Noninvasive measurement of myocardial activity concentrations and perfusion defect sizes in rats with a new small-animal positron emission tomograph

Background-We explored the feasibility of measuring regional tracer activity concentrations and flow defects in myocardium of rats with a high spatial resolution small-animal PET system (microPET). Methods and Results-Myocardial images were obtained after intravenous F-18-fluorodeoxyglucose ((18)FDG) in 11 normal rats (group 1) and assembled into polar maps. Regional F-18 activity concentrations were measured in 9 regions of interest and compared with tissue activity concentrations measured by well counting. In another 9 rats (group 2). myocardial perfusion images were acquired with N-13-ammonia at baseline and during coronary Occlusion. On the polar maps recorded during coronary occlusion, the size of perfusion defects was measured as the myocardium with <50% of maximum activity and expressed as percent total myocardium and was correlated with the area at risk, defined by postmortem staining. The diagnostic quality of (18)FDG and N-13-ammonia microPET image,, was good to excellent; the images were easily assembled into polar maps. In group 1, regional F-18 concentrations by microPET and Postmortem were correlated linearly (r=0.99; P<0.01 for average and r=0.97; P<0.01 for regional concentrations). In group 2. perfusion defect sizes by microPET and postmortem were correlated linearly (P<0.01; r = 0.93). Conclusions-The findings indicate the feasibility of noninvasive studies of the myocardium in rats with a dedicated small-animal PET-imaging device.