Volumetric R2* mapping using z‐shim multi‐echo gradient echo imaging. Issue 3 (24th March 2014)

• Record Type: Journal Article
• Authors: Han, Dongyeob; Nam, Yoonho; Gho, Sung‐Min; Kim, Dong‐Hyun
• Is Part Of: Magnetic resonance in medicine. Volume 73:Issue 3(2015:Mar.)
• Page Start: 1164
• Page End: 1170
• Publication Date: 2014-03-24
• Subjects: Nuclear magnetic resonance -- Periodicals; Electron paramagnetic resonance -- Periodicals; 616.07548
• DOI: 10.1002/mrm.25206
• Languages: English
• ISSNs: 0740-3194

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <sec id="mrm25206-sec-0001" sec-type="section"> <title>Purpose</title> <p>To introduce macroscopic B<sub>0</sub> field inhomogeneity‐compensated volumetric R<sub>2</sub>* mapping method with a three‐dimensional (3D) z‐shim multi‐echo acquisition.</p> </sec> <sec id="mrm25206-sec-0002" sec-type="section"> <title>Methods</title> <p>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<sub>0</sub> inhomogeneity‐compensated field map that was shown to play a critical role for accurate R<sub>2</sub>* mapping. A modified signal model based on recently suggested model for 3D acquisition was proposed for R<sub>2</sub>* quantification.</p> </sec> <sec id="mrm25206-sec-0003" sec-type="section"> <title>Results</title> <p>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<sub>2</sub>* map quality for the different subjects.</p> </sec> <sec id="mrm25206-sec-0004" sec-type="section"> <title>Conclusion</title> <p>The proposed method improves R<sub>2</sub>* estimation, especially in the frontal and temporal regions. <bold>Magn Reson Med 73:1164–1170, 2015. © 2014 Wiley Periodicals, Inc.</bold></p> </sec> </abstract>