Frequency Focused Ultrasonic Transducers And Its Radiated Sound Field To Activate The Chemical Effects Of Hematoporphyrin

A malignant tumor is a kind of disease directly threatening human's life.At present,the diagnosis and treatment of a tumor ,especially a malignant tumor is an important topic in internal and external studies.To inhibit tumor's growth and damage tumor cells using ultrasound have become a "hot" problem. Because compared with optical wave,ultrasound can penetrate deeper and be easier to focus,there is a promising prospective to apply ultrasound to the treatment of tumors in deep tissue. Among many methods of the treatment of tumors using ultrasound (high intensity focused ultrasound(HIFU) surgery,ultrasound thermaltreatment, sonodynamic treatment) ,there are deficiencies and difficulties to apply the first two to clinic, and the photosensitive drug (such as hematoporphyrin) in the third methods is of the property of selective aggregation,therefore sonodynamic treatment is welcome.Many scholars,especially Japanese scholars S.Umemura and N.Yumita have done many researches on it,and acquired some primary results,but those studies are limited to the suspension of tumor cells and in vivo transplanted tumors in little animals,so there is a long way to go to apply it to clinic.In order to make this methods apply to clinic ,and effectively and conveniently activate photosensitive drugs to treat tumors in human's body,based on the internal and external studies ,and combined the National Science Fund item ,this paper has designed a bi-frequency focused ultrasound transducer and chemically tested the efficiency of hematoporphyrin activation by the sound field radiated by this transducer.The author has designed 400kHz+800kHz,400kHz+1.2MHz two bi-frequency focused ultrasound transducers.Based on the formula of sound radiation,the axial distribution of different frequency ultrasonic fields radiated by the two transducers are derived and computed by using numerical method,and the focal areas are decided.The properties of the radiated ultrasonic fields are investigated in an acoustic absorbing cistern with a precise three-dimension positioning system.The theoretical positions of focal areas are in good agreement with the experimental results,and the goal of two different frequency ultrasonic superimposition can be carried out.Moreover the spectrums of the focal areas of sound fields radiated by the transducers are measured by a spectrum analyzer and the phenomenon of scattering sound by sound is observed.Based on the bubble's equation and the theory of the rectified diffusion ,the optimum conditions of the enhancement of cavitationby harm0nic superimposition are numerically solved.In the experiment withultrasonic activation of hematoporphyrin,the author has established a set ofexperimental facility about sonodynamically insonatinghematoporphyrin.The relations of the effciency of ultrasonically activatinghematoporphyrin with the sound parameters(intensity,frequency,time)and the HPD concentration are studied.The optimum parametric reignshave been sought and the comparative studies of the activation effciencies ofa single frequency ultrasound and bi-frequency ultrasounds have beenmade.The studies above provide important parameters for the following invitro and in vivo experiments and are of great significance for thedevelopment of the sonodynamic treatment.