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Results for “Tomography, Optical Coherence”

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PubMed2003

Morphological changes in blood vessels produced by hyperosmotic agents and measured by optical coherence tomography.

Optical tissue clearing by hyperosmotic chemical agents significantly increases light depth penetration in skin and may improve light-based therapeutics such as laser treatment of cutaneous vascular lesions. A feasibility study was conducted to evaluate the potential role of optical clearing by glycerol in laser treatment of cutaneous vessels. Optical imaging was performed to investigate the morphological effects of glycerol on blood vessels of skin. Blood vessels were imaged using Doppler optical coherence tomography in in vivo hamster skin treated with glycerol. Images were obtained from the subdermal side to assess morphological changes in the blood vessels caused by glycerol and from the epidermal side to assess enhanced Doppler imaging of blood vessels. Application of glycerol to the subdermis resulted in venule stasis and for prolonged treatment times, arteriole stasis. In cases where flow remained in arterioles, an improved Doppler signal was detected from blood vessels when imaging transepidermally compared with the native condition. Intensity images indicated changes in blood optical properties and improved contrast of skin cross sections after glycerol application. The observed optical and morphological effects were reversed upon hydration of the skin with phosphate-buffered saline. The combination of increased depth of light penetration and the temporary slowing or cessation of flow in blood vessels could mean improved laser treatment of vessels.

Animals↗

PubMed2003

Optical biopsy using tissue spectroscopy and optical coherence tomography.

'Optical biopsy' or 'optical diagnostics' is a technique whereby light energy is used to obtain information about the structure and function of tissues without disrupting them. In fluorescence spectroscopy, light energy (usually provided by a laser) is used to excite tissues and the resulting fluorescence provides information about the target tissue. Its major gastrointestinal application has been in the evaluation of colonic polyps, in which it can reliably distinguish malignant from benign lesions. Optical coherence tomography (OCT) has been used in the investigation of Barrett's epithelium (and dysplasia), although a variety of other applications are feasible. For example, OCT could assist in the identification and staging of mucosal and submucosal neoplasms, the grading of inflammation in the stomach and intestine, the diagnosis of biliary tumours and the assessment of villous architecture. OCT differs from endoscopic ultrasound, a complementary modality, in that it has a much higher resolution but lesser depth of penetration. The images correlate with the histopathological appearance of tissues, and the addition of Doppler methods may enable it to evaluate the vascularity of tumours and the amount of blood flow in varices. Refinements in these new optical techniques will likely make them valuable in clinical practice, although their specific roles have yet to be determined.

Animals↗

PubMed1996

Optic coherence tomography of optic disk pit maculopathy.

PURPOSE: To define the structure of optic disk pit maculopathy. METHODS: A patient was examined with optic coherence tomography before and after an intravitreal gas tamponade. RESULTS: Before intravitreal gas injection, optic coherence tomography defined a separation between the inner and outer layers of the retina that connected with the optic disk pit. An outer retinal layer detachment that centered on the fovea was also present. After pneumatic displacement of the intraretinal and subretinal fluid, optic coherence tomography disclosed that the two layers were opposed and in contact with the retinal pigment epithelium. CONCLUSIONS: Optic coherence tomography confirmed the two-layer structure of optic disk pit maculopathy and demonstrated the positive effect of pneumatic displacement.

Humans↗

PubMed2006

Optical coherence tomography of the optic nerve head: interindividual reproducibility.

