This technology includes the design and implementation for 1H-nuclear magnetic resonance imaging (MRI) that allows single transmit hardware to be "transformed" for another nucleus excitation to perform multi-nuclear MR. A radiofrequency (RF) optically controlled switch-mode amplifier prototype is tuned for excitation of two nuclei. The amplifier received the nuclei carrier signals optically through a single fiber. This signal is amplified first through a broadband low current stage that provides a pair of gate-source voltage signals 180 degrees out of phase to switch ON a pair of field effect transistors (FETs) in push-pull class-D configuration (FET are turned ON only during half a cycle). In this preamplification stage gate circuitry has been dual tuned, through a dual-resonance LC network, for maximizing the gate-source voltage to fully switch ON the FETs at the selected nuclei frequencies. A similar approach is followed to permit the gate control signals to fully switch ON the FETs of the power stage in Current-Mode Class-D topology. A prototype for 1H and 31P excitation at 7T was implemented, tested on the bench and MRI scanner.
This prototype can be used in the implementation of a versatile parallel transmission system for 1H imaging that allows one or more transmit channels to be "transformed" for another nucleus excitation to perform multi-nuclear MR with a single transmit hardware.
To simplify the implementation of multi-nuclear multi-channel hardware, I designed, implemented and tested an optically controlled dual-tuned on-coil current-source amplifier for 1H and X-nuclei excitation. On-coil current-source amplification has been proposed for the practical implementation of 1H pTx systems. I expect this new prototype will allow a more flexible multi-nuclear multi-channel transmitter hardware by eliminating the need of multiple cable traps, matching networks and coaxial connections as needed for each resonance frequency in conventional broadband voltage mode amplification available in commercial scanners with multi-nuclear capability.