Helical-Antenna Radio-Frequency Coil for MRI

At a Glance

To advance next-generation MRI scanners at higher magnetic field strengths, it is critical to improve radiofrequency (RF) coils and RF magnetic fields. This invention features a new RF coil that takes advantage of multi-channel RF technology and the design can be based on a multi-channel (typically 4-channel or 8-channel) helical antenna. The goal of this approach is to enable multi-channel methods and create a more uniform circularly polarized RF magnetic field that can also be shimmed if required. When compared to the existing RF coil concepts and designs, this model provides:

  • Improved uniformity of the B1 field
  • Better circular polarization of the field
  • Increased field of view in the axial direction
  • Use in parallel transmission to enable all multi-transmit channel RF technology

Background

Magnetic resonance imaging (MRI) scanners are typically identified by their static axial magnetic field strength, which influences the strength of the signal that can be collected and the quality of image that will be generated (signal to noise ratio – SNR). The current MRI scanners that can be found in hospitals operate at 1.5 T or 3 T in strength, but research into next generation instruments is focused on exploring strengths >4 T. Higher strength magnets help create more detailed images, along with some other improvements. When modifying the magnetic strength, other aspects of the machine must be adapted, such as the RF coils. RF coils impact the resolution, sensitivity, and uniformity in MRI imaging. The standard RF coil shape used for magnetic fields ≤3 T does not produce a uniform magnetic field distribution when applied to higher magnetic strengths. To continue MRI development at higher magnetic field strengths, new solutions to RF coils shape must be introduced.

Overview

Investigators at Colorado State University and Massachusetts General Hospital have developed a novel RF coil design for MRI scanners at high (>3 T) magnetic strength. A sample is placed inside a 4- or 8-channel helical antenna. Prototypes of both designs have been developed and tested in 7 T and 10.5 T scanners. Excellent consistency has been demonstrated between numerical simulations and these experimental results as can be seen in Figure 1. Helical antennas can also be used as head coils, and coils for scanning arms, hands, wrists, legs, knees, ankles, etc. This coil design provides uniformity to the magnetic field, a large field of view, and excellent circular polarization and is a viable replacement for traditional RF coils, such as a birdcage coil that is found in clinical scanners at 3 T. It also has clear advantages over patch antennas implemented in MRI systems ≥ 7 T. This new method for RF excitation is universal and not limited to any particular strength or frequency and could be applied to the entire spectrum of available and future scanners 3T and up.

Benefits

  • More homogeneous field distribution
  • Better signal-to-noise ratio
  • Larger field of view
  • Excellent coupling of the field/wave with the phantom
  • Strong field penetration
  • Appropriate Specific Absorption Rate (much below the acceptable and allowable levels) at every point
  • Increased sensitivity and functionality, overall
  • Not limited to any particular frequency or field strength

Applications

  • Applications in research, pre-clinical, and clinical MRI systems
  • Helical antennas can also be used as head coils, and coils for scanning arms, hands, wrists, legs, knees, ankles, etc.
Last Updated: January 2024
Diagram of a subject loaded MRI
Opportunity

Available for Licensing
TRL: 3

IP Status
Inventors

Branislav M. Notaroš
Milan M. Ilić
Alexey Tonyushkin
Nada J. Šekeljić
Pranav Athalye

Reference Number
15-030
Licensing Manager

Aly Hoeher
Aly.Hoeher@colostate.edu
970-491-7100