FDG PET superior to SPECT for telling Alzheimer’s from DLB

Dementia imaging with FDG PET was more accurate, sensitive and specific in a comparison between Alzheimer’s disease (AD) and dementia with Lewy bodies (DLB), according to a study published online Nov. 5 in the Journal of Nuclear Medicine.

Researchers including John T. O’Brien, a professor of neuroscience in the department of psychiatry at Cambridge University in the U.K., conducted the head-to-head study comparing metabolic PET imaging with F-18 FDG and SPECT imaging of brain blood flow with hexamethylpropyleneamine oxime (HMPAO).

“Our main findings showed the significant superiority of F-18 PET over HMPAO SPECT in the differentiation of degenerative dementia (AD and DLB combined) from healthy controls and for the differentiation of AD from DLB,” wrote O’Brien et al.  

Using an endpoint of visual diagnostic interpretation, researchers found that F-18 FDG PET had a sensitivity of 85 percent and specificity of 90 percent when making a dementia vs. no-dementia determination. In contrast, SPECT had a sensitivity of 71 percent and a specificity of 70 percent for the same read.

“The high diagnostic accuracy of F-18 FDG PET is consistent with previous literature, demonstrating that it is a robust marker for assessing neurodegeneration in both AD and DLB,” the authors wrote. “Our findings therefore strongly support its incorporation in imaging diagnostic guidelines and as a biomarker of degeneration in newly proposed diagnostic criteria for AD.”

The researchers concluded that the perfusion SPECT scans were significantly less accurate than FDG PET for differentiation of disease. A dual-answer, dementia or no dementia task could be performed, but clinical decisions involving a diagnosis of either Alzheimer’s or DLB was found to be “disappointingly poor.”