Research Pushes Back Threshold of Early Cancer Detection (4/16/2008)

Early detection is the single, most important factor in cancer survival. That's why regular checkups and early testing are so necessary.

Unfortunately, current testing methodologies have limitations that prevent very early cancer detection. Cell abnormalities have to reach about 1 mm in size before they can be seen by CT, MRI or ultrasound scans.

Sometimes problems at the 1 mm scale are hard to detect with other imaging technologies. In addition, many testing procedures are expensive, time consuming, and, in the case of CT scans, involve radiation. For those reasons, testing isn't normally done on a frequent basis.

University of Arizona professor Jennifer Barton is working to overcome these technical limitations through her research on Optical Coherence Tomography, known as OCT.

OCT is a noninvasive technique that concentrates a beam of near-infrared light on tissue. The light penetrates a few millimeters and is reflected back. This reflected light is compared with a reference beam - using a process called interferometry - to build up an image of the cells below the surface.

OCT is an optical analog of ultrasound, which uses sound waves, and radar, which uses radio waves. Since light waves are so much shorter than the shortest sound and radio waves, OCT can provide much higher resolution.

"Most cancers arise in the thin layer that covers the body," said Barton, a professor in the UA's division of biomedical engineering and the electrical and computer engineering department. "The skin, lining of the colon, esophagus, and the covering of the ovaries are all epithelial tissues." The epithelium is a tissue layer that covers the surfaces and cavities of the body.

"Subtle changes in tissues, such as when cells are starting to deviate from normal, are not easy to see," she said. "The advantage of optics is the extremely high sensitivity. In fact, with certain systems, we can detect single molecules."

The downside is that the light penetrates only a few millimeters. So the light can't be beamed at internal tissues from outside the body, such as with MRIs or CT scans. However, Barton, her students and other OCT researchers have been successful in creating tiny catheters that can take optic fibers into the body. These catheters can be made so small that they will fit inside coronary arteries.

Three Research Applications

Researchers in Barton's lab now are working on OCT applications in three cancer areas: the skin, colon and ovaries.

Research on skin cancer involves early detection of certain kinds of pre-cancers, including work at the Arizona Cancer Center, where ressearchers are testing new lotions that can prevent cancer. OCT can help them monitor the effects of the drugs on a test subject's skin. The technology also can be used to accurately determine if a skin lesion is pre-cancerous.

"This method is about twice as specific at identifying skin cancer as a dermatologist," Barton said. "This makes sense, of course, because the dermatologist will want to err on the safe side and call some things cancerous that aren't. But OCT can be used to follow up the diagnosis because it is highly accurate in determining whether a pre-cancerous condition actually exists."

The colon research involves using tiny catheters to monitor changes in the colons of lab mice. This research can help speed drug development because researchers can use OCT to monitor the progression of disease and the effects of various drug therapies.

The ovarian imaging is being carried out as an operating-room procedure in cooperation with Dr. Kenneth Hatch, in the UA College of Medicine's department of obstetrics and gynecology.

"Ovarian cancer is the deadliest type of gynecological malignancy," Barton said. "Once it's diagnosed, it's usually very, very advanced." OCT is being used in this research to screen the ovaries of women who are at high risk for the disease. The tiny probes used for this procedure are inserted into the patient's abdomen through small incisions.

Other OCT Applications

OCT has many other applications, Barton noted. The U.S. Food and Drug Administration already has approved a device that is being used by some ophthalmologists to look at retinal nerve fiber thickness. This is important in monitoring the progression of glaucoma. The technology also can be used to look for macular holes, retinal detachment and other eye problems.

Researchers also are using OCT to look inside arteries for plaques that are likely to rupture or to determine if stents have been properly placed.

"In the future, we want to improve the performance of our system with faster imaging speed, higher resolution, faster data acquisition and better analysis techniques to extract more information from the images," Barton said. "We also want to develop some contrast agents that will help us target cancer cells."

"The ultimate goals are to improve patient care and to educate the next generation of engineers and scientists," she added.

Barton has been pursuing OCT research in collaboration with researchers in the Arizona Cancer Center, the BIO5 Institute, the UA College of Medicine, the department of molecular and cellular biology, and the department of physiology.

During the past eight years, Barton has worked with more than a dozen graduate students, four undergraduates and a high school intern on OCT research. These students have come from several disciplines in the UA colleges of engineering, medicine, science and optical sciences.

Note: This story has been adapted from a news release issued by the University of Arizona

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