Comparison of histometric data obtained by optical coherence tomography and routine histology

There is a lack of systematic investigations comparing optical coherence tomography (OCT) with histology. OCT assessments were performed on the upper back of 16 healthy subjects. Epidermis thickness (ET) was assessed using three methods: first, peak-to-valley analysis of the A-scan (ET-OCT-V); second, manual measurements in the OCT images (ET-OCT-M); third, light microscopic determination using routine histology (ET-Histo). The relationship between the different methods was assessed by means of the Pearson correlation procedure and Bland and Altman plots. We observed a strong correlation between ET-Histo (79.4+/-21.9 microm) and ET-OCT-V (79.2+/-15.5 microm, r=0.77) and ET-OCT-M (82.9+/-15.8 microm, r=0.75), respectively. Bland and Altman plots revealed a bias of -0.19 microm (95% limits of agreement: -27.94 microm to 27.56 microm) for ET-OCT-V versus ET-Histo and a bias of 3.44 microm (95% limits of agreement: -24.9 microm to 31.78 microm) for ET-OCT-M versus ET-Histo. Despite the strong correlation and low bias observed, the 95% limits of agreement demonstrated an unsatisfactory numerical agreement between the two OCT methods and routine histology indicating that these methods cannot be employed interchangeably. Regarding practicability, precision, and indication spectrum, ET-OCT-V and ET-OCT-M are of different clinical value.     

Rotationally acquired four-dimensional optical coherence tomography of embryonic chick hearts using retrospective gating on the common central A-scan

We introduce a new method of rotational image acquisition for four-dimensional (4D) optical coherence tomography (OCT) of beating embryonic chick hearts. The rotational axis and the central A-scan of the OCT are identical. An out-of-phase image sequence covering multiple heartbeats is acquired at every angle of an incremental rotation of the deflection mirrors of the OCT system. Image acquisition is accomplished after a rotation of 180°. Comparison of a displayed live M-mode of the central A-scan with a reference M-mode allows instant detection of translational movements of the embryo. For calculation of 4D data sets, we apply an image-based retrospective gating algorithm using the phase information of the common central A-scan present in all acquired images. This leads to cylindrical three-dimensional data sets for every time step of the cardiac cycle that can be used for 4D visualization. We demonstrate this approach and provide a video of a beating Hamburger and Hamilton stage 16 embryonic chick heart generated from a 4D OCT data set using rotational image acquisition.     

Speckle reduction in optical coherence tomography by "path length encoded" angular compounding

Speckle, the dominant factor reducing image quality in optical coherence tomography (OCT), limits the ability to identify cellular structures that are essential for diagnosis of a variety of diseases. We describe a new high-speed method for implementing angular compounding by path length encoding (ACPE) for reducing speckle in OCT images. By averaging images obtained at different incident angles, with each image encoded by path length, ACPE maintains high-speed image acquisition and requires minimal modifications to OCT probe optics. ACPE images obtained from tissue phantoms and human skin in vivo demonstrate a qualitative improvement over traditional OCT and an increased SNR that correlates well with theory.     

Combined multiplanar optical coherence tomography and confocal scanning ophthalmoscopy

We demonstrate the clinical application of a multiplanar imaging system that simultaneously acquires en face (C-scan) optical coherence tomography (OCT) and the corresponding confocal ophthalmoscopic images, along with cross-sectional (B-scan) OCT at specifiable locations on the confocal image. The advantages of the simultaneous OCT and confocal acquisition as well as the challenges of interpreting the C-scan OCT images are discussed. Variations in tissue inclination with respect to the coherence wave surface alter the sampling of structures within the depth of the retina, producing novel slice orientations that are often challenging to interpret. We have evaluated for the first time the utility of C-scan OCT for a variety of pathologies, including melanocytoma, diabetic retinopathy, choroidal neovascular membrane, and macular pucker. Several remarkable new aspects of clinical anatomy were revealed using this new technique. The versatility of selective capture of C-scan OCT images and B-scan OCT images at precise points on the confocal image affords the clinician a more complete and interactive tool for 3-D imaging of retinal pathology.     