PURPOSE: Optical coherence tomography may be a new technique for quantitative 3-dimensional assessment of the optic nerve head for diagnosis of optic nerve anomalies and diseases such as the glaucomas. The purpose of the present study was to examine its reproducibility. PATIENTS AND METHODS: The clinical noninterventional study included 10 randomly chosen eyes of 10 healthy individuals who underwent 24 optical coherence tomographic examinations with the high-resolution and fast scan program, interactively corrected or uncorrected. The pupils were not dilated. All examinations were performed by 3 examiners independently of one another. The coefficient of variation was calculated as the ratio of the mean of the standard deviations divided by the mean of the means. RESULTS: The coefficients of variation for redetermination of optic disc area, ranging between 0.047 and 0.119, were lowest for the manually corrected fast scan mode and highest for the uncorrected fast scan mode. For remeasurements of the neuroretinal rim area, the best mean coefficient of variation was 0.073+/-0.026 (corrected fast scan mode). CONCLUSIONS: In healthy eyes, the morphometric measurements of the optic nerve head by optical coherence tomography show a relatively high reproducibility with mean coefficients of variation lower than 10% for remeasurements of the optic disc and neuroretinal rim area. With undilated pupils, reproducibility is better with the fast scan mode with interactive correction of the outlining of the optic disc border than it is with the high-resolution mode.

Adult↗

PubMed2006

Identifying intestinal metaplasia at the squamocolumnar junction by using optical coherence tomography.

BACKGROUND: Optical coherence tomography (OCT) is an optical imaging method that produces high-resolution cross-sectional images of the esophagus. The accuracy of OCT for differentiating tissue types at the squamocolumnar junction (SCJ) has not been established. OBJECTIVE: The purpose of this study was to identify and validate OCT image criteria for distinguishing metaplastic from nonmetaplastic tissue at the SCJ. DESIGN: A total of 196 biopsy-correlated OCT images of the SCJ were acquired from 113 patients undergoing upper endoscopy. A pathologist blinded to the OCT results reviewed each pathology specimen and determined the presence of the following histopathology: gastric cardia, squamous mucosa, pancreatic metaplasia, and intestinal metaplasia. An algorithm for diagnosing specialized intestinal metaplasia (SIM) was created by reviewing a training set of 40 biopsy-correlated OCT images. Two blinded investigators prospectively tested the algorithm on a validation set of 123 images. RESULTS: OCT images of squamous mucosa were characterized by a layered appearance without epithelial glands; gastric cardia, by vertical pit and gland structure, a well-defined epithelial surface reflectivity, and relatively poor image penetration; and SIM by an irregular architecture and good image penetration. The OCT criteria were 85% sensitive and 95% specific for SIM when applied retrospectively to the training set. When applied to the validation set, the algorithm was 81% sensitive for both OCT readers and 66% and 57% specific for diagnosing SIM. The interobserver agreement was good (kappa = 0.53). CONCLUSIONS: OCT imaging can identify SIM at the SCJ with an accuracy similar to that of endoscopy.

Algorithms↗

PubMed2006

Three-dimensional optic axis determination using variable-incidence-angle polarization-optical coherence tomography.

Polarization optical coherence tomography (PSOCT) is a powerful technique to nondestructively map the retardance and fast-axis orientation of birefringent biological tissues. Previous studies have concentrated on the case where the optic axis lies on the plane of the surface. We describe a method to determine the polar angle of the optic axis of a uniaxial birefringent tissue by making PSOCT measurements with a number of incident illumination directions. The method is validated on equine flexor tendon, yielding a variability of 4% for the true birefringence and 3% for the polar angle. We use the method to map the polar angle of fibers in the transitional region of equine cartilage.

Animals↗

PubMedDate not supplied

Computational methods for analysis of human breast tumor tissue in optical coherence tomography images.

Optical coherence tomography (OCT) has been demonstrated as a promising means of identifying the boundaries between normal and diseased breast tissue. This capability has yielded promise for the development of OCT techniques for biopsy guidance, surgical margin assessment, and minimally invasive evaluation of disease states. We present methods for the assessment of human breast tissue based on spatial and Fourier-domain analysis. Derived from preliminary OCT data, these methods are aimed at the development of automated diagnostic tools that will aid in the translation of this technology into the clinical environment.

Algorithms↗

PubMed2003

Imaging of non-parabolic velocity profiles in converging flow with optical coherence tomography.

