Quantitative assessment of cardiac phosphocreatine metabolism under physiological and pharmacological stress using chemical exchange saturation transfer magnetic resonance imaging.

backgroundPhosphocreatine (PCr) exhibits a distinct chemical exchange saturation transfer (CEST) resonance at ∼2.5 ppm with slower exchange kinetics and lower pH sensitivity than creatine. This pilot study evaluated the feasibility of quantifying myocardial PCr-dominated concentration ([PCr]

methodsPhantoms with varied concentrations of PCr and Cr were scanned to characterize PCr CEST signals under physiological conditions. Experiments were conducted at both room temperature and 37 °C with full Z-spectra acquisition. For the study in vivo, CEST imaging was performed in normal canines (n = 13), at rest and after regadenoson vasodilation, and during dobutamine stress (n = 5). In addition, healthy volunteers (n = 9) underwent rest-exercise-recovery studies with in-magnet plantar-flexion exercise. Both CEST images and ³¹P-MRS were acquired in separate exercise sessions. WASSR-derived corrected The Z-spectra corrected by derived B₀ maps were fitted with a three-pool Bloch-McConnell model (water, PCr, magnetization transfer) to estimate [PCr]

resultsIn phantoms, PCr-dominated CEST contrast increased monotonically with PCr concentration across pure and mixed PCr/Cr solutions, while Cr-only phantoms did not produce artifactual PCr estimates. In canines, myocardial [PCr]

conclusionCEST-CMR enables noninvasive estimation of myocardial [PCr]