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Multicoil shimming of the mouse brain
Christoph Juchem1, Peter B Brown, Terence W Nixon
1Department of Diagnostic Radiology, Yale University School of Medicine, MR Research Center (MRRC), New Haven, Connecticut 06520, USA. christoph.juchem@yale.edu
Magnetic Resonance in Medicine
|March 29, 2011
Summary
Achieving uniform magnetic fields in mouse brains for MRI is challenging. A novel 48-coil system significantly reduces field distortions, improving brain imaging quality and signal gain.
Area of Science:
- Neuroimaging
- Magnetic Resonance Imaging (MRI)
- Biophysics
Background:
- High magnetic field homogeneity is essential for accurate MRI and spectroscopy of brain function and physiology.
- Shimming the magnetic field in small objects like the mouse brain is difficult due to complex susceptibility-induced distortions.
- Current methods struggle to achieve satisfactory whole-brain shimming in mice at high field strengths (e.g., 9.4 Tesla).
Purpose of the Study:
- To develop and evaluate a novel multicoil system for improved magnetic field homogenization (shimming) in the mouse brain at 9.4 Tesla.
- To assess the effectiveness of this system in reducing field distortions and enhancing image quality compared to conventional methods.
Main Methods:
- A custom-designed system with 48 circular coils (13 mm diameter) arranged in a 32 mm diameter cylinder was used.
- Individual coils were driven with dynamic current ranges of ±1 A.
- Static and slice-specific dynamic shimming approaches were tested.
- Performance was evaluated by measuring the standard deviation of Larmor frequencies and signal gains in gradient echo imaging.
Main Results:
- The multicoil system substantially reduced magnetic field distortions in the mouse brain.
- Static multicoil shimming decreased Larmor frequency standard deviation by 31% compared to second-order spherical harmonics.
- Dynamic, slice-specific multicoil shimming achieved a 66% narrowing of Larmor frequencies.
- Multicoil shimming minimized signal voids in gradient echo imaging and increased overall signal by up to 51%.
Conclusions:
- The novel 48-coil system offers a significant advancement in achieving high-quality magnetic field shimming for mouse brain MRI.
- This technology overcomes previous limitations, enabling more precise noninvasive studies of brain function and physiology in mice.
- The demonstrated improvements in field homogeneity and signal quality have broad implications for neuroscience research using MRI.
