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Nam, Kim, Zho, and Kim: Background Gradient Correction using Excitation Pulse Profile for Fat and T2* Quantification in 2D Multi-Slice Liver Imaging
Original Article
Journal of the Korean Society of Magnetic Resonance in Medicine

Journal of the Korean Society of Magnetic Resonance in Medicine 2012; 16(1): 6-15.

Published online: 30 April 2012

DOI: https://doi.org/10.0000/jksmrm.2012.16.1.6

Background Gradient Correction using Excitation Pulse Profile for Fat and T2* Quantification in 2D Multi-Slice Liver Imaging

Yoonho Nam1, Hahnsung Kim1, Sang-Young Zho1, Dong-Hyun Kim1, 2

1Department of Electrical and Electronic Engineering, Yonsei University, Korea.

2Department of Radiology, Yonsei University, Korea.

Corresponding author: Dong-Hyun Kim, Ph.D., Department of Electrical and Electronic Engineering, Yonsei University, 134 Shinchon-dong, Seodaemun-gu, Seoul 120-749, Korea. Tel. 82-2-2123-5874, Fax. 82-2-313-2879, donghyunkim@yonsei.ac.kr

Received 22 February 2012       Revised 6 April 2012       Accepted 13 April 2012

Copyright © 2012 Korean Society of Magnetic Resonance in Medicine

Abstract

Purpose

The objective of this study was to develop background gradient correction method using excitation pulse profile compensation for accurate fat and T2* quantification in the liver.

Materials and Methods

In liver imaging using gradient echo, signal decay induced by linear background gradient is weighted by an excitation pulse profile and therefore hinders accurate quantification of T2* and fat. To correct this, a linear background gradient in the slice-selection direction was estimated from a B0 field map and signal decays were corrected using the excitation pulse profile. Improved estimation of fat fraction and T2* from the corrected data were demonstrated by phantom and in vivo experiments at 3 Tesla magnetic field.

Results

After correction, in the phantom experiments, the estimated T2* and fat fractions were changed close to that of a well-shimmed condition while, for in vivo experiments, the background gradients were estimated to be up to approximately 120 µT/m with increased homogeneity in T2* and fat fractions obtained.

Conclusion

The background gradient correction method using excitation pulse profile can reduce the effect of macroscopic field inhomogeneity in signal decay and can be applied for simultaneous fat and iron quantification in 2D gradient echo liver imaging.

Keywords: Fat quantification, T2* measurement, IDEAL, field inhomogeneity, pulse profile, liver imaging

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