活体中高强度聚焦超声（HIFU）场的测量与研究

The real time measurement techniques of high intensity focused ultrasound (HIFU) in free field in water and in tissues, especially in vivo have been studied in the item. They are either the technical fundamentals of the medical research on the physical and biophysical characteristics in field of HIFU or one of the key techniques of the engineering of HIFU, and have the decisive significance for the dose control of HIFU therapy and surgery, safety test and quality examine of instrument.Two heatproof types of PVDF needlelike hydrophone for HIFU measurement have been researched. The expression formula of the acoustic pressure sensitivity is derived and the sensitivity is calculated. A hydrophone is calibrated by three independent methods of absolute calibration and all results are close. Its linear dynamic range is up to 20 MPa in 1.5MHz, the spatial resolution is very good, and one of them has been applied in some product examine. The research shows these types could be developed as a superior hydrophone for measuring HIFU field.A fiber-optic hydrophone system based on Michelson interferometer and fiber-tip method is studied. The acoustic transfer function of system and the influence from the fiber bar vibration are analyzed. The initial experiment of the system in water is fulfilled in the laboratory. An invention patent of the systemt was applied for in 2002. As a spreading research , two types of fiber-optic sensor for detecting bilirubin have been studied and two patents are applying for.The reciprocity theorem on a focusing electro-acoustic transducer of spherical wave is studied at the first place. The reciprocity principle of the free field convergent spherical acoustic wave was proposed and the formula of reciprocity coefficient is derived. A series of diffraction corrective factor curves was calculated. Using these formulae and corrective factors, a focusing transducer is calibrated by the self-reciprocity method in the laboratory. This work establishes the fundamental of the calibration and standardization of focusing transducer of convergent spherical acoustic wave in theory and in experiment. It will effect the development of calibration method of electro-acoustic transducer profoundly. The synthetical study of 2D planer scan calibration on the focal plane in high intensity, the reciprocity calibration, and the comparison method in low acoustic intensity is applied to explore the absolute calibration method of sensitivity of PVDF miniature hydrophone in the HIFU field. The close results of three calibrations show that PVDF piezoelectric membrane has a very wide linear dynamic range and the synthetical calibration method is feasible. The spheroidal equation (SBE) and FDTD method are adopted in the first time to study the linear and nonlinear acoustic field distributions of the spherical bowl transducer and the hold transducer, the medium absorption effect on the acoustic field characteristic, and the model is supported by the experiment.. In the research of acoustic propagation, the abdominal layered tissue model is studied. The pseudospectral method is adopted to study the effects of attenuation and nonlinearity in different tissues. A two-layer Back-Propagation neural network is used to learn the relationship between the lesion size and exposure time on the constant acoustic power of HIFU system.Above-mentioned research of acoustic field simulation and temperature field prediction is of important significance for working out therapy plan and controlling the dose in HIFU surgery and high temperature hyperthermia.. A novel needle sensor with double function for measuring acoustic pressure and temperature in tissue imultaneously is developed and a iological effect experiment system of HIFU for tissue in vitro have been designed and built up . Their performance has been tested. The experiment of real time measurement of HIFU field in vivo and the study of biological effect are putting into practice.

研究强度聚焦超声（HIFU）在自由场中的计量技术和在活体中声场实时测量技术。包括耐焦域局部高热（70 以上）的微型超声传感器阵列与校准技术、HIFU计量技术、活体中靶组织谏苟浠头植嫉牟饬考际酢Ｎ钐逯卸垦芯縃IFU生物效应、HIFU治疗系统声参量舛ā⒈曜蓟土俅布亮康恼肥褂茫峁┲С偶际鹾涂蒲б谰荨