The objective of this project is to demonstrate new, quantitative, ultrasound, imaging techniques for improve early breast cancer diagnosis. Computer simulations of the operation of a 3-D breast scanner and the actual scanning of test objects, tissue samples and a whole breast radical mastectomy sample in a laboratory mechanical rotational scanner will be done. A 1-D transmitting transducer array and a 1.5-D receiving transducer array will be used to collect data to form a 339 pixel diameter images of a 5 inch diameter circular cross section through the breast. These quantitative images of sound speed and absorption will have 0.75 mm spatial resolution. Effects of out of plane scattering will be minimized by the use of vertical transmitter and receiver focusing. Synthetic focus images of 677 pixel diameter, with spatial resolution of 0.28 mm will be made using a l.5-D, 4 MHz common transmitter/receiver transducer array. The path to explore a fully electronic scanned ring of transducers for rapid imaging of patients to remove motion artifacts will be provided by modifying a commercial clinical scanner connected to a small ring of 256 transducers operating at 2.25 MHz. PROPOSED COMMERCIAL APPLICATION: Our new generation of breast cancer scanners will provide images that are far superior to present commercial scanners. In addition to creating this new market, this work, these algorithms, and inverse scattering in particular, has applications in non medical areas: mine detection, buried waste imaging, sonar imaging, and non destructive testing (NDT).