Diagnosis of Dementia Using Nuclear Medicine Imaging Modalities

Dementia describes the loss of brain function that occurs with certain diseases, and which has the potential to affect memory, thinking, language, judgment, and behavior. Most types of dementia involve irreversible neurodegeneration, and Alzheimer's disease (AD) is the most common form. Beyond AD however, there are many other diseases that can lead to dementia including dementia with Lewy bodies (DLB), frontotemporal dementia (FTD), Parkinson’s disease with dementia, corticobasal degeneration (CBD) and progressive supranuclear palsy (PSP). Dementia can also be the result of many small strokes and, in such cases, is called vascular dementia. Whilst such clinically and neuropathologically overlapping dementia diseases can be predicted by clinical diagnosis, definitively differentiating them from one another has typically been attempted using high-risk diagnostic procedures (e.g. brain biopsy, Lumbar puncture) or, more commonly, during a post-mortem examination. This makes it difficult to a) differentiate dementias and treat each appropriately before patient death; b) manage the diseases early, before the onset of cognitive decline; c) select appropriate patients for assisting in dementia-related drug development; and d) track the impact of new dementia therapeutics in clinical trials. Therefore, new non-invasive diagnostic methods for managing dementia are in high demand and, reflecting this, many radiopharmaceuticals (drugs tagged with a radioactive isotope) have been developed over the last 2 decades that allow noninvasive examination of dementia pathophysiology in living human subjects using nuclear medicine imaging techniques. Such techniques include positron emission tomography (PET) and single photon emission computed tomography (SPECT) imaging, and have greatly enhanced diagnostic confidence across the entire dementia disease spectrum in recent years. This chapter reviews radiopharmaceuticals commonly employed clinically in the management of dementia patients, suffering from the diseases outlined above, with nuclear medicine modalities. The chapter is divided by disease entity, and progress in imaging the pathophysiology of each disease is highlighted. In addition to those radiopharmaceuticals with approval for human use discussed herein, there are many experimental radiopharmaceuticals for dementia in pre-clinical development, which have not yet been translated into clinical use. Comprehensive review of such pre-clinical radiopharmaceuticals is outside the scope of this book, and pertinent examples are highlighted only when necessary to indicate key concepts involved in imaging dementia patients. The interested reader can obtain additional information on radiopharmaceuticals currently in development