Saturation-Transfer Effects and Longitudinal Relaxation Times of 31P Metabolites in Fibroglandular Breast Tissue at 7T

Purpose: To investigate longitudinal relaxation times and saturation-transfer effects of phosphorous metabolites in breast fibroglandular tissue in vivo with P-31 MR spectroscopy at 7T. Methods: Progressive saturation with adiabatic half passage excitation was used to determine T-1 values of P-31 metabolites in a group of six healthy volunteers. Saturation-transfer experiments were performed in seven healthy volunteers by saturating at 0 ppm and 10 ppm with sinc-Gaussian pulses (90 ms; 10-ms pulse interval; B-1 = 17 mu T) prior to excitation. Localization was performed by surface coils and one-dimensional chemical shift imaging. Data were analyzed via spectral fitting with the JMRUI software package, and T-1 values were obtained by fitting the data to the signal equation. Results: The determined longitudinal relaxation time values at 7T were as follows: phosphoethanolamine, 4.0 +/- 0.2 s; phosphocholine, 1.8 +/- 0.2 s; inorganic phosphate, 6.1 +/- 0.1 s; phosphodiesters, glycerophosphatidylethanolamine plus glycerophosphocholine, 2.1 +/- 0.1, and glycerophosphatidylethanolamine, 1.5 +/- 0.1s; gamma-ATP, 2.1 +/- 0.1 s; and alpha-ATP, 2.0 +/- 0.1 s. Saturation-transfer measurements with saturation pulses at 0 ppm showed a significant signal reduction in the phosphodiester 2-3 ppm range, whereas the g-ATP signal at -2.5 ppm was not affected significantly. Conclusion: Longitudinal relaxation times of phosphorous metabolites in fibroglandular tissue revealed relatively low T-1 values for phosphodiesters. Saturation-transfer measurements showed that the phosphodiester signals were the only signals that were affected significantly, possibly indicating the presence of mobile phospholipids. (C) 2015 Wiley Periodicals, Inc.