Quantitative measurement of attenuation coefficients of bladder biopsies using optical coherence tomography for grading urothelial carcinoma of the bladder

Real-time grading of bladder urothelial carcinoma (UC) is clinically important, but the current standard for grading (histopathology) cannot provide this information. Based on optical coherence tomography (OCT)-measured optical attenuation (μ(t)), the grade of bladder UC could potentially be assessed in real time. We evaluate ex vivo whether μ(t) differs between different grades of UC and benign bladder tissue. Human bladder tissue specimens are examined ex vivo by 850-nm OCT using dynamic focusing. Three observers independently determine the μ(t) from the OCT images, and three pathologists independently review the corresponding histology slides. For both methods, a consensus diagnosis is made. We include 76 OCT scans from 54 bladder samples obtained in 20 procedures on 18 patients. The median (interquartile range) μ(t) of benign tissue is 5.75 mm(-1) (4.77 to 6.14) versus 5.52 mm(-1) (3.47 to 5.90), 4.85 mm(-1) (4.25 to 6.50), and 5.62 mm(-1) (5.01 to 6.29) for grade 1, 2, and 3 UC, respectively (p = 0.732). Interobserver agreement of histopathology is "substantial" [Kappa 0.62, 95% confidence interval (IC) 0.54 to 0.70] compared to "almost perfect" [interclass correlation coefficient (ICC) 0.87, 95% CI 0.80 to 0.92] for OCT. Quantitative OCT analysis (by μ(t)) does not detect morphological UC changes. This may be due to factors typical for an ex-vivo experimental setting.     

Enhancing the signal-to-noise ratio in ophthalmic optical coherence tomography by image registration--method and clinical examples

Optical coherence tomography (OCT) has already proven an important clinical tool for imaging and diagnosing retinal diseases. Concerning the standard commercial ophthalmic OCT systems, speckle noise is a limiting factor with respect to resolving relevant retinal features. We demonstrate successful suppression of speckle noise from mutually aligning a series of in vivo OCT recordings obtained from the same retinal target using the Stratus system from Humphrey-Zeiss. Our registration technique is able to account for the axial movements experienced during recording as well as small transverse movements of the scan line from one scan to the next. The algorithm is based on a regularized shortest path formulation for a directed graph on a map formed by interimage (B-scan) correlations. The resulting image enhancement typically increases the contrast-to-noise ratio (CNR) with a factor of three or more and facilitates segmentation and quantitative characterization of pathologies. The method is currently successfully being applied by medical doctors in a number of specific retinal case studies.     

The reproducibility of estimates of critical power and anaerobic work capacity in upper-body exercise

The purposes of this study were to apply the linear power versus inverse of time relationship to high-intensity upper-body exercise and to assess the repeatability of the parameters critical power (CP) and anaerobic working capacity (AWC), using limits of agreement (Bland and Altman 1986). Sixteen active male subjects (aged 20–34 years), performed two sets of five constant-power exercises on an adapted cycle ergometer. There were no significant differences between mean estimates of CP [96 (16) W and 95 (17) W] and AWC [7457 (2011) J and 7608 (1684) J] from the first and second sets of bouts. Despite the lack of systematic bias, there was evidence of large random error. Ratio limits of agreement for time to exhaustion during constant-power exercises suggested that a repeat measurement might be expected in 95% of cases to be between 0.64 and 1.59 times the original measurement. The 95% limits of agreement for CP were –15 W to +17 W. The ratio limits of agreement for AWC suggest that in 95% of cases a repeat measurement might be between 0.57 and 1.67 times the original estimate. The results of this study suggest a poor repeatability of constant-power upper-body exercises to exhaustion, which may contribute to a poor repeatability of CP and AWC determined from the linear power versus inverse of time model. Electronic Publication     

Reduction of image artifacts in three-dimensional optical coherence tomography of skin in vivo

This paper presents results of in vivo studies on the effect of refractive index-matching media on image artifacts in optical coherence tomography (OCT) images of human skin. These artifacts present as streaks of artificially low backscatter and displacement or distortion of features. They are primarily caused by refraction and scattering of the OCT light beam at the skin surface. The impact of the application of glycerol and ultrasound gel is assessed on both novel skin-mimicking phantoms and in vivo human skin, including assessment of the epidermal thickening caused by the media. Based on our findings, recommendations are given for optimal OCT imaging of skin in vivo.     

