Tomographic Visualization of Breast Calcifications by Ultrasound Scattering

Various types of malignant and benign breast tumors are associated with clusters of calcifications with grain sizes 0.1 to 1 mm spread out over volumes of a few cm3. These clusters have shapes ranging from spherical to elongated chains. A series of phantoms was made and the ultrasound scattering pattern from calcium carbonate grains embedded in a gelatin mixture was measured with 2.25 and 5 MHz transducers. A single send transducer with a few receive transducers placed at angles of 120° to 160° relative to the forward direction was used. Tomographic images of these distributions were obtained by a combination of transit time recording and positioning of the transducer array. Measurements have been done on grain sizes as small as 0.2 mm and show a clean signal above tissue scattering background.