Ultrasonic Refractive Index Tomography

Ultrasonic computed tomography (UCT) is one of the methods capable of tissue characterization. It is expected to provide not only a quantitative image but also diagnostic information. As in X-ray CT, UCT requires a projection data to reconstruct a cross-sectional image. In UCT such projection data are derived from the received broadband ultrasonic signal. In this paper, two methods for deriving the integrated refractive index from transmission mode signal are evaluated. The first method derives the integrated refractive index from time delay of the signal while the second method uses the phase shift of signal instead. The experimental results show the resistivity to noise of the phase shift method, especially at the center frequency of the broadband pulse.