Diagnosis of myocardial viability by fluorodeoxyglucose distribution at the border zone of a low uptake region.

Purpose: In cardiac 2-[F-18]fluoro-2-deoxy-D-glucose (FDG)-positron emission tomography (PET) examination, interpretation of myocardial viability in the low uptake region (LLTR) has been difficult without additional perfusion imaging. We evaluated distribution patterns of FDG at the border zone of the LUR in the cardiac FDG-PET and established a novel parameter for diagnosing myocardial viability and for discriminating the LUR of normal variants. Materials and Methods: Cardiac FDG-PET was performed in patients with a myocardial ischemic event (n = 22) and in healthy volunteers (n = 22). Whether the myocardium was not a viable myocardium (not-VM) or an ischemic but viable myocardium (isch-VM) was defined by an echocardiogram under a low dose of dobutamine infusion as the gold standard. FDG images were displayed as gray scaled-bull's eye mappings. FDG-plot profiles for LUR (= true ischemic region in the patients or normal variant region in healthy subjects) were calculated. Maximal values of FDG change at the LUR border zone (a steepness index; S-max scale/pixel) were compared among not-VM, isch-VM, and normal myocardium. Results: S-max was significantly higher for n-VM compared to those with isch-VM or normal myocardium (ANOVA). A cut-off value of 0.30 in S-max demonstrated 100%. sensitivity and 83% specificity for diagnosing n-VM and isch-VM. S-max less than 0.23 discriminated LUR in normal myocardium from the LUR in patients with both n-VM and isch-VM with a 94% sensitivity and a 93% specificity. Conclusion: S-max of the LUR in cardiac FDG-PET is a simple and useful parameter to diagnose n-VM and isch-VM, as well as to discriminate thr LUR of normal variants.