Ultra-High-Field MRI Using Slotted Waveguide Array RF Coil

At a Glance

Investigators at Colorado State University have designed a novel method and apparatus for the excitation of radiofrequency (RF) magnetic fields in ultra-high field magnetic resonance imaging (MRI) systems utilizing a slotted waveguide array. Each element in the circular array is itself a slotted waveguide antenna, which in turn is a linear array of slots in a waveguide wall. Numerical modeling of the design shows enhanced performance over numerical models of competing RF coil designs currently in use. Potential applications include research, pre-clinical, and clinical MRI/NMR systems.

Background

There is active and growing research and development of MRI related to higher static magnetic fields. Current MRI technology uses  relatively low static magnetic field (≤ 3 T).  Ultra-high field (≥ 7 T) increases sensitivity and functionality of MRI overall, but have additional challenges.  At higher magnetic fields, the RF wavelength decreases. The effects of this decrease lead to an undesired and highly nonuniform RF magnetic field, impacting the data quality that can be collected. Recent research in this field has either been unsuccessful at mitigating this factor (ex: transverse electromagnetic – TEM body coil) or suffer from intolerably low RF power efficiency (twisting bird cage, traveling-wave coil).

Overview

Researchers at Colorado State University have developed a novel method and coil for excitation of RF magnetic fields that uses a slotted waveguide array. The array is made up of several slotted waveguide antennas in a robust structure capable of handling high powers. It provides a RF magnetic field with excellent circular polarization and good uniformity, providing clear advantages over other existing solutions. The design also allows for parallel imaging, which helps reduce total imaging time, while the ability to configure different arrangements of slots allows for optimization to a particular environment to yield maximum radiation efficiency.  A comprehensive numerical study of the performance of this type of RF coil at 7 T resulted in high quality simulated imaging, especially when compared to the state-of-the-art microstrip TEM array coil as seen in Figure 2.

Benefits

  • Provides RF magnetic field with: (1) high field-uniformity, (2) high efficiency, (3) excellent circular polarization, (4) arbitrary large field of view
  • Each waveguide antenna can be near perfectly decoupled from all other elements in the array
  • Allows for multichannel excitation with decoupled channels to allow parallel imaging and RF shimming in order to achieve optimal magnetic field distribution within the imaged subjects
  • Universal / Not limited to any particular field strength or any particular frequency
  • Slotted waveguide array coils can be used as body, head, limb, torso, or partial body coil

Applications

  • Research, pre-clinical, and clinical MRI systems
Last Updated: December 2023
Diagram of Ultra-High-Field MRI
Opportunity

Available for Licensing
TRL: 2

IP Status

US Patent: US11313929
US Patent: US11808829

Inventors

Branislav M. Notaroš
Milan M. Ilić

Reference Number
17-019
Licensing Manager

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