Automated identification of basal cell carcinoma by polarization-sensitive optical coherence tomography

We report an automated classifier to detect the presence of basal cell carcinoma in images of mouse skin tissue samples acquired by polarization-sensitive optical coherence tomography (PS-OCT). The sensitivity and specificity of the classifier based on combined information of the scattering intensity and birefringence properties of the samples are significantly higher than when intensity or birefringence information are used alone. The combined information offers a sensitivity of 94.4% and specificity of 92.5%, compared to 78.2% and 82.2% for intensity-only information and 85.5% and 87.9% for birefringence-only information. These results demonstrate that analysis of the combination of complementary optical information obtained by PS-OCT has great potential for accurate skin cancer diagnosis.OCIS codes: (170.4500) Optical coherence tomography, (170.1870) Dermatology, (110.5405) Polarimetric imaging, (100.2960) Image analysis, (170.3880) Medical and biological imaging     

Conical scan polarization-sensitive optical coherence tomography

We report on a new articular cartilage imaging technique with potential for clinical arthroscopic use, by supplementing the variable-incidence-angle polarization-sensitive optical coherence tomography method previously developed by us with a conical beam scan protocol. The technique is validated on bovine tendon by comparing experimental data with simulated data generated using the extended Jones matrix calculus. A unique capability of this new optical technique is that it can locate the “brushing direction” of collagen fibers in articular cartilage, which is structural information that extends beyond established methods such as split-line photography or birefringent fast-axis measurement in that it is uniquely defined over the full azimuthal-angle range of (-π, + π). The mapping of this direction over the cartilage surface may offer insights into the optimal design of tissue-engineering scaffolds for cartilage repair.OCIS codes: (170.4500) Optical coherence tomography, (170.3880) Medical and biological imaging, (170.3890) Medical optics instrumentation, (260.1440) Birefringence, (260.5430) Polarization     

Henle fiber layer phase retardation measured with polarization-sensitive optical coherence tomography

Abstract: We developed a method based on polarization-sensitive optical coherence tomography (PS-OCT) to quantify the double pass phase retardation (DPPR) induced by Henle fiber layer in three subjects. Measurements of the retina were performed at a mean wavelength of 840 nm using two polarization states that were perpendicular in a Poincaré sphere representation and phase retardation contributions from tissue layers above and below the Henle fiber layer were excluded using appropriately placed reference and measurement points. These points were semi-automatically segmented from intensity data. Using a new algorithm to determine DPPR, the Henle fiber layer in three healthy subjects aged 50-60 years showed elevated DPPR in a concentric ring about the fovea, with an average maximum DPPR for the three subjects of 22.0° (range: 20.4° to 23.0°) occurring at an average retinal eccentricity of 1.8° (range: 1.5° to 2.25°). Outside the ring, a floor of approximately 6.8° was measured, which we show can mainly be attributed to phase noise that is induced in the polarization states. We also demonstrate the method can determine fast axis orientation of the retardation, which is found consistent with the known radial pattern of Henle fibers.OCIS codes: (110.4500) Optical coherence tomography, (130.5440) Polarization-selective devices, (170.5755) Retina scanning, (170.6935) Tissue characterization     

Optical tractography of the mouse heart using polarization-sensitive optical coherence tomography

We developed a method to image myocardial fiber architecture in the mouse heart using a Jones matrix-based polarization-sensitive optical coherence tomography (PSOCT) system. The “cross-helical” laminar structure of myocardial fibers can be clearly visualized using this technology. The obtained myocardial fiber organization agrees well with existing knowledge acquired using conventional histology and diffusion tensor magnetic resonance imaging.OCIS codes: (110.4500) Optical coherence tomography, (230.5440) Polarization     

Design considerations for polarization-sensitive optical coherence tomography with a single input polarization state

