In a new review of imaging studies spanning more than ten years, scientists find that a method of positron emission tomography (PET) safely and accurately detects dementia, including the most common and devastating form among the elderly, Alzheimer's disease. This research is featured in the January issue of the Journal of Nuclear Medicine.
Researchers reviewed numerous PET studies to evaluate a molecular imaging technique that combines PET, which provides functional images of biological processes, with an injected biomarker called 18F-FDG to pinpoint key areas of metabolic decline in the brain indicating dementia. Having physiological evidence of neurodegenerative disease by imaging patients with PET could give clinicians the information they need to make more accurate diagnoses earlier than ever before.
"The new data support the role of 18F-FDG PET as an effective addition to other diagnostic methods used to assess patients with symptoms of dementia," says Nicolaas Bohnen, MD, PhD, lead author of the study and professor of radiology and neurology at the University of Michigan, Ann Arbor, Mich. "The review also identified new literature showing the benefit of this imaging technique for not only helping to diagnose dementia but also for improving physician confidence when diagnosing a patient with dementia. This process can be difficult for physicians, especially when evaluating younger patients or those who have subtle signs of disease."
Dementia is not a specific illness but a pattern of symptoms characterized by a loss of cognitive ability. These disorders can be caused by injury or progressive disease affecting areas of the brain that control attention, memory, language and mobility. While Alzheimer's is most commonly associated with progressive memory impairment, dementia with Lewy bodies, another form of the disease, can be associated with symptoms of Parkinson's and prominent hallucinations, while another disorder, called frontotemporal dementia, can be seen in patients showing uncharacteristic personality changes and difficulties in relating and communicating. Physicians can use FDG-PET with high accuracy to not only help diagnose dementia but also differentiate between the individual disorders. The role molecular imaging plays in the diagnosis of dementia has expanded enough that the official criteria physicians use to diagnose patients now includes evidence from molecular imaging studies.
"For the first time, imaging biomarkers of Alzheimer's disease are included in the newly revised clinical diagnostic criteria for the disease," says Bohnen. "This is a major shift in disease definition, as previously an Alzheimer's diagnosis was based mainly on a process of evaluating patients to exclude possible trauma, hemorrhage, tumor or metabolic disorder. Now it is becoming a process of inclusion based on biomarker evidence from molecular imaging."