using Pearson’s correlation.Results1. Compared to the HC group, the mean value of MK, Ka and Kr in AD groupsignificantly decreased in parietal lobe-WM, temporal lobe-WM, external capsule andthalamus; MK and Kr value also decreased in occipital lobe-WM and hippocampus;MK and Ka value decreased in anterior limb of the internal capsule and genu of thecorpus callosum; MK and Kr value decreased in trunk of the corpus callosum; Ka valuedecreased in splenium of the corpus callosum, posterior limb of the internal capsule anddentate nucleus; Kr value decreased in hemispherium cerebelli (all P＜0.05).While, MK, Ka and Kr value markedly increased in substantia nigra; MK valueincreased in head of caudate nucleus (P＜0.05).2. Compared to the HC group, MD, Da and Dr value in AD group significantlyincreased in frontal lobe-WM, anterior limb of the internal capsule, trunk of the corpuscallosum, hemispherium cerebelli, head of caudate nucleus and dentate nucleus; MDand Dr value increased in parietal lobe-WM, temporal lobe-WM and external capsule;MD and Da value increased in splenium of the corpus callosum, thalamus and putamen;MD value increased in posterior limb of the internal capsule, genu of the corpuscallosum and red nucleus; Da and Dr value increased in globus pallidus; Dr valueincreased in occipital lobe-WM and hippocampus (all P＜0.05).3. Compared to the HC group, FA value in AD group significantly decreased infrontal lobe-WM, parietal lobe-WM, occipital lobe-WM, temporal lobe-WM, trunk ofthe corpus callosum, genu of the corpus callosum, anterior limb of the internal capsule,external capsule, hippocampus, globus pallidus and substantia nigra (P＜0.05).Whileas, FA value markedly increased in head of caudate nucleus, red nucleus anddentate nucleus (P＜0.05). 4. The biggest area under ROC curve (AUC) value of0.954belongs to Dr value inthe temporal lobe-WM, and then Dr value of0.758was calculated as the cutoff fordiagnosing AD with the sensitivity of0.938and specificity of0.870. In turn, the AUCof0.880,0.840,0.823,0.810and0.804was attributed to the Dr value in hippocampusand frontal lobe-WM, the MD value in temporal lobe-WM, the Dr value in globuspallidus and parietal lobe-WM.5. In all regions, the MK value, Ka value and Kr value showed the positivecorrelation with MMSE score (P＜0.05) in addition to the negative correlation for Kavalue and MMSE in substantia nigra. In addition to negative correlation of FA valuewith MMSE score in head of caudate nucleus, the FA value in the remaining regionsexhibited the positive correlation with MMSE score. Furthermore, the negativecorrelation was present between MD value, Da value, Dr value and MMSE score in allregions.Conclusion1. As a new MRI technique, DKI can quantitatively evaluate and diagnosis of ADpatients.2. DKI parameters may be more accurate in the assessment of microstructuredamage and mental status in AD patients. The temporal lobe, parietal lobe andhippocampus are the vulnerable structures in patients with AD.3. The Dr value in the temporal lobe-WM can be as the best individual biomarkersof differentiation AD to controls.