Ultrasound imaging and identification of microcalcification clusters by correlation of scatter from multiple angles

Various types of malignant and benign breast tumors are associated with clusters of calcifications with grain sizes 0.1 to a few mm spread out over volumes of a few cc. A series of phantoms containing calcium carbonate grains embedded in a gelatin mixture were made and the ultrasound scattering patterns were measured with 2.25 MHz transducers. Scatterings from the calcifications were distinguished from the larger reflections from tissue interfaces by computer correlation of the signals obtained from transducers placed at three different angles. An automatic gain control detection system was developed for the purpose of amplifying the signal to the right level for the computer correlation and to compensate for the attenuation of the ultrasound in the tissue.