The optical coherence tomography method was explored for two-dimensional flow mapping of a highly scattering fluid in flow with complex geometry. Converging flow (capillary entry) with 4:1 constriction was used for demonstration of non-invasive and remote methods of mapping varying velocity profiles. Downstream of the geometry was scanned with approximately 10 x 10 x 10 microm3 spatial resolution and structural imaging of the lumen and images of one particular velocity were acquired. Stable concave, blunted and parabolic profiles are obtained at different distances of the inlet length. Application of the technique for the blood circulation is also discussed.

Algorithms↗

PubMed2005

Interstitial Doppler optical coherence tomography.

Doppler optical coherence tomography (OCT) can image tissue structure and blood flow at micrometer-scale resolution but has limited imaging depth. We report a novel, linear-scanning, needle-based Doppler OCT system using angle-polished gradient-index or ball-lensed fibers. A prototype system with a 19-guage (diameter of approximately 0.9 mm) echogenic needle is constructed and demonstrates in vivo imaging of bidirectional blood flow in rat leg and abdominal cavity. To our knowledge, this is the first demonstration of Doppler OCT through a needle probe in interstitial applications to visualize deeply situated microcirculation.

Animals↗

PubMed2004

In vivo visualization of Tradescantia leaf tissue and monitoring the physiological and morphological states under different water supply conditions using optical coherence tomography.

The optical coherence tomography (OCT) capabilities of plants were evaluated using leaves of Tradescantia pallida (Rose) D. Hunt. The internal structure of the leaf tissues was visualized in vivo and the physiological and morphological states of the tissues under different water supply conditions were monitored using OCT. The OCT technique provides non-invasive two-dimensional images directly on intact plants. The acquisition time of a two-dimensional image with a size of 200x200 pixels and a spatial resolution of 15 microm is 1-3 s. It was shown that OCT is a useful tool for monitoring the physiological and morphological states of plant tissues supplied with varying amounts of water and under the influence of different chemical factors.

Dehydration↗

PubMed2004

Group velocity dispersion effects with water and lipid in 1.3 microm optical coherence tomography system.

Optical coherence tomography (OCT) has been introduced for the diagnosis of vulnerable plaques in the coronary arteries. When an OCT system images through tissue and biological liquids, group velocity dispersion (GVD) will occur, which may be useful in tissue characterization. This study compares the water and lipid induced GVD effects, important constituents in plaque, on the axial resolution. The point-spread function (PSF) was measured when a target mirror was immersed in either water or lipid. A Fourier transform was performed on the PSF data. No significant GVD was observed in oil up to 15 mm thickness. Water depths greater than 6 mm significantly broadened the PSF. This indicates that the distortion of the spectrum can be attributed to the GVD in water. These results suggest that when imaging through tissue (such as when performing intravascular imaging in vivo) one may be able to distinguish different tissue types for diagnostic purposes.

Biomimetic Materials↗

PubMed2006

Evaluation of rabbit tracheal inflammation using optical coherence tomography.

BACKGROUND: Optical coherence tomography (OCT) is an evolving technology that is capable of delivering real-time, high-resolution images of tissues. The purpose of this study was to evaluate the feasibility of using OCT for detecting airway pathology in a septic animal model. METHODS: The tracheas of New Zealand white rabbits were inoculated endobronchially with various concentrations of live Streptococcus pneumoniae bacteria. After the development of pneumonia/sepsis, the animals were killed. OCT tracheal images and corresponding histologic specimens from these experimental animals were compared to control rabbit tracheas for morphologic features and quantitative tracheal mucosal thickness measurements. RESULTS: The results revealed significant airway mucosal thickening in the experimental group that was consistent with tracheal edema. Morphologic changes, including epithelial denuding and mucosal sloughing, were evident in regions of the experimental tracheas. CONCLUSION: This study suggests that OCT is a potentially valuable imaging modality that is capable of evaluating superficial airway pathology with high-resolution in vivo images. Numerous applications of OCT can be envisioned in the realm of pulmonary medicine and thoracic surgery that may substantially increase the precision and accuracy of current bronchoscopic diagnostic and surgical techniques.

