Abstract 4143256: Non-invasive, Radiation-free, Non-contrast Myocardial Volume Oxygen Consumption Quantification Using Free-breathing MR Blood Oximetry

Background: Myocardial oxygen consumption (MVO 2 ) is a central marker in measuring cardiac energetics. Current methods to quantify MVO 2 are inaccessible due to the requirement of invasive procedures or PET agents that require onsite cyclotrons. Hypothesis A free-breathing, non-ECG-gated, motion-resolved Cardiac MR blood oximetry technique can noninvasively quantify MVO 2 in standard clinical MRI scanners without using ionizing radiation and contrast agents. Method: The developed free-breathing CMR imaging technique was prescribed in a 3T clinical scanner to the mid left ventricle (LV) and the cross-section of the coronary sinus(CS) slices of the heart to obtain the corresponding blood oxygenation (SbO 2 ) and the hematocrit (Hct) in heart chambers. 2D phase contrast CMR was performed in the CS to quantify the myocardial blood flow (MBF). The MVO 2 was quantified with Fick’s law (MVO 2 =arterio-venous oxygen difference x MBF). We examined the developed method in healthy pigs (N=7) under rest and adenosine stress and validated it against invasive blood sampling. In addition, we tested the method’s clinical feasibility in healthy human volunteers (N=4). Results: Comparable blood oxygenation levels (SbO 2 ) and MVO 2 were measured and compared between the non-invasive CMR and invasive ground truth (Fig. 1). Significantly increased coronary sinus SbO 2 is observed in both methods during adenosine infusion. It is accompanied by decreased MVO 2 and rate pressure product (RPP) (Rest: CMR=10.2±2.7ml/min, Inv.=10.8±6.9 ml/min, RPP=7956.9±620.9 mmHg/min; Stress: CMR=5.3±1.9 ml/min, Inv=6.3±3.6 ml/min, RPP=5338.2±618.3 mmHg/min). In Fig. 2, the healthy human volunteers' MVO 2 estimations(14.1±6.7ml/min) shows no statistical difference compared to the previous invasive measurements(16.5±4.8 ml/min, Ganz, et al. circulation 1971). Conclusions: The proposed noninvasive CMR technique can quantify MVO 2 in standard MRI scanners without using a needle. It has the potential to provide an accessible, risk-free assessment of myocardial metabolism for patients with potential metabolism impairments.