Endoscopic Optical Coherence Angiography Enables 3-Dimensional Visualization of Subsurface Microvasculature
2014; Elsevier BV; Volume: 147; Issue: 6 Linguagem: Inglês
10.1053/j.gastro.2014.08.034
ISSN1528-0012
AutoresTsung-Han Tsai, Osman O. Ahsen, Hsiang‐Chieh Lee, Kaicheng Liang, Marisa Figueiredo, Yuankai K. Tao, Michael G. Giacomelli, Benjamin Potsaid, Vijaysekhar Jayaraman, Qin Huang, Alex Cable, James G. Fujimoto, Hiroshi Mashimo,
Tópico(s)Retinal Diseases and Treatments
ResumoEndoscopic imaging technologies such as confocal laser endomicroscopy1Wallace M. Lauwers G.Y. Chen Y. et al.Miami classification for probe-based confocal laser endomicroscopy.Endoscopy. 2011; 43: 882-891Crossref PubMed Scopus (209) Google Scholar and narrow band imaging (NBI)2Sharma P. Bansal A. Mathur S. et al.The utility of a novel narrow band imaging endoscopy system in patients with Barrett's esophagus.Gastrointest Endosc. 2006; 64: 167-175Abstract Full Text Full Text PDF PubMed Scopus (340) Google Scholar have been used to investigate vascular changes as hallmarks of early cancer in the gastrointestinal tract. However, the limited frame rate and field of view make confocal laser endomicroscopy imaging sensitive to motion artifacts, whereas NBI has limited resolution and visualizes only the surface vascular pattern. Endoscopic optical coherence tomography (OCT) enables high-speed volumetric imaging of subsurface features at near-microscopic resolution,3Vakoc B.J. Shishko M. Yun S.H. et al.Comprehensive esophageal microscopy by using optical frequency-domain imaging (with video).Gastrointest Endosc. 2007; 65: 898-905Abstract Full Text Full Text PDF PubMed Scopus (152) Google Scholar, 4Adler D.C. Chen Y. Huber R. et al.Three-dimensional endomicroscopy using optical coherence tomography.Nature Photonics. 2007; 1: 709-716Crossref Scopus (281) Google Scholar and can image microvasculature without exogenous contrast agents,5Yang V.X. Tang S.J. Gordon M.L. et al.Endoscopic Doppler optical coherence tomography in the human GI tract: initial experience.Gastrointest Endosc. 2005; 61: 879-890Abstract Full Text Full Text PDF PubMed Scopus (112) Google Scholar such as fluorescein, which obliterates the image in areas of bleeding, or after biopsies and resections. OCT has been used for visualizing microvasculature in small animal models6Vakoc B.J. Lanning R.M. Tyrrell J.A. et al.Three-dimensional microscopy of the tumor microenvironment in vivo using optical frequency domain imaging.Nat Med. 2009; 15: 1219-1223Crossref PubMed Scopus (611) Google Scholar and larger vasculature in swine3Vakoc B.J. Shishko M. Yun S.H. et al.Comprehensive esophageal microscopy by using optical frequency-domain imaging (with video).Gastrointest Endosc. 2007; 65: 898-905Abstract Full Text Full Text PDF PubMed Scopus (152) Google Scholar; however, the speed, resolution, and stability of previous systems were not sufficient for 3-dimenstional visualization of microvasculature in endoscopic clinical applications.5Yang V.X. Tang S.J. Gordon M.L. et al.Endoscopic Doppler optical coherence tomography in the human GI tract: initial experience.Gastrointest Endosc. 