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Transmission ultrasound computer-assisted tomography has been developed for detection and diagnosis of cancer in the breast. Pulses of ultrasound (8 MHz ±3 MHz) are transmitted through the breast in a coronal plane from a plurality of directions. The received signal is processed for arrival time and for changes in amplitude. The measured values for arrival time and attenuation are used in a convolution-back projection reconstruction algorithm to obtain estimates of the two-dimensional distribution of acoustic speed and attenuation within the scanned planes of the breast. Over 1000 images in breasts of approximately 150 patients have been scanned of whom 30 had biopsy proven cancer. Some common characteristics of the reconstructed images which are associated with cancer are 1) increased speed relative to the embedding tissue associated with 2) decreased attenuation in central region of the lesion usually with 3) a ring of higher attenuation at the border of the lesion. Current estimates of sensitivity and specificity of this system for cancer are approaching those of X-ray mammography techniques.
Greenleaf et al. (Sun,) studied this question.