P3J-5 High-Frequency Pulsed-Wave Ultrasound Doppler System for Biomedical Applications with PMN-PT Needle Transducer and 30 MHz Linear Array

In this paper, we report the development of a bidirectional high-frequency (HF) PW ultrasound Doppler system, using either a 45 MHz PMN-PT (lead magnesium niobate-lead titanate) needle transducers or 30-35 MHz linear arrays. The system included the HF directional pulsed-wave Doppler block which can be operated independently with a single element transducer. For 30 MHz linear arrays, a HF analog beamformer was used to focus the beam. Delayed and summed echoes were directly fed to the HF PW Doppler block. The system was evaluated and calibrated on a wire phantom and a micro flow phantom which consisted of polyimide tube with inner diameter 127 mum. The results shows that the system is capable of detecting motion velocity of the wire phantom as low as 0.1 mm/s, and detecting blood-mimicking flow velocity in the 127 mum tube lower than 7 mm/s. With the PMN-PT needle transducer, in vivo experiments have been carried out in rabbit eyes. Blood flow in both the retinal vein and retinal artery with diameter less than 200 mum were measured in real-time. The average maximum velocity in the retinal vein was approximately 1 cm/s, and the average maximum velocity in the retinal artery was approximately 3 cm/s