Direct measurement of spin‐lattice relaxation times of Phosphorus Metabolites in Human Myocardium

Abstract

T1 values of phosphorus metabolites visible in human cardiac ³¹P‐MR spectra were determined in 12 volunteers at 1.5 T. Consecutive spectra were acquired with varying pulse repetition time (TR) from 1.6 to 24 s; volume selection was achieved with ISIS. T 1's of creatine phosphate (CP), [γ‐P], [α‐P], and [β‐P] ATP, 2‐3 diphosphoglycerate, and phosphodiesters were 6.1 ± 0.5, 5.4 ± 4 0.5, 5.5 ± 0.5, 5.8 ± 1.0, 7.6 ± 1.0, and 5.0 ± 1.0 s, respectively. CP/ATP ratios showed little change with varying TR; linear regression of CP/ATP vs TR was of borderline significance (r = 0.28, P = 0.06). T1'S for CP and ATP were also determined in standard solution (20 mM CP, 10 mM ATP) yielding TI_cp of 8.7 ± 0.2 and T1_{[γ‐P]‐atp}of 9.9 ± 0.7 s. Thus, T1'S for CP and ATP were similar at 1.5 T in both human heart and standard solution. In human cardiac ³¹P‐MR spectra, CP/ATP ratios may need little correction for partial saturation.