Visualization of subsurface blood vessels by color Doppler optical coherence tomography in rats: before and after hemostatic therapy

Evaluation of segmentation algorithms for optical coherence tomography images of ovarian tissue

Ovarian cancer has the lowest survival rate among all gynecologic cancers predominantly due to late diagnosis. Early detection of ovarian cancer can increase 5-year survival rates from 40% up to 92%, yet no reliable early detection techniques exist. Optical coherence tomography (OCT) is an emerging technique that provides depth-resolved, high-resolution images of biological tissue in real-time and demonstrates great potential for imaging of ovarian tissue. Mouse models are crucial to quantitatively assess the diagnostic potential of OCT for ovarian cancer imaging; however, due to small organ size, the ovaries must first be separated from the image background using the process of segmentation. Manual segmentation is time-intensive, as OCT yields three-dimensional data. Furthermore, speckle noise complicates OCT images, frustrating many processing techniques. While much work has investigated noise-reduction and automated segmentation for retinal OCT imaging, little has considered the application to the ovaries, which exhibit higher variance and inhomogeneity than the retina. To address these challenges, we evaluate a set of algorithms to segment OCT images of mouse ovaries. We examine five preprocessing techniques and seven segmentation algorithms. While all preprocessing methods improve segmentation, Gaussian filtering is most effective, showing an improvement of 32 % ± 1.2 % . Of the segmentation algorithms, active contours performs best, segmenting with an accuracy of 94.8 % ± 1.2 % compared with manual segmentation. Even so, further optimization could lead to maximizing the performance for segmenting OCT images of the ovaries.

Can we predict necrosis intra-operatively? Real-time optical quantitative perfusion imaging in surgery: study protocol for a prospective, observational, in vivo pilot study

BACKGROUND

Compromised perfusion as a result of surgical intervention causes a reduction of oxygen and nutrients in tissue and therefore decreased tissue vitality. Quantitative imaging of tissue perfusion during reconstructive surgery, therefore, may reduce the incidence of complications. Non-invasive optical techniques allow real-time tissue imaging, with high resolution and high contrast. The objectives of this study are, first, to assess the feasibility and accuracy of optical coherence tomography (OCT), sidestream darkfield microscopy (SDF), laser speckle contrast imaging (LSCI), and fluorescence imaging (FI) for quantitative perfusion imaging and, second, to identify/search for criteria that enable risk prediction of necrosis during gastric tube and free flap reconstruction.

METHODS

This prospective, multicenter, observational in vivo pilot study will assess tissue perfusion using four optical technologies: OCT, SDF, LSCI, and FI in 40 patients: 20 patients who will undergo gastric tube reconstruction after esophagectomy and 20 patients who will undergo free flap surgery. Intra-operative images of gastric perfusion will be obtained directly after reconstruction at four perfusion areas. Feasibility of perfusion imaging will be analyzed per technique. Quantitative parameters directly related to perfusion will be scored per perfusion area, and differences between biologically good versus reduced perfusion will be tested statistically. Patient outcome will be correlated to images and perfusion parameters. Differences in perfusion parameters before and after a bolus of ephedrine will be tested for significance.

DISCUSSION

This study will identify quantitative perfusion-related parameters for an objective assessment of tissue perfusion during surgery. This will likely allow early risk stratification of necrosis development, which will aid in achieving a reduction of complications in gastric tube reconstruction and free flap transplantation.

TRIAL REGISTRATION

Clinicaltrials.gov registration number NCT02902549. Dutch Central Committee on Research Involving Human Subjects registration number NL52377.018.15.

