Magnetic resonance imaging (MRI) is able to spot signs of Alzheimer's disease and other forms of dementia before patients start exhibiting symptoms, according to new research.

Dementia affects more than 35 million people worldwide, according to the World Health Organization (WHO). That number is expected to double by the year 2030. Of the various forms of dementia, Alzheimer's is the most common. The first symptoms come in the form of mild cognitive impairment (MCI), which can later develop into full dementia.

Cognitive reserve, the ability of the human brain to utilize one part of its structure when another is damaged, is beneficial in the short term, but can hide the effects of reduced blood flow and other conditions. These problems can be present in patients for years before any symptoms are noticed, causing delays in diagnosis and treatment. However, patients eventually develop losses of cognitive ability. Early treatment is critical in reducing damage done by various forms of dementia.

Arterial spin labeling (ASL), a form of MRI, measures the penetration of blood into brain tissue, known as perfusion. The process does not require the injection of any drugs into the patient to assist with imaging. Researchers used this technique to show where blood flow is reduced in brain tissue.

Researchers studied 148 healthy senior subjects, along with 65 volunteers diagnosed with mild cognitive impairment. Each of the volunteers were examined utilizing a MRI scan, and participated in a neuropsychological assessment. During 18 months of follow-up research, 73 showed signs of cognitive decline, while 75 remained unchanged.

Those showing a decline in their skills had previously displayed reduced perfusion when first measured for the study. The posterior cingulate cortex, a part of the brain most active when not centered on a specific activity, was found to be most-often associated with such losses. When blood absorption by areas of the brain is limited, processing in that region is reduced.

"ASL MRI is simple to perform, doesn't require special equipment and only adds a few minutes to the exam," Sven Haller of the University of Geneva in Switzerland, said.

This research could help develop a new screening process for patients, to determine who may be at the greatest risk for dementia. Unlike positron emission tomography (PET) scans, ASL scans produce no radiation, and can easily be carried out in most doctor's offices.  

Discovery of how dementia can be detected in its early stages using MRI techniques was detailed in the journal Radiology.

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