A practical double-tuned 1H/31P quadrature birdcage headcoil optimized for 31P operation

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Biophysics
• Medical Physics

Background:

• Developing advanced MRI coils is crucial for improving image quality and enabling novel spectroscopic techniques.
• Simultaneous proton (1H) and phosphorus-31 (31P) imaging offers complementary information about tissue metabolism and structure.
• Birdcage coil designs are widely used in MRI due to their excellent B1 field homogeneity.

Purpose of the Study:

• To describe the design and performance of a novel double-tuned 1H/31P birdcage head coil for 1.5 T MRI.
• To evaluate the coil's suitability for proton-decoupled 31P spectroscopy of the human brain.
• To optimize sensitivity and radiofrequency (RF) field homogeneity for both 1H and 31P channels.

Main Methods:

• Design and construction of a double-tuned birdcage head coil operating at 1H (63.87 MHz) and 31P (25.85 MHz) frequencies.
• Incorporation of an RF mirror for enhanced B1 homogeneity.
• Utilized inductive matching and capacitively shortened bazookas for efficient tuning, matching, and suppression of cable currents.
• Evaluated proton sensitivity and B1 homogeneity at both frequencies.

Main Results:

• Achieved similar B1 homogeneity for both 1H and 31P frequencies.
• Demonstrated optimized sensitivity for 31P detection.
• Proton sensitivity was sufficient for shimming and scout imaging, despite a twofold reduction compared to a dedicated 1H coil.
• Successfully acquired proton-decoupled 31P spectra of the human brain.

Conclusions:

• The developed double-tuned 1H/31P birdcage head coil is a practical and effective tool for simultaneous 1H imaging and 31P spectroscopy in human brain studies at 1.5 T.
• The coil design offers a good balance between 1H and 31P performance, enabling valuable metabolic information acquisition.
• This coil represents a significant advancement for in vivo 31P Magnetic Resonance Spectroscopy (MRS).