Purpose: To evaluate the impact of heating-induced frequency drifts on single-voxel spectroscopy and to demonstrate correction strategies based on the interleaved reference scan technique.
Materials and methods: Frequency drifts induced by gradient heating are assessed for two clinical 3 Tesla (T) whole body MR systems. The interleaved reference scan (IRS) method is used for correcting these frequency drifts in 1H spectra in vitro and in vivo. For severely drift-affected spectroscopy experiments, a feedback-based version of the IRS sequence is proposed, which adds the functionality of a frequency lock to prevent a degradation of the water suppression.
Results: It is shown that the line widths of the spectral resonances can be largely reduced with the interleaved reference scan method, resulting in considerably improved peak resolution and signal-to-noise ratio. The feedback-based IRS method additionally allows for stable water suppression, even in the presence of very strong frequency drifts.
Conclusion: If spectroscopy scans are combined with imaging scans with a high gradient duty cycle such as diffusion-weighted imaging or functional MRI, a drift correction with IRS can considerably improve the validity of data analysis in research studies.
Copyright © 2011 Wiley-Liss, Inc.