Optical Biopsy of Lymph Node Morphology using Optical Coherence Tomography

Optical diagnostic imaging techniques are increasingly being used in the clinical environment, allowing for improved screening and diagnosis while minimizing the number of invasive procedures. Diffuse optical tomography, for example, is capable of whole-breast imaging and is being developed as an alternative to traditional X-ray mammography. While this may eventually be a very effective screening method, other optical techniques are better suited for imaging on the cellular and molecular scale. Optical Coherence Tomography (OCT), for instance, is capable of high-resolution cross-sectional imaging of tissue morphology. In a manner analogous to ultrasound imaging except using optics, pulses of near-infrared light are sent into the tissue while coherence-gated reflections are measured interferometrically to form a cross-sectional image of tissue. In this paper we apply OCT techniques for the high-resolution three-dimensional visualization of lymph node morphology. We present the first reported OCT images showing detailed morphological structure and corresponding histological features of lymph nodes from a carcinogen-induced rat mammary tumor model, as well as from a human lymph node containing late stage metastatic disease. The results illustrate the potential for OCT to visualize detailed lymph node structures on the scale of micrometastases and the potential for the detection of metastatic nodal disease intraoperatively.

Imaging of skin microvessels with optical coherence tomography: potential uses in port wine stains

The knowledge of vascular structures of port wine stains (PWSs) may be useful to select treatment doses and improve therapeutic efficacy. Biopsies are impractical to implement, therefore, it is necessary to develop non-invasive techniques for morphological evaluation. This study aimed to evaluate the application of a novel optical coherence tomography (OCT) system to characterize the vascular structures of PWSs. First, OCT images were obtained from the skin of healthy rabbit ears and compared with the histopathological images. Second, OCT was used to document the differences between PWS lesions and contralateral normal skin; the size and depth of the vascular structures of two clinical types of PWSs were measured and statistically analyzed. The dermal blood vessels of healthy rabbit ears were clearly distinguished from other tissue. There was no statistical difference between the vascular diameter or depth measured by OCT images and histopathological sections (P>0.05). The OCT images of the PWSs could be distinguished from normal skin. There was no statistical difference in the depth of vessels between the purple-type and the proliferative-type PWSs (P>0.05), while there was statistical difference in the diameter of vessels between them (P<0.01). Therefore, OCT is a promising, real-time, in vivo and non-invasive tool with which to characterize the vascular structures of PWSs.

New diagnostic imaging technologies in nonvariceal upper gastrointestinal bleeding

This article covers new endoscopic imaging modalities in nonvariceal upper gastrointestinal bleeding, such as Doppler ultrasound probe technology, endoscopic ultrasonography, color Doppler optical coherence tomography, and magnification endoscopy. A more in-depth discussion of these modalities and the published evidence supporting their use are included. Furthermore, the shift in focus from identification of conventional visual surface stigmata of recent hemorrhage to an assessment and understanding of subsurface blood flow as it relates to the bleeding lesion is discussed.

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.

Statistical properties of phase-decorrelation in phase-resolved Doppler optical coherence tomography

Decorrelation noise limits the ability of phase-resolved Doppler optical coherence tomography systems to detect smaller vessels exhibiting slower flow velocities, which limits the utility of the technique in many clinical and biological settings. An understanding of the statistical properties of decorrelation noise can aid in the optimal design of these systems and guide the development of noise mitigating strategies. In this work, the statistical properties of decorrelation noise are derived from the underlying statistics of the coherent imaging system and validated through comparison with empirical results and Monte Carlo modeling. Expressions for the noise distribution and the noise variance as a function of relevant imaging system parameters are given, and the implications of these results on both system and algorithm design are discussed.

Gastrointestinal optical coherence tomography: clinical applications, limitations, and research priorities

Optical coherence tomography provides the highest resolution available of any of the technologies currently used in endoscopic imaging. There are several potential clinical applications for optical coherence tomography, particularly with precancerous conditions of the gastrointestinal tract. The future of optical coherence tomography is discussed.

Best candidates for capsule endoscopy for obscure gastrointestinal bleeding

BACKGROUND AND AIM

Capsule endoscopy (CE) has an important role in the diagnosis of patients with obscure gastrointestinal bleeding. However, there was still controversy regarding the best candidates for CE. The present retrospective study aimed to access the best candidates for CE.

