Contrast‐enhanced optical coherence tomography for melanoma detection: An in vitro study

Optical coherence tomography (OCT), with a high‐spatial resolution (<10 microns), intermediate penetration depth (~1.5 mm) and volumetric imaging capability is a great candidate to be used as a diagnostic‐assistant modality in dermatology. At this time, the accuracy of OCT for melanoma detection is lower than anticipated. In this letter, we studied for the first time, the use of a novel contrast agent consist of ultra‐small nanoparticles conjugated to a melanoma biomarker to improve the accuracy of OCT for differentiation of melanoma cells from nonmelanoma cells, in vitro. We call this approach SMall nanoparticle Aggregation‐enhanced Radiomics of Tumor (SMART)‐OCT imaging. This initial proof of concept study is the first step toward the broad utilization of this method for high accuracy all types of tumor detection applications.     

Investigation of the mesoscale structure and volumetric features of biofilms using optical coherence tomography

Optical coherence tomography (OCT) was successfully applied to visualize the mesoscale structure of three different heterotrophic biofilms. For this purpose, biofilm volumes of 4 × 4 × 1.6 mm³ were scanned with spatial resolutions lower than 20 µm within an acquisition time of 2 min. A heterogeneous structure was detected for biofilms cultivated in laminar as well as transient flow conditions. The structure was found to be more homogeneous for the biofilm grown in turbulent flow. This biofilm structure was characterized by a volumetric porosity of 0.36, whereas the porosity calculated for biofilms grown in laminar and transient conditions was 0.65. These results were directly generated from the distribution of porosity calculated from the OCT images acquired and can be linked to structural properties. Up to now, the mesoscale biofilm structure was only observable with time‐consuming and expensive studies, for example, magnetic resonance microscopy. OCT will most certainly be helpful for improved understanding and prediction of biofilm physics with respect to macroscale processes, for example, mass transfer and detachment as the information about mesoscale is easily accessible using this method. In the context of this study, we show that CLSM images do not necessarily provide an accurate representation of the biofilm structure at the mesoscale. Additionally, the typical characteristic parameters obtained from CLSM image stacks differ largely from those calculated from OCT images. Nevertheless, to determine the local distribution of biofilm constituents, microscopic methods such as confocal laser scanning microscopy are required. Biotechnol. Bioeng. 2010;107: 844–853. © 2010 Wiley Periodicals, Inc.     

采用OCT系统对组织光学通透的研究

组织通透方法采用高折射率化学试剂对生物组织进行渗透,改变组织的光学均匀性,可以有效地改善光学成像的穿透深度,受到生物医学光学研究领域的重视。利用光学相干层析成像技术,测量通透过程中不同测量深度下组织的散射特征的变化。通过采用系统信号对数的梯度值近似地表征光学散射系数,研究了通透过程中组织的散射特征随渗透时间和测量深度的动态关系。实验证明了组织通透可以有效地增加光子的穿透深度,并改善成像质量。研究发现:不同测量深度处组织的散射系数及其变化幅度、变化过程和变化趋势等均存在一定的差异性,并与组织的微观结构、其通透效果,化学试剂在组织中的渗透行为等有密切关系,有助于组织通透过程的理解,并为组织通透机制提供可能的实验依据。     

基于OCT技术的鼠皮肤激光热损伤修复过程的监测

采用Er:YAG激光(波长为2 940 nm,能量密度为:2.5 J/cm2单光斑,扫描次数为4)照射活体小白鼠皮肤,利用光学相干层析成像(optical coherence tomography,OCT)技术在活体小鼠上观察其皮肤组织在激光作用之前及作用之后光热损伤修复的整个过程,得到了激光光热作用下引起损伤的皮肤组织在此过程中皮肤光学特性参数的变化情况,发现皮肤修复过程中光学参数有显著差异,并分析了这些差异引起的原因,以揭示激光美容中并发症主要因素。     

Dynamic imaging and quantification of subcellular motion with eigen‐decomposition optical coherence tomography‐based variance analysis

