A simple method for mapping the B1 field distribution of linear RF coils

Area of Science:

• Medical Physics
• Magnetic Resonance Imaging (MRI)
• Radio Frequency Engineering

Background:

• Inhomogeneity in the radio frequency (RF) B1 field causes significant intensity variations in MRI scans.
• This B1 field inhomogeneity also leads to spatial variations in spectral line amplitudes, affecting quantitative analysis.
• Accurate characterization of the B1 field is crucial for optimizing MRI performance and data interpretation.

Purpose of the Study:

• To present a straightforward method for measuring the B1 field components of an unsegmented linear coil.
• To develop a technique applicable to coils operating at frequencies up to 20 MHz.
• To provide a practical approach for B1 field mapping in MRI systems.

Main Methods:

• The B1 field distribution is modeled as a static magnetic field generated by direct current (DC) flowing through the coil.
• The coil is rotated by 90 degrees to align the measured B1 component with the main static magnetic field (B0).
• Resonance frequency shifts are measured using a spectroscopic imaging sequence to quantify the B1 field.

Main Results:

• Experimental measurements demonstrated good agreement with theoretical calculations.
• The proposed method effectively quantifies B1 field components.
• The technique is validated for linear coils operating up to 20 MHz.

Conclusions:

• The described method offers a simple and effective way to measure B1 field components in linear RF coils.
• This technique can help correct for B1 inhomogeneity, leading to more accurate MRI images and spectral data.
• The findings contribute to improved quantitative MRI and spectral analysis.