2005; 61: 879-890Abstract Full Text Full Text PDF PubMed Scopus (112) Google Scholar Herein, we have presented an ultra–high-speed endoscopic OCT technology that achieves >10 times faster imaging speed than commercial systems and high frame-to-frame stability, enabling OCT angiography in the human gastrointestinal tract. Endoscopic OCT angiography of normal esophagus, nondysplastic Barrett's esophagus (BE) and normal rectoanal junction are demonstrated. An endoscopic OCT system with a 600 kHz7Tsai T.H. Ahsen O.O. Lee H.C. et al.Ultrahigh speed endoscopic swept source optical coherence tomography using a VCSEL light source and micromotor catheter.Proc. SPIE 8927, Endoscopic Microscopy IX; and Optical Techniques in Pulmonary Medicine. 2014; 89270T: 1-6Google Scholar axial scan rate and a micromotor catheter were used to acquire circumferential, cross-sectional images at 400 frames per second. The combination of high axial scan rate and rotary speed provides densely sampled datasets with minimal motion artifacts, essential for performing endoscopic OCT angiography. Total image acquisition time was 8 seconds for each dataset, covering an area >100 mm2. The microvasculature contrast was generated by calculating the intensity decorrelation between sequentially acquired images at a given voxel.8Jonathan E. Enfield J. Leahy M.J. Correlation mapping method for generating microcirculation morphology from optical coherence tomography (OCT) intensity images.J Biophotonics. 2011; 4: 583-587Crossref PubMed Scopus (75) Google Scholar Decorrelation in the OCT signal intensity is caused by erythrocytes moving in the cross-sectional OCT image plane at a particular voxel. Voxels with high-intensity variation yield higher decorrelation and are associated with flowing erythrocytes. A distal micromotor was used to rotate a reflecting micromirror. The OCT beam was reflected and focused outside of the catheter (Video 1). By pulling back the imaging assembly, a helical OCT scan pattern was performed. Cross-sectional frames can be unwrapped to visualize different tissue orthoplanes. Microvasculature can be visualized without exogenous contrast by detecting the intensity decorrelation generated by moving erythrocytes. The endoscopic OCT structural images of the normal esophagus show uniform en face features in the lamina propria (LP) layer and well-defined layered architecture, and corresponding OCT angiograms show 3-dimenstional microvasculature (Video 2). Vascular features are difficult to identify using structural images (Figure 1A, B). Endoscopic OCT angiography generates microvascular contrast, enabling visualization of the vessel network (Figure 1C). The cross-sectional OCT angiogram shows clear vascular features in the LP layer. High signal in the submucosa layer is due to the OCT beam diverging away from focal plane, so the spot size becomes too large to resolve individual vessels (Figure 1D). The endoscopic OCT images of a normal recto-anal junction show the dentate line separating rectum (columnar) and anal verge (squamous), delineated based on the subsurface structural features (Figure 1E). A corresponding OCT angiogram (Figure 1F) is generated from the same depth. A honeycomb-like vascular network around the crypts can be visualized on the rectum side, whereas little angiographic signal observed on the anal canal side, consistent with the structural differences between columnar and squamous epithelium. Endoscopic OCT angiography was also performed in a patient with nondysplastic BE (Video 2; Figure 2A). The en face intensity image at a depth corresponding to the LP layer shows the squamocolumnar junction can be delineated