Methods Of Noninvasive Temperature Estimation In HIFU Therapy Based On B Ultrasonic Image Processing

High Intensity Focused Ultrasound(HIFU) therapy is a kind of noninvasive treatment, tumor patients and doctors pay much attention to it because of its non-toxic and non-side effects. During the HIFU therapy, temperature monitoring is very important for the therapeutic effect, but invasive temperature thermometry will increase the patients’ suffering,and most of noninvasive thermometry is not suitable for HIFU therapy or costs too much at present. Therefore, the study of noninvasive thermometry in HIFU therapy has become a hotspot in recent years. Noninvasive thermometry based on B ultrasonic image processing has been paid so much attention due to simple equipment, operating easily, good compatibility and real-time.Using HIFU therapy equipment, B ultrasonic diagnostic equipment and temperature measuring equipment, we set up a HIFU monitoring system to get the B ultrasonic images before and after irradiating the vitro tissue, and the temperature information of the tissue. As to the B ultrasonic image, we research into noninvasive thermometry combine with the temperature. The main contents are shown as follow:(1) Pre-treating the B ultrasonic images of vitro tissue which obtained by B ultrasonic diagnostic equipment. In order to use the images data more convenient in next processing, we should transform the color B ultrasonic image of Color Space, clip images size and do logically operation.(2) Using two-dimensional discrete Walsh transform to process the image. Extracting low frequency component after processing the subtract images by two-dimensional discrete Walsh transform and curve fitting with temperature, we find that there is an approximately linear relationship between the low frequency component and temperature in a certain temperature range.(3) Using gray probability distribution-cross entropy method to calculate the difference between different images. By calculating the entropy between B ultrasonic images and 37 ℃ B ultrasonic images under different temperature, we will let entropy and temperature curve fitting, then find that there is an approximately linear relationship between the cross-entropy and temperature in a certain temperature range.Through the analysis, we find that using different methods to process the B ultrasonic images, which can reveal characteristic parameters and temperature have a approximately linear relationship, and these parameters can reflect the temperature variation accurately. Therefore, by processing B ultrasonic images, this research can measure the temperature of HIFU treatment area accurately, and has an important reference value for noninvasive thermometry research.