Using a generalized design for a polarization-sensitive optical coherence tomography (PS-OCT) system with a single input polarization state (SIPS), we prove the existence of an infinitely large design space over which it is possible to develop simple PS-OCT systems that yield closed form expressions for birefringence. Through simulation and experiment, we validate this analysis by demonstrating new configurations for PS-OCT systems, and present guidelines for the general design of such systems in light of their inherent inaccuracies. After accounting for systemic errors, alternative designs exhibit similar performance on average to the traditional SIPS PS-OCT system. This analysis could be extended to systems with multiple input polarization states and could usher in a new generation of PS-OCT systems optimally designed to probe specific birefringent samples with high accuracy.OCIS codes: (110.4500) Optical coherence tomography, (230.5440) Polarization-selective devices, (120.3890) Medical optics instrumentation     

Differentiation of ex vivo human breast tissue using polarization-sensitive optical coherence tomography

Successful treatment of breast cancer typically requires surgical removal of the tumor. Optical coherence tomography (OCT) has been previously developed for real-time imaging of the surgical margin. However, it can be difficult to distinguish between normal stromal tissue and cancer tissue based on scattering intensity and structure alone. Polarization-sensitive optical coherence tomography (PS-OCT) is sensitive to form birefringence of biological tissue. We report on the development of a high-speed PS-OCT system and imaging of ex vivo human breast tissue, showing enhanced contrast between healthy and cancerous tissues based upon collagen content confirmed with corresponding histology. These results demonstrate the feasibility of using PS-OCT to supplement structural OCT as a possible method for intraoperative tumor margin evaluation.OCIS codes: (110.4500) Optical coherence tomography, (170.4500) Optical coherence tomography, (170.3880) Medical and biological imaging, (260.1440) Birefringence, (110.5405) Polarimetric imaging, (170.6935) Tissue characterization     

In vivo evaluation of human skin anisotropy by polarization-sensitive optical coherence tomography

We performed an in vivo three-dimensional analysis of anisotropic changes in the dermal birefringence of mechanically deformed human skin using polarization-sensitive optical coherence tomography (PS-OCT). The papillary-dermal birefringence of the forehead increased significantly when the skin was shrunk parallel to the body axis, and decreased significantly when the skin was shrunk perpendicular to the body axis. En-face images of the papillary-dermal birefringence revealed variations among individual subjects, and that both shrinking parallel to and stretching in perpendicular to the body axis promoted the formation of macro rope-like birefringent domains. We found that PS-OCT is useful for understanding anisotropic properties of collagen structure in the skin.     

Differentiation of breast tissue types for surgical margin assessment using machine learning and polarization-sensitive optical coherence tomography

We report an automated differentiation model for classifying malignant tumor, fibro-adipose, and stroma in human breast tissues based on polarization-sensitive optical coherence tomography (PS-OCT). A total of 720 PS-OCT images from 72 sites of 41 patients with H&E histology-confirmed diagnoses as the gold standard were employed in this study. The differentiation model is trained by the features extracted from both one standard OCT-based metric (i.e., intensity) and four PS-OCT-based metrics (i.e., phase difference between two channels (PD), phase retardation (PR), local phase retardation (LPR), and degree of polarization uniformity (DOPU)). Further optimized by forward searching and validated by leave-one-site-out-cross-validation (LOSOCV) method, the best feature subset was acquired with the highest overall accuracy of 93.5% for the model. Furthermore, to show the superiority of our differentiation model based on PS-OCT images over standard OCT images, the best model trained by intensity-only features (usually obtained by standard OCT systems) was also obtained with an overall accuracy of 82.9%, demonstrating the significance of the polarization information in breast tissue differentiation. The high performance of our differentiation model suggests the potential of using PS-OCT for intraoperative human breast tissue differentiation during the surgical resection of breast cancer.     

