High intensity focused ultrasound for tumor therapy(二)

 This method is simple in the idea and convenient to implement, but because the image accuracy of the B-ultrasound itself is not high, and the information contained the two orthogonal sections itself which is not enough to represent the entire lesion itself, the shape of the tumor is not mostly ellipsoidal. The target of the lesion is rough and the error is large,HIFU piezoelectric crystal leads to more normal tissue killing. 

B-scanning image positioning method is to perform B-ultrasound scan in the fixed direction, then outline the tumor at the current scanning position, depict the lesion area, and then guide the high intensity focused ultrasound sensor on the treatment point. Then complete a slice treatment and then slice from one slice to another until it is complete. Compared with the orthogonal scanning and positioning method, this method has higher precision and can handle irregular shape tumors, but the experience of medical personnel is relatively high, and the labor intensity is also relatively large. The images are layered, and the contours of the organs on each slice are drawn out under the intervention and sketching of experienced medical personnel. After superposition, the three-dimensional shape of the lesion is obtained by curve-based surface reconstruction technology. Its accuracy is relatively high, . It can give an intuitive three-dimensional model of lesions, which realize online treatment path planning or real-time position adjustment, but high focus piezo crystal requires experienced medical staff to analyze and operate, and the workload is not less than the slice scanning method. In fact, although some of these functions have already been implemented in the software for some commercial machines, a large number of applications are actually combined with orthogonal scanning positioning and/or slice scanning positioning. M class guides the positioning of foreign companies in the clinical trials mainly using Mm guidance mode positioning. Compared with ultrasonic positioning, MRI has high imaging resolution, which ensures high positioning accuracy and acceptable speed. More importantly, M rent can accurately judge

Evaluation of therapeutic effects is generally believed that high-intensity focused ultrasound relies primarily on the thermal and mechanical effects to cause irreversible coagulative necrosis of tissue at the treatment site. (High-intensity ultrasound focusing treatment machine clinical analysis method) It is pointed out that the clinical research effect analysis of high-intensity focused ultrasound tumor treatment machine should be based on the imaging analysis. General case is using CT

MRI images or PET , bone tumors using E C T , digital subtraction can also be used, but ultrasound alone cannot be used as an evaluation tool. However, the domestic commercialized treatment machine can only compare the change of the gray level of of the B-ultrasound to determine whether coagulative necrosis occurs and its position is correct. In the literature, it is mentioned that the computer uses HIFU piezo transducer for medical to treat the ultrasound image of the target area after treatment, and the self-control gray scale value is 10 db, which means that the treatment is effective. In fact, due to the acoustic characteristics of human tissue, the acoustic impedance is caused by the occurrence of tissue degeneration. which cause grayscale changes, affected by piezoelectric material HIFU piezo and many other factors, and it is impossible to determine the actual temperature and coagulative necrosis in the focal region due to grayscale changes. Further developments in the basic research work should be the ability to measure temperature changes in the focal region .