Animals↗

PubMed2004

Histomorphologic correlation with routine histology and optical coherence tomography.

BACKGROUND: Optical coherence tomography (OCT) is a new and promising diagnostic technique for investigation of skin tumours. We describe a method that makes evaluation and definition of specific morphologic structures of skin tumours via OCT more accurate. MATERIALS AND METHOD: We investigated three patients with basal cell carcinoma and three patients with melanocytic nevi. Three-dimensional (3D) images were obtained from these skin tumours via OCT according to previously applied marks, which were tattooed with special histological marking dye after excision of the tumours. Corresponding to these marks, we investigated serial histological sections (haematoxylin&eosin staining). RESULTS: We could prove similar morphological structures both in OCT and histology. Due to tissue deformation, the compared measurements of structures like cell nests or epidermal thickness were slightly deviated. However, by this method we could prove similar tissue formations in OCT and histology. CONCLUSIONS: Due to the deformation by histological processing and slightly different sectioning levels, the comparison of histological pictures and OCT images seems difficult. Nevertheless, in two cases it was possible to demonstrate the same morphological structures with OCT imaging and histological investigation. Our method could play an important role for further evaluation of OCT images. We estimate better evaluation of OCT imaging using a 3D reconstruction method.

Basal Cell Carcinoma↗

PubMed2006

Spectrum of foveal development in albinism detected with optical coherence tomography.

BACKGROUND: Optical coherence tomography (OCT) has shown the absence of a foveal depression in an individual with oculocutaneous albinism, type 1 (OCA1) and best-corrected visual acuity (BCVA) of 20/400. However, the presence of an annular light reflex in the macula has been noted with indirect ophthalmoscopy in other patients with albinism who have better vision. We studied macular architecture in albinism with OCT when binocular BCVA was > or = 20/60 and compared this to detection of foveal development with binocular indirect ophthalmoscopy. METHODS: Eleven patients with albinism and BCVA > or = 20/60 were recruited for OCT. Average central macular thickness was recorded. Presence of an oval annular reflex was determined with binocular indirect ophthalmoscopy. RESULTS: Mean binocular BCVA was 20/39 (range: 20/20 to 20/50). Twelve eyes had a rudimentary annular reflex detected with ophthalmoscopy. OCT was reliable in 20 of 22 eyes. A foveal depression was identified with OCT in four eyes. Mean macular thickness for these four eyes was 233 microm (+/- 22.5 microm). We found a weak inverse correlation between BCVA (logMAR) and thickness (r = -0.21). CONCLUSIONS: OCT shows the spectrum of foveal development in albinism, from complete absence of development to a central depression corresponding to a rudimentary annular reflex detected with ophthalmoscopy. The reduced rate of detection of foveal development with OCT compared with ophthalmoscopy is likely related to poor fixation in patients with nystagmus.

Adolescent↗

PubMed2005

Evaluation of radiation-induced oral mucositis by optical coherence tomography.

PURPOSE: Optical coherence tomography (OCT) imaging was evaluated to determine if radiation-induced mucosal damage could be noninvasively monitored in real time and correlated with histopathologic findings. EXPERIMENTAL DESIGN: Female C3H mice, ages 7 to 9 weeks, four per group, were immobilized in a custom-made Lucite jig and received 0, 15, 22.5, and 25 Gy in a single fraction to their oral cavity. OCT images were acquired of proximal, middle, and distal aspects of the dorsum of the tongue on days 0, 1, 3, 5, and 7 post-irradiation. Animals were sacrificed on day 7 and samples taken for histologic evaluation. OCT images were visually examined and also quantified by image analysis and compared with histologic findings. RESULTS: Tongues removed 7 days post-irradiation showed no visible damage; however, upon staining with toluidine blue, ulcers at the base of the tongue became visible (100% for 25 Gy, 75% after 22.5 Gy, and 0% after 15 Gy). Visual inspection of OCT images qualitatively compared with histologic findings and quantitative image analysis of the OCT images (effective light penetration depth) revealed significant changes 7 days post-irradiation compared with unirradiated controls for the base of the tongue. CONCLUSIONS: OCT allows for direct noninvasive real-time acquisition of digitally archivable images of oral mucosa and can detect radiation-induced changes in the mucosa before visual manifestation. OCT may be a useful technique to quantify subclinical radiation-induced mucosal injury in experimental chemoradiation clinical trials.

