Enhanced-Resolution Optical Coherence Tomography Imaging

2016 ◽  
Vol 235 (3) ◽  
pp. 163-172 ◽  
Author(s):  
Akihito Uji ◽  
Tomoaki Murakami ◽  
Shigeta Arichika ◽  
Yuki Muraoka ◽  
Shin Yoshitake ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Image Quality ◽  
Super Resolution ◽  
Processing Technique ◽  
Image Processing Technique ◽  
Optical Coherence ◽  
Enhanced Resolution ◽  
Opinion Score ◽  
Significant Difference ◽  
Bicubic Interpolation

Purpose: The effect of the enhanced-resolution imaging (ERI) technique on optical coherence tomography (OCT) images was evaluated. Methods: A total of 5 healthy subjects and 20 patients diagnosed with various eye diseases were recruited into the study. ERI, a novel image processing technique, was accomplished by using super-resolution technology, and was assessed by objectively and subjectively comparing the image quality among three different image groups: images enlarged without bicubic interpolation (NONE), with bicubic interpolation (IP), and with ERI. Results: ERI showed a higher ratio of the detailed variance to the background variance than NONE, whereas no significant difference was detected between NONE and IP. The mean opinion score of 5 experienced retinal specialists for ERI was significantly higher than that for IP. Conclusions: ERI generated a sharper image and clearly visualized small objects. Additionally, it is effective in enhancing OCT image quality.

scholarly journals Swept Source Optical Coherence Tomography Angiography for Contact Lens-Related Corneal Vascularization

2016 ◽  
Vol 2016 ◽  
pp. 1-3 ◽  
Author(s):  
Marcus Ang ◽  
Yijun Cai ◽  
Anna C. S. Tan
Keyword(s):  
Optical Coherence Tomography ◽  
Image Quality ◽  
Contact Lens ◽  
Optical Coherence Tomography Angiography ◽  
Quality Score ◽  
Image Quality Score ◽  
Optical Coherence ◽  
Swept Source ◽  
Corneal Vascularization ◽  
Significant Difference

Purpose. To describe a novel technique of adapting a swept-source optical coherence tomography angiography (OCTA) to image corneal vascularization.Methods. In this pilot cross-sectional study, we obtained 3 × 3 mm scans, where 100,000 A-scans are acquired per second with optical axial resolution of 8 μm and lateral resolution of 20 μm. This was performed with manual “XYZ” focus without the anterior segment lens, until the focus of the corneoscleral surface was clearly seen and the vessels of interest were in focus on the corresponding red-free image. En face scans were evaluated based on image quality score and repeatability.Results. We analyzed scans from 10 eyes (10 patients) with corneal vascularization secondary to contact lens use in 4 quadrants, with substantial repeatability of scans in all quadrants (mean image quality score 2.7 ± 0.7;κ=0.75). There was no significant difference in image quality scores comparing quadrants (superior temporal: 2.9 ± 0.6, superior nasal: 2.8 ± 0.4, inferior temporal: 2.5 ± 0.9, and inferior nasal: 2.4 ± 1.0;P=0.276) and able to differentiate deep and superficial corneal vascularization.Conclusion. This early clinical study suggests that the swept-source OCTA used may be useful for examining corneal vascularization, which may have potential for clinical applications such as detecting early limbal stem cell damage.

scholarly journals Investigation of Light Parameters on Image Quality and Optical Coherence Tomography

2021 ◽  
Vol 2021 ◽  
pp. 1-6
Author(s):  
Boka Fikadu ◽  
Bulcha Bekele ◽  
Leta Tesfaye Jule ◽  
Anatol Degefa ◽  
N. Nagaprasad ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Image Quality ◽  
Time Domain ◽  
Glass Sample ◽  
Michelson Interferometer ◽  
Signal Strength ◽  
Optical Coherence ◽  
Time Domain Signal ◽  
Significant Difference ◽  
The Time Domain

In this work, image quality and optical coherence tomography were studied. The results of the study show that there is a very significant difference between ultrasound and optical coherence tomography to produce an image with a different wave. To understand this, we studied the basic principle of optical coherence tomography in the Michelson interferometer using monochromatic and broadband sources. Time-domain and spectral-domain measurements, which exist at the detector level, are briefly described using a glass sample. The time-domain signal strength of the Michelson interferometer using a broadband source is a Gaussian envelope.

scholarly journals Repeatability of binarization thresholding methods for optical coherence tomography angiography image quantification

