C- and D-weighted ultrasonic imaging using the translating apertures algorithm.
Conventional ultrasonic imaging systems depict tissue backscatter, that is, the ultrasonic energy reflected directly back toward the transmitter. Although diagnostically useful, these systems fail to exploit the information available in components of the sound field scattered in other directions. This paper describes a new method of imaging this angular scatter. First, the translating apertures algorithm (TAA) is used to acquire data at two scattering angles. Then, these data are processed to yield an image of the common scattering with angle and the differential scattering with angle. This paper explores the potential of these common-weighted (c-weighted) and difference-weighted (d-weighted) images using theory and simulations. In addition, it describes and analyzes the performance of the TAA when it is applied using multiple receive elements. Analysis is presented that shows that, in Rayleigh scattering environments, c- and d-weighted images depict compressibility and density variations, respectively. A simulated image and accompanying analysis are presented that show the potential of these techniques to improve soft tissue contrast and to increase the detectability of microcalcifications. A comparison with previous angular scatter measurement techniques shows that use of the TAA significantly reduces statistical variability in measured angular scatter profiles. Spatially localized, statistically reliable angular scatter measurements will enable a broad range of angular scatter imaging techniques. C- and d-weighted imaging may ultimately be applied clinically to identify calcification in atherosclerotic plaques and breast tumors.
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