| Summary: | 碩士 === 國立陽明大學 === 醫學工程研究所 === 90 === Temperature affects survivability of human tissue, representing the conditions of the metabolism, tissue inflammation and local blood circulation. Ultrasonic temperature monitoring becomes more potentially for its non-invasive and real-time scanning.
In recent years, ultrasound temperature estimation methods were studied based on the backscattered ultrasound power and the time shift of the received RF signals. A linear relationship between these shifts and the rise of the tissue temperature is derived from cross-correlation function was experimentally validated. However, it was too time-consuming.
In this research, the auto-correlation method was used to calculate the phase shift caused by the time shift from echo signals and then the temperature distribution was estimated. An ultrasound temperature measurement algorithm was developed to validate the temperature distribution of bovine liver tissue during RF ablation therapy. First, the K parameter, which is the rate of the linear relationship between echo-shift and temperature, was determined by the cross-correlation analysis of the RF signals of an in-vitro bovine liver tissue which was heated by a temperature controlled apparatus. The echo signals of a 2-D ultrasound imaging system was analyzed and, by using the K parameter, the tissue temperature distribution during RF ablation therapy was calculated. Finally, the B-mode image and the temperature distribution image were combined to show the temperature distribution of a bovine liver.
The temperature distribution image could be clearly identified during 30℃ to 50℃ and 70℃ in RF ablation therapy. These images showed the temperature increase and the heat extent nearby the heating region. In addition, the central temperature begin to decay but still extend in the nearby region right after turning off the RF ablation.
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