Hyperpolarized ¹³C urea myocardial first-pass perfusion imaging using velocity-selective excitation

A velocity-selective binomial excitation scheme for myocardial first-pass perfusion measurements with hyperpolarized ¹³C substrates, which preserves bolus magnetization inside the blood pool, is presented. The proposed method is evaluated against gadolinium-enhanced ¹H measurements in-vivo.

The proposed excitation with an echo-planar imaging readout was implemented on a clinical CMR system. Dynamic myocardial stress perfusion images were acquired in six healthy pigs after bolus injection of hyperpolarized ¹³C urea with the velocity-selective vs. conventional excitation, as well as standard ¹H gadolinium-enhanced images. Signal-to-noise, contrast-to-noise (CNR) and homogeneity of semi-quantitative perfusion measures were compared between methods based on first-pass signal-intensity time curves extracted from a mid-ventricular slice. Diagnostic feasibility is demonstrated in a case of septal infarction.

Velocity-selective excitation provides over three-fold reduction in blood pool signal with a two-fold increase in myocardial CNR. Extracted first-pass perfusion curves reveal a significantly reduced variability of semi-quantitative first-pass perfusion measures (12-20%) for velocity-selective excitation compared to conventional excitation (28-93%), comparable to that of reference ¹H gadolinium data (9-15%). Overall image quality appears comparable between the velocity-selective hyperpolarized and gadolinium-enhanced imaging.

The feasibility of hyperpolarized ¹³C first-pass perfusion CMR has been demonstrated in swine. Comparison with reference ¹H gadolinium data revealed sufficient data quality and indicates the potential of hyperpolarized perfusion imaging for human applications.