OCT于大鼠脱水组织中光散射特性的分析研究

目的:探讨活体组织液体含量的改变对OCT成像的影响,以期提高OCT在诊断组织病理性质方面的能力。方法:实验中复制脱水大鼠病理模型,应用光学相干层析成像设备,进行大鼠舌浅表组织在体显微成像检测,并对图像中组织的信号衰减特性进行量化分析。结果:正常对照组大鼠体重明显增加,病理模型组显著下降,病理模型组于脱水3天和5天后组织的平均OCT信号衰减系数明显高于正常对照组(P<0.01),且5天较3天的病理模型组组织的信号衰减系数变化尤其显著(P<0.01)。结论:改变组织含液量,可显著改变OCT成像效果,且通过对OCT图像中信号的衰减系数分析,可获得组织细微的散射变化,从而有望提高OCT技术在组织性质方面的诊断能力。     

Investigation of changes in optical attenuation of bone and neuronal cells in organ culture or three-dimensional constructs in vitro with optical coherence tomography: relevance to cytochrome oxidase monitoring

Changes in optical attenuation, relevant to cytochrome oxidase, of the rat bone periosteal tissue in explanted culture and human neuronal cells in three-dimensional agarose constructs have been monitored by the use of optical coherence tomography (OCT), with potential applications in tissue engineering and diagnosis. A superluminescent diode (SLD) with a peak emission wavelength (lambda = 820 nm) that is the near-infrared absorption band of the oxidized form of CytOx was employed. The attenuation coefficient was obtained from the depth-resolved reflectance profiles of liquid phantoms (naphthol green B with intralipid), explant culture (periosteum of calvaria from rats) and cells in 3D agarose constructs. The absorption coefficient of naphthol green B can be accurately quantified by the linear relationship between attenuation coefficients and the concentration. The difference in the attenuation coefficient of astrocytoma cells in agarose before and after reduction of CytOx is 0.26 +/- 0.10 mm(-1) ( n = 9), whereas no attenuation is observed with the agarose control. Reduction of the enzyme in periosteal tissue leads to a change in attenuation coefficient of 0.43 +/- 0.24 mm(-1) ( n = 7). For comparison, using a biochemical assay, the absorption coefficient of the oxidized-reduced form of CytOx is measured at approximately 8.3 +/- 1.5x10(-3) mm-1 ( n = 4) and 8.7 +/-2.5x10(-3) mm-1 ( n = 4) at 820 nm for astrocytoma cells and rat periosteum, respectively. The lower value of CytOx concentration using biochemical versus OCT measurements may result from shifts in the scattering profile and the amplifying influences of multiple heme-based oxidases, indicating that conventional OCT is not specific enough to monitor redox changes in cytochrome oxidase. However, qualitative shifts in oxidation state are apparent using the technique. Our results suggest the potential application of OCT in providing high-resolution tomographic imaging of tissues in organ culture and cells grown in three-dimensional constructs in vitro.     

General model for depth‐resolved estimation of the optical attenuation coefficients in optical coherence tomography

We present the proof of concept of a general model that uses the tissue sample transmittance as input to estimate the depth‐resolved attenuation coefficient of tissue samples using optical coherence tomography (OCT). This method allows us to obtain an image of tissue optical properties instead of intensity contrast, guiding diagnosis and tissues differentiation, extending its application from thick to thin samples. The performance of our method was simulated and tested with the assistance of a home built single‐layered and multilayered phantoms (~100 μm each layer) with known attenuation coefficient on the range of 0.9 to 2.32 mm^?1. It is shown that the estimated depth‐resolved attenuation coefficient recovers the reference values, measured by using an integrating sphere followed by the inverse adding doubling processing technique. That was corroborated for all situations when the correct transmittance value is used with an average difference of 7%. Finally, we applied the proposed method to estimate the depth‐resolved attenuation coefficient for a thin biological sample, demonstrating the ability of our method on real OCT images.     

