Predicting SNR gains from constructive averaging of proton spectra: theory and practice
Bottomley P, Gabr R, Schr M, Sathyanarayana S, Weiss R
Johns Hopkins University
Physiological motion causes dephasing which can undermine the signal-to-noise ratio (SNR) advantage of averaging 1H STEAM and PRESS acquisitions to measure weak metabolites including creatine and choline in the torso. Constructive averaging, wherein each acquisition is individually phased prior to averaging, can reverse SNR loss, but the benefits are highly variable. Here an analytical theory is presented which correctly predicts the SNR advantage of constructive averaging based on measures of the phase variation. The theory is validated with in vivo 1H spectra from the human heart and leg, demonstrating useful SNR gains of up to 7-fold.