RF Head Coil Design With Improved RF Magnetic Near-Fields Uniformity for Magnetic Resonance Imaging (MRI) Systems
- 1 August 2014
- journal article
- Published by Institute of Electrical and Electronics Engineers (IEEE) in IEEE Transactions on Microwave Theory and Techniques
- Vol. 62 (8), 1784-1789
- https://doi.org/10.1109/tmtt.2014.2331621
Abstract
Higher magnetic field strength in magnetic resonance imaging (MRI) systems offers higher signal-to-noise ratio (SNR), contrast, and spatial resolution in MR images. However, the wavelength in ultra-high fields (7 tesla and beyond) becomes shorter than the human body at the Larmor frequency with increasing static magnetic field (B0) of MRI system. At short wavelengths, interference effect appears resulting in non- uniformity of the RF magnetic near-field (B1) over the subject and MR images may have spatially anomalous contrast. The B1 near-field generated by the transverse electromagnetic (TEM) RF coil’s microstrip line element has a maximum near the center of its length and falls off towards both ends. In this study, a double trapezoidal shaped microstrip transmission line element is proposed to obtain uniform B1 field distribution by gradual impedance variation. Two multi-channel RF head coils with uniform and trapezoidal shape elements were built and tested with a phantom at 7T MRI scanner for comparison. The simulation and experimental results show stronger and more uniform B1+ near-field with the trapezoidal shape.Keywords
This publication has 12 references indexed in Scilit:
- The future of ultra-high field MRI and fMRI for study of the human brainNeuroImage, 2011
- 9.4T human MRI: Preliminary resultsMagnetic Resonance in Medicine, 2006
- Electromagnetic perspective on the operation of RF coils at 1.5–11.7 TeslaMagnetic Resonance in Medicine, 2005
- Whole-body MRI at high field: technical limits and clinical potentialEuropean Radiology, 2005
- Efficient high‐frequency body coil for high‐field MRIMagnetic Resonance in Medicine, 2004
- High field MRI in preclinical researchEuropean Journal of Radiology, 2003
- Analysis of wave behavior in lossy dielectric samples at high fieldMagnetic Resonance in Medicine, 2002
- Effect of RF coil excitation on field inhomogeneity at ultra high fields: a field optimized TEM resonatorMagnetic Resonance Imaging, 2001
- 7T vs. 4T: RF power, homogeneity, and signal‐to‐noise comparison in head imagesMagnetic Resonance in Medicine, 2001
- TEM wave properties of microstrip transmission linesProceedings of the Institution of Electrical Engineers, 1968