Accurate Coronary Sinus MR Oximetry with Auto-Hematocrit Calibration - Proof of Concept Study in Pigs with Invasive Validation

Motivation: Accurate measurements of blood hematocrit (HCT) and oxygenation saturation (SbO2) in the coronary sinus (CS) can facilitate non-invasive myocardial oxygen extractions and assess cardiac metabolism. Goal(s): Develop a high-resolution, motion-resolved, self-calibrated MR oximetry sequence in the CS to quantify HCT and SbO2 in the beating hearts noninvasively. Approach: Healthy swine were scanned at 3T with a free-breathing 3D Radial GRE T2Prep-IR sequence combined with a self-calibrated oximetry model and validated against invasive ground truth. Results: The CMR-derived CS HCTs and SbO2 are closely correlated to the invasive ground truth. (HCT: y=1.29-2.80, R2 = 0.623; SbO2: y=0.95+2.59,R2 = 0.965). Impact: The proposed free-breathing, multiparametric, self-calibrated MR Oximetry can accurately measure HCT in the coronary sinus. It can help with precise noninvasive blood characterization in deep vessels and be adapted to other MRI parameters (e.g., extracellular volume) that require HCT measurements.