Rubidium-82 PET imaging is feasible in a rat myocardial infarction model

Background: Small-animal myocardial infarct models are frequently used in the assessment of new cardioprotective strategies. A validated quantification of perfusion using a non-cyclotron-dependent PET tracer would be of importance in monitoring response to therapy. We tested whether myocardial PET perfusion imaging is feasible with Rubidium-82 (⁸²Rb) in a small-animal scanner using a rat myocardial infarct model. Methods: 18 Sprague-Dawley rats underwent permanent coronary artery ligation (infarct group), and 11 rats underwent ischemia-reperfusion (reperfusion group) procedure. ⁸²Rb-PET and magnetic resonance imaging (MRI) were conducted before and after the intervention. Perfusion was compared to both left ventricle ejection fraction (LVEF) and infarct size assessed by MRI. Results: Follow-up global ⁸²Rb-uptake correlated significantly with infarct size (infarct group: r = −0.81, P < 0.001 and reperfusion group: r = −0.61, P = 0.04). Only ⁸²Rb-uptake in the infarct group correlated with LVEF. At follow-up, a higher segmental ⁸²Rb-uptake in the infarct group was associated with better wall motion (β = 0.034, CI [0.028;0.039], P < 0.001, R² = 0.30), and inversely associated with scar transmurality (β = −2.4 [−2.6; −2.2], P < 0.001, R² = 0.59). The associations were similar for the reperfusion group. Conclusion: ⁸²Rb-PET is feasible in small animal scanners despite the long positron range and enables fast and time-efficient myocardial perfusion imaging in rat models.