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Updated: May 24, 2026
Simultaneous PET/MRI Imaging During Mouse Cerebral Hypoxia-ischemia
Published on: September 20, 2015
Analysis and correction of count rate reduction during simultaneous MR-PET measurements with the BrainPET scanner
Christoph Weirich1, Daniel Brenner, Jürgen Scheins
1Institute of Neuroscience and Medicine, Forschungszentrum Jülich GmbH, Jülich, Germany. c.weirich@fz-juelich.de
Abstract:
In hybrid magnetic resonance-positron emission tomography (MR-PET) studies with the Siemens 3T MR-BrainPET scanner an instantaneous reduction of the PET sensitivity was observed during execution of certain MR sequences. This interference was investigated in detail with custom-made as well as standard clinical MR sequences. The radio-frequency pulses, the switched gradient fields and the constant magnetic field were examined as the relevant parameters of the magnetic resonance imaging (MRI) system as well as the air temperature within the PET detectors. Our investigation comprised the analysis of the analog PET signals, the total count rates, the geometric distribution of the count rate reduction within the BrainPET detector as well as reconstructed images. The fast switching magnetic field gradients were identified to distort the analog PET detector signals. The measured count rate reduction was found to be less than 3%, but only up to 2% in the case of echo planar imaging sequences, as applied in functional MRI. For clinical sequences routinely used in hybrid MR-BrainPET measurements, a correction method has been designed, implemented, and evaluated .
Insights
Magnetic Resonance Imaging (MRI) sequences can reduce Positron Emission Tomography (PET) sensitivity in hybrid MR-PET scanners. Fast switching magnetic field gradients were identified as the cause, leading to a correction method for improved hybrid imaging.
Area of Science:
- Medical Imaging Physics
- Hybrid Imaging Systems
Background:
- Hybrid Magnetic Resonance-Positron Emission Tomography (MR-PET) systems combine anatomical and functional imaging.
- Certain Magnetic Resonance Imaging (MRI) sequences have been observed to interfere with Positron Emission Tomography (PET) sensitivity during simultaneous acquisition.
Purpose of the Study:
- To investigate the cause of PET sensitivity reduction during specific MRI sequences in a Siemens 3T MR-BrainPET scanner.
- To analyze the impact of MRI parameters (RF pulses, gradient fields, magnetic field, air temperature) on PET detector performance.
- To develop and evaluate a correction method for the observed interference.
Main Methods:
- Detailed analysis of analog PET signals, total count rates, and count rate distribution within the BrainPET detector.
- Evaluation of custom-made and standard clinical MRI sequences, including echo planar imaging (EPI).
- Investigation of MRI system parameters and air temperature within PET detectors.
- Design, implementation, and evaluation of a correction method for clinical sequences.
Main Results:
- Fast switching magnetic field gradients were identified as the primary cause of PET signal distortion and sensitivity reduction.
- Observed PET count rate reduction was less than 3%, and up to 2% for functional MRI echo planar imaging sequences.
- A correction method was successfully designed, implemented, and evaluated for clinical MR-PET sequences.
Conclusions:
- Switching magnetic field gradients in MRI systems significantly impact PET sensitivity in hybrid MR-PET scanners.
- The developed correction method effectively mitigates the interference, improving the reliability of hybrid MR-PET measurements.
- This research contributes to optimizing hybrid imaging protocols for enhanced diagnostic accuracy.