Characterizing thrombus with multiple red blood cell compositions by optical coherence tomography attenuation coefficient

Embolectomy is one of the emergency procedures performed to remove emboli. Assessing the composition of human blood clots is an important diagnostic factor and could provide guidance for an appropriate treatment strategy for interventional physicians. Immunostaining has been used to identity compositions of clots as a gold-standard procedure, but it is time-consuming and cannot be performed in situ. Here, we proposed that the optical attenuation coefficient of optical coherence tomography (OCT) can be a reliable indicator as a new imaging modality to differentiate clot compositions. Fifteen human blood clots with multiple red blood cell (RBC) compositions from 21% to 95% were prepared using healthy human whole blood. A homogeneous gelatin phantom experiment and numerical simulation based on the Lambert–Beer's law were examined to verify the validity of the attenuation coefficient estimation. The results displayed that optical attenuation coefficients were strongly correlated with RBC compositions. We reported that attenuation coefficients could be a promising biomarker to guide the choice of an appropriate interventional device in a clinical setting and assist in characterizing blood clots.     

Characterizing biochemical and morphological variations of clinically relevant anatomical locations of oral tissue in vivo with hybrid Raman spectroscopy and optical coherence tomography technique

This study aims to characterize biochemical and morphological variations of the clinically relevant anatomical locations of in vivo oral tissue (ie, alveolar process, lateral tongue and floor of the mouth) by using hybrid Raman spectroscopy (RS) and optical coherence tomography (OCT) technique. A total of 1049 in vivo fingerprint (FP: 800‐1800 cm^?1) and high wavenumber (HW: 2800‐3600 cm^?1) Raman spectra were acquired from different oral tissue (alveolar process = 331, lateral tongue = 339 and floor of mouth = 379) of 26 normal subjects in the oral cavity under the OCT imaging guidance. The total Raman dataset were split into 2 parts: 80% for training and 20% for testing. Tissue optical attenuation coefficients of alveolar process, lateral tongue and the floor of the mouth were derived from OCT images, revealing the inter‐anatomical morphological differences; while RS uncovers subtle FP/HW Raman spectral differences among different oral tissues that can be attributed to the differences in inter‐ and intra‐cellular proteins, lipids, DNA and water structures and conformations, enlightening biochemical variability of different oral tissues at the molecular level. Partial least squares‐discriminant analysis implemented on the training dataset show that the integrated tissue optical attenuation coefficients and FP/HW Raman spectra provide diagnostic sensitivities of 99.6%, 82.3%, 50.2%, and specificities of 97.0%, 75.1%, 92.1%, respectively, which are superior to using either RS (sensitivities of 90.2%, 77.5%, 48.8%, and specificities of 95.8%, 72.1%, 88.8%) or optical attenuation coefficients derived from OCT (sensitivities of 75.0%, 78.2%, 47.2%, and specificities of 96.2%, 67.7%, 85.0%) for the differentiation among alveolar process, lateral tongue and the floor of the mouth. Furthermore, the diagnostic algorithms applied to the independent testing dataset based on hybrid RS‐OCT technique gives predictive diagnostic sensitivities of 100%, 76.5%, 51.3%, and specificities of 95.1%, 77.6%, 89.6%, respectively, for the classifications among alveolar process, lateral tongue and the floor of the mouth, which performs much better than either RS or optical attenuation coefficient derived from OCT imaging. This work suggests that inter‐anatomical morphological and biochemical variability are significant which should be considered as an important parameter in the interpretation and rendering of hybrid RS‐OCT technique for oral tissue diagnosis and characterization.      

In vivo detection of endotracheal tube biofilms in intubated critical care patients using catheter‐based optical coherence tomography

The formation of biofilms in the endotracheal tubes (ETTs) of intubated patients on mechanical ventilation is associated with a greater risk of ventilator‐associated pneumonia and death. New technologies are needed to detect and monitor ETTs in vivo for the presence of these biofilms. Longitudinal OCT imaging was performed in mechanically ventilated subjects at 24‐hour intervals until extubation to detect the formation and temporal changes of in vivo ETT biofilms. OCT‐derived attenuation coefficient images were used to differentiate between mucus and biofilm. Extubated ETTs were examined with optical and electron microscopy, and all imaging results were correlated with standard‐of‐care clinical test reports. OCT and attenuation coefficient images from four subjects were positive for ETT biofilms and were negative for two subjects. The processed and stained extubated ETTs and clinical reports confirmed the presence/absence of biofilms in all subjects. Our findings confirm that OCT can detect and differentiate between biofilm‐positive and biofilm‐negative groups (P < 10^?5). OCT image‐based features may serve as biomarkers for direct in vivo detection of ETT biofilms and help drive investigation of new management strategies to reduce the incidence of VAP.      

