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Quantitative Magnetic Resonance Imaging of Skeletal Muscle Disease
Published on: December 18, 2016
Software compensation of eddy current fields in multislice high order dynamic shimming.
Saikat Sengupta1, Malcolm J Avison, John C Gore
1Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN 37235, USA. saikat.sengupta@vanderbilt.edu
Journal of Magnetic Resonance (San Diego, Calif. : 1997)
|April 5, 2011
Summary
Dynamic B(0) shimming improves MRI field homogeneity but is limited by eddy currents. A novel eddy field compensation method effectively reduces these currents without extra hardware, enhancing image quality in multislice acquisitions.
Area of Science:
- Magnetic Resonance Imaging (MRI)
- Biophysics
- Medical Physics
Background:
- Dynamic B(0) shimming (DS) enhances MRI field homogeneity over static methods.
- Eddy currents from switching higher-order unshielded shims degrade DS performance in multislice imaging.
Purpose of the Study:
- To introduce a novel eddy field compensation (EFC) method for higher-order shim-induced eddy currents in multislice DS.
- To demonstrate EFC's effectiveness without requiring shim shielding, extra hardware, or subject-specific prescan calibration.
Main Methods:
- Modeling interactions between shim harmonics to derive 'correction factors' for eddy fields.
- Assuming steady-state conditions for medium and long time-constant eddy fields.
- Validating correction factors' invariance across different objects, shim patterns, and shim values.
Main Results:
- Demonstrated significant reductions in field gradients and offsets in phantom and human head experiments.
- Achieved substantial improvements in image quality using the EFC method.
- Showcased the method's efficacy without hardware-based eddy current compensation.
Conclusions:
- The proposed EFC method effectively compensates for eddy currents in higher-order multislice DS.
- This technique offers a promising, cost-effective alternative to hardware-based eddy current compensation.
- The generalized correction factors enable prospective application in advanced MRI shimming.
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