Integrated PET/MR systems are showing promise when it comes to analyzing spatially and temporally co-registered multimodal and multiparametric 3D images, one physician wrote in Radiology this month—but the technique is nowhere near ready for prime time.
Gloria C. Chiang, MD, said in the journal that while radiology’s job when it comes to dementia has long been identifying structural and treatable causes of the disease, the field took on a heavier load after 2011, when the National Institute on Aging-Alzheimer’s Association released a set of guidelines for diagnosing the illness. Imagers were soon playing a major role in Alzheimer's diagnosis, which is currently indicated with PET or MRI exams.
FDG PET has had a better track record of sensitivity and specificity in diagnosing Alzheimer's than MRI, Chiang said, but because PET imaging is so expensive and comes with added radiation exposure, researchers have explored arterial spin-labeling (ASL) perfusion as an alternative for finding the same information. ASL uses endogenous blood water to estimate cerebral blood flow rather than glucose metabolism.
Ciang cited a Radiology study—the first of its kind, she said—that looked into the use of an integrated PET/MR system to determine the concordance of FDG PET, ASL MR and gray matter difference maps in a cognitively diverse group of patients.
“The benefit of performing this study with an integrated PET/MRI system is that the FDG PET and ASL MR images are acquired simultaneously, resulting in intrinsically spatially and temporally co-registered images, which limits potential false-positive or false-negative findings related to spatial misregistration and differences in brain states,” she wrote.
Amid validation of those researchers’ hypothesis of a characteristic pattern of reduced cerebral blood flow, they also found significant differences between their mild cognitive impairment cohort and healthy participants with FDG PET, but not at ASL MR. This suggests FDG PET may be more sensitive than ASL, Chiang said, at least in early stages of disease, and that ASL has a lot of developing to do before it could replace PET in diagnosing Alzheimer's. Still, she said, there’s potential.
“Riederer et al. provide the most robust evidence to date that abnormalities observed at ASL and FDG PET demonstrate spatial concordance in differentiating patients with Alzheimer's disease and healthy control participants,” she wrote. “Combined with the high level of accuracy reported previously, the use of ASL as an alternative to FDG PET in diagnosis of Alzheimer's disease may be on the horizon.”
After graduating from Indiana University-Bloomington with a bachelor’s in journalism, Anicka joined TriMed’s Chicago team in 2017 covering cardiology. Close to her heart is long-form journalism, Pilot G-2 pens, dark chocolate and her dog Harper Lee.