C linical imaging such as FDG-PET and SPECT has been well established in the diagnosis of Alzheimer's disease (AD) and other neurological disorders, but the diagnostic value of arterial spin labeling (ASL) MRI, a relatively new noninvasive imaging technique, has not been validated or confirmed. Comparative studies that compared ASL with FDG-PET, 15 O-water-PET, SPECT, dynamic susceptibility contrast-enhanced (DSC), or dynamic contrast-enhanced (DCE) MRI are important to reveal the concordance and discordance between ASL and these clinical imaging tests. This paper reviews such studies in healthy subjects and patients with AD or other neurological disorders. These comparative studies have demonstrated that ASL and FDG-PET/
15O-water-PET had overall concordance and regional variability in healthy subjects, and the regional hypoperfusion that ASL depicted in diseases such as AD was largely concordant with the abnormalities identified by FDG-PET/ SPECT (the diagnostic performance was comparable), which suggests that ASL may have a similar diagnostic value as FDG-PET/SPECT. In addition, there are mixed findings in ASL cerebral blood flow (CBF) measurements compared with 15 O-water-PET, and ASL may be less sensitive than DSC (or DCE) in the diagnosis of neurological disorders such as stroke. Studies with large samples are needed to further validate the diagnostic value of ASL and its CBF measurement. Furthermore, it is necessary to optimize and standardize ASL parameters and explore new techniques to overcome the limitations of ASL and make it a clinical imaging alternative to invasive FDG-PET/SPECT/DSC/ DCE in the diagnosis of AD and other neurological disorders.IT IS OFTEN difficult to differentiate early-stage Alzheimer's disease (AD) from other neurodegenerative dementias or mild cognitive impairment (MCI).1 MRI, FDG-PET, and SPECT have been the major clinical imaging tests used for the diagnosis of dementia. FDG-PET or SPECT uses radioactive tracers to image glucose metabolism or brain perfusion. Since reductions in cerebral glucose uptake and brain perfusion often precede brain atrophy, measures of FDG-PET/SPECT can serve as early biomarkers for preclinical or mild AD. 2 FDG-PET/SPECT imaging in neurodegenerative disorders is based on the coupling of neural activity and glucose metabolism to reduced regional cerebral blood flow (CBF) 3 due to the synchronization of cerebral metabolic demands to regional blood supply. Thus, spatial patterns of regional CBF in perfusion imaging tend to mirror FDG-PET glucose metabolism results unless neurovascular coupling is compromised.
4In addition, CBF measurements are important in the assessment of AD and other neurological disorders such as stroke.15 O-water-PET (PET imaging with 15 O-water tracer) is considered a gold standard for quantifying CBF. 5 The diagnostic value of PET View this article online at wileyonlinelibrary.com.