Pilot feasibility study of in vivo intraoperative quantitative optical coherence tomography of human brain tissue during glioma resection

This study investigates the feasibility of in vivo quantitative optical coherence tomography (OCT) of human brain tissue during glioma resection surgery in six patients. High‐resolution detection of glioma tissue may allow precise and thorough tumor resection while preserving functional brain areas, and improving overall survival. In this study, in vivo 3D OCT datasets were collected during standard surgical procedure, before and after partial resection of the tumor, both from glioma tissue and normal parenchyma. Subsequently, the attenuation coefficient was extracted from the OCT datasets using an automated and validated algorithm. The cortical measurements yield a mean attenuation coefficient of 3.8 ± 1.2 mm^?1 for normal brain tissue and 3.6 ± 1.1 mm^?1 for glioma tissue. The subcortical measurements yield a mean attenuation coefficient of 5.7 ± 2.1 and 4.5 ± 1.6 mm^?1 for, respectively, normal brain tissue and glioma. Although the results are inconclusive with respect to trends in attenuation coefficient between normal and glioma tissue due to the small sample size, the results are in the range of previously reported values. Therefore, we conclude that the proposed method for quantitative in vivo OCT of human brain tissue is feasible during glioma resection surgery.     

Characterization of the human myocardium by optical coherence tomography

Imaging of cardiac tissue structure plays a critical role in the treatment and understanding of cardiovascular disease. Optical coherence tomography (OCT) offers the potential to provide valuable, high‐resolution imaging of cardiac tissue. However, there is a lack of comprehensive OCT imaging data of the human heart, which could improve identification of structural substrates underlying cardiac abnormalities. The objective of this study was to provide qualitative and quantitative analysis of OCT image features throughout the human heart. Fifty human hearts were acquired, and tissues from all chambers were imaged with OCT. Histology was obtained to verify tissue composition. Statistical differences between OCT image features corresponding to different tissue types and chambers were estimated using analysis of variance. OCT imaging provided features that were able to distinguish structures such as thickened collagen, as well as adipose tissue and fibrotic myocardium. Statistically significant differences were found between atria and ventricles in attenuation coefficient, and between adipose and all other tissue types. This study provides an overview of OCT image features throughout the human heart, which can be used for guiding future applications such as OCT‐integrated catheter‐based treatments or ex vivo investigation of structural substrates.     

Image reconstruction of optical attenuation coefficient variation in biological tissues

A procedure for non-invasive imaging of the optical attenuation coefficient variation of in vivo thick organs/tissues is developed. The laser back-scattered surface profiles at various locations of human forearm, by multi-probe reflectometer, are measured. These profiles are matched by iterative procedure, with that as obtained by Monte Carlo simulation and the corresponding values of attenuation coefficient (equal to the sum of absorption and reduced scattering coefficients) are determined. By interpolation of this data a 100 x 100 grid is constructed and after median filtering of this data a color-coded image of the variability of the optical attenuation coefficient of the forearm is obtained. These images in different subjects show variation due to change in overall tissue composition and blood pooling. This non-invasive imaging procedure may help in identifying the diseased affected regions in healthy tissues and in application of photodynamic therapy.     

