To create a 3D image, the researchers combined 100 two-dimensional images taken from different angles. The resulting images are essentially 3D maps of the refractive index of the cell's organelles. The entire process took about 10 seconds, but the researchers recently reduced this time to 0.1 seconds.
The team's image of a cervical cancer cell reveals the cell nucleus, the nucleolus and a number of smaller organelles in the cytoplasm. The researchers are currently in the process of better characterizing these organelles by combining the technique with fluorescence microscopy and other techniques.
One key advantage of the new technique is that it can be used to study live cells without any preparation, said Kamran Badizadegan, principal research scientist in the Spectroscopy Laboratory and assistant professor of pathology at Harvard Medical School, and one of the authors of the paper. With essentially all other 3D imaging techniques, the samples must be fixed with chemicals, frozen, stained with dyes, metallized or otherwise processed to provide detailed structural information.
When you fix the cells, you can't look at their movements, and when you add external contrast agents you can never be sure that you haven't somehow interfered with normal cellular function, said Badizadegan.
The current resolution of the new technique is about 500 nanometers, or billionths of a meter, but the team is working on improving the resolution. We are confident that we can attain 150 nanometers, and perhaps higher resolution is possible, Feld said. We expect this new technique to serve as a complement to electron microscopy, which has a resolution of approximately 10 nanometers.
|Contact: Elizabeth Thomson|
Massachusetts Institute of Technology