Living Cells Scanned in 3-D for First Time
A 3D image of the nematode C. elegans, taken using a new imaging technique developed at MIT. The scale bar (lower left) is 50 micrometers.
Credit: Michael Feld Laboratory, MIT.

Scientists can now scan a living cell and render it as a 3-D image in a process similar to CT scanning used in health care.

"Accomplishing this has been my dream and a goal of our laboratory for several years," Michael Feld, director of MIT's Spectroscopy Laboratory, told LiveScience.

The imaging technique could set a new research standard in dozens of fields, ranging from immunology to neurology, in which experts will benefit from detailed images of cell organelles, or components such as nuclei and mitochondria.

"This will open up the possibility of imaging through tissues, which will have a significant impact on life science," said Wonshik Choi, first author of the study describing the technique. The study is published in the Aug. 12 online edition of Nature Methods.

Until now, techniques for rendering cells in 3-D required the application of chemicals and stains, freezing and other invasive processes. These techniques interfere with normal cellular function to varying degrees, but that has not stopped their widespread use.

"Most scientists have learned to live with these purely technical limitations as necessary evils," said study leader Kamran Badizadegan.

The new technology can be used on live cells in their native state, with no preparation.

Developing this process required that the scientists look to other fields that depend heavily on 3-D imaging techniques.

Computed Tomography (CT) scans are used in paleontology to study fragile bones and by physicians to model patients' brains and other organs. The scan collects several narrow X-ray cross sections, or slices, of a 3-D object. The cross sections depict the density highs and lows of one thin section. Think of this image as a slice of bread.

Many slices are collected from several different orientations and then stitched together into a contiguous solid, much like building a loaf of bread out of individual slices.

The MIT researchers used visible light instead of X-rays, but had to compensate for the fact that cells absorb very little light. To compose the images, they had to measure how much the light waves passing through the cell slowed, a property known as refractive index.

After taking 100 slices measuring the cell's refractive index, the researchers composed a 3-D map that detailed the cell's many parts, from membrane to mitochondria.

Badizadegan was optimistic about the future use of such refractive index mapping, predicting that it "will open a new era in biomedical microscopy."