Physicists at Purdue University have developed a new digital holographic imaging system. This device permits to watch in 3-D how anticancer drugs fight tumors. It uses a laser which does not harm living tissues and a common microchip used in your digital cameras to see inside tumor cells. The real innovation of this system is that the holograms generated are not permanently recorded. These shimmering holograms recorded on holographic film "change in time, tracking and adjusting to changes in the image intensity and phase," according to one of the researchers. Of course, this device can have other applications in drug development and medical imaging.
This system has been developed by David Nolte, professor of physics, and his team at the Adaptive Optics and Biophotonics Group.
Below you can see David Nolte (right) working "with graduate assistant Kwan Jeong on their digital holographic imaging system. Nolte's team used the device to observe the response of tumors to anticancer drugs in real-time, 3-D images" (Credit: Purdue News Service photo/David Umberger). Here is a link to a larger version.
But what exactly is a shimmering hologram? It's simply a moving hologram, as explain the researchers.
What would happen if a hologram recorded on holographic film could change in time, tracking and adjusting to changes in the image intensity and phase? What could we do with this? An amazing number of things!
We can, for instance, "see" through turbid media, such as skin or other tissue, looking for lesions and carcinomas that cannot be seen by eye alone. We can create a sensitive holographic ear that can listen for ultrasound signals using lasers. We can receive femtosecond laser pulses that have been distorted by propagation down a fiber optic, and remove the distortion automatically as the system even adapts in real-time to changing distortions. In each of these applications, we rely on the moving hologram to adapt to a changing environment. The holograms "shimmer", so to speak, as they track changing image information.
But let's go back to this new digital holographic imaging system and at how it works.
Holography uses the full spectrum of information available from light, more than what the human eye can detect, to create a 3-D image called a hologram. By shining a laser on both the object and directly on the CCD (charged couple device) chip of the digital camera, the system screens the pattern of light reflected back from the object and allows the camera to record very detailed information, including depth and motion on a scale of microns, or 0.0001 centimeter.
And are the results satisfactory?
"We can look at a fairly large section of the object, about a 30-micron-thick section of a 700-micron-thick tumor," Nolte said. "At the same time, we can retrieve information within the micron scale. 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."
The researchers don't say anything about the availability of this system. This probably means that several years will pass before this medical imaging system emerges from the lab.
Sources: Purdue University news release, March 6, 2007; and various websites
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