The present invention describes a four-ring birdcage coil having at least one moveable tuning ring for double resonance MRI. This apparatus includes a low-pass configuration in both channels so that the HF mode only requires a small capacitance for resonance. Therefore it enable easy modification of a single resonance coil into a double resonance coil by incorporation of non-contact coupling rings whose capacitive coupling with the rungs generates enough capacitance to introduce the high-frequency resonance mode. The coil also includes at least one moving ring for broad range tuning in the HF channel. The LF channel is adjusted by a variable capacitor that is not directly connected to the coil, thus the frequency adjustment on each channel is independent. The HF channel is connected to the input cable by coupling capacitor. The LF channel is connected to the input cable by coupling inductor. This alternating driving scheme provides sufficient channel isolation and obviates the need for an external isolation network.
This invention enables the production of double resonance coil with simpler procedure but comparable performance. It can be used in multi-frequency Magnetic Resonance Imaging. Additionally, the technique of multi-frequency MRI can correlate the anatomical information obtained from proton density image with the chemical information obtained from heteronuclear image, thus provide deeper insight into the metabolic and pathogenic pathways.