METHODS

There were 91 consecutive patients referred to the present study for 94 CE examinations from May 2002 to January 2005. They were divided into two groups (41 with active bleeding, and 50 with previous bleeding).

RESULTS

The CE findings were positive in 74.7%, suspicious in 11% of cases and negative in 14.3% of cases, respectively. The positive and suspected positive yield of CE were 75.6% and 19.5% in the active bleeding group, 74% and 4% in the previous bleeding group (P = 0.01), 75.7% and 21.6% in the overt bleeding group, 75% and 0% in the occult bleeding group (P = 0.206), 89.7% and 3.4% in patients who bled 2 weeks previously, 52.38% and 4.76% in patients who bled >2 weeks previously (P = 0.003), 75.6% and 19.5% in active bleeding group, 89.7% and 3.4% in patients who bled 2 weeks ago (P = 0.128).

CONCLUSIONS

The best candidates for the procedure are those with active bleeding, or active bleeding in the previous 2 weeks.

Utility of capsule endoscopy for the classification of Crohn's disease: a multicenter study in Korea

Capsule endoscopy can detect lesions associated with Crohn's disease in the small bowel that go unrecognized by conventional radiologic imaging. The aim of this study was to assess the value of capsule endoscopy in the classification of patients with Crohn's disease. This study was carried out on 52 patients with known Crohn's disease. Small bowel follow-through findings were compared with capsule endoscopic findings. All patients were classified according to the extent of the disease: small bowel-colon type, small bowel type, or colon type. Seventeen patients who were reported as being normal showed evidence of small bowel Crohn's disease according to capsule endoscopy. Differences were observed between the small bowel follow-through and the capsule endoscopy classification (kappa=0.54). Treatment was changed based on the results of wireless capsule endoscopy in 15 patients.

Comprehensive esophageal microscopy by using optical frequency-domain imaging (with video)

BACKGROUND

Optical coherence tomography (OCT) has been used for high-resolution endoscopic imaging and diagnosis of specialized intestinal metaplasia, dysplasia, and intramucosal carcinoma of the esophagus. However, the relatively slow image-acquisition rate of the present OCT systems inhibits wide-field imaging and limits the clinical utility of OCT for diagnostic imaging in patients with Barrett's esophagus.

OBJECTIVE

This study describes a new optical imaging technology, optical frequency-domain imaging (OFDI), derived from OCT, that enables comprehensive imaging of large esophageal segments with microscopic resolution.

DESIGN

A prototype OFDI system was developed for endoscopic imaging. The system was used in combination with a balloon-centering catheter to comprehensively image the distal esophagus in swine.

RESULTS

Volumetric images of the mucosa and portions of the muscularis propria were obtained for 4.5-cm-long segments. Image resolution was 7 microm in depth and 30 microm parallel to the lumen, and provided clear delineation of each mucosal layer. The 3-dimensional data sets were used to create cross-sectional microscopic images, as well as vascular maps of the esophagus. Submucosal vessels and capillaries were visualized by using Doppler-flow processing.

CONCLUSIONS

Comprehensive microscopic imaging of the distal esophagus in vivo by using OFDI is feasible. The unique capabilities of this technology for obtaining detailed information of tissue microstructure over large mucosal areas may open up new possibilities for improving the management of patients with Barrett's esophagus.

Interstitial Doppler optical coherence tomography monitors microvascular changes during photodynamic therapy in a Dunning prostate model under varying treatment conditions

