Journal
MAGNETIC RESONANCE IN MEDICINE
Volume 77, Issue 1, Pages 170-179Publisher
WILEY-BLACKWELL
DOI: 10.1002/mrm.26105
Keywords
gradient calibration; gradient nonlinearity; diffusion MRI; quantitative MRI; cyclooctane
Funding
- Engineering and Physical Sciences Research Council, UK [EP/J013250/1]
- BHF Centre of Regenerative Medicine, Oxford [RM/13/3/30159]
- BHF Centre for Research Excellence
- BHF [FS/11/50/29038]
- Wellcome Trust [090532/Z/09/Z]
- EPSRC [EP/J013250/1] Funding Source: UKRI
- British Heart Foundation [FS/11/50/29038] Funding Source: researchfish
- Engineering and Physical Sciences Research Council [EP/J013250/1] Funding Source: researchfish
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PurposeTo propose a method for calibrating gradient systems and correcting gradient nonlinearities based on diffusion MRI measurements. MethodsThe gradient scaling in x, y, and z were first offset by up to 5% from precalibrated values to simulate a poorly calibrated system. Diffusion MRI data were acquired in a phantom filled with cyclooctane, and corrections for gradient scaling errors and nonlinearity were determined. The calibration was assessed with diffusion tensor imaging and independently validated with high resolution anatomical MRI of a second structured phantom. ResultsThe errors in apparent diffusion coefficients along orthogonal axes ranged from -9.2%0.4% to+8.8%+/- 0.7% before calibration and -0.5%+/- 0.4% to+0.8%+/- 0.3% after calibration. Concurrently, fractional anisotropy decreased from 0.14 +/- 0.03 to 0.03 +/- 0.01. Errors in geometric measurements in x, y and z ranged from -5.5% to+4.5% precalibration and were likewise reduced to -0.97% to+0.23% postcalibration. Image distortions from gradient nonlinearity were markedly reduced. ConclusionPeriodic gradient calibration is an integral part of quality assurance in MRI. The proposed approach is both accurate and efficient, can be setup with readily available materials, and improves accuracy in both anatomical and diffusion MRI to within +/- 1%. Magn Reson Med 77:170-179, 2017. (c) 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.
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