Imaging Biomarkers of Alzheimer’s disease: The crucial role of Molecular Imaging

Objectives: 1. To present the value of imaging biomarkers in Alzheimer’s disease (AD). 2. To overview the current status of neuroimaging with SPECT and PET in AD. 3. To demonstrate the role of different radioligands in the imaging of the pathophysiology and other molecular processes in AD. Abstract Body: Increase in aging population is associated with increased number of patients with complaints of cognitive impairment. The most prevalent cause of dementia in the elderly individuals is AD. In AD, there is abnormal build-up of two proteins, amyloid and tau. Amyloid accumulates as plaques and tau as neurofibrillary tangles. Abnormal build-up of these proteins causes the neurons to work less efficiently. There is progressive damage to the neurons and connections between them, leading eventually to neuronal death. The clinical diagnosis of AD, especially in the early stages, remains debatable, while the differential diagnosis of AD from other causes such as vascular dementia, frontotemporal dementia and Lewy body dementia is also difficult. Therefore, it is necessary to improve the certainty that the basis of the clinical dementia syndrome is the AD pathophysiological process. Certain diagnostic criteria for AD are established, including imaging biomarkers. Functional and molecular nuclear medicine imaging with single-photon emission computed tomography (SPECT) and positron emission tomography (PET) techniques provides valuable information about the underlying pathological processes. Nuclear Medicine has made great progress in AD in the past two decades and has extended beyond the traditional role of brain perfusion and glucose metabolism evaluation. In this exhibit, we will review the current knowledge about the radioligands for imaging the pathophysiology and other molecular processes in AD with SPECT and PET. The role of regional cerebral blood flow imaging will be addressed and finally we will summarize the available methods for interpretation of SPECT and PET studies and their contribution in the diagnosis of AD.