The dynamic properties of subcellular organism are important biomarkers of the health. Imaging subcellular level dynamics provides effective solutions for evaluating cell metabolism and testing the responses of cells to pathogens and drugs in pharmaceutical engineering. In this paper, we demonstrate an innovative approach to contrast the subcellular motion by using eigen decomposition (ED)‐based variance analysis of time‐dependent complex optical coherence tomography signals. This method reveals a superior advantage of contrast to noise ratio when compared with the approach that employs intensity decorrelation. Furthermore, the eigen values derived from ED processing are calculated and applied to assess the power ratios of complex signal invariance that decreases exponentially along time dimension. The validation experiments are performed on the patterned samples of yeast powder mixed with gelatin/TiO2 water solution. Additionally, the proposed method is used to image mouse cerebral cortex in normal and pathological conditions, suggesting the practicality of variance power mapping in analyzing cortical neural activities. The technique promises efficient measurement of subcellular motions with high sensitivity and high throughput for in vivo and in situ applications.     

光学相干层析成像技术用于裸鼠皮肤霉菌感染研究

利用中心波长为850 nm的宽带光源SLD实现了纵向分辨率为8μm的光学相干层析成像系统。系统采用傅里叶域光学延迟线实现了深度扫描速度为160 mm/s,成像深度为3 mm。获得了裸鼠皮肤霉菌感染部位和健康皮肤的光学相干层析(optical coherence tom ography,OCT)图像,皮肤病变前后的内部结构信息清晰可见。     

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。     

Optical coherence tomography to detect acute esophageal radiation‐induced damage in mice: A validation study

Radiation therapy for patients with non‐small‐cell lung cancer is hampered by acute radiation‐induced toxicity in the esophagus. This study aims to validate that optical coherence tomography (OCT), a minimally invasive imaging technique with high resolution (~10 μm), is able to visualize and monitor acute radiation‐induced esophageal damage (ARIED) in mice. We compare our findings with histopathology as the gold standard. Irradiated mice receive a single dose of 40 Gy at proximal and distal spots of the esophagus of 10.0 mm in diameter. We scan mice using OCT at two, three, and seven days post‐irradiation. In OCT analysis, we define ARIED as a presence of distorted esophageal layering, change in backscattering signal properties, or change in the esophageal wall thickness. The average esophageal wall thickness is 0.53 mm larger on OCT when ARIED is present based on histopathology. The overall sensitivity and specificity of OCT to detect ARIED compared to histopathology are 94% and 47%, respectively. However, the overall sensitivity of OCT to assess ARIED is 100% seven days post‐irradiation. We validate the capability of OCT to detect ARIED induced by high doses in mice. Nevertheless, clinical studies are required to assess the potential role of OCT to visualize ARIED in humans.      

维生素C对光化学法诱导皮肤光损伤的光保护作用:OCT定量研究

8-甲氧补骨脂素(8-MOP)联合UVA辐射(即光化学疗法PUVA)因诱导皮肤光损伤的副作用,常被用于实验动物皮肤光损伤模型的构建。为研究维生素C(Vc)对皮肤光损伤的保护效应,本研究在Balb/c小鼠背部皮肤涂抹0.1%8-MOP溶液1h后进行UVA辐照(10 J/cn2)。然后分别涂抹7.5%、15%和30%浓度的Vc溶液的进行光保护治疗,利用光学相干层析成像分析皮肤厚度和光信号衰减的变化,从而评估Vc对皮肤的光保护作用。结果显示,相对于溶媒组,Vc治疗组皮肤厚度减小,光衰减系数增加,其中15%效果尤为明显结果表明,局部涂抹Vc溶液具有一定的光损伤保护效应。     

Origin of improved depth penetration in dual‐axis optical coherence tomography: a Monte Carlo study

Recent studies have demonstrated that extended imaging depth can be achieved using dual‐axis optical coherence tomography (DA‐OCT). By illuminating and collecting at an oblique angle, multiple forward scattered photons from large probing depths are preferentially detected. However, the mechanism behind the enhancement of imaging depth needs further illumination. Here, the signal of a DA‐OCT system is studied using a Monte Carlo simulation. We modeled light transport in tissue and recorded the spatial and angular distribution of photons exiting the tissue surface. Results indicate that the spatial separation and offset angle created by the non‐telecentric scanning configuration promote the collection of more deeply propagating photons than conventional on‐axis OCT.      