Three‐dimensional mapping of the attenuation coefficient in optical coherence tomography to enhance breast tissue microarchitecture contrast

Effective intraoperative tumor margin assessment is needed to reduce re‐excision rates in breast‐conserving surgery (BCS). Mapping the attenuation coefficient in optical coherence tomography (OCT) throughout a sample to create an image (attenuation imaging) is one promising approach. For the first time, three‐dimensional OCT attenuation imaging of human breast tissue microarchitecture using a wide‐field (up to ~45 × 45 × 3.5 mm) imaging system is demonstrated. Representative results from three mastectomy and one BCS specimen (from 31 specimens) are presented with co‐registered postoperative histology. Attenuation imaging is shown to provide substantially improved contrast over OCT, delineating nuanced features within tumors (including necrosis and variations in tumor cell density and growth patterns) and benign features (such as sclerosing adenosis). Additionally, quantitative micro‐elastography (QME) images presented alongside OCT and attenuation images show that these techniques provide complementary contrast, suggesting that multimodal imaging could increase tissue identification accuracy and potentially improve tumor margin assessment.     

Investigation of optical attenuation imaging using optical coherence tomography for monitoring of scars undergoing fractional laser treatment

We demonstrate the use of the near‐infrared attenuation coefficient, measured using optical coherence tomography (OCT), in longitudinal assessment of hypertrophic burn scars undergoing fractional laser treatment. The measurement method incorporates blood vessel detection by speckle decorrelation and masking, and a robust regression estimator to produce 2D en face parametric images of the attenuation coefficient of the dermis. Through reliable co‐location of the field of view across pre‐ and post‐treatment imaging sessions, the study was able to quantify changes in the attenuation coefficient of the dermis over a period of ～20 weeks in seven patients. Minimal variation was observed in the mean attenuation coefficient of normal skin and control (untreated) mature scars, as expected. However, a significant decrease (13 ± 5%, mean ± standard deviation) was observed in the treated mature scars, resulting in a greater distinction from normal skin in response to localized damage from the laser treatment. By contrast, we observed an increase in the mean attenuation coefficient of treated (31 ± 27%) and control (27 ± 20%) immature scars, with numerical values incrementally approaching normal skin as the healing progressed. This pilot study supports conducting a more extensive investigation of OCT attenuation imaging for quantitative longitudinal monitoring of scars.

En face 2D OCT attenuation coefficient map of a treated immature scar derived from the pre‐treatment (top) and the post‐treatment (bottom) scans. (Vasculature (black) is masked out.) The scale bars are 0.5 mm.     

Revealing structural modifications in thermomechanical reshaping of collagenous tissues using optical coherence elastography

Moderate heating of such collagenous tissues as cornea and cartilages by infra‐red laser (IR laser) irradiation is an emerging technology for nondestructive modification of the tissue shape and microstructure for a variety of applications in ophthalmology, otolaryngology and so on. Postirradiation high‐resolution microscopic examination indicates the appearance of microscopic either spheroidal or crack‐like narrow pores depending on the tissue type and irradiation regime. Such examinations usually require special tissue preparation (eg, staining, drying that affect microstructure themselves) and are mostly suitable for studying individual pores, whereas evaluation of their averaged parameters, especially in situ, is challenging. Here, we demonstrate the ability of optical coherence tomography (OCT) to visualize areas of pore initiation and evaluate their averaged properties by combining visualization of residual irradiation‐induced tissue dilatation and evaluation of the accompanying Young‐modulus reduction by OCT‐based compressional elastography. We show that the averaged OCT‐based data obtained in situ fairly well agree with the microscopic examination results. The results obtained develop the basis for effective and safe applications of novel nondestructive laser technologies of tissue modification in clinical practice. PICTURE: Elastographic OCT‐based images of an excised rabbit eye cornea subjected to thermomechanical laser‐assisted reshaping. Central panel shows resultant cumulative dilatation in cornea after moderate (~45‐50°C) pulse‐periodic heating by an IR laser together with distribution of the inverse Young modulus 1/E before (left) and after (right) IR irradiation. Significant modulus decrease in the center of irradiated region is caused by initiated micropores. Their parameters can be extracted by analyzing the elastographic images.      

