Optical coherence tomography in the gastrointestinal tract
- Shai Friedland, MD
Shai Friedland, MD
- Assistant Professor of Medicine
- Palo Alto VA and Stanford University Medical Center
- Jacques Van Dam, MD, PhD
Jacques Van Dam, MD, PhD
- Professor of Medicine
- USC School of Medicine, Los Angeles, CA
Components borrowed from the telecommunications industry have been applied to medical imaging to improve resolution as never before. Optical coherence tomography (OCT) is an emerging medical imaging technology that relies on the backscattering of light to obtain cross-sectional images of tissue. Many of the early applications of OCT were in ophthalmology, where the transparency of anterior structures of the eye facilitated high-resolution imaging of the retina. More recently, there have been several pilot studies using OCT in the gastrointestinal tract. These have demonstrated the feasibility of this technology to enhance endoscopic imaging of the superficial layers of the esophagus, stomach, bile ducts, pancreatic duct, and colon. OCT imaging has demonstrated anatomic structures such as crypts and glands that could potentially permit endoscopists to diagnose mucosal abnormalities such as Barrett's esophagus. In 2013, an OCT system designed for imaging the esophagus became commercially available. (See 'Technical advances' below.)
OCT is similar in principle to ultrasonography but uses light waves rather than acoustical waves. As in B-mode ultrasonography, a quantitative measurement of backscattering is performed at each axial depth, and the measurements are repeated at different transverse positions. In this manner, a linear or radial two-dimensional map of backscattering strength is acquired [1-3].
Measurement of optical backscattering is performed by low coherence interferometry . This method uses a low coherence light source such as a superluminescent diode, which typically has a coherence length of approximately 20 micrometers. The incident light is split in two by an optical beam splitter, with one beam directed to the tissue via an optical fiber and the other beam directed to a mirror located at a precisely controlled distance. The backscattered light from the tissue is combined with the reflected light from the mirror. This results in interference only when the path lengths match to within the 20 microns of the coherence length of the light source. A quantitative measurement of optical backscattering at different depths is obtained by measuring the degree of interference at each mirror position as the mirror is moved.
The coherence length of the light source determines the maximal axial resolution that can be obtained. Transverse resolution is determined by the spot size of the focused beam directed at the tissue and the amount that the apparatus is translated at each during the scan; it is typically also approximately 20 microns. OCT is typically performed with near infrared light because tissue is relatively transparent; longer wavelengths penetrate deeper into biological tissues at these frequencies. Scattering of light in tissue limits the depth of scanning to approximately 1 to 2 mm in the gastrointestinal tract, generally restricting OCT imaging to the mucosa and submucosa when performed during endoscopy.
OCT is typically performed using catheters passed through the accessory channel of standard gastroscopes, colonoscopes, or duodenoscopes (picture 1):To continue reading this article, you must log in with your personal, hospital, or group practice subscription. For more information on subscription options, click below on the option that best describes you:
- Fujimoto JG, Brezinski ME, Tearney GJ, et al. Optical biopsy and imaging using optical coherence tomography. Nat Med 1995; 1:970.
- Tearney GJ, Brezinski ME, Southern JF, et al. Optical biopsy in human gastrointestinal tissue using optical coherence tomography. Am J Gastroenterol 1997; 92:1800.
- Tearney GJ, Brezinski ME, Bouma BE, et al. In vivo endoscopic optical biopsy with optical coherence tomography. Science 1997; 276:2037.
- Wax A, Terry NG, Dellon ES, Shaheen NJ. Angle-resolved low coherence interferometry for detection of dysplasia in Barrett's esophagus. Gastroenterology 2011; 141:443.
- Das A, Sivak MV Jr, Chak A, et al. High-resolution endoscopic imaging of the GI tract: a comparative study of optical coherence tomography versus high-frequency catheter probe EUS. Gastrointest Endosc 2001; 54:219.
- Hsiung PL, Pantanowitz L, Aguirre AD, et al. Ultrahigh-resolution and 3-dimensional optical coherence tomography ex vivo imaging of the large and small intestines. Gastrointest Endosc 2005; 62:561.
- Chen Y, Aguirre AD, Hsiung PL, et al. Ultrahigh resolution optical coherence tomography of Barrett's esophagus: preliminary descriptive clinical study correlating images with histology. Endoscopy 2007; 39:599.
- Chen Y, Aguirre AD, Hsiung PL, et al. Effects of axial resolution improvement on optical coherence tomography (OCT) imaging of gastrointestinal tissues. Opt Express 2008; 16:2469.
- ASGE Technology Committee. Enhanced imaging in the GI tract: spectroscopy and optical coherence tomography. Gastrointest Endosc 2013; 78:568.
- Leggett CL, Gorospe EC, Owens VL, et al. Can volumetric LASER endomicroscopy detect dysplasia in Barrett's esophagus? Gastrointest Endosc 2013; 77:AB327.
- Wong RC, Yazdanfar S, Izatt JA, et al. Visualization of subsurface blood vessels by color Doppler optical coherence tomography in rats: before and after hemostatic therapy. Gastrointest Endosc 2002; 55:88.
- Yang VX, Tang SJ, Gordon ML, et al. Endoscopic Doppler optical coherence tomography in the human GI tract: initial experience. Gastrointest Endosc 2005; 61:879.
- Li XD, Boppart SA, Van Dam J, et al. Optical coherence tomography: advanced technology for the endoscopic imaging of Barrett's esophagus. Endoscopy 2000; 32:921.
