Optical coherence tomography in the gastrointestinal tract

Differential diagnosis of acute and chronic colitis in mice by optical coherence tomography

BACKGROUND

The differential diagnosis of acute and chronic colitis remains a common clinical problem. Optical coherence tomography (OCT) is a non-invasive, high-resolution imaging technique that can be used to measure morphological changes in the intestinal wall and estimate intestinal inflammation. We aimed to conduct an ex vivo experiment on a mouse model investigate the value of OCT as a tool for the differential diagnosis of acute and chronic colitis.

METHODS

Mice were administered dextran sulfate sodium salt (DSS) to construct acute and chronic colitis models. Acutely- and chronically-affected intestinal walls were scanned by OCT, and then the scanned colonic tissue samples were stained with hematoxylin and eosin (HE). Structural and morphological changes indicating inflammation in the intestinal wall were evaluated in the HE sections and OCT images using different parameters. The parameters were used in one-way analysis of variance (ANOVA) to screen for a differential diagnosis of acute or chronic colitis.

RESULTS

For the HE sections, the angle of the mucosal folds, length of the basilar part, and submucosal height and area were statistically significant parameters in the comparisons between the mice with acute colitis and the control-group mice (P<0.05). In the comparisons between chronic colitis mice and control-group mice, the angle of the mucosal folds, length of the basilar part, submucosal height and area, muscularis thickness, submucosal height + muscularis thickness, and mucosal thickness were statistically significant parameters (P<0.05). Finally, in the comparisons between acute colitis mice and those with chronic colitis, the angle of the mucosal folds, submucosal height and area, muscularis thickness, submucosal height + muscularis thickness, and mucosal thickness were statistically significant parameters (P<0.05). For the OCT images, only the length of the basilar part and submucosal height + muscularis thickness were statistically significant parameters between the acute colitis mice and control-group mice (P<0.05). The length of the basilar part and submucosal height + muscularis thickness were statistically significant between chronic colitis mice and control-group mice (P<0.05). In the comparisons between acute colitis mice and those with chronic colitis, only submucosal height + muscularis thickness was a statistically significant parameter (P<0.05).

CONCLUSIONS

Certain intestinal wall parameters in OCT can be used to make a differential diagnosis between acute and chronic colitis possible. This study contributes to constructing a potential diagnostic system for evaluating colorectal inflammation using OCT.

Three-dimensional, distendable bladder phantom for optical coherence tomography and white light cystoscopy

We describe a combination of fabrication techniques and a general process to construct a three-dimensional (3-D) phantom that mimics the size, macroscale structure, microscale surface topology, subsurface microstructure, optical properties, and functional characteristics of a cancerous bladder. The phantom also includes features that are recognizable in white light (i.e., the visual appearance of blood vessels), making it suitable to emulate the bladder for emerging white light+optical coherence tomography (OCT) cystoscopies and other endoscopic procedures of large, irregularly shaped organs. The fabrication process has broad applicability and can be generalized to OCT phantoms for other tissue types or phantoms for other imaging modalities. To this end, we also enumerate the nuances of applying known fabrication techniques (e.g., spin coating) to contexts (e.g., nonplanar, 3-D shapes) that are essential to establish their generalizability and limitations. We anticipate that this phantom will be immediately useful to evaluate innovative OCT systems and software being developed for longitudinal bladder surveillance and early cancer detection.

Endoscopic Optical Coherence Tomography (OCT): Advances in Gastrointestinal Imaging

In the rapidly evolving field of endoscopic gastrointestinal imaging, Optical Coherence Tomography (OCT) has found many diverse applications. We present the current status of OCT and its practical applications in imaging normal and abnormal mucosa in the esophagus, stomach, small and large intestines, and biliary and pancreatic ducts. We highlight technical aspects and principles of imaging, assess published data, and suggest future directions for OCT-guided evaluation and therapy.

