Optical Coherence Tomography Artifacts Research Articles

High Prevalence of Artifacts in Optical Coherence Tomography With Adequate Signal Strength.

This study aims to investigate the prevalence of artifacts in optical coherence tomography (OCT) images with acceptable signal strength and evaluate the performance of supervised deep learning models in improving OCT image quality assessment. We conducted a retrospective study on 4555 OCT images from 546 patients, with each image having an acceptable signal strength (≥6). A comprehensive analysis of prevalent OCT artifacts was performed, and five pretrained convolutional neural network models were trained and tested to infer images based on quality. Our results showed a high prevalence of artifacts in OCT images with acceptable signal strength. Approximately 21% of images were labeled as nonacceptable quality. The EfficientNetV2 model demonstrated superior performance in classifying OCT image quality, achieving an area under the receiver operating characteristic curve of 0.950 ± 0.007 and an area under the precision recall curve of 0.985 ± 0.002. The findings highlight the limitations of relying solely on signal strength for OCT image quality assessment and the potential of deep learning models in accurately classifying image quality. Application of the deep learning-based OCT image quality assessment models may improve the OCT image data quality for both clinical applications and research.

Multi-shaping sparse-continuous reconstruction for an optical coherence tomography sidelobe suppression.

Optical coherence tomography (OCT) images are commonly affected by sidelobe artifacts due to spectral non-uniformity and spectral leakage. Conventional frequency domain spectral shaping methods widen the mainlobe and compromise axial resolution. While image-domain deconvolution techniques can address the trade-off between axial resolution and artifact suppression, their reconstruction quality relies on accurate measurement or estimation of system point spread function (PSF). Inaccurate PSF estimation leads to loss of details in the reconstructed images. In this Letter, we introduce multi-shaping sparse-continuous reconstruction (MSSCR) for an OCT image, a novel, to the best of our knowledge, framework that combines spectral multi-shaping and iterative image reconstruction with sparse-continuous priors. The MSSCR achieves sidelobe suppression without requiring any PSF measurement or estimation and effectively preserving the axial resolution. The experimental results demonstrate that the MSSCR achieves sidelobe suppression of more than 8 dB. We believe that the MSSCR holds potential for addressing sidelobe artifacts in OCT.

Birefringence-derived scleral artifacts in optical coherence tomography images of eyes with pathologic myopia

We investigated birefringence-derived scleral artifacts in optical coherence tomography (OCT) images of eyes with pathologic myopia. This study included 76 eyes of 42 patients with pathologic myopia. Five sets of OCT B-scan images of the macula were obtained using commercial swept-source OCT. A dataset of prototype swept-source polarization-diversity OCT images was used to identify polarization-dependent OCT images (i.e., complex averaging of OCT signals from two polarization channels) and polarization-independent OCT images (i.e., intensity averaging of two OCT signals). Polarization-dependent OCT images and commercial OCT images were assessed for the presence of birefringence-derived artifacts by comparison with polarization-independent OCT images. Both polarization-dependent OCT images and commercial OCT images contained scleral vessel artifacts. Scleral vessel artifacts were present in 46 of 76 eyes (60.5%) imaged by polarization-dependent OCT and 17 of 76 eyes (22.4%) imaged by commercial OCT. The proportion of images that showed scleral vessel artifacts was significantly greater among polarization-dependent OCT images than among commercial OCT images (P < 0.001). Additionally, polarization-dependent OCT images showed low-intensity band artifacts. This study demonstrated the existence of birefringence-derived scleral artifacts in commercial OCT images and indicated that polarization-diversity OCT is an effective tool to evaluate the presence of these artifacts.

Higher-Order Core-Like Modes in Double-Clad Fiber Contribute to Multipath Artifacts in Optical Coherence Tomography

Double-clad fiber (DCF) has enabled the combination of endoscopic optical coherence tomography (OCT) with secondary optical modalities. While DCF offers an additional optical channel, it is widely understood that its use reduces the quality of OCT owing to the introduction of multipath artifacts. We show here that an unexpected higher-order mode (HOM) with its energy confined to the DCF core can contribute to these artifacts. The existence of this HOM is confirmed using the spatially and spectrally (S <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) resolved imaging method. The group delay difference of the HOM is shown to be consistent with the delay of the diffuse ghost artifact in DCF-acquired OCT images.

Inpainting for Saturation Artifacts in Optical Coherence Tomography Using Dictionary-Based Sparse Representation

Saturation artifacts in optical coherence tomography (OCT) occur when received signal exceeds the dynamic range of spectrometer. Saturation artifact shows a streaking pattern and could impact the quality of OCT images, leading to inaccurate medical diagnosis. In this paper, we automatically localize saturation artifacts and propose an artifact correction method via inpainting. We adopt a dictionary-based sparse representation scheme for inpainting. Experimental results demonstrate that, in both case of synthetic artifacts and real artifacts, our method outperforms interpolation method and Euler’s elastica method in both qualitative and quantitative results. The generic dictionary offers similar image quality when applied to tissue samples which are excluded from dictionary training. This method may have the potential to be widely used in a variety of OCT images for the localization and inpainting of the saturation artifacts.

Optical Coherence Tomography Artifacts Are Associated With Adaptive Optics Scanning Light Ophthalmoscopy Success in Achromatopsia.

