Functional Imaging in Alzheimer's Disease: A Systematic Review and Meta-Analysis of ASL-MRI and FDG-PET.

Background: Alzheimer's disease (AD) and mild cognitive impairment (MCI) are two common conditions associated with cognitive decline. With global dementia cases rising, identifying the most accurate imaging method for diagnosis is essential.

Methods: Following Preferred Reporting Items for Systematic review and Meta-Analysis Protocols, we systematically reviewed studies utilizing arterial spin labeling magnetic resonance imaging (ASL-MRI) and [18F]-2-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) for neurodegenerative disorders. Searches in PubMed/MEDLINE, Scopus, and Embase led to 17 studies directly comparing these modalities for MCI/AD diagnosis. Seven studies met criteria for meta-analysis based on interreader agreement and area under the curve (AUC) data. Meta-analysis was performed using the R "Mada" package, with study heterogeneity assessed via the Zhou and Dendukuri approach.

Results: Meta-analysis of seven studies showed FDG-PET had a slightly higher AUC (0.864, sensitivity 0.81, specificity 0.80) compared to ASL-MRI (AUC 0.836, sensitivity 0.73, specificity 0.80), but no statistically significant difference. Low heterogeneity was observed (I: 9.4% for FDG-PET, 6.5% for ASL-MRI). In MCI subgroup analysis, FDG-PET outperformed ASL-MRI with significantly higher sensitivity (0.90 vs. 0.75), specificity (0.91 vs. 0.73), and AUC (0.92 vs. 0.80, p < 0.001).

Conclusion: FDG-PET and ASL-MRI demonstrate comparable diagnostic accuracy for AD and MCI. Selection between modalities may depend on availability, cost, and safety considerations.

Clinical Relevance/application: Both FDG-PET and MRI-ASL are effective at identifying MCI and AD, enabling accurate diagnosis. The choice of which modality to use may be addressed by cost, availability, and consideration of other potential diagnoses.