The general objective of this project is to improve the clinical utility of ultrasonic techniques for noninvasive diagnosis through the measurement and modelling of intrinsic ultrasonic propagation and scattering properties of tissue and through the development of a new quantitative imaging technique based on the measurement of ultrasonic scattering. The research has six specific aims. The first is to measure ultrasonic scattering as a function of angle and frequency using a ring of transducers and also to measure attenuation as a function of frequency using radiation force. These measurements will employ liver, spleen, pancreas, and breast freshly obtained at autopsy or during surgery. The second is to calculate from the measured scattering and attenuation data and known system parameters intrinsic properties that include the average differential scattering cross section, the power spectrum of compressibility variations, and the power spectrum of density variations. The third is to calculate volume scattering using an analysis of thin sections visualized through a microscope and comparison of this data with ultrasonic scattering from the same tissue. The fourth is to characterize pulse wave propagation in fresh abdominal wall, chest wall, fat, liver, and breast by measurement and modelling of the distortion that ultrasonic pulses undergo as well as by a unified analysis of adaptive compensation techniques that remove pulse distortion and permit the use of larger apertures than may be employed effectively in practice today. The fifth is to measure ultrasonic scattering by renal calculi before, during, and after lithotripsy to describe noninvasively from time and frequency domain analyses the response of these calculi to treatment and also to model the stress response of kidney stones to arbitrarily shaped temporal pulse waveforms for the determination of lithotripsy waveforms that disintegrate calculi most efficiently. The sixth is to develop a new exact technique for the reconstruction of quantitative ultrasonic images from measurements of scattering made around the scattering region without any weak scattering approximation and using an adaptive system in which transmitted signals are modified according to scattering characteristics. This will employ the same transducer ring as the measurements of angular scattering and initially tissue-mimicking phantoms but later scattering data from fresh specimens. The results are expected to provide a foundation for a significant increase in diagnostic utility of ultrasound from intrinsic parameters and images of tissue that can be employed to distinguish between normal and diseased tissue and also to determine the severity of disease in circumstances not currently possible.
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