Animals↗

PubMed2006

Method analysis for optimal continuous imaging using intravascular optical coherence tomography.

OBJECTIVES: Optical coherence tomography(OCT)is a high-resolution imaging method that can clearly visualize vessels through the displacement of blood with flushing agents. Continuous imaging methods have not been established. This study investigated optimal methods for continuous OCT imaging. METHODS: Thirty-four arteries with stent implantation (24 peripheral and 10 coronary arteries)in 14 pigs were examined using OCT with a motorized pullback device. Two imaging methods (flush alone by liquid substance and flush with occlusion) were compared. Adequate image acquisition was defined as the entire circumferential intimal layer being detectable within continuous segments. To investigate factors that could influence image quality, stented regions were divided into 4-5 mm segments. RESULTS: The flush with occlusion method provided better OCT images compared to flush alone (flush with occlusion: 60.9%, flush alone: 8.7%, p = 0.0002). Using the flush with occlusion method, the rate of adequate image acquisition was 64.4% and visualization of > 75% intimal circumference was 83.5%. Intravascular ultrasound could detect all stented regions. Segmental analyses found more adequate images were detected in smaller vessels (adequate segment: 3.8 +/- 0.4 mm, inadequate segment: 4.2 +/- 0.8 mm, p < 0.0001) or with centered image wire position (adequate segment: center 35%, inadequate segment: center 14%, p = 0.003). In addition, side branches did not affect image quality. CONCLUSIONS: To acquire continuous OCT images, the flush with occlusion method was more effective compared to flush alone. Moreover, image quality is affected by vessel size and imaging wire position. These results suggest that optimized OCT imaging can provide continuous vessel detection.

Animals↗

PubMed2004

Changes in function and morphology of normal human skin: evaluation using optical coherence tomography.

BACKGROUND: Optical coherence tomography (OCT) is a noninvasive morphological method for investigating human skin. It allows high-resolution in vivo imaging of inflammatory skin diseases and tumours. Because it is a newly developed method, systematic studies on standardization and on evaluation of factors influencing the representation of the skin have not yet been performed. OBJECTIVES: In this study, normal human skin was treated with various external stimuli which induce changes of function and morphology. Changes in stratum corneum thickness as well as changes induced by pigmentation, oedema and erythema were investigated using OCT. METHODS: Healthy skin of human volunteers was treated with tape stripping, ultraviolet A irradiation, water, histamine, nicotinic acid and various ointments. RESULTS: In the tape stripping experiment, the thickness of the horny layer was quantified and monitored. Pigmentation increased the light attenuation of the tissue, whereas hydration and erythema led to a slight decrease of scattering. Topical treatment of the skin gave a nonspecific increase of penetration depth of the light due to the lower reflectivity of the surface. CONCLUSIONS: There are various physiological conditions which influence optical properties of the skin. These parameters should be considered when performing standardized OCT studies.

Adult↗

PubMed2005

Speckle reduction by I-divergence regularization in optical coherence tomography.

For optical coherence tomography (OCT), ultrasound, synthetic-aperture radar, and other coherent ranging methods, speckle can cause spurious detail that detracts from the utility of the image. It is a problem inherent to imaging densely scattering objects with limited bandwidth. Using a method of regularization by minimizing Csiszar's I-divergence measure, we derive a method of speckle minimization that produces an image that both is consistent with the known data and extrapolates additional detail based on constraints on the magnitude of the image. This method is demonstrated on a test image and on an OCT image of a Xenopus laevis tadpole.

Algorithms↗