Automatic Resonance Frequency Retuning of Stretchable Liquid Metal Receive Coil for Magnetic Resonance Imaging.

Stretchable magnetic resonance (MR) receive coils show shifts in their resonance frequency when stretched. An in-field receiver measures the frequency response of a stretchable coil. The receiver and coil are designed to operate at 128MHz for a 3T MR scanner. Based on the measured frequency response, we are able to detect the changes of the resonance frequency of the coil. We show a proportional-integral-derivative (PID) controller that tracks the changes in resonance frequency and retunes the stretchable coil. The settling time of the control loop is less than 3.8 ms. The retuning system reduces the loss in signal to noise ratio of phantom images from 1.6 dB to 0.3 dB when the coil is stretched by 40% and the coil is retuned to 128MHz.