We measure the tumor vascular response to varying irradiance rates during photodynamic therapy (PDT) in a Dunning rat prostate model with interstitial Doppler optical coherence tomography (IS-DOCT). Rats are given a photosensitizer drug, Photofrin, and the tumors are exposed to light (635 nm) with irradiance rates ranging from 8 to 133 mWcm(2) for 25 min, corresponding to total irradiance of 12 to 200 Jcm(2) (measured at surface). The vascular index computed from IS-DOCT results shows the irradiance rate and total irradiance dependent microvascular shutdown in the tumor tissue during PDT. While faster rates of vascular shutdown were associated with increasing PDT irradiance rate and total irradiance, a threshold effect was observed as irradiance rates above 66 mWcm(2) (surface), where no further increase in vascular shutdown rate was detected. The maximum post-treatment vascular shutdown (81%) without immediate microcirculatory recovery was reached with the PDT condition of 33 mWcm(2) and 50 Jcm(2). Control groups without Photofrin show no significant microvascular changes. Microvascular shutdown occurs at different rates and shows correlation with PDT total irradiance and irradiance rates. These dependencies may play an important role in PDT treatment planning, feedback control for treatment optimization, and post-treatment assessment.

Small Bowel Obstruction by Wireless Enteroscopic Capsule and Unrecognized Intestinal Stricture

The wireless enteroscopy capsule (WEC) was approved for noninvasive visualization of small bowel. We report an unusual case of a previously healthy man with history of bowel resection and anastomosis who developed small bowel obstruction after ingestion of a WCE. At operation, an anastomotic stricture site was noted and the WEC was proximal to this stricture, causing obstruction. This case emphasizes the importance of a good history and physical examination, as well as vigilant follow-up and retrieval of WEC.

The evolution of endoscopy: wireless capsule cameras for the diagnosis of occult gastrointestinal bleeding and inflammatory bowel disease

Occult gastrointestinal bleeding and lesions associated with inflammatory bowel disease represent a diagnostic dilemma because they often lie in areas of the small bowel that are difficult to access with flexible fiberoptic endoscopy. Capsule endoscopy has been developed to access these areas in a way that avoids the pain and anesthesia risks of push endoscopy. The diagnostic yield of capsule endoscopy has proven to be superior to both flexible small-bowel endoscopy and radiologic studies in several prospective trials. Capsule endoscopy transmits a large number of images that do not correlate well with the standard endoscopic view, creating a diagnostic challenge for the endoscopist. Complications of this procedure include capsule retention in diverticulae or at stricture sites. The technology of this procedure continues to evolve through improving image resolution and diagnostic accuracy. Capsule endoscopy also represents an overall economic saving despite a high unit price compared with the expense of repeat diagnostic testing. Because the diagnostic yield of capsule endoscopy is nearly twofold greater than conventional endoscopy, it has become the procedure of choice for the dilemma of assessing small-bowel pathology for many clinicians. Further studies are needed to determine whether the capsule endoscope can replace conventional endoscopy in the first-line diagnosis of pathology in other parts of the alimentary tract.

Endoscopic Doppler optical coherence tomography in the human GI tract: initial experience

BACKGROUND

Expanding the current endoscopic optical coherence tomography (OCT) system with Doppler capability may augment this novel high-resolution cross-sectional imaging technique with functional blood flow information. The aim of this feasibility study was to assess the clinical feasibility of an endoscopic Doppler OCT (EDOCT) system in the human GI tract.

METHODS

During routine endoscopy, 22 patients were imaged by using a prototype EDOCT system, which provided color-Doppler and velocity-variance images of mucosal and submucosal blood flow at one frame per second, simultaneously with high-spatial-resolution (10-25 mum) images of tissue microstructure. The images were acquired from normal GI tract and pathologic tissues.

OBSERVATIONS

Subsurface microstructure and microcirculation images of normal and pathologic GI tissues, including Barrett's esophagus, esophageal varices, portal hypertensive gastropathy, gastric antral vascular ectasia, gastric lymphoma, and duodenal adenocarcinoma, were obtained from 72 individual sites in vivo. Differences in vessel diameter, distribution, density, and blood-flow velocity were observed among the GI tissue pathologies imaged.

CONCLUSIONS

To our knowledge, this is the first study to demonstrate the feasibility of EDOCT imaging in the human GI tract during routine endoscopy procedures. EDOCT may detect the different microcirculation patterns exhibited by normal and diseased tissues, which may be useful for diagnostic imaging and treatment monitoring.