Birefringence measurement of cornea and anterior segment by office-based polarization-sensitive optical coherence tomography

We present a case series of cornea and anterior segment disorders investigated by an office-based polarization-sensitive optical coherence tomography (PS-OCT). Blebs of glaucoma patients treated by trabeculectomy, and corneas of keratoconus and keratoplasty patients were measured by PS-OCT. Birefringence formations in trabeculectomy bleb were measured in 1 control eye and 3 eyes of trabeculectomy model rabbits. Polarization insensitive scattering OCT and the depth-resolved birefringence were measured simultaneously by PS-OCT. Abnormal birefringence was observed in keratoconus cases with advanced thinning and with a rupture of Descemet's membrane. The graft-host interface of the keratoplasty case showed abnormal birefringence. The appearance of abnormal birefringence in the cornea was likely to be an indication of cross-linking of collagen fibrils. The measurement of rabbit showed abnormal birefringence in the scarring eyes. Wide regions of strong birefringence were observed in the eyes of trabeculectomy patients who had high intraocular pressure. Visualization of scarring in bleb by PS-OCT may be useful for the planning of secondary surgery. PS-OCT showed promising for the study and diagnosis diseases related to abnormal fibrous tissues of the cornea and anterior eye segment.     

Polarization mode dispersion correction in endoscopic polarization-sensitive optical coherence tomography with incoherent polarization input states

The incorporation of polarization sensitivity into optical coherence tomography (PS-OCT) imaging can greatly enhance utility by allowing differentiation via intrinsic contrast of many types of tissue. In fiber-based OCT systems such as those employing endoscopic imaging probes, however, polarization mode dispersion (PMD) can significantly impact the ability to obtain accurate polarization data unless valuable axial resolution is sacrificed. In this work we present a new technique for compensating for PMD in endoscopic PS-OCT with minimal impact on axial resolution and without requiring mutually coherent polarization inputs, needing only a birefringent structure with known orientation in view (such as the catheter sheath). We then demonstrate the advantages of this technique by comparing it against the current state of the art approach.     

Automated quantification of lung structures from optical coherence tomography images

Characterization of the size of lung structures can aid in the assessment of a range of respiratory diseases. In this paper, we present a fully automated segmentation and quantification algorithm for the delineation of large numbers of lung structures in optical coherence tomography images, and the characterization of their size using the stereological measure of median chord length. We demonstrate this algorithm on scans acquired with OCT needle probes in fresh, ex vivo tissues from two healthy animal models: pig and rat. Automatically computed estimates of lung structure size were validated against manual measures. In addition, we present 3D visualizations of the lung structures using the segmentation calculated for each data set. This method has the potential to provide an in vivo indicator of structural remodeling caused by a range of respiratory diseases, including chronic obstructive pulmonary disease and pulmonary fibrosis.OCIS codes: (110.4500) Optical coherence tomography, (100.0100) Image processing, (100.2960) Image analysis     

En-face polarization-sensitive optical coherence tomography to characterize early-stage esophageal cancer and determine tumor margin

Current imaging tools are insufficiently sensitive to the early diagnosis of esophageal squamous cell carcinoma (ESCC). The application of polarization-sensitive optical coherence tomography (PS-OCT) to detect tumor-stroma interaction is an interesting issue in cancer diagnosis. In this translational study, we found that en-face PS-OCT effectively characterizes protruding, flat, and depressive type ESCC regardless of animal or human specimens. In addition, the tumor contour and margin could also be drawn and determined on a broad en-face view. The determined tumor margin could be in the proximity of 2 mm to the actual tumor margin, which was proved directly using histology.     

Computational refocusing of Jones matrix polarization-sensitive optical coherence tomography and investigation of defocus-induced polarization artifacts

Here we demonstrate a long-depth-of-focus imaging method using polarization sensitive optical coherence tomography (PS-OCT). This method involves a combination of Fresnel-diffraction-model-based phase sensitive computational refocusing and Jones-matrix based PS-OCT (JM-OCT). JM-OCT measures four complex OCT images corresponding to four polarization channels. These OCT images are computationally refocused as preserving the mutual phase consistency. This method is validated using a static phantom, postmortem zebrafish, and ex vivo porcine muscle samples. All the samples demonstrated successful computationally-refocused birefringence and degree-of-polarization-uniformity (DOPU) images. We found that defocusing induces polarization artifacts, i.e., incorrectly high birefringence values and low DOPU values, which are substantially mitigated by computational refocusing.     