Characterization of planktonic and biofilm cells from two filamentous cyanobacteria using a shotgun proteomic approach

Abstract

Cyanobacteria promote marine biofouling with significant impacts. A qualitative proteomic analysis, by LC-MS/MS, of planktonic and biofilm cells from two cyanobacteria was performed. Biofilms were formed on glass and perspex at two relevant hydrodynamic conditions for marine environments (average shear rates of 4?s^?1 and 40?s^?1). For both strains and surfaces, biofilm development was higher at 4?s^?1. Biofilm development of Nodosilinea sp. LEGE 06145 was substantially higher than Nodosilinea sp. LEGE 06119, but no significant differences were found between surfaces. Overall, 377 and 301 different proteins were identified for Nodosilinea sp. LEGE 06145 and Nodosilinea sp. LEGE 06119. Differences in protein composition were more noticeable in biofilms formed under different hydrodynamic conditions than in those formed on different surfaces. Ribosomal and photosynthetic proteins were identified in most conditions. The characterization performed gives new insights into how shear rate and surface affect the planktonic to biofilm transition, from a structural and proteomics perspective.     

Retinal imaging with optical coherence tomography and low‐loss adaptive optics using a 2.8‐mm beam size

As data acquisition for retinal imaging with optical coherence tomography (OCT) becomes faster, efficient collection of photons becomes more important to maintain image quality. One approach is to use a larger aperture at the eye's pupil to collect more photons that have been reflected from the retina. A 2.8‐mm beam diameter system with only seven reflecting surfaces was developed for low‐loss retinal imaging. The larger beam size requires defocus and astigmatism correction, which was done in a closed loop adaptive optics method using a Shack‐Hartmann wavefront sensor and a deformable mirror (DM) with 140 actuators and a ±2.75 μm stroke. This DM facilitates defocus correction ranging from approximately ?3 D to +3 D. Comparing the new system with a standard 1.2‐mm system on a model eye, a signal‐to‐noise gain of 4.5 dB and a 2.3 times smaller speckle size were measured. Measurements on the retinas of five subjects showed even better results, with increases in dynamic range up to 13 dB. Note that the new sample arm only occupies 30 cm × 60 cm, which makes it highly suitable for imaging in a clinical environment. Figure: B‐scan images obtained over a width of 8 deg from the right eye of a 31‐year‐old Caucasian male. While the left side was imaged with a standard 1.2‐mm OCT system, the right side was imaged with the 2.8‐mm system. Both images were collected with the same integration time and incident power, after correction of aberrations. Using the dynamic range within the images, which is determined by comparing the highest pixel value to the noise floor, a difference in dynamic range of 10.8 dB was measured between the two systems.      

Quantitative discrimination of NPC cell lines using optical coherence tomography

We tried to explore the intrinsic differences in the optical properties of the four representative NPC cell lines on the models of radiobiology and metastasis by OCT. The scattering coefficients and anisotropies were extracted by fitting the average a‐scan attenuation curves based on the multiple scatter effect. The values of scattering coefficients and anisotropy factors were 5.21 ± 0.11, 5.30 ± 0.09, 5.92 ± 0.21, 6.97 ± 0.22, and 0.892 ± 0.009, 0.886 ± 0.006, 0.884 ± 0.009, 0.86 ± 0.01 for CNE1, CNE2, 5‐8F and 6‐10B pellets (p < 0.05, P = 0.07 for CNE1 and CNE2), respectively. The results showed that the radiobiology and metastasis cell's model could be distinguished obviously; which implied that the corresponding types of NPC tissue might be potentially differentiated by OCT. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

