Premium
Volumetric R 2 * mapping using z‐shim multi‐echo gradient echo imaging
Author(s) -
Han Dongyeob,
Nam Yoonho,
Gho SungMin,
Kim DongHyun
Publication year - 2015
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.25206
Subject(s) - shim (computing) , gradient echo , echo (communications protocol) , nuclear magnetic resonance , echo time , nuclear medicine , magnetic resonance imaging , physics , materials science , computer science , medicine , radiology , erectile dysfunction , computer network
Purpose To introduce macroscopic B 0 field inhomogeneity‐compensated volumetric R 2 * mapping method with a three‐dimensional (3D) z‐shim multi‐echo acquisition. Methods The proposed z‐shim sequence acquired conventional and z‐shimmed echoes alternately with bipolar readout gradients. A constant‐valued z‐shim gradient was applied prior to each negative readout gradient lobe. A phase combination algorithm was also proposed based on this pulse sequence, which acquires a B 0 inhomogeneity‐compensated field map that was shown to play a critical role for accurate R 2 * mapping. A modified signal model based on recently suggested model for 3D acquisition was proposed for R 2 * quantification. Results To validate the performance of the proposed method, phantom and in vivo experiments were performed and compared with other methods. An increase in the range of field inhomogeneity correction was shown in the phantom results. For in vivo studies, the proposed method showed enhanced R 2 * map quality for the different subjects. Conclusion The proposed method improves R 2 * estimation, especially in the frontal and temporal regions. Magn Reson Med 73:1164–1170, 2015. © 2014 Wiley Periodicals, Inc.