- Faber DJ, Mik EG, Aalders MC, van Leeuwen TG. Toward assessment of blood oxygen saturation by spectroscopic optical coherence tomography. Opt Lett 2005; 30:1015.
- Kobayashi K, Izatt JA, Kulkarni MD, et al. High-resolution cross-sectional imaging of the gastrointestinal tract using optical coherence tomography: preliminary results. Gastrointest Endosc 1998; 47:515.
- Bouma BE, Tearney GJ, Compton CC, Nishioka NS. High-resolution imaging of the human esophagus and stomach in vivo using optical coherence tomography. Gastrointest Endosc 2000; 51:467.
- Sivak MV Jr, Kobayashi K, Izatt JA, et al. High-resolution endoscopic imaging of the GI tract using optical coherence tomography. Gastrointest Endosc 2000; 51:474.
- Boppart SA, Brezinski ME, Fujimoto JG. Optical coherence tomography imaging in developmental biology. Methods Mol Biol 2000; 135:217.
- Jäckle S, Gladkova N, Feldchtein F, et al. In vivo endoscopic optical coherence tomography of esophagitis, Barrett's esophagus, and adenocarcinoma of the esophagus. Endoscopy 2000; 32:750.
- Jäckle S, Gladkova N, Feldchtein F, et al. In vivo endoscopic optical coherence tomography of the human gastrointestinal tract--toward optical biopsy. Endoscopy 2000; 32:743.
- Zuccaro G, Gladkova N, Vargo J, et al. Optical coherence tomography of the esophagus and proximal stomach in health and disease. Am J Gastroenterol 2001; 96:2633.
- Hatta W, Uno K, Koike T, et al. Optical coherence tomography for the staging of tumor infiltration in superficial esophageal squamous cell carcinoma. Gastrointest Endosc 2010; 71:899.
- Poneros JM, Brand S, Bouma BE, et al. Diagnosis of specialized intestinal metaplasia by optical coherence tomography. Gastroenterology 2001; 120:7.
- Evans JA, Poneros JM, Bouma BE, et al. Optical coherence tomography to identify intramucosal carcinoma and high-grade dysplasia in Barrett's esophagus. Clin Gastroenterol Hepatol 2006; 4:38.
- Poneros J. Optical coherence tomography and the detection of dysplasia in Barrett's esophagus. Gastrointest Endosc 2005; 62:832.
- Qi X, Sivak MV, Isenberg G, et al. Computer-aided diagnosis of dysplasia in Barrett's esophagus using endoscopic optical coherence tomography. J Biomed Opt 2006; 11:044010.
- Evans JA, Bouma BE, Bressner J, et al. Identifying intestinal metaplasia at the squamocolumnar junction by using optical coherence tomography. Gastrointest Endosc 2007; 65:50.
- Zhou C, Tsai TH, Lee HC, et al. Characterization of buried glands before and after radiofrequency ablation by using 3-dimensional optical coherence tomography (with videos). Gastrointest Endosc 2012; 76:32.
- Hatta W, Uno K, Koike T, et al. A prospective comparative study of optical coherence tomography and EUS for tumor staging of superficial esophageal squamous cell carcinoma. Gastrointest Endosc 2012; 76:548.
- Westphal V, Rollins AM, Willis J, et al. Correlation of endoscopic optical coherence tomography with histology in the lower-GI tract. Gastrointest Endosc 2005; 61:537.
- Masci E, Mangiavillano B, Albarello L, et al. Pilot study on the correlation of optical coherence tomography with histology in celiac disease and normal subjects. J Gastroenterol Hepatol 2007; 22:2256.
- Pitris C, Jesser C, Boppart SA, et al. Feasibility of optical coherence tomography for high-resolution imaging of human gastrointestinal tract malignancies. J Gastroenterol 2000; 35:87.
- Familiari L, Strangio G, Consolo P, et al. Optical coherence tomography evaluation of ulcerative colitis: the patterns and the comparison with histology. Am J Gastroenterol 2006; 101:2833.
- Pfau PR, Sivak MV Jr, Chak A, et al. Criteria for the diagnosis of dysplasia by endoscopic optical coherence tomography. Gastrointest Endosc 2003; 58:196.
- Shen B, Zuccaro G, Gramlich TL, et al. Ex vivo histology-correlated optical coherence tomography in the detection of transmural inflammation in Crohn's disease. Clin Gastroenterol Hepatol 2004; 2:754.
- Shen B, Zuccaro G Jr, Gramlich TL, et al. In vivo colonoscopic optical coherence tomography for transmural inflammation in inflammatory bowel disease. Clin Gastroenterol Hepatol 2004; 2:1080.
- Seitz U, Freund J, Jaeckle S, et al. First in vivo optical coherence tomography in the human bile duct. Endoscopy 2001; 33:1018.
- Poneros JM, Tearney GJ, Shiskov M, et al. Optical coherence tomography of the biliary tree during ERCP. Gastrointest Endosc 2002; 55:84.
- Arvanitakis M, Hookey L, Tessier G, et al. Intraductal optical coherence tomography during endoscopic retrograde cholangiopancreatography for investigation of biliary strictures. Endoscopy 2009; 41:696.
- Testoni PA, Mangiavillano B, Albarello L, et al. Optical coherence tomography to detect epithelial lesions of the main pancreatic duct: an Ex Vivo study. Am J Gastroenterol 2005; 100:2777.
- Boppart SA, Herrmann J, Pitris C, et al. High-resolution optical coherence tomography-guided laser ablation of surgical tissue. J Surg Res 1999; 82:275.