Frequency and phase drift correction of magnetic resonance spectroscopy data by spectral registration in the time domain

TLDR

Frequency and phase drifts are common in in‑vivo MRS and cause peak broadening, line‑shape distortion, and reduced SNR. The authors present a new method for estimating and correcting frequency and phase drifts in in‑vivo MRS data. The method fits each spectral average to a reference scan in the time domain by adjusting frequency and phase terms, analogous to image registration, and was evaluated against two existing methods using simulated data across SNR levels. Spectral registration accurately estimates frequency and phase drifts, outperforming the other methods, and offers a versatile correction that does not require navigator echoes or specific resonances. Magn Reson Med 73:44–50, 2015; © 2014 Wiley Periodicals, Inc.

Abstract

Purpose Frequency and phase drifts are a common problem in the acquisition of in vivo magnetic resonance spectroscopy (MRS) data. If not accounted for, frequency and phase drifts will result in artifactual broadening of spectral peaks, distortion of spectral lineshapes, and a reduction in signal‐to‐noise ratio (SNR). We present herein a new method for estimating and correcting frequency and phase drifts in in vivo MRS data. Methods We used a simple method of fitting each spectral average to a reference scan (often the first average in the series) in the time domain through adjustment of frequency and phase terms. Due to the similarity with image registration, this method is referred to as “spectral registration.” Using simulated data with known frequency and phase drifts, the performance of spectral registration was compared with two existing methods at various SNR levels. Results Spectral registration performed well in comparison with the other methods tested in terms of both frequency and phase drift estimation. Conclusions Spectral registration provides an effective method for frequency and phase drift correction. It does not involve the collection of navigator echoes, and does not rely on any specific resonances, such as residual water or creatine, making it highly versatile. Magn Reson Med 73:44–50, 2015. © 2014 Wiley Periodicals, Inc.