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Nihaal Mehta ◽  
Phillip X. Braun ◽  
Isaac Gendelman ◽  
A. Yasin Alibhai ◽  
Malvika Arya ◽  
...  
Keyword(s):  
Image Processing ◽  
Optical Coherence Tomography ◽  
Optical Coherence Tomography Angiography ◽  
Histogram Equalization ◽  
Processing Technique ◽  
Image Processing Technique ◽  
Foveal Avascular Zone ◽  
Optical Coherence ◽  
Multiple Devices ◽  
Processing Techniques

Abstract Binarization is a critical step in analysis of retinal optical coherence tomography angiography (OCTA) images, but the repeatability of metrics produced from various binarization methods has not been fully assessed. This study set out to examine the repeatability of OCTA quantification metrics produced using different binarization thresholding methods, all of which have been applied in previous studies, across multiple devices and plexuses. Successive 3 × 3 mm foveal OCTA images of 13 healthy eyes were obtained on three different devices. For each image, contrast adjustments, 3 image processing techniques (linear registration, histogram normalization, and contrast-limited adaptive histogram equalization), and 11 binarization thresholding methods were independently applied. Vessel area density (VAD) and vessel length were calculated for retinal vascular images. Choriocapillaris (CC) images were quantified for VAD and flow deficit metrics. Repeatability, measured using the intra-class correlation coefficient, was inconsistent and generally not high (ICC < 0.8) across binarization thresholds, devices, and plexuses. In retinal vascular images, local thresholds tended to incorrectly binarize the foveal avascular zone as white (i.e., wrongly indicating flow). No image processing technique analyzed consistently resulted in highly repeatable metrics. Across contrast changes, retinal vascular images showed the lowest repeatability and CC images showed the highest.

Feature Based Differentiator for Fluid Filled Retinal Abnormalities in Retina Using Optical Coherence Tomography Images

2020 ◽  
Vol 10 (3) ◽  
pp. 566-571
Author(s):  
K. Venkatraman ◽  
M. Sumathi
Keyword(s):  
Optical Coherence Tomography ◽  
Vision Loss ◽  
Fluid Collection ◽  
Wiener Filter ◽  
Detection Algorithm ◽  
Processing Technique ◽  
Input Image ◽  
Optical Coherence ◽  
Significant Difference ◽  
Overall Performance

Introduction: The Optical Coherence Tomography is widely used in ophthalmic imaging to assess the condition of retina. It serves as an effective tool in diagnosing various fluid related abnormalities in retina, which are prior stages to vision loss. The overall pattern of fluid collection is a vital tool in disease identification. Aim: To classify various fluid filled retinal abnormalities, like, Cystoid Macular Edema (CME), Choroidal Neo Vascular Membrane (CNVM), and Macular Hole (MH) based on various features. Materials and Methods: A total of 114 images were acquired using TOPCONN and ZEISS OCT devices. The obtained images were converted to grayscale and subjected to pre-processing technique. Homomorphic Wiener filter was used to remove the speckle noises. The Region of Interest was then identified by basic edge detection algorithm, for which, various features were extracted and utilised for classification. Outputs were cross verified with a medical expert and the performance of the proposed system was evaluated. Results: Based on the proposed system of classification of various fluid filled retinal disorders, the input image was classified as Class 0—Normal, Class 1—CME, Class 2—CNVM, and Class 3—MH based on the pattern of fluid accumulation. The overall performance was compared and evaluated and it was identified that the system exhibited 91.65% accuracy, 90.36% Sensitivity, 92.95% Specificity and Youden's Index value of 0.83. Conclusion: As OCT serves an important tool for pre-screening of blindness, automations in these areas remains of higher potential. The classification is based on the features used, which showed a significant difference between the various classes as classified. The overall performance seems to be satisfactory and would thus help in early detection of fluid related abnormalities and also can be used as an expert tool to analyse the efficiency of the therapies.

scholarly journals Evaluation of Crack Formation and Propagation with Ultrasonic Root-End Preparation and Obturation Using a Digital Microscope and Optical Coherence Tomography

Scanning ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-6
Author(s):  
Bayan Rashed ◽  
Yoshiko Iino ◽  
Arata Ebihara ◽  
Takashi Okiji
Keyword(s):  
Optical Coherence Tomography ◽  
Crack Formation ◽  
Mineral Trioxide Aggregate ◽  
Optical Coherence ◽  
Micro Ct ◽  
Weak Correlation ◽  
Significant Difference ◽  
Digital Microscope ◽  
Ultrasonic Preparation ◽  
End Resection

