Development of a real time digital high frequency annular array ultrasound imaging system

The development of a real time high frequency ultrasound imaging system for imaging with an annular array transducer is described in this study. The system is composed of a six-element transducer, a six-channel analog front end, a field programmable gate array (FPGA) based beamformer and a scan converter with a DSP microprocessor as the central unit. A PC is used as the user interface showing the real time images. The experimental results show that the transducer has a 300 μm -6 dB beam width measured with hydrophone system. The beamformer that apply delays to the echoes from each channel is implemented with the strategy of combining the coarse and fine delays. The coarse delays that are integer multiples of the clock period are achieved by using a first-in-first-out structure and the fine delays are accomplished with a fractional delay filter. The image obtained from a wire target shows that the system is capable of achieving fairly uniform spatial resolution through the depth of the view.