In vivo detection of Hirschsprung's disease by optical coherence tomography in rats

Hirschsprung's disease (HSCR) is a developmental intestinal obstruction, which is often diagnosed with a repeated biopsy. Optical coherence tomography (OCT) is a noninvasive, real-time imaging modality. This study aims to investigate the feasibility of diagnosis of HSCR, the targeted biopsies of suspicious tissues and the location of operative treatment using OCT. An HSCR Sprague-Dawley (SD) rat model (benzalkonium chloride-treated (BAC-treated)) was used. Colon tissues with BAC-treated and without BAC-treated were imaged using OCT. To establish OCT criteria for identification of HSCR, OCT images were compared with corresponding histology images and muscle layer thickness was measured. Furthermore, attenuation coefficients of OCT signals were calculated to illustrate the differences between tissues with BAC-treated and without BAC-treated. Our results show that OCT images of colon tissues with HSCR are well correlated with histology images. In comparison with a muscle layer without HSCR, the thickness of muscle layer with HSCR is increased significantly. The muscle layer in colon tissues with HSCR for 6 weeks had a higher attenuation coefficient than those without HSCR. However, the attenuation coefficient of those with HSCR for 3 weeks had no obvious change. In conclusion, the study demonstrates for the first time that OCT has the potential for diagnosis, biopsy and location of HSCR in vivo.

Optical coherence tomography and Doppler optical coherence tomography in the gastrointestinal tract

Optical coherence tomography (OCT) is a noninvasive, high-resolution, high-potential imaging method that has recently been introduced into medical investigations. A growing number of studies have used this technique in the field of gastroenterology in order to assist classical analyses. Lately, 3D-imaging and Doppler capabilities have been developed in different configurations, which make this type of investigation more attractive. This paper reviews the principles and characteristics of OCT and Doppler-OCT in connection with analyses of the detection of normal and pathological structures, and with the possibility to investigate angiogenesis in the gastrointestinal tract.

Quantitative tool for rapid disease mapping using optical coherence tomography images of azoxymethane-treated mouse colon

Optical coherence tomography (OCT) can provide new insight into disease progression and therapy by enabling nondestructive, serial imaging of in vivo cancer models. In previous studies, we have shown the utility of endoscopic OCT for identifying adenomas in the azoxymethane-treated mouse model of colorectal cancer and tracking disease progression over time. Because of improved imaging speed made possible through Fourier domain imaging, three-dimensional imaging of the entire mouse colon is possible. Increased amounts of data can facilitate more accurate classification of tissue but require more time on the part of the researcher to sift through and identify relevant data. We present quantitative software for automatically identifying potentially diseased areas that can be used to create a two-dimensional "disease map" from a three-dimensional Fourier domain OCT data set. In addition to sensing inherent changes in tissue that occur during disease development, the algorithm is sensitive to exogeneous highly scattering gold nanoshells that can be targeted to disease biomarkers. The results of the algorithm were compared to histological diagnosis. The algorithm was then used to assess the ability of gold nanoshells targeted to epidermal growth factor receptor in vivo to enable functional OCT imaging.

Optical coherence tomography for bile and pancreatic duct imaging

Optical coherence tomography (OCT) is an optical imaging modality introduced in 1991 that performs high-resolution, cross-sectional, subsurface tomographic imaging of the microstructure in materials and biologic systems by measuring backscattered or backreflected infrared light. OCT has been used for biomedical applications where many factors affect the feasibility and effectiveness of any imaging technique. The highly scattering and absorbing living tissues greatly limit the application of optical imaging modalities. In the last decade, OCT technology has evolved from an experimental laboratory tool to a new diagnostic imaging modality with a wide spectrum of clinical applications in medical practice, including the gastrointestinal (GI) tract and pancreaticobiliary ductal system.

Optical coherence tomography in detection of dysplasia and cancer of the gastrointestinal tract and bilio-pancreatic ductal system

