A team from Northwestern University and NorthShore University HealthSystem (formerly Evanston Northwestern Healthcare) describes the first application of their new technique in the journal, which they call partial wave microscopic spectroscopy. This technique allows them to examine cell samples taken from people who have undergone screening for pancreatic cancer to detect signs of the disease.
Pancreatic cancer is typically diagnosed by hospital pathologists who look for telltale changes to the morphology of pancreatic cells when they examine cell biopsies under the microscope. The problem is that in the early stages of cancer, many early-stage cancer cells appear normal. By the time the cancerous cells undergo observable changes, it may be too late in the disease progression for effective treatment.
In fact, only 7 percent of people with pancreatic cancer are diagnosed in the earliest stages of the disease, when the cancer is still confined to its primary site. More than half of all people with the disease are not diagnosed until it has already metastasized.
"In the beginning, cells look normal," says Vadim Backman, a professor of biomedical engineering at Northwestern University who developed partial wave microscopic spectroscopy with his former graduate students Yang Liu and Hariharan Subramanian and postdoctoral fellow Prabhakar Pradhan. The new technique measures nanoscopic changes to the interior architecture of cells - changes that may signal signs of cancer even in cells that look normal under the microscope.
To test their technique, Backman and Subramanian collaborated with gastroenterologists Hemant K. Roy and Randall Brand, who had collected tissue samples from people undergoing biopsies to detect pancreatic cancer.
The new technique works by detecting fluctuations in the cells' refractive index (an optical property that measures how cells bend light passing through them). No other technique has ever measured this quantitatively, says Backman. These fluctuations are influenced by nanoscopic changes to the cells' interior architecture that often occur much earlier than the changes pathologists can detect under their microscopes. The more architectural disorder there is inside the cell, the more the refractive index fluctuates.
The Chicago researchers showed that by quantifying these fluctuations, partial wave spectroscopy could identify cancer cells even in cases where they had not been detected by pathologists.
Partial wave microscopic spectroscopy may be a boon to medicine, if it proves effective in clinical trials at detecting cancers early - especially for people with pancreatic cancer, which is one of the most deadly forms of cancer. According to the National Cancer Institute, more than 37,000 men and women in the United States were diagnosed with pancreatic cancer in 2008, and statistically 95 percent of them will succumb to the disease within five years.
Reference: The research was funded by a National Science Foundation SGER grant, the National Institutes of Health and the V Foundation.
Paper: "Partial wave microscopic spectroscopy detects sub-wavelength refractive index fluctuations: an application to cancer diagnosis," Hariharan Subramanian et al., Optics Letters, Vol. 34, No. 4, Feb. 15, 2009.
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