Endoscopic OCT system could improve cancer screening

Massachusetts Institute of Technology (MIT; Cambridge, MA) researchers have developed an endoscopic optical coherence tomography (OCT) system to enable 3-D imaging of microscopic pre-cancerous changes in the esophagus or colon.

As standard endoscopy can only examine the surface of tissues in the colon or esophagus, it could miss important changes occurring inside tissue that indicate cancer development. Described in the August 1 issue of the journal Biomedical Optics Express, the endoscopic OCT system developed by the MIT team—led by OCT pioneer James G. Fujimoto—captures data at 980 fps, is nearly 10 times faster than previous devices, and images microscopic features less than 8 millionths of a meter in size.

In collaboration with clinicians at the VA Boston Healthcare System and Harvard Medical School, the team is investigating endoscopic OCT as a method for guiding excisional biopsy—the removal of tissue for histological examination—to reduce false negative rates and improve diagnostic sensitivity.

Endoscopic OCT requires miniature optical catheters or probes—just a few millimeters in diameter—that can scan an optical beam in two dimensions to generate high-resolution 3-D data sets. Scanning the beam in one transverse direction generates an image in a cross-sectional plane, whereas scanning the beam in two directions generates a stack of cross-sectional images—that is, a 3-D (or volumetric) image.

3-D OCT volumetric data set from an excised human colon specimen. a) En face view showing regular organization of normal colon, and b) and c) Cross-sectional views along two different directions showing sub-surface features. Two cross-sections are shown as examples; however, multiple cross-sectional views can be extracted from the 3-D OCT data. Scale bar: 500 µm. (Image courtesy of the Massachusetts Institute of Technology)

“This device development is one of the major technical challenges in endoscopic OCT because probes must be small enough so that they can be introduced into the body, but still be able to scan an optical beam at high speeds,” says Fujimoto. “Increasing imaging speeds has also been an important research objective because high-resolution volumetric imaging requires very large amounts of data in order to cover appreciable regions of tissue, so rapid image acquisition rates are a powerful advantage.”

The optical catheter developed by the MIT researchers and their collaborators uses a piezoelectric transducer, a miniature device that bends in response to electrical current, allowing a laser light-emitting optical fiber to be rapidly scanned over the area to be imaged.

So far, the device—which must be further reduced in size, notes Fujimoto, before it can be deployed with the standard endoscopes now used—has only been used in animal models and in samples of human colons that had been removed during surgical procedures; further development and testing of the technology is needed before it can be tested in human patients. “The ultimate clinical utility of new devices must be established by large clinical studies, which assess the ability of the technology to improve diagnoses or therapy,” he says. “This is a much more complex and lengthy task than the initial development of the technology itself.”

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Posted by Lee Mather

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