Automated choroidal neovascularization detection algorithm for optical coherence tomography angiography

Optical coherence tomography angiography has recently been used to visualize choroidal neovascularization (CNV) in participants with age-related macular degeneration. Identification and quantification of CNV area is important clinically for disease assessment. An automated algorithm for CNV area detection is presented in this article. It relies on denoising and a saliency detection model to overcome issues such as projection artifacts and the heterogeneity of CNV. Qualitative and quantitative evaluations were performed on scans of 7 participants. Results from the algorithm agreed well with manual delineation of CNV area.OCIS codes: (170.4500) Optical coherence tomography, (170.3880) Medical and biological imaging, (100.0100) Image processing     

基于光学相干断层成像量化评估平滑面早期牙釉质龋的研究进展

背景：平滑面早期牙釉质龋虽然已发生脱矿改变但无肉眼可见的龋洞形成,目前临床采用的常规检测方法难以对其准确诊断。目的：应用光学相干断层成像技术对平滑面早期牙釉质龋的量化研究进展进行综述。方法：由第一作者检索CNKI和EBSCO HOST数据库中1979/2011发表的关于光学相干断层成像技术定量研究平滑面早期龋的相关文献,以＂光学相干断层成像,早期龋,平滑面,量化评估＂和＂optical coherence tomography,early caries,smooth surface,quantitative assessment＂为检索词进行检索。纳入31篇进行综述。结果与结论：新兴的光学相干断层成像技术能够检测龋变牙釉质的背向散射信号使脱矿牙釉质成像,并应用深度、反射率、衰减系数等定量指标对平滑面早期牙釉质龋进行量化评估,为牙釉质早期龋的诊断提供了新的方法。     

基于光学相干断层成像量化评估平滑面早期牙釉质龋的研究进展

背景:平滑面早期牙釉质龋虽然已发生脱矿改变但无肉眼可见的龋洞形成,目前临床采用的常规检测方法难以对其准确诊断.目的:应用光学相干断层成像技术对平滑面早期牙釉质龋的量化研究进展进行综述.方法:由第一作者检索CNKI和EBSCO HOST数据库中1979/2011发表的关于光学相干断层成像技术定量研究平滑面早期龋的相关文献,以光学相干断层成像,早期龋,平滑面,量化评估和optical coherence tomography,early caries,smooth surface,quantitative assessment为检索词进行检索.纳入31篇进行综述.结果与结论:新兴的光学相干断层成像技术能够检测龋变牙釉质的背向散射信号使脱矿牙釉质成像,并应用深度、反射率、衰减系数等定量指标对平滑面早期牙釉质龋进行量化评估,为牙釉质早期龋的诊断提供了新的方法.     

Performance comparison between 8- and 14-bit-depth imaging in polarization-sensitive swept-source optical coherence tomography

Recently the effects of reduced bit-depth acquisition on swept-source optical coherence tomography (SS-OCT) image quality have been evaluated by using simulations and empirical studies, showing that image acquisition at 8-bit depth allows high system sensitivity with only a minimal drop in the signal-to-noise ratio compared to higher bit-depth systems. However, in these studies the 8-bit data is actually 12- or 14-bit ADC data numerically truncated to 8 bits. In practice, a native 8-bit ADC could actually possess a true bit resolution lower than this due to the electronic jitter in the converter etc. We compare true 8- and 14-bit-depth imaging of SS-OCT and polarization-sensitive SS-OCT (PS-SS-OCT) by using two hardware-synchronized high-speed data acquisition (DAQ) boards. The two DAQ boards read exactly the same imaging data for comparison. The measured system sensitivity at 8-bit depth is comparable to that for 14-bit acquisition when using the more sensitive of the available full analog input voltage ranges of the ADC. Ex-vivo structural and birefringence images of equine tendon indicate no significant differences between images acquired by the two DAQ boards suggesting that 8-bit DAQ boards can be employed to increase imaging speeds and reduce storage in clinical SS-OCT/PS-SS-OCT systems. One possible disadvantage is a reduced imaging dynamic range which can manifest itself as an increase in image artifacts due to strong Fresnel reflection.