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Abstract: Noninvasive monitoring of hyperthermia is important for treatment guidance and thermal dose control. One potential approach is to monitor the change of temperature or coagulated zones through ultrasonic backscattered signal processing. In this paper, we presented a noninvasive method for hyperthermia monitoring based on the analysis of microstructural characteristics of in vitro porcine liver tissues at different temperature (20°C-60°C) including normal and coagulated tissues by estimating the center frequency of scatterers (CFS) using the autoregressive (AR) cepstrum of ultrasonic backscattered signals. The method is based on the discrete scattering model described in the tissue characterization literature and the observation that most biological tissues are semi-regular scattering lattices. A total of 20 in vitro porcine liver samples were used and heated by the water bath in the experiments. Experimental results show that the CFS in porcine liver tissues decreases as the temperature increases. The CFS obtained using this method may be used as a characteristic parameter for tissue characterization in noninvasive monitoring of hyperthermia. [Copyright &y& Elsevier]