AsianScientist (Apr. 9, 2018) – In a study published in Nature Photonics, a team of scientists in South Korea has developed a method to image mice brains through their skulls.
When entering a complex and opaque environment like a human or an animal body, the trajectory of light is disrupted by all the components it encounters. For this reason, only a small fraction of light waves propagating inside biological tissues reach their desired target, while the majority is scattered and randomly diffused. This scattering hinders most applications of optical imaging for deep biological samples.
In the present study, researchers at the Institute for Basic Science (IBS) in South Korea reported a method to preferentially enhance the intensity of light waves that interact with the target tissue over the waves that do not. They achieved this by measuring the time taken for light waves to travel to the target and be reflected. This was followed by ‘injecting’ light into those ‘lanes’ that were found to interact with the target.
The researchers demonstrated a more than ten-fold improvement of light energy delivery to targets that were too deeply embedded to visualize with current optical imaging techniques. Using their technique, they were able to obtain images through the 340 μm-thick skull of a young mouse. Importantly, this non-invasive technique does not cause any damage to tissues and does not need injections of fluorescent molecules to label the target.
The scientists suggest that their technique could be used to visualize myelin, the lipid layer that wraps neurons and guarantees fast transmission of electrical signals. This is because myelin has a larger refractive index than the neurons it surrounds. The team hopes to apply this method to the nerve cells, bone marrow and brain tissue of living animals and humans.
“Optical imaging can generally work at the depth of roughly 1 mm of biological tissue. Our technique goes deeper into tissue, at nearly twice the depth,” said Dr. Jeong Seungwon of IBS who led the study, adding that this work could lay the foundation for in vivo experiments using light in biomedical imaging, optogenetics and tumor treatment.
The article can be found at: Jeong et al. (2018) Focusing of Light Energy Inside a Scattering Medium by Controlling the Time-gated Multiple Light Scattering.
Source: Institute for Basic Science.
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