Volumetric wireless coil based on periodically coupled split-loop resonators for clinical wrist imaging

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Radiofrequency (RF) Coil Technology
• Biomedical Engineering

Background:

• Standard MRI receive coils often use cables that can limit flexibility and introduce artifacts.
• Wireless coil technology offers potential advantages in patient comfort and imaging flexibility.
• Improving RF field homogeneity and signal reception is crucial for high-quality MRI, especially for small anatomical regions like the wrist.

Purpose of the Study:

• To design and characterize a novel inductively driven wireless coil (WLC) for wrist imaging at 1.5 Tesla.
• To achieve high B1 field homogeneity by focusing the birdcage body coil's field.
• To evaluate the WLC as a potential replacement for conventional cable-connected receive coils.

Main Methods:

• The WLC was designed using a volumetric self-resonant periodic structure of inductively coupled split-loop resonators.
• Electromagnetic simulations were performed to optimize the WLC and analyze its interaction with a birdcage coil (BC).
• The manufactured WLC was characterized through on-bench measurements, phantom studies, and in vivo wrist imaging, comparing it to a standard cable-connected coil.

Main Results:

• The WLC, when placed inside the BC, increased the BC's B1+ field by 8.6 times for the same accepted power.
• Phantom and in vivo wrist imaging demonstrated that the BC with the WLC achieved signal-to-noise ratios equal to or higher than conventional setups.
• No artifacts were observed, and safety assessments confirmed low specific absorption rate and reflected transmit power.

Conclusions:

• The proposed wireless coil (WLC) is a viable alternative to standard cable-connected receive coils in clinical MRI.
• The WLC enabled high-quality wrist imaging at 1.5 T with excellent signal-to-noise ratio and safety, using a full-body birdcage coil for transmit and receive.
• This wireless approach offers improved flexibility and performance for specific MRI applications.