Alzheimer's disease (AD) is the most common form of dementia among older people. Dementia is a brain disorder that seriously affects a person's ability to carry out daily activities. AD begins slowly, first involves the parts of the brain that control thought, memory and language. Alzheimer's is a progressive disease, where slowly symptoms worsen over a number of years. Alzheimer's is a physical disease which attacks brain cells, brain nerves and neurotransmitters which leads to loss of ability to remember, speak, think and make decisions is disrupted. Alzheimer's is the sixth leading cause of death in the United States.

The structural and functional imaging is required for the early detection of Alzheimer's disease. MRI and CT are most widely used modalities to distinguish Alzheimer's disease from other forms of dementias. MRI diagnosis the tumors, infections, inflammation, and damage due to head injury.PET and SPECT are used to evaluate the disturbances of blood flow through arteries and veins in the brain and measure metabolism.