Retrospective ECG-gated micro-PET and cMRI images of a representative rat. (A, E, I) End-diastolic and (B, F, J) end-systolic frames during rest on micro-PET and cMRI, respectively. (C, G, K) End-diastolic and (D, H, L) end-systolic images during pharmacological stress in the same rat. The lower ESV in stress condition is clearly observed on both micro-PET and cMRI. (left panel: PET maximum intensity projection images, central panel: axial MRI images, right panel: axial PET images).