Correcting dynamic distortions in 7T echo planar imaging using a jittered echo time sequence

Dymerska, Barbara, Poser, Benedikt A., Bogner, Wolfgang, Visser, Eelke, Eckstein, Korbinian, Cardoso, Pedro, Barth, Markus, Trattnig, Siegfried and Robinson, Simon D. (2016) Correcting dynamic distortions in 7T echo planar imaging using a jittered echo time sequence. Magnetic Resonance in Medicine, 76 5: 1388-1399. doi:10.1002/mrm.26018


Author Dymerska, Barbara
Poser, Benedikt A.
Bogner, Wolfgang
Visser, Eelke
Eckstein, Korbinian
Cardoso, Pedro
Barth, Markus
Trattnig, Siegfried
Robinson, Simon D.
Title Correcting dynamic distortions in 7T echo planar imaging using a jittered echo time sequence
Journal name Magnetic Resonance in Medicine   Check publisher's open access policy
ISSN 1522-2594
0740-3194
Publication date 2016-11-01
Year available 2015
Sub-type Article (original research)
DOI 10.1002/mrm.26018
Open Access Status DOI
Volume 76
Issue 5
Start page 1388
End page 1399
Total pages 12
Place of publication Hoboken, NJ, United States
Publisher John Wiley & Sons
Language eng
Subject 2741 Radiology Nuclear Medicine and imaging
Abstract Purpose: To develop a distortion correction method for echo planar imaging (EPI) that is able to measure dynamic changes in B. Theory and Methods: The approach we propose is based on single-echo EPI with a jittering of the echo time between two values for alternate time points. Field maps are calculated between phase images from adjacent volumes and are used to remove distortion from corresponding magnitude images. The performance of our approach was optimized using an analytical model and by comparison with field maps from dual-echo EPI. The method was tested in functional MRI experiments at 7T with motor tasks and compared with the conventional static approach. Results: Unwarping using our method was accurate even for head rotations up to 8.2°, where the static approach introduced errors up to 8.2 mm. Jittering the echo time between 19 and 25 ms had no measurable effect on blood oxygenation level–dependent (BOLD) sensitivity. Our approach reduced the distortions in activated regions to <1 mm and repositioned active voxels correctly. Conclusion: This method yields accurate distortion correction in the presence of motion. No reduction in BOLD sensitivity was observed. As such, it is suitable for application in a wide range of functional MRI experiments. Magn Reson Med 76:1388–1399, 2016.
Formatted abstract
Purpose: To develop a distortion correction method for echo planar imaging (EPI) that is able to measure dynamic changes in B0.

Theory and Methods: The approach we propose is based on single-echo EPI with a jittering of the echo time between two values for alternate time points. Field maps are calculated between phase images from adjacent volumes and are used to remove distortion from corresponding magnitude images. The performance of our approach was optimized using an analytical model and by comparison with field maps from dual-echo EPI. The method was tested in functional MRI experiments at 7T with motor tasks and compared with the conventional static approach.

Results: Unwarping using our method was accurate even for head rotations up to 8.2°, where the static approach introduced errors up to 8.2 mm. Jittering the echo time between 19 and 25 ms had no measurable effect on blood oxygenation level–dependent (BOLD) sensitivity. Our approach reduced the distortions in activated regions to <1 mm and repositioned active voxels correctly.

Conclusion: This method yields accurate distortion correction in the presence of motion. No reduction in BOLD sensitivity was observed. As such, it is suitable for application in a wide range of functional MRI experiments. 
Keyword Dynamic distortion correction
EPI
Field mapping
FMRI
Respiration effects
Ultra-high field
Q-Index Code C1
Q-Index Status Provisional Code
Grant ID KLI 264
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: HERDC Pre-Audit
Centre for Advanced Imaging Publications
 
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