Bland-Altman图评价高频超声和病理测量大鼠皮肤厚度的一致性研究

目的探讨高频超声测量大鼠供皮区皮肤各层厚度的准确性。 方法以购自海军军医大学动物实验中心的10只SD大鼠为对象，每只大鼠构建4个供皮区模型，共40个供皮区模型，分别应用高频超声和组织病理学方法，测量大鼠供皮区表皮厚度、真皮厚度、全层皮肤厚度以及断层皮片厚度，Bland-Altman散点图计算测量数据的95%一致性界限(95%LOA)。 结果Bland-Altman散点图显示两种方法测量表皮厚度、真皮厚度、全层皮肤厚度以及断层皮片厚度差值的95%LOA分别为(－15.80～14.30 μm，P＝0.54)、(－9.99～8.59 μm, P＝0.36)、(－32.33～32.03 μm, P＝0.95)、(－33.62～32.87 μm, P＝ 0.89)。两种方法测量表皮厚度差值和断层皮片厚度差值的点都分别在其95%LOA内，真皮厚度、全层皮肤厚度差值各仅有1个点落其95%LOA外。真皮厚度、全层皮肤厚度以及断层皮片厚度测量差值的95%LOA全部在临床可接受的范围内，表皮厚度测量差值的95%LOA有95%的点在临床可接受的范围内。 结论高频超声测量大鼠供皮区皮肤各层厚度的数据与组织病理学测量数据具有较好的一致性。高频超声作为一种无创、快速、准确、客观的方法，可望在供皮区取皮深度评估中得到广泛应用。     

Mechanical Analysis of Atherosclerotic Plaques Based on Optical Coherence Tomography

Finite element analysis is a powerful tool for investigating the biomechanics of atherosclerosis and has thereby provided an improved understanding of acute myocardial infarction. Structural analysis of arterial walls is traditionally performed using geometry contours derived from histology. In this paper we demonstrate the first use of a new imaging technique, optical coherence tomography (OCT), as a basis for finite element analysis. There are two primary benefits of OCT relative to histology: 1) imaging is performed without excessive tissue handling, providing a more realistic geometry than histology and avoiding structural artifacts common to histologic processing, and 2) OCT imaging can be performed in vivo, making it possible to study disease progression and the effect of therapeutic treatments in animal models and living patients. Patterns of mechanical stress and strain distributions computed from finite element analysis based on OCT were compared with those from modeling based on "gold standard" histology. Our results indicate that vascular structure and composition determined by OCT provides an adequate basis for investigating the biomechanical factors relevant to atherosclerosis and acute myocardial infarction.     

Evaluating the use of optical coherence tomography for the detection of epithelial cancers in vitro

Optical coherence tomography (OCT) is a noninvasive imaging methodology that is able to image tissue to depths of over 1 mm. Many epithelial conditions, such as melanoma and oral cancers, require an invasive biopsy for diagnosis. A noninvasive, real-time, point of care method of imaging depth-resolved epithelial structure could greatly improve early diagnosis and long-term monitoring in patients. Here, we have used tissue-engineered (TE) models of normal skin and oral mucosa to generate models of melanoma and oral cancer. We have used these to determine the ability of OCT to image epithelial differences in vitro. We report that while in vivo OCT gives reasonable depth information for both skin and oral mucosa, in vitro the information provided is less detailed but still useful. OCT can provide reassurance on the development of TE models of skin and oral mucosa as they develop in vitro. OCT was able to detect the gross alteration in the epithelium of skin and mucosal models generated with malignant cell lines but was less able to detect alteration in the epithelium of TE models that mimicked oral dysplasia or, in models where tumor cells had penetrated into the dermis.     

Contrasting properties of gold nanoparticles for optical coherence tomography: phantom, in vivo studies and Monte Carlo simulation

The possibility of using silica-gold nanoshells with 150 nm silica core size and 25 nm thick gold shell as contrasting agents for optical coherence tomography (OCT) is analyzed. Experiments on agar biotissue phantoms showed that the penetration of nanoshells into the phantoms increases the intensity of the optical coherence tomography (OCT) signal and the brightness of the corresponding areas of the OCT image. In vivo experiments on rabbit skin demonstrated that the application of nanoshells onto the skin provides significant contrasting of the borders between the areas containing nanoshells and those without. This effect of nanoshells on skin in vivo is manifested by the increase in intensity of the OCT signal in superficial parts of the skin, boundary contrast between superficial and deep dermis and contrast of hair follicles and glands. The presence of nanoshells in the skin was confirmed by electron microscopy. Monte Carlo simulations of OCT images confirmed the possibility of contrasting skin-layer borders and structures by the application of gold nanoshells. The Monte Carlo simulations were performed for two skin models and exhibit effects of nanoparticles similar to those obtained in the experimental part of the study, thus proving that the effects originate exactly from the presence of nanoparticles.     

