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.