Review of methods and applications of attenuation coefficient measurements with optical coherence tomography

Chang, Shuang; Bowden, Audrey K.

doi:10.1117/1.jbo.24.9.090901

Cited by 73 publications

(55 citation statements)

References 77 publications

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“…To account for the variable amount of incident light, pixel intensity can be normalised to that of a reference layer 41,42,48 . Alternatively, as in our study, depth‐resolved attenuation coefficients can be used to determine intrinsic optical properties of retinal tissue independent of the amount of light received as well as of additional segmentation requirements 30,31,49 . Whilst this method is expected to reduce artefacts, one investigation suggested that age and scan quality may still have a significant effect on attenuation coefficients 49 .…”

Section: Discussionmentioning

confidence: 97%

“…The greatest depth explored with this method (193.5 µm) was selected in order to include the maximum expected cpRNFL thickness for a 50‐year‐old healthy individual. As proposed elsewhere, 10 we extracted attenuation coefficients instead of the raw intensity of each pixel using equations 17 and 18 from Vermeer et al 30 Attenuation coefficients are purported to describe how quickly incident light is attenuated when passing through the retinal portion of interest irrespective of the amount of light received 31 . Although attenuation coefficients were originally developed to minimise shadowing effects of blood vessels on underlying tissue, they should also minimise reflectance artefacts from media opacities and poor quality B‐scans 10 .…”

Section: Methodsmentioning

confidence: 99%

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Depth‐resolved variations in visibility of retinal nerve fibre bundles across the retina in enface OCT images of healthy eyes

Cheloni

Denniss

2020

Ophthalmic Physiologic Optic

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Purpose Recent developments in optical coherence tomography (OCT) technology enable direct enface visualisation of retinal nerve fibre bundle (RNFB) loss in glaucoma. However, the optimum depth at which to visualise RNFBs across the retina is unknown. We aimed to evaluate the range of depths and optimum depth at which RNFBs can be visualised across the retina in healthy eyes. Methods The central ± 25° retina of 10 healthy eyes from 10 people aged 57–75 years (median 68.5 years) were imaged with spectral domain OCT. Slab images of maximum axial resolution (4 μm) containing depth‐resolved attenuation coefficients were extracted from 0 to 193.5 μm below the inner limiting membrane (ILM). Bundle visibility within 10 regions of a superimposed grid was assessed subjectively by trained optometrists (n = 8), according to written instructions. Anterior and posterior limits of RNFB visibility and depth of best visibility were identified for each grid sector. Effects of retinal location and individual eye on RNFB visibility were explored using linear mixed modelling with likelihood ratio tests. Intraclass correlation coefficient (ICC) was used to measure overall agreement and repeatability of grading. Spearman’s correlation was used to measure correlation between depth range of visible RNFBs and retinal nerve fibre layer thickness (RNFLT). Results Retinal location and individual eye affected anterior limit of visibility (χ2(9) = 58.6 and 60.5, both p < 0.0001), but none of the differences exceeded instrument resolution, making anterior limit consistent across the retina and different eyes. Greater differences were observed in the posterior limit of visibility across retinal areas (χ2(9) = 1671.1, p < 0.0001) and different eyes (χ2(9) = 88.7, p < 0.0001). Optimal depth for visualisation of RNFBs was around 20 µm below the ILM in most regions. It varied slightly with retinal location (χ2(9) = 58.8, p < 0.0001), but it was not affected by individual eye (χ2(9) = 10.7, p = 0.29). RNFB visibility showed good agreement between graders (ICC 0.89, 95%CI 0.87–0.91), and excellent repeatability (ICC 0.96–0.99). Depth range of visible RNFBs was highly correlated with RNFLT (ρ = 0.9, 95%CI: 0.86–0.95). Conclusions The range of depths with visible RNFBs varies markedly across the healthy retina, consistently with RNFLT. To extract all RNFB information consistently across the retina, slab properties should account for differences across retinal locations and between individual eyes.

