High-frequency ultrasound imaging system with Doppler features for biomedical applications using 30~35 mHz linear arrays and an analog beamformer

UnrestrictedSmall animal research is gaining more attention since mice and rats are preferred animal models for gene and drug therapy. High-frequency (HF) ultrasound imaging, capable of achieving superior spatial resolution at an affordable price, has been shown to be useful for imaging and visualizing blood flow in small animals for biological and pharmaceutical research. The utilization of HF arrays in a HF imaging system can alleviate the limitations of the current systems with single element transducers, such as the uneven image quality and frame rate.; In this dissertation, a HF ultrasound B-mode imaging system and a HF ultrasound Doppler system using 30~35 MHz linear arrays and an analog beamformer were investigated, visualizing both the movements and blood flow of the mouse heart. First the B-mode imaging system, which included HF linear arrays, timing control circuits, analog front-end circuits, a 16-channel analog receiving beamformer and an 8-bit digitizer, was developed. The system with the 48-element linear arrays was used to image rabbit eyes in vitro and mice heart in vivo in real time. Furthermore, this system was used to successfully acquire images of mouse heart movements at 100 frame/s. For further improving the performance of the B-mode imaging system, efficient bipolar pulsers, low-noise front-end electronics, and a 14-bit digitizer were studied. Meanwhile, a HF pulsed-wave Doppler system, which can be interfaced to either a single element transducer or the analog beamformer with arrays, was developed. The Doppler system was capable of detecting blood flow in vessels with diameters less than 200 [microns] and measuring velocities from 100 [microns]/s to 1 m/s. In addition, this Doppler system with intraocular needle transducers can be used to evaluate the treatment of retinal vein occlusion. Finally, based on the Doppler system and part of the improved B-mode imaging system, an array-based HF Doppler system, which can perform pulsed-wave Doppler, color Doppler, and power Doppler measurements, was implemented and used in small animal cardiovascular research. The experimental results have demonstrated that the HF ultrasound system with the arrays and analog beamformer may achieve better performance and higher frame rate than current systems with single element transducers