Removal of the outer lines of the citrate multiplet in proton magnetic resonance spectra of the prostatic gland by accurate timing of a point-resolved spectroscopy pulse sequence.

Proton MR spectra of a healthy human prostatic gland show a major signal for citrate appearing as an AB-type multiplet. After application of multipulse localization sequences, the outer lines of this multiplet often appear with dispersion line shapes disturbing the baseline and interfering with proper quantification of citrate itself and other nearby resonances. Based upon analytical descriptions of the time evaluation of an AB spin system during a point resolved spectroscopy (PRESS) pulse sequence (90x-tau 1-180y-tau 2-180y-t), equations were derived representing the intensity of the absorption and dispersion line shape of the outer lines of the citrate multiplet at the top of echo t = tau 2-tau 1. From these equations, it was calculated that the outer lines of citrate can be removed almost completely using a PRESS pulse sequence with tau 1 = 11 ms and tau 2 = 60 ms. The theoretical description was confirmed by the almost complete disappearance of the two outer citrate resonances in in vitro and in vivo proton MR spectra acquired with this pulse sequence timing.