Raw Optical Coherence Tomography Data Research Articles

Live Acquisition of Internal Fingerprint With Automated Detection of Subsurface Layers Using OCT

Recently, optical coherence tomography (OCT) was introduced as a novel fingerprint scanning technique. This approach is resistant to fake fingerprint attacks, and is robust against poor fingertip conditions, i.e., wet or stained fingers. The method proceeds by scanning a fingertip in three dimensions and capturing a fingerprint from the subsurface layer. Although OCT has the potential to be widely used as a new standard in fingerprint scanning, it is hindered by its low scanning speed and the lack of computing power available for reproducing raw OCT data into images in real time; for instance, this process can take minutes to obtain barely one fingerprint image. In this letter, we introduce a novel spectral-domain OCT-based 3-D fingerprint scanner that is capable of obtaining an internal fingerprint image within 2 s. In order to obtain internal fingerprint images from raw OCT data in real time, we used graphics processing unit for massive parallel computation, along with an automated method for extracting the internal fingerprint from a 3-D scan of a fingertip. In addition, the robustness of the OCT fingerprint scanner was established by comparing fingerprint images—of wet, stained, and damaged fingertips—that were obtained by the OCT system with those from a commercially available optical fingerprint scanner.

Macrophage content detection in an experimental rabbit model of atherosclerotic plaque by optical coherence tomography

To evaluate the feasibility of detecting macrophage content on atherosclerotic plaques by optical coherence tomography (OCT) technique. Thirty New Zealand white rabbits were equally divided into 3 groups at random: Control group (fed normal rabbit chow, n = 10); lipid diet group (fed regular chow supplemented with cholesterol, n = 10) and balloon injury+ lipid diet group (balloon catheter injury of the common carotid artery after 2 weeks lipid diet, n = 10). After 12 weeks, all rabbits underwent pharmacological triggering with Chinese Russell's viper venom (CRVV, 15 mg/kg, i.p.) and histamine (0.02 mg/kg, i.v.). Common carotid arteries were detected with OCT and the Movat pentachrome stain respectively. OCT and histological examination results were compared and the correlation was analyzed. The intra thickness measured by Movat pentachrome stain and by the OCT was (15.2 ± 0.9) µm and (20.2 ± 7.6) µm, the medial thickness was (434.2 ± 86.5) µm and (453.8 ± 87.2) µm, the plaque thickness was (330.2 ± 87.1) µm and (392.2 ± 134.5) µm, the fibrous cap thickness was (58.3 ± 5.6) µm and (61.2 ± 4.9) µm, respectively (all P > 0.05). The normalized standard deviation of the OCT signal (NSD) was compared with immunohistochemical detection. The OCT signal within the cap is relatively homogeneous for low macrophage density in high lipid diet group. For the raw OCT data, a correlation of r = 0.846 (P < 0.01) was found between OCT NSD and a CD68 area<10%, whereas for the base 10 logarithm OCT data, a correlation of r = 0.646 (P < 0.05) was found between OCT NSD and a CD68 area<10%. In balloon injury + high lipid diet group, the OCT signal within the cap was relatively heterogeneous for high macrophage content. For the raw OCT data, a correlation of r = 0.906 (P < 0.01) was found between OCT NSD and a CD68 area >10%, whereas for the base 10 logarithm OCT data, a correlation of r = 0.593 (P < 0.05) was found between OCT NSD and a CD68 area >10%. For the raw OCT signal NSD, a range of NSDs (7.12% to 7.35%) demonstrated 100% sensitivity and specificity (Kappa value 1.0) for differentiating caps containing >10% CD68 staining. For the base 10 logarithm OCT signal, NSD values ranging from 7.81% to 7.92% provided 70% sensitivity and 75% specificity (value 0.44) for identifying caps containing >10% CD68 staining. OCT is an effective tool to determine macrophage content in this model. OCT imaging can clearly visualize different types of atherosclerotic plaques and provide detailed information on plaque characteristics.

Application of an OCT data-based mathematical model of the foveal pit in Parkinson disease.

Spectral-domain Optical coherence tomography (OCT) has shownremarkable utility in the study of retinal disease and has helped to characterize the fovea in Parkinson disease (PD) patients. We developed a detailed mathematical model based on raw OCT data to allow differentiation of foveae of PD patients from healthy controls. Of the various models we tested, a difference of a Gaussian and a polynomial was found to have "the best fit". Decision was based on mathematical evaluation of the fit of the model to the data of 45 control eyes versus 50 PD eyes. We compared the model parameters in the two groups using receiver-operating characteristics (ROC). A single parameter discriminated 70% of PD eyes from controls, while using seven of the eight parameters of the model allowed 76% to be discriminated. The future clinical utility of mathematical modeling in study of diffuse neurodegenerative conditions that also affect the fovea is discussed.

