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Updated: Jan 31, 2026
10:53
Functional Imaging of Brown Fat in Mice with 18F-FDG micro-PET/CT
Published on: November 23, 2012
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MR image corrections for PET-induced gradient distortions.
Nicolas Gross-Weege1, Teresa Nolte, Volkmar Schulz
1Department of Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging, RWTH Aachen University, Aachen Germany.
Physics in Medicine and Biology
|December 19, 2018
Summary
Integrating positron emission tomography (PET) with magnetic resonance imaging (MRI) is enhanced by minimizing PET insert interference. Measuring the gradient impulse response function (GIRF) corrects MRI k-space trajectories, significantly reducing image distortions caused by PET inserts.
Area of Science:
- Medical Imaging
- Biophysics
- Instrumentation
Background:
- Combined PET-MRI offers synergistic diagnostic capabilities.
- PET inserts in MRI scanners face challenges from electromagnetic interference.
- Gradient magnetic fields in MRI are crucial for spatial encoding and susceptible to distortion.
Purpose of the Study:
- To evaluate the impact of a preclinical PET insert (Hyperion II) on MRI gradient performance.
- To characterize the gradient impulse response function (GIRF) with and without the PET insert.
- To demonstrate the effectiveness of GIRF-based k-space trajectory correction for mitigating PET-induced MRI distortions.
Main Methods:
- Determined GIRFs up to second-order spherical harmonics using frequency-swept gradient pulses and an NMR probe.
- Measured GIRFs with and without the Hyperion II PET insert in a 3 T MRI scanner.
- Calculated corrected k-space trajectories for a single-shot spiral sequence using measured GIRFs.
Main Results:
- The PET insert exhibited high gradient transparency, causing only a slight increase in the gradient system's low-pass characteristic.
- A minor influence of the PET insert on GIRFs was observed.
- PET-induced blurring and distortion in MRI images were substantially reduced using first-order spherical harmonic GIRF correction.
Conclusions:
- The Hyperion II PET insert minimally affects MRI gradient performance.
- GIRF measurement and correction are effective strategies for reducing PET-induced MRI image artifacts.
- Further improvements may require accounting for higher-order spherical harmonics or static magnetic field distortions.
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