Ashley N. Paddock
CAMBRIDGE, Mass. – A new optical coherence tomography system can look below the surface with greater detail than traditional screening methods can, enabling high-speed 3-D imaging of microscopic precancerous changes in the esophagus or colon.
Endoscopy is the current method for screening esophageal and colon cancer, which are diagnosed in more than 1.5 million people worldwide each year, according to the American Cancer Society. However, standard endoscopy examines only the surface of tissues, so malignant changes occurring at greater depths may be missed.
OCT, however, examines layers of tissue below the surface and can visualize structures just a few microns in size. Over the past two decades, OCT has become commonplace in ophthalmology, where it has been used to generate images of the retina and to diagnose and monitor diseases such as glaucoma. It can be performed inside the body through the use of miniature fiber optic scanning catheters or probes, either on their own or in combination with standard endoscopes, colonoscopes or laparoscopes.
“OCT for cancer imaging is one of the most challenging research applications because of its clinical complexity and the demands on the technology,” said OCT pioneer James Fujimoto, professor of electrical engineering at MIT. “We have been working on endoscopic OCT imaging for over a decade. We believe that this is one of the most important current areas of investigation and has a high potential for future impact.”
These images represent 3-D OCT volumetric data sets from an excised human colon specimen: (a) En face view shows the regular organization of a normal colon; (b, c) cross-sectional views along two directions show subsurface features. Although just two cross sections are shown as examples, multiple cross-sectional views can be extracted from the data. Scale bar = 500 µm. Courtesy of MIT.
The new endoscopic OCT imaging system from MIT works at record speeds to capture data at a rate of 980 fps (equivalent to 480,000 axial scans) – nearly 10 times faster than previous devices – while imaging microscopic features less than 8 µm in size. At such high speeds and resolution, the system promises to enable 3-D microscopic imaging of precancerous changes in the esophagus and colon.
The findings were described in the July issue of Biomedical Optics Express (doi: 10.1364/BOE.2.002438). In collaboration with clinicians at the VA Boston Healthcare System and Harvard Medical School, the team has begun to investigate endoscopic OCT as a method for guiding excisional biopsy – the removal of tissue for histological examination – to reduce false negative rates and to improve diagnostic sensitivity.
The device has been used in animal models and in samples of human colons that have been removed during surgical procedures. Further development and testing of the technology is needed before it can be used in humans. The team expects to introduce the next-generation OCT technology within the next half-year, Fujimoto said.