based on different structural features (Figure 2B). The left region exhibits atypical glandular structures consistent with BE. The enlarged view shows clear demarcation between normal (right) and BE (left) regions (Figure 2C). The cross-sectional OCT image across the squamocolumnar junction shows BE mucosa adjacent to squamous mucosa, exhibiting glandular structure without significant distortion of the layered architecture. Histology (Figure 2D) from the imaged region confirmed nondysplastic BE. Figure 2E, F shows en face endoscopic OCT angiograms at depths of the epithelium and LP layers, respectively. In Figure 2E, a more prominent vascular network is present in the BE region, consistent with the surface vascular pattern typically observed in NBI. The vasculature along the squamocolumnar junction is denser than other regions, which may be a marker of disease progression. These results demonstrate that endoscopic OCT angiography can image the subsurface vascular pattern in BE and may provide valuable information for identification of premalignancy. Endoscopic OCT angiography enables visualization of 3-dimenstional microvasculature in tissue without requiring exogenous contrast, augmenting the diagnostic capability of endoscopic OCT. The ability to visualize subsurface vasculature and structure is a unique feature of endoscopic OCT compared with confocal laser endomicroscopy and NBI, which may improve detection of premalignant diseases in the gastrointestinal tract. Furthermore, this capability may be beneficial for investigating other vascular diseases such as radiation proctitis, gastric antral vascular ectasia, and ischemic colitis, as well as tumor-associated angiogenesis. The authors gratefully acknowledge WooJhon Choi for suggesting angiographic imaging as well as Jonathan J. Liu and Chen D. Lu at MIT for helpful technical assistance and discussions. We also thank James Jiang, Jens Peupelmann, Peter J.S. Heim, Scott Jobling, Pak Cho, Changyi Lin, Alan Donaldson, John Hryniewicz, and Anjul Davis at Thorlabs, Inc. for technical support in the development of the high speed light source and OCT system. eyJraWQiOiI4ZjUxYWNhY2IzYjhiNjNlNzFlYmIzYWFmYTU5NmZmYyIsImFsZyI6IlJTMjU2In0.eyJzdWIiOiI3ODY1YjBhMDkyNmZkZDZhMjIwZGQ1ZDJiYzc5YTM4YSIsImtpZCI6IjhmNTFhY2FjYjNiOGI2M2U3MWViYjNhYWZhNTk2ZmZjIiwiZXhwIjoxNzA4MjE2NzEyfQ.PZUyeLH_BnDkiyKe9uX1Yyex2G2puHqtr1hAbc1AvogQg8Q0SalaF1cLFvjsG-H4f4OSk885fc9vk6GtSjsqUVcBl0QjgZucMl1uwcTfJqxqT8_zYAW3OKXvyNgPT1VeDyQZCfmiz9IkC4s7FBAC_tob-fev_F5DLeLaIqnNzVvZsAvz7mwwiSmBUM65jmW-oc7hf4z_WV2gReoUtJbZD8ROcCISJHg7UnVrn0o1u7vIfXA1Mo7eJNbUp4_OliR2GjrJ4Mwhq9UnNUVgBdE6jy6l0tJH7Tqpv_Ih12ihON9Q2BJvHxpw6YvcjpnGyQ1CuBDKDMQFgZeY8hsnokahkg Download .mp4 (30.81 MB) Help with .mp4 files Video 1eyJraWQiOiI4ZjUxYWNhY2IzYjhiNjNlNzFlYmIzYWFmYTU5NmZmYyIsImFsZyI6IlJTMjU2In0.eyJzdWIiOiI1NzE4ZTg1NTExOTZmODM2NjgzNmY1OGY1ZDkxZmJlYiIsImtpZCI6IjhmNTFhY2FjYjNiOGI2M2U3MWViYjNhYWZhNTk2ZmZjIiwiZXhwIjoxNzA4MjE2NzEyfQ.gUfEb4YtdPfWiMuwQ_flerjC4TUrA4oqO6QNmkn9MWfjScXRwZ3QXTEvaIZbHIw0C7Y9veoxoefbbagjUgOgTzqT3CUUndxWhFeRCjDSr3SJNQGmTf9Sz5R8w3RrW2tWtWHdsHQLCe1Bdi5W35SmWynmoxn4FnXcRNRJwIM64KORiSn3R5NwuldBbIsFsA_H6ZBPkg6evrIH4iCFXWUiETtkeA9GQ_SgbG8Epwfbs3M53zBoGptLlc8lut1s2OF9zeq4YGk91R5_xqGuKlAThaB9rHbx7p0q5Mw1kCm-SxFeh7MlqS1ihGqgG-dO4eXJA8HJX_vuqPTPpzB3bf_5cw Download .mp4 (31.61 MB) Help with .mp4 files Video 2
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