Assessment of accuracy and repeatability of anterior segment optical coherence tomography and reproducibility of measurements using a customised software program

Purpose: The aim was to study the reliability of measurements of the RTVue (Optovue, Fremont, CA, USA) anterior segment optical coherence tomographer (AS‐OCT) and assess how results can be improved by analysing raw optical coherence tomography data with customised image analysis software and applying correction factors.Methods: Five RTVue AS‐OCT instruments (ver. 4.0) were assessed by imaging gauge blocks of three different lengths, single/stepped glass plate (microscope slides) and flat window glass to check for width, depth and linearity of the measurement scans. Five repeats per calibration tool were imaged and averaged. Raw data were exported and loaded into customised image analysis software written in LabWindows/CVI for further analysis. Using two calibration balls with different radii, measurement scans were validated. Repeatability of the optical coherence tomographs and the edge detection procedure were checked and statistical analyses performed.Results: Variations ranging from 0.01 to 1.93-mm in scan width and 0.1 to 0.17-mm in scan depth were found between the five instruments. Slight curvature distortion of 0.06 ± 0.01-mm (mean and standard deviation) was found in the raw images. By isolating the three sources of image distortion and applying individual correction factors, accuracy for corneal curvature measurements could be improved to better than 0.1-mm. Manual edge detection limited the coefficient of repeatability value to 0.06 and 0.08-mm for anterior and posterior radii of curvature, respectively. The coefficient of repeatability of corneal thickness measurements was less than 8 µm.Conclusions: Accuracy of the RTVue AS‐OCT varied between instruments. By applying calibration scale factors calculated by customised software, accuracy of thickness and curvature values of the anterior eye was improved. The achievable precision is sufficient to detect clinically relevant corneal curvature variations.

Evaluation of macular morphology in patients with multiple sclerosis

Abstract Purpose To assess macular morphology in patients with multiple sclerosis (MS) with and without history of optic neuritis (ON). Methods Twenty‐six MS patients were recruited in this study, and 26 randomly eyes were selected from 26 age‐matched healthy subjects as controls. Optical coherence tomography (OCT) examination was performed on each eye using a Stratus OCT device. The raw OCT data were exported from the device and further processed using a custom‐built algorithm (OCTRIMA). Thickness measurements of 7 intraretinal layers and the total retina were obtained. Eyes from MS patients were divided into 2 groups for statistical analyses. The ON+ group contained 26 eyes which had ON at least 6 months prior to enrollment. Twenty‐three eyes had no history of ON (ON‐ group). All thickness measurements were compared among the 3 groups using ANOVA with Newman‐Keuls post‐hoc analysis. Results Significant decrease in thickness was observed in ON+ and ON‐ eyes compared to controls for the macula (290±6µm, 283±12µm and 267±12µm in the control, ON‐ and ON+ group, respectively), retinal nerve fiber layer (38±2µm, 35±2µm and 31±4µm, respectively) and ganglion cell layer and inner plexiform layer complex (71±4µm, 64±7µm and 53±7µm, respectively). No statistically significant difference in thickness was found for the remaining intraretinal layers between the 3 groups analyzed. Conclusion Atrophy of the ganglion cells and nerve fibers in the macula of MS patients was observed even without previous history of ON. Therefore, thickness measurements of ganglion cells might be useful in the diagnosis and follow‐up of MS patients.

Interferometric Synthetic Aperture Microscopy: Inverse Scattering for Optical Coherence Tomography

L coherence interferometry has a long history for accurately probing depths in biological media.1 In an effort to better visualize the resulting scattering maps, we used optical coherence tomography (OCT), which provided crosssectional images and three-dimensional volumes using only oneor two-dimensional scanning, respectively. Over the past 15 years, OCT has been shown to be useful in many biomedical applications, including ophthalmology, cardiology, developmental biology and microscopy.2 With the use of near-infrared light, OCT facilitates the noninvasive monitoring of cellular and nuclear organization, proliferation and functionality. A strength of OCT is its ability to recreate object structure based on first-order object scattering, provided that only the data in the confocal region of the lens was used. OCT has vastly improved the visualization of biological processes. However, it remains unable to resolve features imaged outside of the confocal region. OCT signals are akin to echo pulses from strip-map radar or sonar, where raw data are plotted in adjacent columns. OCT To demonstrate this technique, we present a collection of scatterers having a mean diameter of 2 μm suspended in silicone and imaged with cross-sectional ISAM. Our ISAM system is similar to that for spectral-domain OCT,5 except with additional instrumentation for phase stability and tighter focusing. The multiplexed raw OCT data set must maintain phase stability to ensure proper reconstruction. The figure displays (a) the original and (b) the reconstruction of an imaging area of 500 μm (transverse) by 1,000 μm (axial), where the bandwidth is 100 nm, and the spot size is 6 μm. The image resolution of point scatterers outside of the confocal region for the original experimental image data is not constant. However, for the reconstruction, the resolution is constant along the entire image with only amplitude variations. The interference between the light scattered from a group of adjacent particles (boxed) is evident in the original image (top magnified). Our method properly rephases the signal from scatterers to produce a well-resolved image (bottom magnified). This method will be extended to imaging biological samples to achieve high, spatially invariant resolution in 3D. t