Evaluation of dental enamel caries assessment using Quantitative Light Induced Fluorescence and Optical Coherence Tomography

An in vitro study of morphological alterations between sound dental structure and artificially induced white spot lesions in human teeth, was performed through the loss of fluorescence by Quantitative Light‐Induced Fluorescence (QLF) and the alterations of the light attenuation coefficient by Optical Coherence Tomography (OCT). To analyze the OCT images using a commercially available system, a special algorithm was applied, whereas the QLF images were analyzed using the software available in the commercial system employed. When analyzing the sound region against white spot lesions region by QLF, a reduction in the fluorescence intensity was observed, whilst an increase of light attenuation by the OCT system occurred. Comparison of the percentage of alteration between optical properties of sound and artificial enamel caries regions showed that OCT processed images through the attenuation of light enhanced the tooth optical alterations more than fluorescence detected by QLF System.

QLF versus OCT imaging of enamel caries: a photonics assessment     

One‐to‐one registration of en‐face optical coherence tomography attenuation coefficients with histology of a prostatectomy specimen

Optical coherence tomography (OCT), enables high‐resolution 3D imaging of the morphology of light scattering tissues. From the OCT signal, parameters can be extracted and related to tissue structures. One of the quantitative parameters is the attenuation coefficient; the rate at which the intensity of detected light decays in depth. To couple the quantitative parameters with the histology one‐to‐one registration is needed. The primary aim of this study is to validate a registration method of quantitative OCT parameters to histological tissue outcome through one‐to‐one registration of OCT with histology. We matched OCT images of unstained fixated prostate tissue slices with corresponding histology slides, wherein different histologic types were demarcated. Attenuation coefficients were determined by a supervised automated exponential fit (corrected for point spread function and sensitivity roll‐off related signal losses) over a depth of 0.32 mm starting from 0.10 mm below the automatically detected tissue edge. Finally, the attenuation coefficients corresponding to the different tissue types of the prostate were compared. From the attenuation coefficients, we produced the squared relative residue and goodness‐of‐fit metric R². This article explains the method to perform supervised automated quantitative analysis of OCT data, and the one‐to‐one registration of OCT extracted quantitative data with histopathological outcomes.      

用组织光学特性鉴别诊断人离体的正常膀胱和膀胱癌组织

研究正常人膀胱和膀胱癌组织在Kube lka-Munk二流模型下对476.5 nm,514.5 nm和808 nm波长的激光的光学特性的差异。采用双积分球系统和Kube lka-Munk二流模型进行测量研究。实验结果表明,正常膀胱和膀胱癌组织在Kube lka-Munk二流模型下对476.5 nm,514.5 nm和808 nm波长的每一个波长的激光的吸收、散射、总衰减、有效衰减系数都有非常显著性的差异(P<0.01)。膀胱癌组织对476.5 nm,514.5 nm和808nm波长的激光的吸收系数明显地较正常膀胱组织对相应波长的激光的吸收系数要大(P<0.01),膀胱癌组织对476.5 nm和514.5 nm波长的激光的散射系数明显地较正常膀胱组织对相应波长的激光的散射系数要小(P<0.01),而膀胱癌组织对808 nm波长的激光的散射系数明显地较正常膀胱组织对同一波长的激光的散射系数要大(P<0.01)。膀胱癌组织对476.5 nm,514.5 nm和808 nm波长的激光的总衰减系数明显地较正常膀胱组织对相应波长的激光的总衰减系数要大(P<0.01),膀胱癌组织对476.5 nm,514.5 nm和808 nm波长的激光的有效衰减系数明显地较正常膀胱组织对相应波长的激光的有效衰减系数要大(P<0.01)。提示使用双积分球系统和Kube lka-Munk二流模型来确定离体的正常膀胱组织和膀胱癌组织对476.5 nm,514.5 nm和808nm波长的激光的光学特性的差异鉴别诊断病变的膀胱组织是一个有效的方法。     

Assessment of simulated osteoporosis in alveolar bone using optical coherence tomography

