Automated tuning and matching of a 16-channel TEM transmit-only array used in conjunction with a 32-channel receive-only loop array for MR cardiac imaging at 7 tesla

Abstract

Radiofrequency (RF) coils are antenna-like devices used in magnetic resonance imaging (MRI) to inductively excite and receive the nuclear magnetic resonance (NMR) signal in anatomy. Recently, coil arrays have shown significant advantages over large single channel volume coils at ultra-high magnetic field strengths. However, to maximize the full potential, each individual coil within the array needs to be “tuned and matched” to the anatomy (load) prior to imaging. Tuning and matching can be a tedious and time consuming process, and has been cited as a problem that precludes ultra-high field strength MRI from a becoming a clinical reality. Here, we have developed an electromechanical solution. A 16-channel transmit-only TEM array was designed and fitted with piezoelectric actuators mechanically linked to sliding cylindrical tuning and matching capacitors to automate the tuning and matching process, based on the coil's reflection coefficient.