Demonstration of High Efficiency on Coil RF Amplifier for 7 Tesla MRI

Hugo Kroeze¹, Jeroen Stroeve¹, Michel Italiaander¹, Ingmar Voogt¹, Giel Mens¹, Peter R. Luijten¹, Dennis W. J. Klomp¹

At high field MRI it is usefull to place the RF amplifiers directly on the coil. To avoid excessive heat in the bore, these amplifiers must be very efficient. A class-E amplifier was constructed with an efficiency of 80%. Class-E amplifiers can not amplify amplitude modulated signals, a modulator was added. This modulator was driven from a gradient waveform board. The amplifier was directly connected to a 50 mm loop coil. Images of a phantom and a wrist were made using this setup. This demonstrates that efficient on coil amplifiers can be connected to MRI scanners without major hardware modification.