Multimodal neuroimaging in dementia and neurodegenerative disorders: complementary roles of clinically available nuclear medicine and MRI in the era of disease-modifying therapies

Abstract The introduction of anti-amyloid-β antibody therapies has fundamentally changed the clinical landscape of dementia, shifting the role of neuroimaging from diagnosis toward therapeutic decision-making. Amyloid positron emission tomography (PET) has become essential for confirming amyloid pathology and determining treatment eligibility. However, amyloid deposition is frequently observed in cognitively normal elderly individuals and in non-Alzheimer neurodegenerative disorders, indicating that amyloid status alone is insufficient to explain clinical symptoms. In this context, imaging modalities reflecting neurodegeneration, including structural magnetic resonance imaging (MRI) and functional imaging such as 18 F-FDG-PET and brain perfusion single-photon emission computed tomography (SPECT), remain important for assessing disease severity and functional impairment. Furthermore, discrepancies between imaging biomarkers—such as the presence of neurodegeneration without amyloid pathology in cases clinically suspected of Alzheimer’s disease, and atypical imaging patterns—are commonly encountered in clinical practice and may reflect underlying pathological heterogeneity. A multimodal imaging approach that integrates multiple biomarkers provides complementary information and may improve diagnostic accuracy and clinical interpretation. In addition, other imaging modalities, including dopamine transporter (DAT) imaging and cardiac sympathetic imaging, can contribute to the evaluation of non-Alzheimer pathologies. This review summarizes the current roles of clinically available multimodal imaging in dementia, with a focus on nuclear medicine and MRI, highlighting their complementary value and clinical implications in the era of disease-modifying therapies.