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A team led by Korean scientists has developed a new type of holographic microscope. The new microscope is said to be able to "see" through intact skulls and enable high-resolution 3D imaging of neural networks inside the brains of living mice without removing the skull.

In order to use light to scrutinize the internal features of a living body, scientists previously needed to provide enough light energy to the sample and then accurately measure the signal reflected from the target tissue. However, in living tissues, when light hits cells, there are often multiple scattering effects and severe aberrations, which makes it difficult to obtain clear images.

A novel holographic microscope can image mouse brains through their skulls to observe neural networks in living mouse brains without removing the skull.

Light is scattered repeatedly in complex structures such as living tissue, which causes photons to change their direction irregularly many times as they pass through the tissue. As a result of this process, most of the image data carried by the light is corrupted.

By correcting for the wavefront distortion of the light reflected from the object being examined, it is possible to see relatively deep features inside the tissue, even with a very small amount of reflected light. However, this correction process is hampered by various scattering effects, the statement said. Therefore, it is critical to reduce the proportion of multiscattered waves and increase it to obtain high-resolution images of deep tissues.

The team was able to quantitatively analyze the interaction of light and matter, which allowed them to further develop earlier microscopy. According to a recent study, an ultra-deep, three-dimensional, time-resolved holographic microscope has been successfully developed to see tissues more deeply than ever before.

Specifically, the researchers devised a method that takes advantage of the fact that they have similar reflected waveforms even when light is input from different angles, allowing single-scattered waves to be preferred.

Resonance modes that maximize constructive interference (interference that occurs when waves of the same phase overlap) can be found by using complex algorithms and numerical operations that analyze the eigenmodes of the medium (the unique waves that transfer light energy into the medium). Between the light wavefronts, the new microscope focuses attention on nerve fibers with more than 80 times more light energy than before, while selectively removing unwanted signals.

"When we first observed the optical resonance of complex media, our work received a great deal of attention from academia," says Professor KIM Moonseok and Dr. Jo Yonghyeon, who developed the basics of holographic microscopy.

"From observing the basic principles of subcranial neural networks in mice to practical applications, we have opened up new ways of brain neuroimaging fusion technology by combining the efforts of talents in physics, life and brain sciences."

Compensation for sample-induced optical aberrations is essential for visualizing microstructure deep within biological tissue. However, strong multiscattering poses a fundamental limitation for identifying and correcting tissue-induced aberrations. Here, we introduce a label-free deep tissue imaging technique called dimensionality reduction adaptive light microscopy (DReAM) to selectively attenuate multiscattering. We establish a theoretical framework in which dimensionality reduction of a time-gated reflection matrix can attenuate uncorrelated multiple scattering while retaining a single scattering signal with strong wave correlation, independent of sample-induced aberrations. We performed in vivo imaging of mouse brain through a complete skull using a detection beam of visible wavelength.

Original link: https://www.xianjichina.com/special/detail_516659.html

Source: Xianji.com

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