The RF Cap: A 26-channel flexible RF coil cap for optimized concurrent TMS/fMRI experiments at 3T

Area of Science:

• Neuroimaging
• Neuroscience
• Biomedical Engineering

Background:

• Combining brain imaging with non-invasive brain stimulation like transcranial magnetic stimulation (TMS) offers significant potential for understanding brain function.
• Existing hardware solutions for concurrent TMS/fMRI are limited, often sacrificing imaging quality.

Purpose of the Study:

• To design, construct, and test a novel hardware solution for feasible concurrent TMS/fMRI at 3 Tesla without compromising image quality.
• To introduce the "RF Cap," a 26-channel flexible RF coil cap optimized for simultaneous TMS and fMRI.

Main Methods:

• Developed a 26-channel flexible RF coil cap (RF Cap) with full brain coverage.
• The RF Cap features a flexible neoprene cap with 26 RF coaxial cable loops and a rigid part for preamplifiers.
• Integrated flexible PCBs and a BALUN to minimize common mode signals for improved performance.

Main Results:

• The RF Cap demonstrated significantly higher signal-to-noise ratio (SNR) compared to a birdcage coil (4x at the center, 10-16x on the cortex).
• Concurrent TMS caused a 10-25% SNR loss in the stimulated region.
• The RF Cap allows TMS administration at most scalp targets with easy setup and neuronavigation compatibility.

Conclusions:

• The RF Cap provides a user-friendly and comfortable solution for concurrent TMS/fMRI acquisitions.
• This innovative hardware has the potential to advance neuroscientific research and facilitate future clinical applications of TMS/fMRI.