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Keywords:

  • spectroscopy;
  • hepatic lipid;
  • T2-correction;
  • relaxation rates;
  • susceptibility

Abstract

Purpose

To investigate the accuracy and reproducibility of hepatic lipid measurements using 1H magnetic resonance spectroscopy (MRS) with T2 relaxation correction, compared to measurements without correction.

Materials and Methods

Experiments were conducted in phantoms of varying lipid and iron-induced susceptibility to simulate fatty liver with variable T2. Single-voxel 1H MRS was conducted with multiple TE values, and percent lipid content (lipid%) was determined at each TE to assess accuracy and TE dependency. Concurrently, T2 and equilibrium values of water and lipid were determined separately, and T2 effects on the lipid% were corrected. A similar procedure was conducted in 12 human subjects to determine susceptibility effects on water and lipid MRS signals and lipid%. Multiple measurements were used to test reproducibility.

Results

The use of T2-correction was found to be more accurate than uncorrected lipid% in phantom samples (<10% error). Uncorrected lipid% error increased with increasing TE (>20% when TE > 24 msec) and with increasing susceptibility effect. In humans, while measurement repeatability was high for both corrected and uncorrected MRS, uncorrected lipid% was sensitive to acquisition TE, with 83.6% of all measurements significantly different than T2-corrected measures (P < 0.05).

Conclusion

Separate T2-correction of water and lipid 1H MRS signals provides more accurate and consistent measurements of lipid%, in comparison to uncorrected estimations. J. Magn. Reson. Imaging 2009;29:629–635. © 2009 Wiley-Liss, Inc.