Optical coherence tomography (OCT) is an optical imaging modality that performs high-resolution, cross-sectional, subsurface tomographic imaging of the microstructure of tissues. The physical principle of OCT is similar to that of B-mode ultrasound imaging, except that it uses infrared light waves rather than acoustic waves. The in vivo resolution is 10-25 times better (about 10 μm) than with high-frequency ultrasound imaging, but the depth of penetration is limited to 1-3 mm, depending upon tissue structure, depth of focus of the probe used, and pressure applied to the tissue surface. In the last decade, OCT technology has evolved from an experimental laboratory tool to a new diagnostic imaging modality with a wide spectrum of clinical applications in medical practice, including the gastrointestinal (GI) tract and pancreatic-biliary ductal system. OCT imaging from the GI tract can be done in humans by using narrow-diameter, catheter-based probes that can be inserted through the accessory channel of either a conventional front-view endoscope, for investigating the epithelial structure of the GI tract, or a side-view endoscope, inside a standard transparent ERCP catheter, for investigating the pancreatico-biliary ductal system. Esophagus and the esophago-gastric junction has been the most widely investigated organ so far; more recently, also duodenum, colon and pancreatico-biliary ductal system have been extensively investigated. OCT imaging of the gastro-intestinal wall structure is characterized by a multiple-layer architecture that permits an accurate evaluation of the mucosa, lamina propria, muscularis mucosae, and part of the submucosa. The technique may be, therefore, used to identify pre-neoplastic conditions of the GI tract, such as Barrett's epithelium and dysplasia, and evaluate the depth of penetration of early-stage neoplastic lesions. OCT imaging of the pancreatic and biliary ductal system could improve the diagnostic accuracy for ductal epithelial changes and the differential diagnosis between neoplastic and non-neoplastic lesions.

Optical coherence tomography in inflammatory bowel disease: prospective evaluation of 35 patients

PURPOSE

Optical coherence tomography is a technique using infrared light in tissues of the gastrointestinal tract and human colon affected by inflammatory diseases. We evaluated whether there are specific patterns of optical coherence tomography for inflammatory bowel disease and compared the technique performance to the histology.

METHODS

Optical coherence tomography was performed in 35 patients (18 men; 31 ulcerative colitis, 4 Crohn's disease). The images were obtained from affected and normal colon at endoscopy. Two biopsies of the sites visualized were taken. Two endoscopists scored the images, and two pathologists, blind to the endoscopy and optical coherence tomography, performed the histologic evaluation.

RESULTS

Three optical coherence tomography patterns were identified: 1) mucosal backscattering alteration, 2) delimited dark areas, and 3) layered colonic wall. Compared with the histology, mucosal backscattering alteration was the most effective in recognizing the disease in patients (P = 0.007 in colon segments affected, and P < 0.001 in normal segments). The sensitivity and specificity have been 100 and 78 percent, respectively.

CONCLUSIONS

The in vivo optical coherence tomography correctly detected inflammatory bowel disease features in affected and apparently normal colon, and allowed to discriminate patterns for active ulcerative colitis and Crohn's disease.

Optical coherence tomography of the cochlea in the porcine model

OBJECTIVES/HYPOTHESIS

To demonstrate the feasibility of optical coherence tomography in microstructural imaging of the porcine cochlea.

STUDY DESIGN

Ex vivo, porcine model.

METHODS

Optical coherence tomographic images of the porcine cochlea were obtained by thinning the bone from the basal turn of the cochlea leaving the endosteum intact. The images were compared with the corresponding histological sections.

RESULTS

In the areas of thinned bone, images were obtained of the stria vascularis, Reissner's membrane, basilar membrane, tectorial membrane, scala media, scala tympani, and scala vestibuli. The bone was too thick for adequate light penetration in the areas where it was not thinned. Good histological correlation was obtained.

CONCLUSIONS

Cochlear and vestibular microanatomic structures of the pig cochlea were clearly identified with histological confirmation, suggesting the potential application of this noninvasive imaging modality for in vivo imaging of the human cochlea.

Detailed comparison between endocytoscopy and horizontal histology of an esophageal intraepithelial squamous cell carcinoma

Endocytoscopy allows the real-time microscopic observation of living cells. Unlike the cross-sectional images obtained by conventional histology, endocytoscopy provides cellular images in a plane parallel to the surface of the mucosa. However, there is little knowledge about the endocytoscopic diagnosis of carcinomas. Using a specimen obtained by the endoscopic submucosal dissection of an intraepithelial esophageal squamous cell carcinoma, a detailed comparison between endocytoscopic and horizontal histological images was made, revealing the similarity between the images. Sharp lateral borders between atypical and normal epithelium and differences in cellularity and the sizes and shapes of the nuclei were clearly identified by endocytoscopy. Further horizontal histological investigations of this case also showed the variety of endocytoscopic images in non-cancerous and cancerous epithelia.