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Section: Discussionmentioning

confidence: 97%

Section: Methodsmentioning

confidence: 99%

Depth‐resolved variations in visibility of retinal nerve fibre bundles across the retina in enface OCT images of healthy eyes

Cheloni

Denniss

2020

Ophthalmic Physiologic Optic

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“…Optical AC is also emerging as an important tissue parameter for measuring how quickly incident light is attenuated when passing through a medium, and this is a function of the underlying medium properties. Loss of light in tissue can be caused by absorption, scattering, or a combination of both 27 . It was hypothesized that homogeneous and healthy tissue has a higher AC compared to pathologic tissue.…”

Section: Discussionmentioning

confidence: 99%

Optical coherence tomography for patch test grading: A prospective study on its use for noninvasive diagnosis of allergic contact dermatitis

et al. 2020

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Background The diagnosis of allergic contact dermatitis should be confirmed by skin patch tests. Distinguishing between irritant and allergic reactions is sometimes difficult. Objectives To analyse the in vivo morphological changes in patch test reactions compared to healthy skin, and to detect subclinical changes in doubtful reactions using optical coherence tomography (OCT). To develop an OCT‐based algorithm to support patch‐test grading. Methods One hundred twenty‐nine skin patch‐test areas were scanned with OCT to evaluate the following features: architectural and vascular morphology, epidermal thickness, optical attenuation coefficient (AC), and blood flow at 0.1, 0.2, and 0.35 mm depth. Results Most common OCT features of acute contact allergic reactions in patch tests were spongiosis with microvesicles (94.8%), macrovesicles (60.3%), and coalescing vesicles (46.6%), the latter useful in differentiating acute allergic from irritant dermatitis (P‐value < .05). Objective quantitative parameters correlated well with the severity grade: epidermal thickness due to spongiosis, AC (P‐value < .05) and blood flow at 0.2 and 0.35 mm (P‐value < .01). Conclusions OCT as a noninvasive diagnostic tool, established for skin cancer diagnosis, is useful for evaluating contact allergic patch‐test reactions. Not only morphological but also objective features such as blood flow and AC correlate with the reaction severity. Further studies are needed to explore the differences in irritant and allergic contact dermatitis.

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“…Data were processed as previously described by Lichtenegger et al [ 30 ]. After image acquisition, surface flattening was performed and attenuation maps were computed from OCM reflectivity data [ 65 , 66 ]. Sub-volumes consisting of 100 B-scans were chosen in a manually defined region of interest and average attenuation coefficients were calculated.…”

Section: Methodsmentioning

confidence: 99%

Improved Diagnostic Imaging of Brain Tumors by Multimodal Microscopy and Deep Learning

Gesperger

Lichtenegger

Roetzer

et al. 2020

Cancers

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Fluorescence-guided surgery is a state-of-the-art approach for intraoperative imaging during neurosurgical removal of tumor tissue. While the visualization of high-grade gliomas is reliable, lower grade glioma often lack visible fluorescence signals. Here, we present a hybrid prototype combining visible light optical coherence microscopy (OCM) and high-resolution fluorescence imaging for assessment of brain tumor samples acquired by 5-aminolevulinic acid (5-ALA) fluorescence-guided surgery. OCM provides high-resolution information of the inherent tissue scattering and absorption properties of tissue. We here explore quantitative attenuation coefficients derived from volumetric OCM intensity data and quantitative high-resolution 5-ALA fluorescence as potential biomarkers for tissue malignancy including otherwise difficult-to-assess low-grade glioma. We validate our findings against the gold standard histology and use attenuation and fluorescence intensity measures to differentiate between tumor core, infiltrative zone and adjacent brain tissue. Using large field-of-view scans acquired by a near-infrared swept-source optical coherence tomography setup, we provide initial assessments of tumor heterogeneity. Finally, we use cross-sectional OCM images to train a convolutional neural network that discriminates tumor from non-tumor tissue with an accuracy of 97%. Collectively, the present hybrid approach offers potential to translate into an in vivo imaging setup for substantially improved intraoperative guidance of brain tumor surgeries.

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Review of methods and applications of attenuation coefficient measurements with optical coherence tomography

Cited by 73 publications

References 77 publications

Depth‐resolved variations in visibility of retinal nerve fibre bundles across the retina in enface OCT images of healthy eyes

Depth‐resolved variations in visibility of retinal nerve fibre bundles across the retina in enface OCT images of healthy eyes

Optical coherence tomography for patch test grading: A prospective study on its use for noninvasive diagnosis of allergic contact dermatitis

Improved Diagnostic Imaging of Brain Tumors by Multimodal Microscopy and Deep Learning

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