Semiautomatic segmentation and quantification of calcified plaques in intracoronary optical coherence tomography images

Coronary calcified plaque (CP) is both an important marker of atherosclerosis and major determinant of the success of coronary stenting. Intracoronary optical coherence tomography (OCT) with high spatial resolution can provide detailed volumetric characterization of CP. We present a semiautomatic method for segmentation and quantification of CP in OCT images. Following segmentation of the lumen, guide wire, and arterial wall, the CP was localized by edge detection and traced using a combined intensity and gradient-based level-set model. From the segmentation regions, quantification of the depth, area, angle fill fraction, and thickness of the CP was demonstrated. Validation by comparing the automatic results to expert manual segmentation of 106 in vivo images from eight patients showed an accuracy of 78±9%. For a variety of CP measurements, the bias was insignificant (except for depth measurement) and the agreement was adequate when the CP has a clear outer border and no guide-wire overlap. These results suggest that the proposed method can be used for automated CP analysis in OCT, thereby facilitating our understanding of coronary artery calcification in the process of atherosclerosis and helping guide complex interventional strategies in coronary arteries with superficial calcification.     

Fluorescein diacetate for determination of cell viability in tissue-engineered skin

Assurance of the quality of cultured skin substitutes (CSSs) currently relies on representative histology and determination of surface hydration, which provide limited sampling at selected points. To evaluate uniformity of cell density on the collagen matrices before clinical use, a field assessment of cell viability is advantageous. This study aimed to develop a field measure of cell viability in CSSs in vitro using fluorescein diacetate (FdA). CSSs were stained 3 days after keratinocyte inoculation using 0.04 mg/mL FdA followed by exposure to 366 nm of ultraviolet light. CSS fluorescence quantified using Metamorph image analysis was correlated with inoculation density, 3-(4,5-dimethylthiazol-2-Yl)-2,5-diphenyltetrazolium bromide (MTT) values and histology of corresponding biopsies. CSS fluorescence correlated significantly with inoculation density (p < 0.001) and MTT values (p < 0.001) of biopsies collected immediately after FdA staining. Fluorescence at day 3 also predicted day 10 MTT values. No toxicity was detected in CSSs, and normal in vitro and in vivo histology was demonstrated after FdA exposure. In conclusion, measurement of intracellular fluorescence with FdA allows for the early, comprehensive measurement of cellular distributions and viability in engineered skin and may therefore facilitate quality assurance.     

Measurement of serum albumin by capillary zone electrophoresis, bromocresol green, bromocresol purple, and immunoassay methods

BACKGROUND/AIMS: The introduction of capillary zone electrophoresis (CZE) to this laboratory has highlighted discrepancies in albumin measured on an Abbott Aeroset by bromocresol green (BCG) and that calculated by CZE on the basis of total protein measured by Biuret. METHODS: This study examined differences in albumin estimation by CZE, Abbott Aeroset BCG, and Aeroset bromocresol purple (BCP), and compared these with albumin estimated by Beckman Array immunoassay. RESULTS: Altman and Bland analysis of results showed a positive bias of BCG with CZE (4.51 g/litre; 95% limits of agreement, 3.77 to 5.26; n = 72) and BCP (3.85 g/litre; 95% limits of agreement, -1.42 to 9.12; n = 72). CZE and BCP agreed closely (0.67 g/litre; 95% limits of agreement, -4.39 to 3.06; n = 72). Analysis of 57 of those samples in which BCG and CZE differed > or = 5 g/litre showed a positive bias of BCG with immunoassay (8.35 g/litre; 95% limits of agreement, 1.54 to 15.16; n =57), with good agreement between CZE and immunoassay (-0.44 g/litre; 95% limits of agreement, -2.82 to 1.94; n = 57). CONCLUSIONS: BCP is superior to BCG for the assay of albumin and has replaced BCG as the routine test for albumin in this laboratory.     