Preliminary evaluation of noninvasive microscopic imaging techniques for the study of vocal fold development

Understanding pediatric voice development and laryngeal pathology is predicated on a detailed knowledge of the microanatomy of the layered structure of the vocal fold. Our current knowledge of this microanatomy and its temporal evolution is limited by the lack of pediatric specimen availability. By providing the capability to image pediatric vocal folds in vivo, a noninvasive microscopy technique could greatly expand the existing database of pediatric laryngeal microanatomy and could furthermore make longitudinal studies possible. A variety of natural-contrast optical imaging technologies, including optical frequency domain imaging (OFDI), full-field optical coherence microscopy (FF-OCM), and spectrally encoded confocal microscopy (SECM) have been recently developed for noninvasive diagnosis in adult patients. In this paper, we demonstrate the potential of these three techniques for laryngeal investigation by obtaining images of excised porcine vocal fold samples. In our study, OFDI allowed visualization of the vocal fold architecture deep within the tissue, from the superficial mucosa to the vocalis muscle. The micron-level resolution of SECM allowed investigation of cells and extracellular matrix fibrils from the superficial mucosa to the intermediate layer of the lamina propria (LP) (350 microm penetration depth). The large field of view (up to 700 microm), penetration depth (up to 500 microm), and resolution (2x2x1microm [XxYxZ]) of FF-OCM enabled comprehensive three-dimensional evaluation of the layered structure of the LP. Our results suggest that these techniques provide important and complementary cellular and structural information, which may be useful for investigating pediatric vocal fold maturation in vivo.

Discrimination of Normal and Malignant Mucosal Tissues of the Colon by Raman Spectroscopy

OBJECTIVE

The objective of this study was to evaluate the applicability of the discrimination parameters Mahalanobis distance, spectral residuals, and limit tests, developed by this group to differentiate normal from malignant colon tissues.

BACKGROUND DATA

Colon cancers are diagnosed using fiberoptic endoscopic localization and a subsequent histopathological examination of biopsied tissue, which is highly dependent on the skill and experience of the investigator. There exists a risk of missing significant lesions, especially with carcinoma in situ lesions. Raman spectroscopy, which is sensitive to biochemical variations in the samples and amenable to multivariate statistical tools, can lead to rapid and objective detection of colon cancer.

METHODS

A total of 102 spectra from 11 normal and 11 malignant ex vivo colon tissues were recorded by conventional near infrared (NIR) Raman spectroscopy (excitation wavelength of 785 nm). Spectral data were analyzed by principal components analysis (PCA) and other discriminating parameters, namely Mahalanobis distance, spectral residuals, and a multiparametric limit test approach.

RESULTS

Mean malignant spectra exhibit relatively stronger bands, suggesting the presence of additional biomolecules such as protein (stronger amide III and I), lipids (1,100, 1,300 cm(1)), and DNA (1,340, 1,470 cm(1)) versus those seen in normal tissue. Mean normal spectra indicate the presence of disordered structures (hump at 1,247 cm(1)). Scores of factor 1 gave good discrimination, and this is further fine-tuned by employing Mahalanobis distance and spectral residuals as discriminating parameters. A limit test approach provided unambiguous objective discrimination.

CONCLUSION

This study further supports the efficacy of Raman spectroscopy, in combination with a limit test, for discrimination of normal and malignant colon tissues. The multiparametric limit test approach is user-friendly, and a clinician or minimally trained individual could directly compare the unknown spectra against the available standard sets to make the decision instantly, objectively, and unambiguously.

Technique of optical coherence tomography of the larynx during microlaryngoscopy

Optical coherence tomography (OCT) is a new, noninvasive imaging technology for the evaluation of superficial lesions. Because of a penetrating depth of a few millimeters and an ultrahigh tissue resolution, it qualifies for use in the larynx and might in the near future play an important role in the pre-, intra-, and postoperative investigation of early laryngeal cancer and its precursor lesions. Especially directed to otolaryngologists, this paper describes the technique of in vivo OCT imaging of the larynx in detail during microlaryngoscopy and supplies a number of personal hints.

Optical coherence tomography evaluation of ulcerative colitis: the patterns and the comparison with histology

HYPOTHESIS

The optical coherence tomography (OCT) is an imaging modality based on infrared light backscattering properties of tissues. OCT studies documented the disappearance of crypts and the alteration in light backscattering as features of ulcerative colitis (UC) in human colon. This technique should be more and more able to identify tissue microstructures with a resolution that is nearly that of histology (optical biopsy).

