Estimation of the phosphocreatine T1 time constant using a clinical NMR scanner

The aim of this study was to determine the "spin-lattice relaxation" or "T1" time constant of phosphocreatine in the human gastrocnemius muscle, both at rest and during aerobic exercise, when a clinical nuclear magnetic resonance (NMR) scanner is available. Using the multipoint saturation recovery technique, we tested four acquisition protocols differing in number and duration of repetition times. Moreover, two mathematical models describing the phenomenon were also evaluated. Protocols and models were tested on a phantom containing 1 kg of distilled water in which were dissolved 5.88 g sodium chloride, 1 cm3 phosphoric acid and 7.58 g sodium phosphate dodecahydrate. One protocol only was used on a group of four healthy volunteers both at rest and during exercise. Each volunteer repeated the rest-exercise sequence three times. On the phantom, the average T1 values for the various protocols and mathematical models used proved to differ widely, ranging from 0.61 s to 7.20 s. On volunteers, the T1 values obtained at rest and during exercise were not significantly different--0.91 s on average. Correction of this T1 value with the results obtained using the phantom provides a T1 value of 5.73 s, which is comparable with the value reported in the literature for resting conditions only.