Assessment of myocardial blood flow (MBF) in humans using arterial spin labeling (ASL): feasibility and noise analysis.

Arterial spin labeling (ASL) is a powerful tool for the quantitative measurement of tissue blood flow, and has been extensively applied to the brain, lungs, and kidneys. ASL has been recently applied to myocardial blood flow (MBF) measurement in small animals; however, its use in humans is limited by inadequate signal-to-noise ratio (SNR) efficiency and timing restrictions related to cardiac motion. We present preliminary results demonstrating MBF measurement in humans, using cardiac-gated flow-sensitive alternating inversion recovery (FAIR) tagging and balanced steady-state free precession (SSFP) imaging at 3T, and present an analysis of thermal and physiological noise and their impact on MBF measurement error. Measured MBF values in healthy volunteers were 1.36 +/- 0.40 ml/ml/min at rest, matching the published literature based on quantitative (13)N-ammonia positron emission tomography (PET), and increased by 30% and 29% with passive leg elevation and isometric handgrip stress, respectively. With thermal noise alone, MBF can be quantified to within +/- 0.1 ml/ml/min with 85.5% confidence, for 3.09 cm(3) regions averaged over 6 breath-holds. This study demonstrates the feasibility of quantitative assessment of myocardial blood flow in humans using ASL, and identifies SNR improvement and the reduction of physiological noise as key areas for future development.