Objective. This study is aimed at determining (1) the effect of root-end resection, ultrasonic root-end preparation, and root-end filling on the incidence of crack formation and propagation by using a digital microscope (DM) and optical coherence tomography (OCT) and (2) the performance of OCT on the detection of cracks by comparing with microcomputed tomography (micro-CT) as a reference standard. Methodology. Thirty extracted lower incisors were endodontically treated and subjected to root-end resection and ultrasonic root-end cavity preparation. Then, the teeth were divided into three groups (n=10, each), and the root-end cavity was either left unfilled or filled with mineral trioxide aggregate (MTA) or super-EBA. The resected surface was observed with OCT and DM after the root-end resection, ultrasonic root-end preparation, and root-end filling, and the frequency of incomplete and complete cracks were recorded. The observation was repeated after two weeks, one month, and two months, and micro-CT scans after two months were taken as the gold standard. Results. The DM results show dentinal crack formation in 47% of the samples following root-end resection and in 87% following ultrasonic preparation. After the ultrasonic preparation, no existing crack propagated to a complete crack, but new cracks were formed. MTA and super-EBA had no effect on crack formation. The Spearman correlation coefficient between OCT and DM was 0.186 (very weak correlation; p=0.015). Sensitivity and specificity in comparison to micro-CT were 0.50 and 0.55 in OCT and 1.00 and 0.35 in DM, respectively. McNemar’s test showed a significant difference between OCT and DM (p<0.05). Conclusion. Apical resection and ultrasonic preparation could form dentinal cracks. OCT and DM showed different detection frequencies of cracks with very weak correlation. DM showed superior sensitivity compared with OCT.

scholarly journals Repeatability of ocular surface vessel density measurements with optical coherence tomography angiography

2019 ◽  
Vol 19 (1) ◽  
Author(s):  
Sijie Cai ◽  
Fengping Zhao ◽  
Chixin Du
Keyword(s):  
Optical Coherence Tomography ◽  
Ocular Surface ◽  
Optical Coherence Tomography Angiography ◽  
Imaging System ◽  
Intraclass Correlation ◽  
Vessel Density ◽  
Optical Coherence ◽  
Significant Difference ◽  
Surface Vessel ◽  
Healthy Eyes

Abstract Background To determine the repeatability of measurements of ocular surface vessel density in normal and diseased eyes using optical coherence tomography angiography (OCTA). Methods Ten normal eyes, 10 pinguecula eyes, and 10 pterygium eyes of 30 volunteers were subjected to OCTA (AngioVue Imaging System, Optovue, Inc.). For scanning, we used the corneal adapter module. Each eye was scanned three times in the nasal and temporal directions, separately. AngioVue software was used to generate the ocular surface vessel density. Ocular surface vessel density was defined as the proportion of vessel area with blood flow to the total measurement area (3 × 3 mm2). Intersession repeatability of the measurement was summarized as the coefficient of variation (CV), and intraclass correlation coefficients (ICC) were calculated by variance component models. Results The CVs were less than 5% in all subjects, and the ICCs exceeded 0.9; thus, all measurements showed good repeatability. The nasal vessels densities differed significantly between healthy eyes and eyes with pterygium (P < 0.05); however, there was no significant difference between healthy eyes and eyes with pinguecula (P = 0.466). Conclusions These results suggest that measurement of ocular surface vessel density by OCTA in normal eyes and eyes with pterygium and pinguecula is repeatable. This preliminary research describes a quantitative and visual method for assessing vessel density of the ocular surface with a high level of consistency.

scholarly journals A Novel Singular Value Decomposition-Based Denoising Method in 4-Dimensional Computed Tomography of the Brain in Stroke Patients with Statistical Evaluation

Sensors ◽  
2020 ◽  
Vol 20 (11) ◽  
pp. 3063 ◽  
Author(s):  
WonSeok Yang ◽  
Jun-Yong Hong ◽  
Jeong-Youn Kim ◽  
Seung-ho Paik ◽  
Seung Hyun Lee ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Image Processing ◽  
Image Quality ◽  
Statistical Evaluation ◽  
Processing Technique ◽  
Singular Value ◽  
Image Processing Technique ◽  
Stroke Patients ◽  
Value Decomposition ◽  
The Brain

