Development of a Micro Self-Focusing Ultrasound Transducer for Treating Cervical Lesions

This paper discusses the design of an annular self-focusing ultrasound transducer with concave spherical surface used to treat cervical lesions .To analyze its focusing performance, axial sound field distribution of annular self-focusing ultrasound transducer was simulated with O'Nell formula . After comparison and analysis, Transducer Ⅰ(8mm inner aperture and 13mm outer aperture) and transducer Ⅱ(5mm inner aperture and 9.8mm outer aperture) were suitable for the treatment . In vitro experiment , transducer Ⅰ and Ⅱ were applied to the beef liver at ultrasound power of 3.5W for 10 seconds, which made the focal region at about 4.0mm depth under the surface of tissue . It showed that the axial length of focal region was 0.8mm with transducer Ⅰ and 1.0mm with transducer Ⅱ, which was consistent with the simulation results. It also showed that energy in focal region was distributed more uniformly for the transducer with higher sound pressure and narrower bandwidth.