Novel low-power ultrasound digital preprocessing architecture for wireless display

A complete hardware-based ultrasound preprocessing unit (PPU) is presented as an alternative to available power-hungry devices. Intended to expand the ultrasonic applications, the proposed unit allows replacement of the cable of the ultrasonic probe by a wireless link to transfer data from the probe to a remote monitor. The digital back-end architecture of this PPU is fully pipelined, which permits sampling of ultrasonic signals at a frequency equal to the field-programmable gate array-based system clock, up to 100 MHz. Experimental results show that the proposed processing unit has an excellent performance, an equivalent 53.15 Dhrystone 2.1 MIPS/MHz (DMIPS/MHz), compared with other software-based architectures that allow a maximum of 1.6 DMIPS/MHz. In addition, an adaptive subsampling method is proposed to operate the pixel compressor, which allows real-time image zooming and, by removing high-frequency noise, the lateral and axial resolutions are enhanced by 25% and 33%, respectively. Realtime images, acquired from a reference phantom, validated the feasibility of the proposed architecture. For a display rate of 15 frames per second, and a 5-MHz single-element piezoelectric transducer, the proposed digital PPU requires a dynamic power of only 242 mW, which represents around 20% of the best-available software-based system. Furthermore, composed by the ultrasound processor and the image interpolation unit, the digital processing core of the PPU presents good power-performance ratios of 26 DMIPS/mW and 43.9 DMIPS/mW at a 20-MHz and 100-MHz sample frequency, respectively.