Sees Through Even When Hidden Behind Biological Tissue... Imaging Technology Developed That Overcomes Light Transmission Limits

UNIST Professor Park Jeong-hoon's Team Successfully Observes Targets Behind 710μm Thick Mouse Brain Tissue

Reduced Light Wavefront Control Area Improves Efficiency, Applicable to Phototherapy and Optogenetic Modification

Fluorescent bead imaging and signal intensity line graph passing through 710μm thick mouse brain tissue. [Image source=UNIST]

[Asia Economy Yeongnam Reporting Headquarters Reporter Kim Yong-woo] Domestic researchers have succeeded in clearly observing substances hidden behind the brain tissue of mice.

This is because an optical microscopy technology that can see through one tissue beyond living tissue has been developed.

Generally, it is difficult to observe living tissue with an optical microscope when the thickness reaches 100μm (micrometers, 10-6m).

This is because the components of living tissue vary, including proteins and lipids, causing significant light scattering. When light scatters, the focus is lost, resulting in a blurry image.

Therefore, it is necessary to rely on ‘wavefront control technology’ that corrects the path of scattered light and sends it to the original target focus.

The research team led by Professor Park Jung-hoon of the Department of Biomedical Engineering at Ulsan National Institute of Science and Technology (UNIST, President Lee Yong-hoon) developed a new wavefront control technology that selectively corrects the path of light passing through the central area of the microscope objective lens to create a clear focus.

Using this technology, Professor Park’s team succeeded in clearly observing spherical fluorescent beads hidden behind 710μm thick mouse brain tissue.

Schematic diagram of an efficient wavefront distortion control experiment. [Image source=UNIST]

The researchers focused on the fact that most light scatters in the forward direction within living tissue. Based on this, they hypothesized that light passing through the edges of the objective lens and entering the tissue obliquely travels the longest distance inside the tissue and collides with cells and other components, resulting in significant energy loss.

The technique developed by the researchers discards the ‘low-energy light’ passing through the edges of the objective lens and selectively sends only the ‘high-energy light’ passing through the central area to the focus, thereby efficiently enhancing the focus intensity.

In fact, when the same wavefront control time was used, the fluorescent signal intensity increased by 8.9 times compared to existing technology, and the signal contrast between the fluorescent beads and the surrounding background improved by 2.1 times.

Jin Hyung-won, a first author and researcher in the Department of Biomedical Engineering, explained, “In media such as living tissue, we proved that selectively wavefront-controlling only high-energy light (light incident at a low angle) rather than the conventional method is a much more efficient imaging method.”

Professor Park said, “The technique developed this time is expected to be expandable to technologies that transmit light through living tissue to treat lesions or optogenetics technologies that control cells in living tissue.”

From the left, Professor Park Jeong-hoon, Researcher Jin Hyung-won, Researcher Hwang Byung-jae, Researcher Lee Sang-won. [Image source=UNIST]

This technology achieved high-quality images despite reducing the numerical aperture (NA), which contrasts with existing theories. Generally, numerical aperture is proportional to image resolution.

The research, in which UNIST Biomedical Engineering researchers Hwang Byung-jae and Lee Sang-won also participated, is scheduled to be published in the April issue of Optica, a prestigious international journal in the field of optics.

The research was conducted with support from the National Research Foundation of Korea (NRF) and the POSCO TJ Park Foundation.

This content was produced with the assistance of AI translation services.