Control of Bubble Formation at the Optical Fiber Tip by Analyzing Ultrasound Acoustic Waves

В В Казаков ,V I Yusupov ,Anton Ivanovich Pavlikov ,В.н Баграташвили ,Vladislav A Kamensky

doi:10.3844/ajeassp.2016.921.927

Abstract

The problems of controlling the processes of generation of acoustic waves and microbubbles at the optical fiber tip of moderate-power surgical lasers with wavelengths of 1.9 µm and 0.97 µm using active and passive acoustic methods are considered. It is shown that microbubbles of various sizes can be detected with an ultrasound method, in which the interaction area is recorded simultaneously at two frequencies. By measuring noise with a receiving transducer of an ultrasonic locator, we determine the frequency range of the acoustic signals occurring when large diameter bubbles, including gas-vapor bubbles, collapse. Model experiments are conducted to detect noise and bubbles in water and in a water-saturated 1.5% agarose phantom at various laser powers with an optical fiber tip having a strongly absorbing coating.

Highlights

Local high-temperature heating of biological tissue by optical radiation is widely used in laser surgery, allowing to increase the speed of tissue cutting, decrease the width of the cutting area and to reduce wound healing time (Romanos, 2013; Kuznetsova et al, 2015; Venugopalan et al, 1996)
In addition to the signals from generated ultrasound waves, the T2 transducer receives acoustic noise originating from the formation and collapse of bubbles inside the medium or on its surface
It has been experimentally demonstrated that by using a dual-frequency ultrasound locator and by passively receiving acoustic signals with the receiver of the same locator, it is possible to monitor processes associated with laser-induced generation of bubbles near the optical fiber tip

Summary

Introduction

Local high-temperature heating of biological tissue by optical radiation is widely used in laser surgery, allowing to increase the speed of tissue cutting, decrease the width of the cutting area and to reduce wound healing time (Romanos, 2013; Kuznetsova et al, 2015; Venugopalan et al, 1996). The most popular method of studying the appearance and formation of bubbles at the optical fiber tip is the high-speed video monitoring in water or in a thin layer of a biological tissue phantom illuminated by an external source (Asshauer et al, 1997; Lü and Li, 2011; Yusupov et al, 2010; Skrypnik, 2015; Belikov et al, 2015). Using this method, specificities of visible-size bubble generation at the fiber tip with a strongly absorbing coating were elucidated and the formation of channels, acoustic flows, was detected. Part of this problem can be solved with ultrasound techniques that are based on remote excitation of bubbles at resonant frequencies and detection of waves generated by the Attribution (CC-BY) 3.0 license

Methods

Results

Conclusion