AIM

To evaluate whether there are OCT patterns specific for UC and to compare the overall technique performance with the histology.

METHODS

A total of 27 patients (20-76 yr) with UC underwent OCT imaging during a total colonoscopy. The OCT images were collected both from affected and normal sites in active UC or disease in remission. Two biopsies of the same sites were acquired. The OCT images were separately scored. Two pathologists blinded to the endoscopic and OCT patterns scored the samples.

RESULTS

Three OCT patterns were identified: the mucosal backscattering alteration (MBA), the delimited dark areas (DDA), and the layered colonic wall (LCW). In colon affected segments of active and UC in remission, these patterns showed a good correspondence with the histology. Moreover, in 14/25 (56%) normal sites above the affected segment, the OCT documented the pathological features, confirmed only in 10/14 by the histology. Thus, the assessed sensitivity and specificity of OCT in normal segments of UC patients have been 100% and 69%, respectively.

CONCLUSIONS

The in vivo OCT correctly detected disease features in endoscopically affected colon segments, but even in apparently normal segments of UC patients.

In vivo ultrahigh-resolution optical coherence tomography of mouse colon with an achromatized endoscope

Endoscopic ultrahigh-resolution optical coherence tomography (OCT) enables collection of minimally invasive cross-sectional images in vivo, which may be used to facilitate rapid development of reliable mouse models of colon disease as well as assess chemopreventive and therapeutic agents. The small physical scale of mouse colon makes light penetration less problematic than in other tissues and high resolution acutely necessary. In our 2-mm diameter endoscopic time domain OCT system, isotropic ultrahigh-resolution is supported by a center wavelength of 800 nm and full-width-at-half-maximum bandwidth of 150 nm (mode-locked titanium:sapphire laser) combined with 1:1 conjugate imaging of a small core fiber. A pair of KZFSN5/SFPL53 doublets provides excellent color correction to support wide bandwidth throughout the imaging depth. A slight deviation from normal beam exit angle suppresses collection of the strong back reflection at the exit window surface. Our system achieves axial resolution of 3.2 microm in air and 4.4-microm lateral spot diameter with 101-dB sensitivity. Microscopic features too small to see in mouse tissue with conventional resolution systems, including colonic crypts, are clearly resolved. Resolution near the cellular level is potentially capable of identifying abnormal crypt formation and dysplastic cellular organization.

Optical coherence tomography compared with histology of the main pancreatic duct structure in normal and pathological conditions: an 'ex vivo study'

BACKGROUND AND STUDY AIMS

Optical coherence tomography permits high-resolution imaging of tissue microstructures by a probe inserted into the main pancreatic duct through a standard ERCP catheter. The aim of this study was to compare optical coherence tomography images of the main pancreatic duct with histology and identify the optical coherence tomography pattern of the normal and pathological structure of the main pancreatic duct.

PATIENTS AND METHODS

Multiple sections of neoplastic and non-neoplastic segments of 10 consecutive surgical pancreatic specimens obtained from patients with pancreatic head adenocarcinoma were investigated by optical coherence tomography scanning within 1h of resection. One hundred optical coherence tomography findings were then compared with the corresponding histopathological diagnoses.

RESULTS

Main pancreatic duct wall architecture appeared at optical coherence tomography investigation as a three-layer structure with a different back-scattered signal from each layer. Optical coherence tomography imaging was concordant with histology in 81.8% and 18.75% of sections with normal tissue and chronic inflammatory changes. The K statistic between the two procedures was equal to 0.059 for non-neoplastic main pancreatic duct wall appearance. In all neoplastic sections optical coherence tomography showed a subverted layer architecture with heterogeneous back-scattering of the signal and was concordant with histology.

CONCLUSIONS

Optical coherence tomography provided images of main pancreatic duct wall structure that were concordant with histology in 100% of cases in presence of neoplastic ductal changes and did not have false-positive or negative results. Optical coherence tomography images were also concordant with histology in about 80% of cases with normal main pancreatic duct structure; however, the differential diagnosis between normal tissue and chronic pancreatitis or dysplastic changes appeared very difficult.

