Study Of Temperature Measurement With Ultrasonic Echo Pulse During HIFU Therapy

High Intensity Focused Ultrasound (HIFU) therapy can succeed only one time and not has the side effect. It is considered as one of the new technologies which have the most potential application for tumor therapy in 21st century. Its key point is whether the temperature is able to be controlled correctly or not. Because of the suffering of the patients the application of the invasive temperature measurements is limited. Therefore, non-invasive thermometry is increasingly becoming the scientist' s investigation focus. For the low cost and the good compatibility, the ultrasonic non-invasive is especially concerned.It fully makes use of the B-mode equipment to set up a HIFU therapy and temperature measurement system and has done abundant experiments in vitro. The ultrasonic echo signals which are irradiated by HIFU are analyzed by many methods. It has discussed which approach is appropriate to open out the tissue temperature and trait change. The main work is summarized as follows:1. The methods of extracting signals irradiated by HIFU are studied. The signal pre-processing methods are determined by analyzing the signal character in time and frequency area.2. The time shift of the ultrasonic echo irradiated by HIFU with the temperature change is analyzed by cross-correlation. The research has discovered that it has bad repetition and is only effective in small area.3. The echo signal energy change is analyzed by echo amplitude and wavelet coefficient methods. The result shows that the echoes energies relative change approaches the linearity along with the temperature increase to increase in the 37℃～60℃, but appears the disorder with the temperature in 60℃above.4. The attenuation of the amplitude and the center frequency content of echo is analyzed. The result shows that the echo signals attenuation change is very small below 45℃, but can accurately reflect the temperature change information in 45℃～65℃.It has been discovered that the trend of the echo parameters changes with temperature in certain extent by using every approach. Although these methods only have good repetition in the certain temperature range, but can accurately open out the tissue denatured region. It is difficult to measure the temperature exactly. However all these results have important consulting value to the temperature monitoring and the tissue denatured determination in HIFU therapy.