The Definition, Rationale, and Effects of Thresholding in OCT Angiography

Cole, Emily; Moult, Eric M.; Dang, Sabin; Choi, WooJhon; Ploner, Stefan B.; Lee, ByungKun; Louzada, Ricardo Noguera; Novais, Eduardo Amorim; Schottenhamml, Julia; Husvogt, Lennart; Maier, Andreas; Fujimoto, James G.; Waheed, Nadia K.; Duker, Jay S.

doi:10.1016/j.oret.2017.01.019

Cited by 46 publications

(37 citation statements)

References 10 publications

(6 reference statements)

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“…The masked OCTA image is then displayed. OCTA images are highly dependent on processing details and parameters, however, this information is proprietary in commercial instruments (From Cole et al, 2017).…”

Section: Interscan Time Determines Octa Sensitivity and Saturationmentioning

confidence: 99%

“…Even if OCT instruments have high sensitivity, all OCT images have regions such as the vitreous and choroid which have low signal and consist mainly of noise. This noise can generate false flow OCTA signals (Cole et al, 2017), and methods aimed at removing these false OCTA signals can themselves generate artifacts where OCTA signals are absent even in the presence of flow.…”

Section: Threshold Masking To Remove Noise and Attenuation Artifactsmentioning

confidence: 99%

“…Fig. 6 shows how threshold levels can affect OCTA display (adapted from Cole et al, 2017). The top row (A.2 to A5) shows a representative OCT cross-section (A.1) and OCTAs with different threshold levels.…”

Section: Threshold Masking To Remove Noise and Attenuation Artifactsmentioning

confidence: 99%

“…OCTA images must always be evaluated with the corresponding en face OCT structural scans segmented at the same level as the choriocapillaris. Dark areas on the OCTA may represent areas of true choriocapillaris loss or may represent areas of shadowing arising from attenuation of OCT signal (Cole et al, 2017). When there is a low or noisy OCT signal, accurate OCTA decorrelation signals cannot be obtained and these regions are threshold masked to remove the invalid OCTA data.…”

Section: Pitfalls To the Evaluation Of Choriocapillaris With Octamentioning

confidence: 99%

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Optical Coherence Tomography Angiography

Spaide

Fujimoto

Waheed

2015

Retina

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189

195

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Optical coherence tomography (OCT) was one of the biggest advances in ophthalmic imaging. Building on that platform, OCT angiography (OCTA) provides depth resolved images of blood flow in the retina and choroid with levels of detail far exceeding that obtained with older forms of imaging. This new modality is challenging because of the need for new equipment and processing techniques, current limitations of imaging capability, and rapid advancements in both imaging and in our understanding of the imaging and applicable pathophysiology of the retina and choroid. These factors lead to a steep learning curve, even for those with a working understanding dye-based ocular angiography. All for a method of imaging that is a little more than 10 years old. This review begins with a historical account of the development of OCTA, and the methods used in OCTA, including signal processing, image generation, and display techniques. This forms the basis to understand what OCTA images show as well as how image artifacts arise. The anatomy and imaging of specific vascular layers of the eye are reviewed. The integration of OCTA in multimodal imaging in the evaluation of retinal vascular occlusive diseases, diabetic retinopathy, uveitis, inherited diseases, age-related macular degeneration, and disorders of the optic nerve is presented. OCTA is an exciting, disruptive technology. Its use is rapidly expanding in clinical practice as well as for research into the pathophysiology of diseases of the posterior pole. Abbreviations AF Autofluorescence AMD Age-related macular degeneration CCD Charge-coupled device CME Cystoid macular edema CMOS Complementary metal oxide semiconductor CNV Choroidal neovascularization CRORA Complete loss of the RPE and outer retina FA Fluorescein angiography ICG Indocyanine green ICGA Indocyanine green angiography MNV Macular neovascularization; includes choroidal neovascularization and Type 3 neovascularization OCT Optical coherence tomography OCTA Optical coherence tomography angiography OMAG Optical microangiography RPE Retinal pigment epithelium SD Spectral domain SS Swept source VEGF Vascular endothelial growth factor VISTA Variable interscan time analysis

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Section: Interscan Time Determines Octa Sensitivity and Saturationmentioning

confidence: 99%

Section: Threshold Masking To Remove Noise and Attenuation Artifactsmentioning

confidence: 99%

Section: Threshold Masking To Remove Noise and Attenuation Artifactsmentioning

confidence: 99%

Section: Pitfalls To the Evaluation Of Choriocapillaris With Octamentioning

confidence: 99%

See 2 more Smart Citations

Optical Coherence Tomography Angiography

Spaide

Fujimoto

Waheed

2015

Retina

Self Cite

189

195

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“…However, it is important to pay attention to frequent presence of attenuation artefacts (for example due to presence of drusen) and projection artefacts from superficial vessels, when evaluating CC images obtained with OCT‐A (Cole et al. ; Spaide et al. ).…”

Section: Introductionmentioning

confidence: 99%

Quantitative choriocapillaris evaluation in intermediate age‐related macular degeneration by swept‐source optical coherence tomography angiography

Vujosevic

Toma

Muraca

et al. 2019

Acta Ophthalmologica

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Purpose: To investigate choriocapillaris (CC) perfusion, by evaluating flow voids (FV), in eyes with intermediate age-related macular degeneration (iAMD) using swept-source optical coherence tomography angiography (SS-OCT-A). Methods: Patients with bilateral or unilateral iAMD and normal controls underwent SS-OCT and OCT-A examination. Choriocapillaris (CC) FVs were quantitatively assessed on OCT-A images using MATLAB (version 2017b; MathWorks, Natick, MA, USA), after a preprocessing aimed at compensating for CC attenuation artefacts. Three different thresholds [1 standard deviation (SD), 1.25 SD and 1.5 SD] were applied. Final FV percentage (FV%) was calculated as the ratio between area with absent flow and total scanned area. Results: Of 41 patients with iAMD and 16 normal subjects enrolled in the study, 39 eyes (39 patients) with iAMD and all 16 normal eyes (16 control subjects) were included in the final analysis. Mean FV% (1 SD) was 13.45 AE 0.66 in controls, 14.19 AE 1.23 in bilateral iAMD and 14.21 AE 0.99 in unilateral iAMD (p = 0.03, for difference between controls and bilateral iAMD). Mean FV% (1.25 SD) was 6.55 AE 0.65 in controls, 7.33 AE 1.4 in bilateral iAMD and 7.06 AE 1.4 in unilateral iAMD (p = 0.048, for difference between controls and bilateral iAMD). Mean FV% (1.5 SD) was 2.71 AE 0.82 in controls, 2.55 AE 1.12 in bilateral iAMD and 3.25 AE 1.17 in unilateral iAMD (p = 0.038, for difference between bilateral and unilateral iAMD). Conclusion: A significantly higher FV% was found in patients with iAMD versus controls. A higher trend in FV% was found in unilateral iAMD (with neovascular AMD in the fellow eye) versus bilateral iAMD, when applying the lowest threshold. Further, larger and longitudinal studies are needed to confirm this data.

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Optical Coherence Tomography Structural and Functional Imaging

Ding

2023

Biomedical Photonic Technologies

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The Definition, Rationale, and Effects of Thresholding in OCT Angiography

Cited by 46 publications

References 10 publications

Optical Coherence Tomography Angiography

Optical Coherence Tomography Angiography

Quantitative choriocapillaris evaluation in intermediate age‐related macular degeneration by swept‐source optical coherence tomography angiography

Optical Coherence Tomography Structural and Functional Imaging

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