Study the effect of aperture angle on the temperature rise in biological tissues induced by a focusing transducer with a wide aperture angle

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Journal of Nanjing University(Natural Sciences) ›› 2017, Vol. 53 ›› Issue (1) : 114.

Qi Meng，Wang Xin，Liu Xiaozhou*

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Abstract

High intensity focused ultrasound(HIFU)is an important technology of modern medicine physical therapy for cancer treatment.The treatment principle is to focus sound energy generated by a large ultrasonic focusing transducer to achieve a high temperature in a focal area in a short period of time，causing tumor tissue to undergo thermal coagulation necrosis.Sometimes it can achieve high sound intensity(103－104 W•cm－2)by focusing sound energy generated by a large ultrasonic focusing transducer to achieve a high temperature(above 65 ℃)in a focal area in a short period of time，causing tumor tissue to undergo thermal coagulation necrosis thus killing cancerous cells.A focusing transducer with a wide aperture angle is a sphericalshell focusing transducer with a spherical halfangle greater than 16.6°.Because such a wide angle focusing transducer has a larger radiating area，stronger focusing effect，smaller focal area radius and better penetrability than that of a small angle focusing transducer，a greater temperature rise can be generated within a tumor while reducing damage to other normal tissues.In the paper，we use the Spheroidal Beam Equation(SBE)model to calculate the sound field produced by a focusing transducer with a wide aperture angle to obtain heat deposition.The SBE equation includes nonlinearity，diffraction and absorption effects，and can be used to predict the sound field of a transducer with a wide aperture angle.And then we solve the Pennes bioheat equation to obtain the resulting temperature field in a biological tissue.We study the temperature rise induced by a focusing transducer with different wide aperture angles.The results show that the effect of the different way to change the aperture on the temperature rise of the biological tissues is different.When we use the aperture to change the aperature angle，when the apertureis bigger，the temperature rise is bigger.When we use the focus length to change the aperture angle，the result is opposite.Then we conduct the experiment to testify the effect of the aperture on the temperature rise in biological tissues.

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Qi Meng，Wang Xin，Liu Xiaozhou*. Study the effect of aperture angle on the temperature rise in biological tissues induced by a focusing transducer with a wide aperture angle[J]. Journal of Nanjing University(Natural Sciences), 2017, 53(1): 114

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