Optical coherence tomography of laryngeal cancer

OBJECTIVES

Optical coherence tomography (OCT) is a high-resolution optical imaging technique that produces cross-sectional images of living tissues using light in a manner similar to ultrasound. This prospective study evaluated the ability of OCT to identify the characteristics of laryngeal cancer and measure changes in the basement membrane, tissue microstructure, and the transition zone at the edge of tumors.

MATERIALS AND METHODS

One hundred thirty-three patients underwent OCT examination during surgical endoscopy of the head and neck. Twenty-two patients with laryngeal cancer or a history of laryngeal cancer were imaged with a fiberoptic OCT system. Tumor and adjacent transition zones were imaged along with uninvolved subsites. OCT images were correlated with histopathology.

RESULTS

Twenty-six OCT examinations were performed in 22 patients. Basement membrane disruption was seen in 18 subjects, all of whom had histology showing classic features of cancer. A transition zone to uninvolved epithelium at the tumor periphery was also often observed. In six studies, benign or premalignant processes were histologically confirmed. In three thin, superficial lesions, an intact basement membrane was observed. The basement membrane could not be identified in three other bulky exophytic, premalignant lesions, primarily because of increased superficial signal backscattering observed in pathologic tissues.

CONCLUSIONS

OCT clearly identifies basement membrane violation from laryngeal cancer and can identify transition zones at the cancer margin. In bulky exophytic lesions, OCT signal may not penetrate deeply enough to show the basement membrane, but for many suspicious lesions that require exclusion of cancer, OCT shows potential for assisting in diagnostic assessment.

Main pancreatic duct, common bile duct and sphincter of Oddi structure visualized by optical coherence tomography: An ex vivo study compared with histology

BACKGROUND

Optical coherence tomography has been proposed to obtain high-resolution imaging of tissue structure of GI tract. Up till now, the optical coherence tomography appearance of the common bile duct, main pancreatic duct and sphincter of Oddi wall structure has not yet been defined.

AIMS

To compare, in a prospective study, optical coherence tomography images of pancreato-biliary ductal system with histology and identify the optical coherence tomography pattern of the normal wall structure of the ducts.

METHODS

Multiple sections of non-neoplastic segments of five consecutive ex vivo human pancreatic specimens were investigated by optical coherence tomography scanning within 1h of resection. Sixty optical coherence tomography images were compared with the corresponding histological findings.

RESULTS

Optical coherence tomography appearance of normal common bile duct, main pancreatic duct and sphincter of Oddi is characterized by a differentiated three-layer architecture with a regular surface and a homogeneous back-scattered signal, corresponding to the single layer of epithelial cells, the connective-muscular layer and the muscular or acinar structure, respectively. Optical coherence tomography and histology findings were concordant in all cases.

CONCLUSIONS

Optical coherence tomography was able to provide in real-time images of wall structure of the normal common bile duct, main pancreatic duct and sphincter of Oddi that are similar to those obtained by histology. These results suggest that optical coherence tomography could enable high-resolution images to be obtained from the pancreato-biliary system during an ERCP procedure.

Emerging technologies in colorectal cancer screening

CRC is a preventable disease through early detection, yet screening rates remain low and mortality rates remain high. The discomfort associated with the preparation and performance of some of the currently available screening modalities and the lack of public awareness about CRC and screening procedures likely account for low rates of screening. CT colonography and stool DNA testing are new promising screening technologies that are less invasive, accurate, and suitable for the public more than the current screening procedures. Before both tests can be promoted for population-based screening programs, several issues that have been detailed in this article must be addressed further, including technical improvements for improving accuracy, development of virtual preparation, test availability, patient and provider acceptability and cost-effectiveness for CTC, and identifying the optimal combination of molecular targets for stool DNA testing. The year 2005 will tell us if the ideal technology from the public health point of view was achieved. A skill-independent, anesthesia-free, self-propelling, self-navigating miniaturized endoscopic device that may move along the entire length of the colon may change the natural history of CRC. We should aim to achieve a new definition of CRC--a rare disease occurring in a subset of the population who has not been screened for the disease.

Measurement of morphologic changes induced by trauma with the use of coherence tomography in porcine vocal cords

BACKGROUND AND OBJECTIVE

To evaluate the ability of optical coherence tomography (OCT) (a noncontact, high-resolution imaging technique that generates detailed cross-sectional images of tissue structure) to image and document acute response to trauma in the larynx.

