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Transparency Allows Better Diagnostic Imaging

PASADENA, Calif., Aug. 6, 2014 — It is now possible to see through large tissue samples under a microscope with a technique that strips cells of their light-blocking parts.

The technique, developed at the California Institute of Technology, could enable new diagnostic medical applications, including better imaging of developmental problems and diseases.

Through the new PARS technique, researchers can make the body, including cells and tissue, transparent for better imaging and analysis. Images courtesy of Bin Yang and Viviana Gradinaru/ California Institute of Technology.

“Large volumes of tissue are not optically transparent. You can’t see through them,” said Dr. Viviana Gradinaru, an assistant professor of biology at Caltech. “If we need to see individual cells within a large volume of tissue, we have to slice the tissue very thin, separately image each slice with a microscope, and put all of the images back together with a computer." 

This shows 3-D visualization of fluorescently labeled kidney cells within kidney tissue.

Lipids in cells provide structural support, but also prevent light from passing through. The new technique, called PARS (perfusion-assisted agent release in situ), involves infusing a sample with a solution of lipid-dissolving detergents. These render the cells transparent, while hydrogel in the solution provides structural support in place of the lipids. 

Confocal and other microscopy methods can then be applied, and single cells marked with fluorescent proteins can be imaged.

When whole-body transparency is not necessary, another method called PACT (passive clarity technique) is equally effective with individual organs, the researchers said.

This 3-D visualization demonstrated fluorescently labeled intestine cells in intact intestine tissue.

Applications that could benefit from the new techniques include the rapid detection of cancer cells in biopsy samples, as well as mapping peripheral nervous system neurons or disease distributions in animal models.

“I think these new techniques are very practical for many fields in biology,” Gradinaru said. “When you can just look through an organism for the exact cells or fine axons you want to see, without slicing and realigning individual sections, it frees up the time of the researcher.”

The research was published in Cell (doi: 10.1016/j.cell.2014.07.017).

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When Kepler pushed the earth out of the center of our universe he made it possible to use natural science to find until now unthinkable ways of techniques. If this idea works - what must be shown in future - well it could replace X-ray that`s not so good for our DNA. Thanks Dr.Hans Hainz
8/15/2014 4:02:35 AM

While it's a great way to visualise tissue ex vivo, I very much doubt we want the lipids in our bodies, which have such important functions in maintaining our health and most cellular processes, to be dissolved and replaced with hydrogel. - Dr Katherine Lau
8/15/2014 4:48:47 AM

The opening sentence is quite misleading. This technique has never been used on an "entire human body". So there is no justification for the initial statement. It should be recognized that this process is not compatible with the organism, or human, being alive. So it will never be used to diagnose disease in a patient in Oder to inform treatment options, although it might be used in an autopsy.
8/14/2014 1:56:36 PM

MWelsh, You were quite right about our lede, and we've edited it to be more faithful to the study. However, it's clear the researchers intend for this technique to be used in biopsies, making it potentially of great use for living patients.
8/14/2014 4:02:47 PM
- James Lowe

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