A New Full Bridge High Intensity Focused Ultrasound Power System with Harmonic Cancellation

The feasibility of a new full bridge high intensity focused ultrasound(HIFU) amplifier system with harmonic cancellation is evaluated in this study. Harmonic cancellation technique is applied to these power amplifiers, which can eliminate the 3rd harmonic and all even harmonics. Since this technique requires two channels of phase signal to control one channel of power amplifier, the signal generator is required to double its output. The transducer array proposed in this study has 100 elements. So we choose an FPGA chip to generate 200 driving signals, and each channel has a phase resolution of 2ns, less than 1°. The phase signal from the FPGA meets the requirement of driving the power amplifiers. The output waveform of one channel of power amplifier(voltage across the transducer) is evaluated, and shows fewer harmonic components.     

Real-Time MRI-Controlled Ultrasound Hyperthermia System for Superficial Tumor Treatment

Ultrasound hyperthermia is one of the most important methods in tumor treatment and characterized by non-invasiveness. Magnetic resonance imaging（MRI）-based temperature mapping techniques are safe compared with invasive methods and have been applied to detect temperature changes for a variety of applications. Among these techniques, the proton resonance frequency（PRF） method is relatively advanced. With a temperature measuring experiment, the effectiveness of PRF method has been proved, because the outcome temperature curve and the real temperature curve fit well. After that, an experiment has been conducted on tumors inside rabbit legs and the result indicates that this system is able to performance hyperthermia at targets based on PRF method in temperature mapping.