Assessment the Changes of Cortical Thickness in Alzheimer’s Disease in MR images using Freesurfer Software

Purpose: In this study, the main goal was to determine the correlation between the thickness of cerebral cortex and the severity of cognitive disorder in Alzheimer's disease Materials and method: Twenty patients diagnosed with Alzheimer’s disease with mean age of 72.95 year(14 women and 6 men) and Ten Cognitively normal (CN) subjects with mean age of 70.50 year( 7 women and 3 men) were included to the study. Of the AD patient and CN subjects, 70% were female and 30% were male. All individual underwent 1.5 T MRI. The MR scanning protocol included 3D MPRAGE (3D-T1W) sequence. All images were analyzed using Freesurfer v5.3 and then calculated the brain cortical thickness in 7 cortex( Inferior temporal, Middle temporal, Superior temporal, parahippocamp, parstriangularis, rostralmiddle frontal, Superior frontal). Result: The Analysis of covariance (ANCOVA) was conducted to compare the means of each region between the patient whilst control group. There was a significant difference in mean of cortical thickness in all regions. In all cases the mean of cortical thickness in CN subjects were greater than AD patients. However, the mean of Parstriangularis left hand in CN subjects was not significantly greater than the one in AD patients. The receiver operating characteristic system (ROC) was designed to evaluate the predictive power of the patient and the healthy person. We have selected a thousand cut-off points from 1.5 to 3.5mm for cortical thickness. When the cut-off points were interval (2.276878, 2.299680) millimeter in left hemisphere, the Youden’s index was maximized. The sensitivity and specificity in this case were 80%. Also when the cut-off points were within the range (2.263278, 2.282278) mm in right hemisphere, the sensitivity and specificity were 90% and 80%, respectively. Conclusion: This study demonstrates the importance of quantify the cortical thickness changes in early diagnosis of Alzheimer’s disease. In addition, examining the pattern of changes and the quantifying the reduction in the thickness of the cortex is an important tool for displaying the local and global atrophy of the brain. Also, this pattern can be used as an alternative marker for the diagnosis of dementia. Finally, to the best of our knowledge, our study is the first one to report finding on the range of cortical thickness that would help clinician to have better differential diagnose and also in this study have checked the possibility of early diagnosis of the disease.