Date of Award
Doctor of Philosophy
Chemical and Biological Engineering
David L. Carlson
Curran S. Swift
Ultrasound applications to the fields of medicine, agriculture, and food are relatively recent developments. In medicine, ultrasound imaging techniques non-invasively obtain information about size and structure of the tissues, and functions of the organs of the body. The research presented in this dissertation involves two important aspects of the ultrasonic imaging, system calibration for quality assurance and tissue characterization. The first part presents the design of tissue-mimicking material for ultrasonic experiments and system calibration. The second part presents results on ultrasonic tissue characterization applied to quality grading of beef;Calibration of ultrasonic system with tissue-mimicking materials is an important part in quality assurance. Also, such materials aid researchers in developing new techniques for imaging and tissue characterization. A part of this research, presented in the first part of the dissertation, was to develop soft-tissue mimicking materials. A method of constructing gelatin based soft-tissue mimicking materials with desired ultrasonic properties was developed. Several materials in different proportions were tried in preliminary experiments for their usefulness as tissue mimicking phantoms. An optimum combination was then derived for the ultrasonic properties (velocity, attenuation and backscatter) in the ranges for the soft-tissues;Ultrasonic tissue characterization involves determination of propagation characteristics of ultrasonic energy in the tissues. In recent years, many ultrasonic parameters, including velocity, attenuation, and scattering, have been found to have potential for tissue characterization. Advanced signal processing and pattern recognition techniques are applied to extract information about particular parameters. As a part of a project on ultrasonic meat quality grading at Iowa State University, several tissue samples were scanned and data were analyzed. Some encouraging results are presented in the second part of the dissertation. This report describes efforts in ultrasonic evaluation of fat marbling in the rib-eye muscle of beef carcass. The development of a regression model for prediction of %fat is discussed. Also, a statistical pattern recognition approach used for classifying the grades of marbling is presented. A simple but accurate classification scheme using linear discriminant analysis has been derived for assigning the marbling grades to the rib-eye samples. This scheme employed easily calculated parameters from the spectrum of the backscattered ultrasonic signal. In the meat industry, this could be applied to differentiate (and ultimately, to grade) meat samples with varying contents and distribution of fat and muscle tissues. A similar approach could be applied for non-invasive characterization and differentiation of infiltrative diseases of organs.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Viren R. Amin
Amin, Viren R., "Tissue characterization by ultrasound: a study of tissue-mimicking materials and quantitative ultrasonics " (1992). Retrospective Theses and Dissertations. 10091.