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Single point measurements of magnetic field gradient waveform
David J Goodyear1, Maurice Shea, Steven D Beyea
1MRI Centre, Department of Physics, P.O. Box 4400, University of New Brunswick, Fredericton, E3B 5A3 New Brunswick, Canada.
Journal of Magnetic Resonance (San Diego, Calif. : 1997)
|July 11, 2003
Summary
Researchers developed a new method to measure magnetic field gradient waveforms in magnetic resonance imaging. This technique accurately detects eddy currents and waveform imperfections, improving image quality.
Area of Science:
- Magnetic Resonance Imaging (MRI)
- Physics
Background:
- Pulsed magnetic field gradients are essential for spatial encoding and diffusion weighting in MRI.
- Physical limitations restrict gradient switching speeds, leading to non-ideal waveforms.
- Eddy currents and finite switching times cause image artifacts.
Purpose of the Study:
- To develop a novel method for measuring the complete magnetic field gradient waveform.
- To directly assess the impact of non-ideal gradient behaviors, including eddy currents.
Main Methods:
- Utilized a heavily doped test sample with short relaxation times (T(1), T(2), T(2)(*)<100 µs).
- Employed a series of closely spaced broadband radiofrequency excitations.
- Incorporated single-point data acquisition to measure evolving signal phase.
Main Results:
- The developed technique directly determines the magnetic field gradient waveform experienced by the sample.
- The method is sensitive to low-level transient magnetic fields from eddy currents.
- The measurement captures short and long time constant non-ideal gradient behaviors.
Conclusions:
- A facile and direct method for measuring magnetic field gradient waveforms has been established.
- This technique allows for a ready experimental check of gradient performance.
- Improved understanding and characterization of gradient behavior can mitigate MRI artifacts.