Overcoming the limitations of traditional medical optical imaging with the world's first ultrasound technology!

On Monday, □ 19, DGIST Dean Yang Kook announced that a joint research team led by Jin Ho Chang and Professor Jae Youn Hwang has developed the world's first laser scanning microscope technology, which can use ultrasound temporarily generated bubbles to make deeper and more detailed observations
of biological tissue.

□ optical imaging and therapeutic techniques are widely used in life science research and clinical practice
.
However, due to the optical scattering that occurs within the tissue, the transmittance of light is low
.
Therefore, there are inherent limitations to image acquisition and processing of deep tissues
.
This greatly hinders the expansion
of the application area.

□ to overcome this problem, in 2017, Professor Jin Ho Chang's team envisioned the use of micron-sized bubbles, which are typically observed when tissue is exposed to high-intensity ultrasound
.
They developed a technique that uses bubbles temporarily generated by ultrasound to align the direction of optical scattering with the propagation direction of incident light, thereby increasing the penetration depth
of light.

The joint research team of Jin Ho Chang and Professor Jae Youn Hwang focuses on the application
of optical imaging techniques using ultrasound-induced bubble amplification.
Confocal fluorescence microscopy is a method of selectively detecting fluorescence signals produced in the focus plane of light and providing high-resolution, high-contrast microstructural images such as cancer cells
.
With its excellent performance, it has become the most widely used instrument
in life science research.
However, at depths of more than 100 μ m, the focus of light becomes blurred due to light scattering that occurs inside the tissue, which greatly limits the application and effectiveness of
confocal fluorescence microscopy.

□ In order to increase the maximum imaging depth of optical imaging methods such as confocal fluorescence microscopy, the photons that make up the irradiated light must not appear to scatter light in the tissue and distort the direction of
its propagation.
However, previously developed methods of generating sparse bubbles based on ultrasound do not solve the problem
.

□ therefore, this joint research group developed ultrasonic techniques that form bubble layers in the desired area, forming dense bubbles within living tissue (with a density of more than 90%), and acquiring images while maintaining the resulting bubbles
.
In this bubble layer, the direction of propagation of the photons is not distorted
.
Therefore, it has been experimentally proven that light focusing is possible even in deeper biological tissues
.
In addition, the application of this technique (i.
e.
, ultrasound-induced tissue transparency) to confocal fluorescence microscopy was the first in the world to develop an ultrasound-induced optical clearance microscope (US-OCM) with an imaging depth of 6 times
that of conventional confocal microscopy.

□ in particular, the US-OCM developed in this study does not cause any damage to the tissue, because when the ultrasound irradiation stops, the resulting bubbles disappear and the optical properties return to the state before the bubbles are generated, which is harmless to living organisms
.

Professor Jin Ho Chang, □ DGIST's Department of Electrical Engineering and Computer Science, said: "By working closely with ultrasound and optical imaging experts, we are able to overcome the inherent limitations
of existing optical imaging and therapeutic technologies.
The techniques obtained through this research will be applied to a variety of optical imaging techniques, including multiphoton microscopy and photoacoustic microscopy, as well as several optical therapies such as photothermal therapy and photodynamic therapy
.
This will enhance the application
of the prior art by increasing the depth of image and processing.
”

Original:

Deep laser microscopy using optical clearing by ultrasound-induced gas bubbles