Using phase information in ultrasonic backscatter for in vivo liver analysis

In recent studies, it has been shown that information about scatterer spacing can be obtained from analyzing the phase of the ultrasound echo from various media. Such information proves to be useful when examining the ultrasonic backscatter from well-organized tissue, such as the liver. By quantifying the deviations in scatterer spacing and/or varying degrees of regularity, conclusions may be drawn about the underlying pathology of the tissue. This paper examines the physical basis of how the scatterer locations affect the phase of the data. Computer simulations were performed that mimic various scattering conditions and that display the effects of differing degrees of regularity, as well as increases in a diffuse random background scattering component. Results of studies on a phantom are also included to investigate and display the phase response under well-controlled scattering conditions. Finally, in vivo data taken from liver scans were analyzed. In this work, it was shown that the phase of the backscattered signal holds valuable information regarding the pathological state of liver tissue. It is suggested that this simple examination of the phase can be refined into a technique to be used as a method to consistently detect the onset of pathological change.