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Based on limited diffraction beam theory, a high frame rate (HFR) imaging method was developed previously. In this method, a plane wave is used in transmission and limited-diffraction array beams are used in reception. Because only one transmission is needed to obtain a 3D image, ultrahigh image frame rate can be achieved. The method was also studied for multiple plane wave and limited-diffraction array beam transmissions to increase image field of view and image quality. Recently, the HFR imaging method was further studied in detail and extended. A theory was established to include explicitly multiple steered plane wave and limited-diffraction array beam transmissions and the relationship between limited-diffraction array beam aperture weightings and the Fourier transform over the transducer aperture was established. Moreover, a method based on square-wave aperture weightings to simplify the transmission subsystem of an ultrasound imaging system was developed. Although the extended HFR imaging methods have many advantages as compared to the conventional imaging methods in terms of image frame rate, resolution, and contrast, there is a concern of the influences of motion artifacts, phase aberration of biological tissues to ultrasound beams, and noise of imaging systems. In this dissertation, studies on the influences of these effects on the extended HFR imaging methods are carried out. In addition, the code excitation techniques are used to increase image frame rate of limited-diffraction array beam imaging that achieves two-way dynamic focusing. To perform both in vitro and in vivo experiments to validate the studies, a HFR imaging system has been developed by a team of researchers in the Ultrasound Lab. The circuit design, construction, and troubleshooting of the system will be discussed.

Modern Automatic Blood Pressure Measurement Techniques are based on measuring the cuff pressure and on sensing the pulsatile amplitude variations. These measurements are very sensitive to motion of the patient or the surroundings where the patient is. The slightest unexpected movements could offset the readings of the automatic Blood Pressure meter by a large amount or render the readings totally meaningless. Every effort must be taken to avoid subjecting the body of the patient or the patient's surroundings to motion for obtaining a reliable reading. But there are situations in which we need Blood Pressure Measurements with the patient or his surroundings in motion; for instance in an ambulance while a patient is being transported to a hospital. In this thesis, we present a technique to reduce the effect of motion artifact from Blood Pressure measurements. We digitize the blood pressure waveform and use Digital Signal Processing Techniques to process the corrupted waveform. We use the differences in frequency spectra of the Blood Pressure signal and motion artifact noise to remove the motion artifact noise. The motion artifact noise spectrum is not very well defined, since it may consist of many different frequency components depending on the kind of motion. The Blood Pressure signal is more or less a periodic signal. That translates to periodicity in the frequency domain. Hence, we designed a digital filter that could take advantage of the periodic nature of the Blood Pressure Signal waveform. The filter is shaped like a comb with periodic peaks around the signal frequency components. Further processing of the filtered signal: baseline restoration and level shifting help us to further reduce the noise corruption.