Ultrasonic target detection in solid, liquid and tissue mediums via pulse-echo estimation

Ultrasonic transducer arrays are used commonly in medical imaging applications and many fields of industry. Using arrays provides focusing to beam as a receiver or transmitter mode. However, it increases hardware cost. Therefore, it is an important research area to be able to improve low cost techniques instead of high cost ones. In this thesis study, ultrasonic wave propagation in solid, liquid and tissue mediums is investigated by using a single transducer instead of transducer array. Echo formed in the wave propagation medium of thin plate which is considered as solid medium is cancelled and excitation point is estimated by means of elastic wave model developed to model the ultrasonic wave propagation. Since ultrasound wave speed with time delay in the modelled wave propagation is related to the distance between excitation point and target, it has been seen that target location has been detected by determining the starting point of impulse response. In liquid mediums, the propagation of ultrasound in liquid is modelled by means of developed elastic wave model and impulse response is estimated. Also, by using developed theoretical model, the propagation of ultrasound in tissue mediums which are inhomogeneous is modelled and attenuation in tissue is investigated in order to detect the variances in the tissue. A new attenuation estimation method has been proposed which decreases the limitations of classical spectral downshift and difference methods. Examining frequency domain methods for estimating the attenuation of ultrasound 2D imaging study is performed for in vivo kidney data. It has been seen that spectral difference-downshift hybrid method proposed in this thesis study can estimate the attenuation coefficient with better performance than classical spectral approaches for both regions which have uniform attenuation and variations in backscattering. Experimental studies with tissue data obtained from biopsy results of different patients are carried out by using derived theoretical model and obtained results are compared by investigating the reflection and propagation of ultrasound wave in order to determine the different structures formed in tissues. Also, it has been seen that results give info about different structures and localizations of bulks in the tissue.