Key Technologies in the Development of High Intensity Focused Ultrasound Tumor Therapy Machine

In recent years, the application of HIFU piezo transducer ultrasound in the field of tumor treatment has been widely concerned at home and abroad. It has been reported that nearly 10 domestic manufacturers have invested a lot of manpower and resources to develop in the clinical applications in the many hospitals,which have achieved quite a lot of successful reports, such as malignant bone tumors, liver cancer, breast cancer soft tissue sarcoma and kidney cancer. In December 2002, the State Food and Drug Administration formulated the“Regulations on Clinical Research Management of High-intensity Ultrasound Focusing Machines”, “Technical Requirements Must Be Covered in High-Strength Ultrasound Focusing Machine Product Standards”, and “High-intensity Ultrasound Focusing Therapy” The technical requirements of HIFU transducer piezo ceramic for the instructions are suitable for use of the machine and the technical requirements for the analysis of the effects of the high-intensity ultrasound focusing machine are published in August 2003 in the food and drug administrations of the provinces (districts, municipalities), and are required to comply with the implementation. Foreign works on the basic research of HIFU is more profound and specific, but due to its clinical laboratory management and resources, it is relatively late in clinical practice. From the perspective of engineering development, this paper comprehensively introduces the key technologies designed in the development of high-intensity focused snoring tumor therapy machines in recent years for further development and reference.

The high-intensity focused ultrasound system directly produces HIFU ultrasound focal spots of sufficient power.corresponding frequency and size act on the lesion in a short period of time .eg, in accordance with the technical requirements that must be included in the product specifications for HIFU ultrasound for medication

therapy machines. It is stipulated that the ultrasonic transducers are used in high-intensity focused ultrasound therapy has an operating frequency between 4. 5 and 5 MHz. The maximum sound intensity of the treatment head focal length is not less than the sow resistance, and the amplitude of the sound field is larger than the main lobe. The amplitude is lower than 8 d B, and the cross-sectional area of the acoustic focal region is bounded by a sound pressure drop of 6 d B. Currently, there are two main types of high-intensity focused ultrasound probes for clinical application: one is multi-array focusing, that is, using multiple small ultrasonic transducer is superimposed in the focal region to achieve a high focal depth power density; the other is a unit transducer. In the center of the probe, a circular hole is generally placed, and a B ultrasonic monitoring probe is placed to to achieve the purpose of lesion location and process monitoring. In general, current high-intensity focused ultrasound transducer piezoelectric use PZT ceramic materials, which have high electromechanical efficiency but are prone to chipping. In terms of transducers, there are mainly two types of vibrator lens and concave spherical shell self-focusing. The high-intensity focusing ultrasound probe of the acoustic lens mode is less efficient due to the attenuation effect of the lens itself, and the acoustic lens itself is the absorption of ultrasonic waves which also easily deforms the acoustic lens.

By changing the appropriate lens, it is easy to adjust the focal length.High intensity focused piezoelectric ceramic ultrasound tumor treatment machine developed and produced in the early stage . The high-intensity focused ultrasound transducer in the self-focusing mode of the concave spherical shell is relatively simple in theoretical analysis and control system of the power amplifier. It has a mature analysis and design method, and it is easy to realize the focal length of the ideal shape. However, large-size high-power concave spherical shell piezoelectric wafers are quite difficult in the manufacturing process; there are also some limitations in use, such as the inability to withstand high-impact impact loads due to the uniformity of wafer materials, and wafers are prone to occur.The focal length of HIFU piezo is directly determined by the geometry, and cannot be adjusted. Therefore, its application also has certain limitations. Typical high-intensity focused ultrasound transducers have a geometry of about 60 to 1 20 m m, a focal length of 40 to 2 80 m, and a focal power density of 300°c c/m.

In order to improve the efficiency of the piezo ceramic for weight loss calculator along with ultrasonic transducer, the structure of the unit transducer is improved, and a cavity is left on the opposite side of the piezoelectric crystal, so that the portion of the ultrasonic wave is propagating in the opposite direction is regularly reflected, with the positive direction ,The superimposed ultrasonic sensor is superimposed, which greatly increases the efficiency of the transducer.