MATERIALS AND METHODS

Porcine larynges were dissected to expose the vocal cords. Vocal cords were imaged with 1310 nanometer (nm) light source with a bandwidth of 75 nm at 1 frame/second (s). Vocal cord injuries were simulated by applying topical phenolic acid, injecting titanium dioxide into the submucosa, and carbon dioxide laser irradiation.

RESULTS

The epithelium, basement membrane, and lamina propria were clearly delineated, and the effect of each intervention could be monitored as lesions progressed. The OCT image corresponded closely with histology.

CONCLUSION

OCT is a powerful imaging tool with the potential for use in real time and has potential for multiple clinical applications in the larynx.

Optical coherence tomography to detect epithelial lesions of the main pancreatic duct: an Ex Vivo study

BACKGROUND

Optical coherence tomography (OCT) permits high-resolution, real-time, infrared-generated imaging of tissue microstructures by a probe inserted through the endoscope operative channel. Resolution is approximately 10 microm and the penetration depth of the near-focus probe is about 1 mm. The probe can be inserted into the main pancreatic duct (MPD) through a standard endoscopic retrograde cholangiopancreatography catheter.

AIMS AND METHODS

To assess the ability of OCT to identify the structure of the MPD, to distinguish normal and malignant MPD epithelium, and to assess intra- and interobserver reproducibility of OCT images. Multiple sections of neoplastic and non-neoplastic segments of 10 consecutive surgical pancreatic specimens were obtained from patients with pancreatic head adenocarcinoma who had undergone Whipple resection, and repeated OCT radial and longitudinal scanning was done within 1 h of resection and before pathological examination. We compared 249 good-quality images with 100 histopathological sections.

RESULTS

OCT recognized a definite, different pattern in 82.9% of tumor-free and in 97.6% of tumor-involved specimens; sensitivity and specificity for discrimination between adenocarcinoma and normal tissue were 78.6% and 88.9%, respectively. Inflammatory and dysplastic changes of the MPD showed an OCT pattern similar to that of the normal tissue in 53.3% of images. Overall, intraobserver reproducibility ranged from 85.1% to 100% and interobserver reproducibility ranged from 69.9% to 100% and from 89.7% to 100% for tumor-free and tumor-involved segments, respectively.

CONCLUSIONS

OCT identified the neoplastic and non-neoplastic MPD layer structure and appeared to be a reproducible technique. In non-neoplastic conditions, OCT appeared unable to differentiate between normal and abnormal tissues in about half of the cases.

In vivo colonoscopic optical coherence tomography for transmural inflammation in inflammatory bowel disease

BACKGROUND & AIMS

Transmural inflammation, a distinguishing feature of Crohn's disease (CD), cannot be assessed by conventional colonoscopy with mucosal biopsy. Our previous ex vivo study of histology-correlated optical coherence tomography (OCT) imaging on colectomy specimens of CD and ulcerative colitis (UC) showed that disruption of the layered structure of colon wall on OCT is an accurate marker for transmural inflammation of CD. We performed an in vivo colonoscopic OCT in patients with a clinical diagnosis of CD or UC using the previously established, histology-correlated OCT imaging criterion.

METHODS

OCT was performed in 40 patients with CD (309 images) and 30 patients with UC (292 images). Corresponding endoscopic features of mucosal inflammation were documented. Two gastroenterologists blinded to endoscopic and clinical data scored the OCT images independently to assess the feature of disrupted layered structure.

RESULTS

Thirty-six CD patients (90.0%) had disrupted layered structure, whereas 5 UC patients (16.7%) had disrupted layered structure (P < .001). Using the clinical diagnosis of CD or UC as the gold standard, the disrupted layered structure on OCT indicative of transmural inflammation had a diagnostic sensitivity and specificity of 90.0% (95% CI: 78.0%, 96.5%) and 83.3% (95% CI: 67.3%, 93.3%) for CD, respectively. The kappa coefficient in the interpretation of OCT images was 0.80 (95% CI: 0.75, 0.86, P < .001).

CONCLUSIONS

In vivo colonoscopic OCT is feasible and accurate to detect disrupted layered structure of the colon wall indicative of transmural inflammation, providing a valuable tool to distinguish CD from UC.