Steoporosis is a skeletal disorder that compromises bone resistance and its diagnosis is usually performed using dual energy X‐ray absorptiometry. Thus, the search for efficient diagnostic methods that do not involve the emission of ionizing radiation is necessary. This study proposed to use the Optical Coherence Tomography (OCT) to evaluate osteoporosis in alveolar bone. Osteoporosis lesions is simulated in vitro in porcine bones, and imaging is performed by OCT and micro‐computed tomography (micro‐CT). A developed algorithm is proposed to calculate the optical attenuation coefficient ( μ _t), mean optical attenuation coefficient (), integrated reflectivity (ΔR) and bone density ( BD). The , ΔR and BD parameters shows a good correlation to micro‐CT parameters (bone volume/tissue volume and total porosity). The μ _t and methods are negatively impacted by non‐uniform intensities distribution in osteoporosis images. In conclusion, BD and ΔR analysis demonstrates to be potential techniques for diagnosis and monitoring of osteoporosis using OCT.      

Lymph vessels visualization from optical coherence tomography data using depth-resolved attenuation coefficient calculation

Multimodal optical coherent tomography grows popularity with researchers and clinicians over the past decade. One of the modalities is lymphangiography, which allows visualization of the lymphatic vessel networks within optical coherence tomography (OCT) imaging volume. In the present study, it is shown that lymphatic vessel visualization obtained from the depth-resolved attenuation coefficient distributions, corrected for the noise, shows improved contrast and detail in comparison with previously proposed approaches. We also argue that the two most popular approaches for lymphatic vessel visualization, namely simple intensity thresholding and vesselness calculation based on local Hessian matrix eigenvalues, imply different definitions of the lymphatic vessel's appearance in the OCT volume and lead to the different networks.     

Investigation of the permeability and optical clearing ability of different analytes in human normal and cancerous breast tissues by spectral domain OCT

The potential of OCT applied for early breast cancer detection attracted significant efforts. The permeability coefficients and the percentages of OCT signal enhancement for normal and cancerous breast tissues have been investigated from the experiments of 20% glucose, 40% glucose, and 20% mannitol in vitro. Obtained results indicate that the permeability coefficient in breast cancer tissue is prominently larger than that in normal breast tissue, while the optical clearing effect is just the reverse to that for each agent. The results suggest that OCT has the ability to distinguish cancer tissue from different aspect. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Diagnosing colorectal abnormalities using scattering coefficient maps acquired from optical coherence tomography

Optical coherence tomography (OCT) has shown potential in differentiating normal colonic mucosa from neoplasia. In this study of 33 fresh human colon specimens, we report the first use of texture features and computer vision-based imaging features acquired from en face scattering coefficient maps to characterize colorectal tissue. En face scattering coefficient maps were generated automatically using a new fast integral imaging algorithm. From these maps, a gray-level cooccurrence matrix algorithm was used to extract texture features, and a scale-invariant feature transform algorithm was used to derive novel computer vision-based features. In total, 25 features were obtained, and the importance of each feature in diagnosis was evaluated using a random forest model. Two classifiers were assessed on two different classification tasks. A support vector machine model was found to be optimal for distinguishing normal from abnormal tissue, with 94.7% sensitivity and 94.0% specificity, while a random forest model performed optimally in further differentiating abnormal tissues (i.e., cancerous tissue and adenomatous polyp) with 86.9% sensitivity and 85.0% specificity. These results demonstrated the potential of using OCT to aid the diagnosis of human colorectal disease.     

Noninvasive cross-sectional observation of three-dimensional cell sheet-tissue-fabrication by optical coherence tomography

Cell sheet engineering allows investigators/clinicians to prepare cell-dense three-dimensional (3-D) tissues, and various clinical trials with these fabricated tissues have already been performed for regenerating damaged tissues. Cell sheets are easily manipulated and 3-D tissues can be rapidly fabricated by layering the cell sheets. This study used optical coherence tomography (OCT) to noninvasively analyze the following processes: (1) adhesions between layered cell sheets, and (2) the beating and functional interaction of cardiac cell sheet-tissues for fabricating functional thicker 3-D tissues. The tight adhesions and functional couplings between layered cell sheets could be observed cross-sectionally and in real time. Importantly, the noninvasive and cross-sectional analyses of OCT make possible to fabricate 3-D tissues by confirming the adherence and functional couplings between layered cell sheets. OCT technology would contribute to cell sheet engineering and regenerative medicine.