Study And Implementation On Wide-beam-excitation-based High-frame-rate Ultrasound Imaging

Ultrasound imaging technology is already a major technology in modern medical ultrasound diagnosis.It has become an indispensable conventional diagnostic technique in clinical diagnosis because of its non-invasive,low-cost,real-time imaging and so on.Although this technique has been widely used clinically,there are still many points in traditional ultrasonic imaging technology that are worth studying and discussing due to some limitations of ultrasonic imaging theory.Conventional ultrasound imaging uses line-by-line scanning method that allows the imaging frame rate can only reach tens of frames per second.Furthermore,due to the use of focused imaging methods,imaging is better only at the focal point and the overall uniformity is poor.With the increasing demand for medical diagnostic equipment,it requires an optimized imaging method to improve the imaging frame rate and to equalize the imaging resolution at each depth.At present,increasing the ultrasound imaging frame rate mainly uses wide beam-excited ultrasound imaging method which can be divided into two wide beam imaging and plane wave imaging methods in this thesis.Both of these imaging modalities change the traditional focus line-by-line scanning.Wide-beam imaging technology could significantly improve the frame rate,uniformity and spatial resolution of the image by using multi-element simultaneous transmit,far point focusing,dynamic aperture apodization and other methods.Ultrasound plane wave imaging achieves full array send ultrasonic plane wave at the same time with no focus which greatly improving the imaging frame rate.And multi-angle plane-wave coherent compound imaging method can not only obtain ultrafast imaging frame rate,and is very advantageous for fast-flowing blood flow imaging,which can improve the sensitivity of blood flow detection.This thesis acquired wide beam raw RF data using the research ultrasound system(V1,Verasonics,USA),and reconstructed wide beam image with beam forming.Besides,the thesis compared wide beam images with conventional focused image and wide beam image of the system.Results show that wide beam method has uniform axial resolution and lateral resolution compared to conventional focused imaging.It also can obtain higher frame rate than the focused imaging.Lateral resolution and axial resolution up to 0.36mm,frame rate up to 320 frames/second.This research performs power Doppler imaging on phantom and living blood flow by high frame rate plane wave coherent compound method according to the principle that power could express ultrasound Doppler information.Human carotid artery were selected in vivo blood flow experiments.The blood flow from the human arteries and phantom can be extracted from the surrounding tissues.Power Doppler imaging method based on plane wave has a high sensitivity and ultrafast frame rate to the detection of blood flow,indicating that the method can be effectively used in blood flow imaging which frame rate up to 1027 frames/second.