Field camera versus phantom-based measurement of the gradient system transfer function (GSTF) with dwell time
M Stich1, J A J Richter2, T Wech3
1Department of Diagnostic and Interventional Radiology, University Hospital Würzburg, Würzburg, Germany; Cardiovascular Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, USA; X-Ray & Molecular Imaging Lab, Technical University Amberg-Weiden, Germany.
Magnetic Resonance Imaging
|June 14, 2020
Summary
Comparing two methods for measuring the gradient system transfer function (GSTF) in MRI, this study found that dwell-time compensation eliminates trajectory deviations and image artifacts. This ensures accurate trajectory correction for improved non-Cartesian MRI reconstruction.
Area of Science:
- Magnetic Resonance Imaging (MRI)
- Medical Physics
- Image Reconstruction
Background:
- The gradient system transfer function (GSTF) is crucial for describing dynamic gradient systems in MRI.
- Accurate GSTF measurement is essential for trajectory correction in non-Cartesian MRI sequences.
- Differences in measurement techniques can lead to discrepancies in GSTF determination.
Purpose of the Study:
- To compare field camera and phantom-based methods for measuring the GSTF.
- To implement dwell-time compensation to address measurement differences.
- To evaluate the impact of GSTF measurement methods on trajectory prediction and image reconstruction.
Main Methods:
- Determined self-term GSTFs using a dynamic field camera and a spherical phantom.
- Applied a box function convolution to the phantom-based GSTF for dwell-time compensation.
- Utilized measured GSTFs for trajectory prediction in retrospective reconstruction of 3D wave-CAIPI phantom images.
Main Results:
- Observed differences in GSTF magnitude response between the two methods.
- Without compensation, phantom-based GSTF resulted in 4% trajectory deviations and image artifacts.
- Dwell-time compensation eliminated deviations in GSTF magnitudes and trajectories (<0.5%) and reduced image artifacts.
Conclusions:
- Dwell-time compensation is effective in reconciling GSTF measurements from field camera and phantom methods.
- Both compensated methods yield negligible deviations and significantly reduce artifacts in MRI reconstruction.
- Accurate GSTF characterization with dwell-time compensation is vital for reliable trajectory correction in non-Cartesian MRI.
