Comparison of contrast in backscatter and angular scatter ultrasonic images

A real time angular scatter imaging system has been implemented on the Duke phased array scanner. One 32 element linear phased array transducer is used as the transmit aperture, and a second 32 element array is used as the receiver. The receive array is positioned adjacent to the transmit array and oriented at an angle of 45° relative to the transmitter so that it detects side scattered echoes. An examination of the theoretical models of acoustic scattering suggests that the angular scatter system will be less sensitive to echoes from Rayleigh scattering structures than conventional backscatter imaging. We suggest that this predicted phenomenon can be exploited to increase the image contrast of small targets in tissue by reducing the background signal level from Rayleigh scattering structures. The potential for contrast enhancement from angular scatter imaging is demonstrated by imaging a phantom consisting of a metal wire embedded in a fine pore foam sponge