The scan, FDG-PET, helped six doctors from three national Alzheimer’s disease centres correctly diagnose frontotemporal dementia (FTD) and Alzheimer’s in almost 90 percent of cases in the study - an improvement of as much as 14 percent from usual clinical diagnostic methods.

FDG stands for fluorodeoxyglucose, a short-lived radioactive form of sugar injected into people during PET scans to show activity levels in different parts of the brain. In Alzheimer’s low activity is mostly in the back part of the brain; in FTD, low activity is mostly in the front of the brain.

Norman L. Foster, M.D., professor of neurology at the University of Utah School of Medicine and colleagues examined the medical records and FDG-PET scans of 45 patients who later had autopsies. Microscopic examination found 31 had Alzheimer’s and 14 had FTD. The researchers summarized the clinical course of the disease in each patient. The expert neurologists at the National Institutes of Health (NIH) centers, who had ten years to 25 years of experience, then were asked to decide what caused each patient’s dementia using clinical information alone or using FDG-PET images.

The experts correctly distinguished FTD and Alzheimer’s using only the clinical methods in 76 to 79 percent of the cases. Using the FDG-PET scans alone, however, the physicians correctly diagnosed the two dementias in 85 to 89 percent of cases. Adding FDG-PET to clinical information increased the correct diagnosis from 79 percent to 90 percent. The highest accuracy in diagnosis was achieved with SSP (stereotactic surface projection) displays, which summarize changes in brain activity and apply a statistical test to show significant areas of damage.

The PET scans also had other benefits. The researchers found in 42 percent of cases, the scans increased the experts’ confidence in a correct diagnosis or made them question and sometimes change an incorrect diagnosis.; Source: University of Utah