Auto-tuning of the RF transmission line coil for high-fields magnetic resonance imaging (MRI) systems

RF coil with microstip transmission line elements have been used for high-fields magnetic resonance imaging (MRI) to inductively excite and receive the nuclear magnetic resonance signals in anatomy. These coil elements have narrow bandwidth due to its high quality factors (Qs). Although high signal-to-noise ratio (SNR) of RF coils is obtained from this property it has a critical drawback, loading (body) effect that causes the resonance frequency and Q of RF coils to change when different human heads or bodies are loaded. There is an alternative to manual tuning that needs a few minutes and remains a major obstacle to the use of RF transmission line coils in high-fields MRI systems. In this study, an adaptive impedance matching technique for 7 Tesla MRI systems is proposed to avoid mismatch of the RF loaded coils at the Larmor frequency (297MHz).