Holographic 3D images are able to show the response of tumors to anti-cancer drugs via new technology developed at Purdue University. The digital holographic imaging system uses a laser and a charged couple device, or CCD, to see inside tumor cells. Researchers hope that the device could also have uses in drug development and medical imaging.
"This is the first time holography has been used to study the effects of a drug on living tissue," said David D. Nolte, the Purdue professor of physics who leads the team. "We have moved beyond achieving a 3-D image to using that image for a direct physiological measure of what the drug is doing inside cancer cells. This provides valuable information about the effects of various doses of the drug and the time it takes each dose to become significantly effective."
Holography uses the full spectrum of information available from light to generate 3D images. The technique is performed by shining a laser on both the object and directly on the CCD chip of the digital camera. Then the system screens the pattern of light reflected back from the object and allows the camera to record very detailed information.
"All living matter is in constant motion, and the laser speckle from a living object is constantly changing with that motion," Nolte said. "This was the key to the diagnostic ability of the technique. The image appears to shimmer with the motion inside the cell. As the anticancer drug works, there is less motion inside the cell and the shimmer effect is reduced. This can be seen right on the screen."
The team detects the motion of organelles inside cancer cells. Organelles are tiny specialized structures that perform internal cell functions and are a common target of anticancer drugs. Colchicine, the anticancer drug studied by the group, limits the ability of organelles to travel throughout the cell and perform their functions.
This reduction in motion translates to less shimmer in the image on the screen and can be quantitatively analyzed by a computer program, Nolte said.
In addition to the technology's sensitivity to motion, the field of view is unique because of its dynamic range, the difference between the largest and smallest scale accessed.
"Biologists currently have to look at things on the cellular level through microscopes. With this technology, we now can detect things on the cellular level and the tissue scale at the same time. In this case, the whole is greater than the sum of its parts. Tissue is more than just an accumulation of cells. It is a communication network in 3-D that behaves differently than 2-D cell cultures," Nolte said.
The findings of this National Science Foundation funded research were detailed in a presentation at the American Physical Society Meeting in Denver, Colo. on March 6.