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Exact temporal eddy current compensation in magnetic resonance imaging systems
M A Morich1, D A Lampman, W R Dannels
1Picker Int. Inc., Highland Heights, OH.
IEEE Transactions on Medical Imaging
|January 1, 1988
Summary
A new step-response method accurately extracts eddy-current properties in MRI systems. This technique enables precise magnetic field compensation, improving image quality, especially for long-term eddy-current effects.
Area of Science:
- Magnetic Resonance Imaging (MRI)
- Applied Physics
- Signal Processing
Background:
- Pulsed field gradients in MRI systems generate intrinsic eddy currents.
- These eddy currents distort magnetic fields, degrading image quality.
- Accurate characterization and compensation of eddy currents are crucial for high-fidelity MRI.
Purpose of the Study:
- To develop a step-response method for extracting eddy-current properties (amplitudes and decay time constants).
- To achieve exact compensation for eddy-current effects in whole-body MRI.
- To demonstrate the method's effectiveness for long-term eddy-current compensation.
Main Methods:
- A step-response method is employed to analyze eddy-current-sourced magnetic fields.
- Polynomial rooting and matrix inversion are used to determine eddy-current properties.
- The method is validated using experimental data for one-, two-, and three-term inversions.
Main Results:
- The method successfully extracts amplitudes and decay time constants of eddy currents.
- Exact eddy-current compensation is achieved through the developed procedure.
- Effective compensation for long-term eddy currents (200-1000 ms) is demonstrated.
- Field-gradient spectral flatness measurements validate the method's performance.
Conclusions:
- The developed step-response method provides accurate characterization of MRI eddy currents.
- This technique enables precise magnetic field equalization for improved MRI.
- The method is particularly useful for challenging long-term eddy-current compensation scenarios.
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