Histological validation of frequency domain optical coherence tomography for the evaluation of neointimal formation after a novel polymer-free sirolimus-eluting stent implantation

Novel polymer-free drug-eluting stents have been developed to reduce polymer-related adverse events. However, neointimal coverage after polymer-free DES implantation is unclear and validation between optical coherence tomography (OCT) and histology is required. Sixteen polymer-free sirolimus-eluting stents were randomly implanted into coronary arteries of 8 normal swine. OCT and histological measurement were conducted at 3 or 6 months after stent placement. For quantitative measures, lumen area, stent area, neointimal area and neointimal thickness were validated in every single OCT and histology matched cross-section. Moreover, for qualitative analysis, OCT signal patterns of neointimal tissue were classified as homogeneous, layered and heterogeneous patterns based on optical intensity and backscatter pattern and peri-strut inflammation was also determined by histology. In total, 70 OCT and histology matched cross-sections were analyzed. At quantitative analysis, good correlations and agreements were found in the measurement of lumen area (ICC = 0.67, P<0.001), neointimal area (ICC = 0.89, P<0.001) and neointimal thickness (ICC = 0.94, P<0.001) except for stent area (ICC 0.19, P = 0.13) between OCT and histology. At qualitative analysis, lymphocyte infiltrations of peri-strut were more frequently seen in heterogeneous sections than in homogeneous sections (10/14 sections, 71.4% vs. 12/50 sections, 24%; P = 0.003). In conclusion, OCT has proper correlation and agreement with histology in assessment of neointimal formation and heterogeneous neointima assessed by OCT may also be associated with peri-strut inflammation detected in histology after polymer-free sirolimus-eluting stents implantation, supporting the use of OCT to evaluate neointimal coverage after polymer-free stent implantation in clinical practice.     

Office-based optical coherence tomographic imaging of human vocal cords

Optical coherence tomography (OCT) is an evolving noninvasive imaging modality and has been used to image the larynx during surgical endoscopy. The design of an OCT sampling device capable of capturing images of the human larynx during a typical office based laryngoscopy examination is discussed. Both patient's and physician's movements were addressed. In vivo OCT imaging of the human larynx is demonstrated. Though the long focal length limits the lateral resolution of the image, the basement membrane can still be readily distinguished. Office-based OCT has the potential to guide surgical biopsies, direct therapy, and monitor disease. This is a promising imaging modality to study the larynx.     

超声图象纹理分析的新方法：—纹理深度法及其实验

本文提出了一种用于B超图象纹理分析的新方法。用此方法可定量计算出有关B超图象纹理的深浅,陡平,疏密或粗细等方面的12个参数,计算机模拟实验结果证实了该方法的可靠性,临床B超图象分析结果表明,该方法有实用价值。     

Enhanced optical clearing of skin in vivo and optical coherence tomography in-depth imaging

The strong optical scattering of skin tissue makes it very difficult for optical coherence tomography (OCT) to achieve deep imaging in skin. Significant optical clearing of in vivo rat skin sites was achieved within 15 min by topical application of an optical clearing agent PEG-400, a chemical enhancer (thiazone or propanediol), and physical massage. Only when all three components were applied together could a 15 min treatment achieve a three fold increase in the OCT reflectance from a 300 μm depth and 31% enhancement in image depth Z(threshold).     

Ultrahigh-speed non-invasive widefield angiography

Retinal and choroidal vascular imaging is an important diagnostic benefit for ocular diseases such as age-related macular degeneration. The current gold standard for vessel visualization is fluorescence angiography. We present a potential non-invasive alternative to image blood vessels based on functional Fourier domain optical coherence tomography (OCT). For OCT to compete with the field of view and resolution of angiography while maintaining motion artifacts to a minimum, ultrahigh-speed imaging has to be introduced. We employ Fourier domain mode locking swept source technology that offers high quality imaging at an A-scan rate of up to 1.68 MHz. We present retinal angiogram over ～48 deg acquired in a few seconds in a single recording without the need of image stitching. OCT at 1060 nm allows for high penetration in the choroid and efficient separate characterization of the retinal and choroidal vascularization.