An update on molecular and structural Imaging techniques for assessment of Alzheimer’s disease

Learning Objectives To review the diagnostic role and the limitations of molecular imaging and magnetic resonance imaging techniques in assessment of patients with AD. To discuss the current and future trends in AD imaging.

Alzheimer’s disease (AD) is the most common neurodegenerative disease among elderly individuals. Due to the potentially irreversible effects, diagnosis in early stages is important. Positron Emission Tomography (PET) using FDG plays an important role in monitoring disease progression especially by showing hypometabolism in posterior regions of the brain. In recent years Amyloid-PET has been introduced to visualize the amyloid plaque, however, the emerging amyloid tracers are not free from caveats. Structural MRI (sMRI) is helpful due to its ability in visualizing specific atrophy patterns and excluding other causes of dementia. Functional MRI using Blood-oxygen-level dependent (BOLD) can discriminate AD from patients with mild cognitive impairment. Arterial Spin Labeling (ASL) has demonstrated hypoperfusion in specific parts of the brain. Tractographic techniques have been used, with moderate success to differentiate patients with AD from controls. MRS has shown decreased N-acetylaspartate (NAA) in different parts of brain which can be interpreted as neuronal loss. The current and future trend in AD imaging is toward the development of functional multimodal imaging techniques. The most powerful neuroimaging tools for AD are FDG-PET combined with sMRI. ASL also can be used as a conjunct tool In this review we discuss these topics: 1. Description of the basic techniques of the following imaging modalities and their role and limitations in detecting AD a. PET based modalities: i. FDG-PET ii. Amyloid-PET b. MRI based modalities: c. sMRI d. fMRI: BOLD and ASL e. Diffusion-Weighted Imaging (DWI) f. Magnetisation Transfer Imaging (MTI) f. Magnetic Resonance Spectroscopy (MRS) 2. Current and future trends in AD diagnosis