Quantification of myocardial blood volume during dipyridamole and doubtamine stress: A perfusion CMR study

Purpose: Myocardial blood volume (MBV) may provide complementary information about myocardial oxygen needs and viability. The aim of this study is to examine a Cardiovascular Magnetic Resonance (CMR) perfusion method to quantify the changes in MBV, in comparison with the radiolabeled99mTc-Red-Blood- Cell (RBC) method. Methods: Normal mongrel dogs (n = 12) were used in this study. Eight dogs were injected intravenously with dipyridamole, and 4 dogs were given dobutamine during the MR scans. CMR first-pass perfusion imaging was performed at rest and during the pharmacological stress. An intravascular contrast agent, Gadomer (Schering AG, Berlin, Germany), was injected (0.015 mmol/kg) as a bolus during the scans. A perfusion quantification method was applied to obtain MBV maps. Radiolabeled-RBCs were injected at the end of the study to measure reference MBV at rest (n = 4), during dipyridamole vasodilation (n = 4), and during dobutamine stress (n = 4). Results: Myocardial blood flow (MBF) increased approximately 3-fold with both dipyridamole and dobutamine injections. Transmural MBV values measured by CMR were closely correlated with those measured by 99mTc method (CMR:MBV = 6.2 ± 1.3, 7.2 ± 0.8, and 8.3 ± 0.5 mL/100g, at rest, with dipyridamole, and with dobutamine, respectively. 99mTc-RBC: MBV = 6.1 ± 0.5, 7.0 ± 0.9, and 8.6 ± 0.7 mL/100g). Dobutamine stress significantly increased MBV by CMR (33%) and 99mTc methods (35%). During dipyridamole induced vasodilation, MBV increased non-significantly by 14% with the 99mTc method and 1 % with CMR method, which agreed well with other reports. Conclusion: First-pass perfusion CMR with the injection of intravascular contrast agents is a promising non-invasive approach for the assessment of MBV both at rest and pharmacologically induced stress.