Abstract:
Sound speeds and densities of breast tissue vary in space, and those of tumors are different from the surrounding tissues. These differences in mechanical properties cause scattering of ultrasonic waves, particularly in dense breasts. An ultrasonic reflection imaging method using a heterogeneous background is presented to properly account for scattering off heterogeneities within the breast. The method is based on downward continuation of ultrasonic wave fields in the frequency-space and frequency-wave-number domains. Synthetic ultrasonic data for scatterers within a heterogeneous breast model were used to investigate the imaging resolution of the method. Imaging examples using ultrasonic data acquired using a clinical prototype, consisting of an ultrasound scanner with a ring transducer array, are presented. The heterogeneous background sound-speed models were obtained using transmission tomography. The imaging results are compared with those obtained using a homogeneous background. The study demonstrates that imaging with heterogeneous backgrounds significantly improves image quality and resolution. [This work was supported through the DOE Laboratory-Directed Research and Development program at Los Alamos National Laboratory.]