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Cardiac Magnetic Resonance Imaging at 7 Tesla
Published on: January 6, 2019
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B0 Magnetic Field Conditions in the Human Heart at 3 T Across One Thousand Subjects: A Numerical Simulation Study
Yun Shang1,2, Sebastian Theilenberg1, Boyu Peng3
1Department of Biomedical Engineering, Columbia University in the City of New York, New York, USA.
NMR in Biomedicine
|February 10, 2025
Summary
Cardiac magnetic resonance imaging (CMR) dark bands are reduced by B0 shimming. This study maps B0 distributions using CT scans, revealing heart anatomy, not demographics, influences shimming for clearer cardiac imaging.
Area of Science:
- Medical Imaging
- Biophysics
- Cardiovascular Research
Background:
- Cardiovascular magnetic resonance (CMR) using balanced steady-state free precession (bSSFP) sequences often exhibits dark band artifacts caused by magnetic field (B0) inhomogeneity.
- Cardiac B0 shimming is the primary method to mitigate these artifacts, but its optimization is limited by incomplete knowledge of B0 conditions in standard clinical CMR orientations.
Purpose of the Study:
- To characterize high-resolution B0 distributions in cardiac imaging planes relevant to clinical CMR.
- To analyze the efficacy of spherical harmonic B0 shimming strategies in the human heart at 3 Tesla.
- To investigate the relationship between B0 conditions, shimming, and subject-specific demographic and anatomical factors.
Main Methods:
- High-resolution B0 distributions were simulated using computed tomography (CT) images from 1008 subjects.
- An oblique slicing method was developed to derive B0 distributions in cardiac imaging planes.
- Theoretical analysis of static global and slice-specific dynamic spherical harmonic B0 shimming was performed for the short-axis view.
Main Results:
- Subject-specific B0 distributions were mapped in cardiac imaging planes.
- Spherical harmonic B0 shimming characteristics showed weak correlations with demographic parameters, indicating subject-specific B0 conditions.
- Segmented lung volume demonstrated stronger associations with B0 conditions than overall body metrics, highlighting the influence of surrounding anatomy.
Conclusions:
- This study provides detailed B0 distribution maps crucial for understanding cardiac B0 inhomogeneity.
- The findings suggest that cardiac B0 conditions are primarily influenced by individual thoracic anatomy, particularly lung volume, rather than general demographics.
- This research lays the groundwork for developing optimized cardiac B0 shimming strategies to improve CMR image quality.
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