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Objective:
Arterial spin labelling (ASL) MR sequence permits absolute quantification of cerebral blood flow (CBF), allowing the assessment of the distinctive pattern of hypoperfusion in patients with Alzheimer’s Dementia (AD). The high spatial and contrast resolution with 3D postprocessing and color-coded segmentation offered by MR volumetric analysis has been shown to allow early diagnosis of dementia before clinical manifestations. In this study, we aim to analyze the cerebral perfusion and gray matter (GM) atrophy changes and understand their intricate relationship with each other.

Materials and Methods:
In this ongoing study, 15 patients with AD and 15 sex- and age-matched healthy controls (HC) were recruited and analyzed for voxel-wise differences in the 3-T MR-derived GM volume and ASL-derived CBF in the following eight candidate areas: namely, hippocampus, thalamus, medial prefrontal cortex, precentral gyrus, anterior cingulate gyrus, posterior cingulate gyrus, precuneus, and cuneus. Volumetric mapping and ROI linear regression analysis were applied to study the differences between patients and controls on MR-volumetry and ASL in these target areas. Linear regression analysis was used to assess the relationship between ASL-derived cerebral hypoperfusion and MR volumetry-derived brain atrophy.

Results:
We observed that GM volume was significantly lower in the posterior cingulate cortex, precuneus, hippocampus, and thalamus in patients with AD than in HC with a p-value of < 0.05. Regional volumetrics showed an accuracy of 85%, sensitivity of 90%, and specificity of 82%. The diagnostic performance of volumetry was more than average (72%). Global perfusion was found to be lower in all patients with AD than in controls. Excellent separation between patients and controls was achieved (93% accuracy, 92% sensitivity, and 90% specificity), as target-area specific CBF values were found to be significantly lower in all candidate regions in patients with AD than in HC (p < 0.05), except for anterior cingulate cortex. Diagnostic performance of ASL was good (80–87%). A comparison of GM volume and CBF values obtained for these candidate areas showed that these values vary similarly with each other but are independent of each other (p > 0.05). The findings suggest that CBF variations contain complementary information to structural modifications in AD, and they support the idea that assessing CBF with ASL MRI may provide information equivalent to that acquired with FDG PET.

Conclusion:
We found that both ASL and MR volumetric analysis are indisputable surrogates to each other in the accurate diagnosis of AD. This might negate the need for additional imaging studies, like PET.