Quantifying labial blood flow using optical Doppler tomography

OBJECTIVES

Changes in the oral microvasculature occur in a variety of diseases. Optical Doppler tomography (ODT) combines laser Doppler flowmetry with optical coherence tomography (OCT) to produce high-resolution tomographic images of biological tissues that also detect the velocity and direction of blood flow. The objective of this study was to determine the feasibility of ODT to image labial blood flow. A prototype ODT imaging system was constructed that characterized and measured labial blood flow in healthy subjects.

MATERIALS AND METHODS

A prototype ODT instrument was constructed using a diode light source with a central wavelength of 1300 nanometers, a 40-nanometer spectral width and 2.4 microwatts output power. To verify the accuracy of the system, the flow rates of a phantom material (Intralipid) pumped through a capillary tube at various speeds was measured. To evaluate the clinical feasibility of the ODT prototye, the mucosal aspect of the upper and lower lips at the midline was imaged in 9 healthy volunteers. The sample arm of the instrument consisted of a fiberoptic probe with a 2-mm in diameter polished glass lens attached to the end. The probe was placed approximately 3 mm from the mucosal surface of the lip and oriented perpendicular to the surface. A motorized translation stage moved the fiber in a superior to inferior direction while the subject's head was stabilized by placing the chin into a chin rest. Imaging time for a 12-mm x 2.5-mm scan was approximately 64 seconds.

RESULTS

The phantom experiments revealed that accuracy of this novel ODT prototype to measure flow was within 5%. In vivo labial blood flow velocity ranged from 11.8 to 43.1 mm/second in the upper lip and 8.2 to 53.2 mm/second in the lower lip. There were no statistically significant differences between flow rates in the upper and lower lips. OCT images and Doppler velocity signals were successfully integrated producing in vivo images of labial blood in all of the subjects (15 images). The resulting cross-sectional images revealed microscopic details of labial structures and, to the best of our knowledge, are the first ODT images of the labial microvasculature.

CONCLUSIONS

The results of this in vivo study prove the feasibility of ODT to quantify labial blood flow and produce high spatial resolution images specifically localizing vessels anatomically. ODT provides both flow speed and flow direction information. ODT is noninvasive and offers the advantages of high volumetric flow sensitivity.

Optical coherence tomography in the gastrointestinal tract

Conventional gastrointestinal endoscopic instruments have provided ready access to the mucosal surface of the esophagus, stomach,small intestinal, colon, bile duct, and pancreatic duct. The evolution of endoscopic ultrasonography has provided an additional dimension to the clinical application of modern endoscopy and imaging technology.

Diagnosis of Barrett's esophagus using optical coherence tomography

The presence of Barrett's esophagus (BE) is determined by histopathologic analysis of biopsy specimens obtained during upper endoscopy. The accuracy of endoscopy for the diagnosis of BE is surprisingly poor, however. Optical coherence tomography (OCT) is an optical technology that has shown promise as a powerful new tool to study BE. Of all the methods of optical biopsy discussed in this issue,perhaps OCT comes closest to this goal in that it provides a two dimensional image that correlates with traditional histopathologic excisional biopsy.

Optical coherence tomography for ultrahigh resolution in vivo imaging

Optical coherence tomography (OCT) is an emerging biomedical optical imaging technique that performs high-resolution, cross-sectional tomographic imaging of microstructure in biological systems. OCT can achieve image resolutions of 1-15 microm, one to two orders of magnitude finer than standard ultrasound. The image penetration depth of OCT is determined by the optical scattering and is up to 2-3 mm in tissue. OCT functions as a type of 'optical biopsy' to provide cross-sectional images of tissue structure on the micron scale. It is a promising imaging technology because it can provide images of tissue in situ and in real time, without the need for excision and processing of specimens.

