A biopsy is often the only way to accurately identify the presence of a tumor, but there are a number of serious possible downsides to taking tissue samples from inside the body. A better way would be to analyze the tissue in situ, essentially miniaturizing a microscope and using it in the body’s interior. Researchers at Johns Hopkins have now developed two new endoscopic probes with imaging capabilities that may, if proven out in clinical trials, end up reducing the need for biopsies in a variety of clinical cases. So far the researchers have tested their probes to image small organs in sheep, mice, and rats.
Image taken by the two-photon endomicroscope shows the metabolic activity of mouse kidney cells. Credit: Xingde Li
The first probe is a two-photon endomicroscope that excites cells to naturally fluoresce, revealing the cellular structure of a tissue they’re in. The technique doesn’t require the use of dyes that can be hazardous to the body if used in situ as they are in the pathology lab. Two-photon microscopes are typically bench-top devices, but the new device is only 2 mm in diameter. It relies on a short-pulsed laser to generate photons that travel through an optical fiber and to the tip of the probe. A difficult to design lens focuses the incoming photons and does the same to the returning light coming from the tissue being imaged. This light travels back through the fiber optics and is then detected using a larger external device.
The second device is an optical coherence tomography (OCT) probe that’s only half a millimeter in diameter, but which produces images at up to four times the resolution of existing larger devices. The Hopkins researchers used a light source that could produce a lot of colors at the same time and focus them on the same spot at the same time. Another novel lens makes this probe possible, which was created at the end of an optical fiber out of silica and coated in gold, but that functions like a more traditional lens. The device is highly flexible and produces high quality images, so we’re hoping that it and the two-photon endomicroscope will soon be seeing the insides of humans.
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