QUANTITATIVE SYNTHETIC APERTURE REFLECTION IMAGING WITH CORRECTION FOR REFRACTION AND ATTENUATION: APPLICATION OF SEISMIC TECHNIQUES IN MEDICINE.

A reflection technique using focused or synthetically focused ultrasound energy has been developed for the synthesis or reconstruction of images of reflection and acoustic impedance. This technique uses digitally sampled reflection and transmission data obtained from an aperture which encloses or circumscribes the subject of study. Three-dimensional maps of attenuation and refractive index are obtained from transmission reconstruction from projections, i. e. , computed tomographic techniques from the same sampled aperture. Data sampling times for focusing at each point in the object space are obtained by integration of refractive index along rays connecting each point and each transducer position on the aperture. Echo amplitude corrections are obtained by similar integrals of attenuation along these rays. These rays are found by a ray tracing technique. Images with resolution of less than one-half the mean wavelength of the transmitted signals have been obtained in simulation studies. Potential diagnostic medical applications such as detection of breast cancer and mapping of internal tissue temperature change are discussed.