Video capsule endoscopy in inflammatory bowel disease: past, present, and future

In this paper, we critically review the rationale, technical issues, and diagnostic findings, difficulties in interpretation, complications, potential clinical uses, and practical obstacles for capsule endoscopy in patients with inflammatory bowel disease (IBD). We will review the currently limited data on its use in IBD and discuss future areas of investigation required to evaluate critically its potential utility in these patients.

In vivo Doppler optical coherence tomography of mucocutaneous telangiectases in hereditary hemorrhagic telangiectasia

BACKGROUND

Hereditary hemorrhagic telangiectasia is characterized by mucocutaneous telangiectases and visceral arteriovenous malformations. Knowledge is limited concerning the development hemodynamics of mucocutaneous telangiectases. Doppler optical coherence tomography can demonstrate microvascular blood flow at flow rates as low as 20 microm/second, which is up to approximately 100 times more sensitive than Doppler US. The aims of this study were to collect in vivo Doppler optical coherence tomography images of mucocutaneous telangiectases and normal surrounding mucosa and skin, and to gain experience for an in vivo GI endoscopic study. It was hypothesized that visibly normal areas may have occult telangiectases and that mucocutaneous telangiectases that have bled may have a higher rate of blood flow than mucocutaneous telangiectases with no history of bleeding.

METHODS

Twelve patients with hereditary hemorrhagic telangiectasia and mucocutaneous telangiectases were studied. Two to 3 visible mucocutaneous telangiectases on the digits, lips, and tongue were imaged with Doppler optical coherence tomography, along with visually normal surrounding areas at each site. The Doppler optical coherence tomography images were obtained in 0.5 second by using 1310 nm light.

RESULTS

A total of 67 mucocutaneous telangiectases from the 12 patients were imaged (38 digit, 16 lip, 13 tongue). Blood flow was demonstrated within every mucocutaneous telangiectasis imaged. Doppler optical coherence tomography did not identify any abnormal vasculature within visually normal areas. Mucocutaneous telangiectases with a history of bleeding (n = 18) were situated closer to the surface, compared with mucocutaneous telangiectases with no bleeding history (n = 49), but there was no difference in the Doppler flow appearance.

CONCLUSIONS

Visually normal areas in patients with hereditary hemorrhagic telangiectasia did not appear to have abnormal vasculature. Mucocutaneous telangiectases with a history of bleeding were more superficial but were otherwise similar to mucocutaneous telangiectases with no bleeding history.

Diagnosis of Barrett's esophagus using optical coherence tomography

OCT is a promising optical technology that permits real-time, high-resolution, cross-sectional imaging of tissue during endoscopy. It has been shown to be a highly sensitive and specific means of identifying the presence of SIM. Preliminary studies suggest that OCT is capable of grading dysplasia occurring within BE and has the potential to assist with the staging of superficial malignancies, particularly squamous cell cancers. In the near future, the capabilities of OCT systems are expected to improve with systems capable of much higher resolution and with Doppler capability becoming available.

Interventional endoscopy

Technologic milestones have been achieved in the field of interventional endoscopy. These have resulted in improved hemostasis, more accurate cancer staging, safer and less invasive methods of removing gastric neoplasms, and endoscopic palliation of malignant gastric outlet obstruction via stenting. However, just as these milestones are achieved, new challenges emerge: (1) How much sedation can one use safely? (2) What is the risk of transmitting infection and how can that be prevented? (3) Can scopes be made smaller and more comfortable? (4) Can optics be improved? (5) Can endoscopic repair of gastric perforations be safely performed? In this section, we review some of these issues. First, we will provide an update on the most recent concepts in the field of light sedation and infection control. Then, a review of the most commonly used interventional endoscopy procedures, including hemostasis, endosonography, endoscopic mucosal resection, stenting, and percutaneous gastrostomy tube placements. Finally, an overview of the ongoing research and development in the field of interventional endoscopy and how it can improve patient comfort, diagnostic accuracy, therapeutic efficacy, and training in the future.