基于主成分分析的随机森林视网膜OCT图像分层算法研究

视网膜是层状结构,临床上可以根据视网膜层厚度改变对一些疾病进行预测和诊断.为了快速且准确地分割出视网膜的不同层带,本论文提出一种基于主成分分析的随机森林视网膜光学相干断层扫描技术(optical coherence tomography,OCT)图像分层算法.该方法使用主成分分析(principal component analysis,PCA)法对随机森林采集到的特征进行重采样,保留重采样后权重大的特征信息维度,从而消除特征维度间的关联性和信息冗余.结果表明,总特征维度在29维的情况下,保留前18维度训练速度提高了23.20%,14维度训练速度提高了42.38%,而对图像分割精度方面影响较小,实验表明该方法有效地提高了算法的效率.     

Interpretation of anatomic correlates of outer retinal bands in optical coherence tomography

By providing the sectioning capability to differentiate individual retinal layers, optical coherence tomography (OCT) is revolutionizing eye disease diagnosis and treatment evaluation. A better understanding of the hyper- and hypo-reflective bands in retinal OCT is essential for accurate interpretation of clinical outcomes. In this article, we summarize the interpretations of clinical OCT and adaptive optics (AO) OCT (AO-OCT) of the outer retina in the human eye, and briefly review OCT investigation of the outer retina in animal models. Quantitative analysis of outer retinal OCT bands is compared to established parameters of retinal histology. The literature review and comparative analysis support that both inner/outer segment (IS/OS) junction and IS ellipsoid zone nonexclusively contribute to the second band; and OS, OS tips, and retinal pigment epithelium apical processes contribute to the third band in conventional OCT. In contrast, AO-OCT might predominantly detect the IS/OS junction and OS tip signals at the second and third bands due to its improved sectioning capability and possible AO effect on the sensitivities for recording ballistic and diffusive photons from different regions of the outer retina.     

Quantitative and rapid estimations of human sub‐surface skin mass using ultra‐high‐resolution spectral domain optical coherence tomography

Non‐invasive and quantitative estimations for the delineation of sub‐surface tumor margins could greatly aid in the early detection and monitoring of the morphological appearances of tumor growth, ensure complete tumor excision without the unnecessary sacrifice of healthy tissue, and facilitate post‐operative follow‐up for recurrence. In this study, a high‐speed, non‐invasive, and ultra‐high‐resolution spectral domain optical coherence tomography (UHR‐SDOCT) imaging platform was developed for the quantitative measurement of human sub‐surface skin mass. With a proposed robust, semi‐automatic analysis, the system can rapidly quantify lesion area and shape regularity by an en‐face‐oriented algorithm. Various sizes of nylon sutures embedded in pork skin were used first as a phantom to verify the accuracy of our algorithm, and then in vivo, feasibility was proven using benign human angiomas and pigmented nevi. Clinically, this is the first step towards an automated skin lesion measurement system.

In vivo optical coherence tomography (OCT) image of angioma (A). Thin red arrows point to a blood vessel (BV).     

Interplane bulk motion analysis and removal based on normalized cross‐correlation in optical coherence tomography angiography

Bulk motion seriously degrades the image quality of optical coherence tomography angiography (OCTA). Conventional correction methods focus on in‐plane displacement, while the bulk motion component perpendicular to B‐scans also introduces noise. This work first presents an evaluation of this component using a specific scan protocol and an approximate expression derived from peak‐normalized cross‐correlation values, and then quantitatively assesses how interplane bulk motion noise reduce the sensitivity of cross‐sectional angiograms. Finally, we developed a repetitive bulk motion correction method based on the estimated displacements and redundant volume scans. The correction does not require registration and angiogram reconstruction of low flow sensitivity frames, and the results of in vivo mice skin OCTA imaging experiments show that the proposed method can effectively reduce bulk motion noise caused by cardiac and respiratory motion and occasional shaking, and improve OCTA image quality, which has practical significance for clinical OCTA diagnosis and analysis.