Computed tomography (CT) is a widely used medical imaging modality for diagnosing various diseases. Among CT techniques, 4-dimensional CT perfusion (4D-CTP) of the brain is established in most centers for diagnosing strokes and is considered the gold standard for hyperacute stroke diagnosis. However, because the detrimental effects of high radiation doses from 4D-CTP may cause serious health risks in stroke survivors, our research team aimed to introduce a novel image-processing technique. Our singular value decomposition (SVD)-based image-processing technique can improve image quality, first, by separating several image components using SVD and, second, by reconstructing signal component images to remove noise, thereby improving image quality. For the demonstration in this study, 20 4D-CTP dynamic images of suspected acute stroke patients were collected. Both the images that were and were not processed via the proposed method were compared. Each acquired image was objectively evaluated using contrast-to-noise and signal-to-noise ratios. The scores of the parameters assessed for the qualitative evaluation of image quality improved to an excellent rating (p < 0.05). Therefore, our SVD-based image-denoising technique improved the diagnostic value of images by improving their quality. The denoising technique and statistical evaluation can be utilized in various clinical applications to provide advanced medical services.

scholarly journals Comparison of two different optical coherence tomography angiography devices in detecting healthy versus glaucomatous eyes – an observational cross-sectional study

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
A. R. Kee ◽  
V. C. H. Yip ◽  
E. L. T. Tay ◽  
C. W. Lim ◽  
J. Cheng ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Diagnostic Accuracy ◽  
Optic Disc ◽  
Optical Coherence Tomography Angiography ◽  
Optical Coherence ◽  
Cross Sectional ◽  
Swept Source ◽  
Retest Reliability ◽  
Significant Difference ◽  
Test Retest Reliability

Abstract Background To understand the differences between two different optical coherence tomography angiography (OCTA) devices in detecting glaucomatous from healthy eyes by comparing their vascular parameters, diagnostic accuracy and test-retest reliability. Methods A cross-sectional observational study was performed on healthy and glaucoma subjects, on whom two sets of OCTA images of optic disc and macula were acquired using both AngioVue (Optovue, USA) and Swept Source (Topcon, Japan) OCTA devices during one visit. A novel in-house software was used to calculate the vessel densities. Diagnostic accuracy of the machines in differentiating healthy versus glaucomatous eyes was determined using area under the receiver operating characteristic curve (AUROC) and test-retest repeatability of the machines was also evaluated. Results A total of 80 healthy and 38 glaucomatous eyes were evaluated. Glaucomatous eyes had reduced mean vessel density compared to healthy controls in all segmented layers of the optic disc and macula using AngioVue (p ≤ 0.001). However, glaucomatous eyes had higher mean vessel density on optic disc scans using Swept Source, with lack of statistically significant difference between healthy and glaucomatous eyes. The AUROC showed better diagnostic accuracy of AngioVue (0.761–1.000) compared to Swept Source (0.113–0.644). The test-retest reliability indices were generally better using AngioVue than Swept Source. Conclusions AngioVue showed better diagnostic capability and test-retest reliability compared to Swept Source. Further studies need to be undertaken to evaluate if there is any significant difference between the various machines in diagnosing and monitoring glaucoma.

Effects of Retinal Angiography on Optical Coherence Tomography Measurements

2015 ◽  
Vol 234 (3) ◽  
pp. 160-166 ◽  
Author(s):  
Young-Joon Jo ◽  
Hyung-Bin Lim ◽  
Soo-Hyun Lee ◽  
Jung-Yeul Kim
Keyword(s):  
Optical Coherence Tomography ◽  
Indocyanine Green ◽  
Retinal Thickness ◽  
Optical Coherence ◽  
Fiber Layer ◽  
Nerve Fiber Layer Thickness ◽  
Interclass Correlation ◽  
Significant Difference ◽  
Before And After ◽  
Sd Oct

Purpose: To evaluate the effects of retinal angiography, using fluorescein and indocyanine green dyes, on optical coherence tomography (OCT) measurements. Methods: In total, 76 eyes from 76 consecutive patients were included. Macular cube 512 × 128 combination scanning and optic disc 200 × 200 scanning using spectral-domain (SD)-OCT were performed twice, before and after retinal angiography, with fluorescein or indocyanine green. Signal strength, regional retinal thickness of the 9 Early Treatment Diabetic Retinopathy Study subfields, total macular volume, and retinal nerve fiber layer thickness obtained before and after angiography were compared. Repeatability was also investigated. Results: Comparing the results of OCT measured before and after retinal angiography, there was no statistically significant difference in any parameter assessed. The interclass correlation values for each measurement were all >0.808 (range 0.808-0.999). Conclusion: Retinal angiography using fluorescein and indocyanine green dyes has no significant effect on OCT measurements.

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