• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1997.04a
• /
• pp.506-512
• /
• 1997

Ultrasonic knives have been successfully used for the surgery of many medical fields. However, the conventional ultrasonic knives for surgical operation cannot be controlled its resonant frequency. So if the material to cut has different characteristic impedance then different ultrasonic knife will be needed. Because the optimum driving frequency of ultrasonic knife is different by characteristic impedance of material. In this work, using a frequency variable ultrasonic transducer made of multi-layered PZT vibrator, a frequency controllable ultrasonic knife will be suggested. The design and computation principles will be also derived. For this work, firstly, the characteristics of this ultrasonic knife will be analyzed by transmission line model equivalent circuit, and the free admittance characteristics and vibrational velocity distributions will be obtained. Secondly, we will design and make the frequency controllable electrical oscillator for driving this ultrasonic knife.

• Journal of Biomedical Engineering Research
• /
• v.34 no.3
• /
• pp.141-147
• /
• 2013

Ultrasonic shears is currently in wide use as an energy device for minimal invasive surgery. There is an advantage of minimizing the carbonization behavior of the tissue due to the vibrational energy transfer system of the transducer by applying a piezoelectric ceramic. However, the vibrational energy transfer system has a pitfall in energy consumption. When the movement of the forceps is interrupted by the tissue, the horn which transfers the vibrational energy of the transducer will be affected. A study was performed to recognize different tissues by measuring the impedance of the transducer of the ultrasonic shears in order to find the factor of energy consumption according to the tissue. In the first stage of the study, the voltage and current of the transducer connecting portion were measured, along with the phase changes. Subsequently, in the second stage, the impedance of the transducer was directly measured. In the final stage, using the handpiece, we grasped the tissue and observed the impedance differences appeared in the transducer To verify the proposed tissue distinguishing method, we used the handpiece to apply a force between 5N and 10N to pork while increasing the value of the impedance of the transducer from 400 ${\Omega}$.. It was found that fat and skin tissue, tendon, liver and protein all have different impedance values of 420 ${\Omega}$, 490 ${\Omega}$, 530 ${\Omega}$, and 580 ${\Omega}$, respectively. Thus, the impedance value can be used to distinguish the type of tissues grasped by the forceps. In the future study, this relationship will be used to improve the energy efficiency of ultrasonic shears.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.11a
• /
• pp.1014-1017
• /
• 2007

Sound focusing technologies has been studied for various purposes from early 1990s. As a result, these technologies make us possible to apply in many uses. For example, we can treat tumors using focused ultrasonic waves without surgical knife and communicate in the ocean using time reversal array. Also applications for personal audio system become issues. Recently, as technologies are developing, in some applications, needs for regional focusing become increasing because previously suggested focusing methods, such as phase conjugation, time reversal and inverse filtering, were all about a point focusing. Therefore, studies on regional focusing method are essentially needed. Regional focusing method was firstly mentioned by Choi and Kim in 2002: acoustic contrast control. However, in regional focusing, physical interpretations between control variables and results are still not easy because of its complexity. In this regard, we tried to understand the relations between control variables and results in wavenumber domain and suggested a solution method for regional focusing: wavenumber spectrum matching. We also showed how to make spatially focused sound shape using the suggested method from the simplest case: line focusing.