Detection of noise spectrum shape by homomorphic filtering.

Abstract

Experimental results based on theoretical investigations are presented. The dual transducer model was constructed and has been used to obtain the information needed to verify the theoretical work. The results indicate that the new transducer model increases dramatically the accuracy of measuring the blood velocity and thereby improves our ability to characterize the blood flow patterns which are valuable for research and diagnostic purposes.

The quantitative capability of Single Transducer Pulsed-Doppler Ultrasound (STP-DU) in clinical practice is limited by the effects of acoustics, tissue, and system parameters, as well as its inability to obtain precise measurement of the Doppler angle, which in most cases must be estimated. In this study, a practical approximation for the backscattering of a damped sine wave by a volume of randomly distributed scattered particles has been developed. The approximation has been applied to the measurement of a volumetric backscattered cross section, taking into account most of the parameters involved in the process. A dual transducer pulsed-Doppler ultrasound (DTP-DU) has then been introduced for direct calculation of the Doppler angle and for accurate determination of blood flow velocities. A comparison was also made between STP-DU and DTP-DU models. The components of the blood flow velocities are used to obtain the blood flow characteristics such as volume rate and shear stress, and to express a relationship between blood flow characteristics and pathological changes, such as stenosis.