engleski

Optimisation of the endoscopic surgical ultrasonic probe

Minimally invasive ultrasonic surgery is one of the most recent field of application of ultrasound in medicine. The introduction of laparoscopic and endoscopic surgery, performed in the visual field of a miniature video camera, has pointed out the need for new solutions concerning micro-surgical instruments. Due to the principle of ultrasonic surgery (direct cutting, cavitation, fragmentation and thermal damage), the irreversible changes in tissues and organs are reported. The aim of our study has been to optimize construction of an endoscopic surgical ultrasonic probe (ESUP) with respect to some specific technical, medicinal and operational/ergonomic requirements. The main design request was possibility of ESUP applications in the diferent surgical procedures. On the basis of the theoretical model, the ESUP was designed and realized as a rod-type resonant vibrating system, con&not ; ; sisting of a half-wave length transducer (piezoceramic material, front metal part made from titanium, rear metal part made from stainless steel, alumina rings, copper electrodes) and resonant wave guide in the form of a specially shaped velocity transformer together with the titanium wire of 1, 6 mm in dimeter. In order to acchieve maximum electro-acoustic efficiency, during the prestressing of the ESUP with the titanium bolt, the shifting of the resonance and anti-resonance frequencies of the transducers were measured with the impedance analyzer hp4192A. Multi functionality of the ESUP was verified with the shaping of the titanium wave guide and by measuring (calculating) all necessary parameters for the weighting of the electrical and acoustical charcteristics of the ESUP. Special attention has been paid to the electro-acoustical characteristics (high efficiency of the transducer, low losses in the wave-guide, stability of the longitudinal vibrations at high amplitudes) of the transducer. Conclusion: The existance of the different modes of the vibration, in the frequency range of (20-40) kHz and as well electroacoustic characteristics of the ESUP at each of modes, enables efficient applications in different surgical applications. Acknowledgment: This work was sponsored by the Ministry of Science and Technology, SRP No. 01920203) and by the Croatian Program for Innovative Technological Development No. TP-01/0220-01.

ultrasound; neurosurgery; NECUP

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