PurposeTo determine whether artifacts in optical coherence tomography (OCT) images are associated with the success or failure of adaptive optics scanning light ophthalmoscopy (AOSLO) imaging in subjects with achromatopsia (ACHM).MethodsPreviously acquired OCT and non-confocal, split-detector AOSLO images from one eye of 66 subjects with genetically confirmed achromatopsia (15 CNGA3 and 51 CNGB3) were reviewed along with best-corrected visual acuity (BCVA) and axial length. OCT artifacts in interpolated vertical volumes from CIRRUS macular cubes were divided into four categories: (1) none or minimal, (2) clear and low frequency, (3) low amplitude and high frequency, and (4) high amplitude and high frequency. Each vertical volume was assessed once by two observers. AOSLO success was defined as sufficient image quality in split-detector images at the fovea to assess cone quantity.ResultsThere was excellent agreement between the two observers for assessing OCT artifact severity category (weighted kappa = 0.88). Overall, AOSLO success was 47%. For subjects with OCT artifact severity category 1, AOSLO success was 65%; for category 2, 47%; for category 3, 11%; and for category 4, 0%. There was a significant association between OCT artifact severity category and AOSLO success (P = 0.0002). Neither BCVA nor axial length was associated with AOSLO success (P = 0.07 and P = 0.75, respectively).ConclusionsArtifacts in OCT volumes are associated with AOSLO success in ACHM. Subjects with less severe OCT artifacts are more likely to be good candidates for AOSLO imaging, whereas AOSLO was successful in only 7% of subjects with category 3 or 4 OCT artifacts. These results may be useful in guiding patient selection for AOSLO imaging.Translational RelevanceUsing OCT to prescreen patients could be a valuable tool for clinical trials that utilize AOSLO to reduce costs and decrease patient testing burden.

Optical Coherence Tomography Can Be Used to Assess Glaucomatous Optic Nerve Damage in Most Eyes With High Myopia.

It is generally assumed that optical coherence tomography (OCT) cannot be used to diagnose glaucomatous optic neuropathy (GON) in high myopes. However, this study presents evidence that there is sufficient information in OCT scans to allow for accurate diagnosis of GON in most eyes with high myopia. The purpose of this study was to test the hypothesis that glaucomatous damage can be accurately diagnosed in most high myopes via an assessment of the OCT results. One hundred eyes from 60 glaucoma patients or suspects, referred for OCT scans and evaluation, had corrected spherical refractive errors worse than -6 D and/or axial lengths ≥26.5 mm. An OCT specialist judged whether the eye had GON, based upon OCT circle scans of the disc and cube scans centered on the macula. A glaucoma specialist made the same judgement using all available information (eg, family history, repeat visits, intraocular pressure, 10-2 and 24-2 visual fields, OCT). A reference standard was created based upon the glaucoma specialist's classifications. In addition, the glaucoma specialist judged whether the eyes had peripapillary atrophy (PPA), epiretinal membrane (ERM), tilted disc (TD), and/or a paravascular inner retinal defect (PIRD). The OCT specialist correctly identified 97 of the 100 eyes using the OCT information. In 63% of the cases, the inner circle scan alone was sufficient. For the rest, additional scans were requested. In addition, 81% of the total eyes had: PPA (79%), ERM (18%), PIRD (26%), and/or TD (48%). For most eyes with high myopia, there is sufficient information in OCT scans to allow for accurate diagnosis of GON. However, the optimal use of the OCT will depend upon training to read OCT scans, which includes taking into consideration myopia related OCT artifacts and segmentation errors, as well as PPA, ERM, PIRD, and TD.

Artifacts in Macular Optical Coherence Tomography.

Purpose:To identify and explain different artifacts in macular optical coherence tomography (OCT).Methods:For this comprehensive review, a PubMed and Google Scholar (January 1995–October 2018) search was conducted by the researchers, using the keywords such as OCT, artifacts, artefact, and macula.Results:We reviewed the main OCT artifacts including software break-down or misidentification of retinal layers, incomplete segmentation error, complete segmentation failure, mirror artifact (inverted artifact), cut edge artifact, degraded image scan, out-of-register artifact, off-center artifact, motion artifact, foveal duplication, segmentation shift, blink artifact, static or fixed image artifact, linear artifact, and perfluorocarbon liquid-producing artifact.Conclusions:There are various artifacts in OCT image scans. The identification of these artifacts may help in accurate interpretations of OCT images in clinical settings that can affect the diagnosis and management of different retinal disorders.

Linear and planar reflection artifacts on swept-source and spectral-domain optical coherence tomography due to hyperreflective crystalline deposits.

To describe novel spectral-domain (SD) and swept-source (SS) optical coherence tomography (OCT) linear and planar reflection artifacts produced by hyperreflective crystalline deposits (HCD). Imaging from 10 eyes with HCD producing linear and planar artifacts on OCT was retrospectively analyzed. All eyes had SD-OCT (Spectralis HRA + OCT, Heidelberg Engineering, Germany) and SS-OCT angiography (PLEX Elite 9000, Carl Zeiss Meditec, Inc., Dublin, CA) acquired on the same day. The horizontal extent of planar artifacts and the corresponding HCD on B-scans was measured using a digital caliper. Artifact features from HCD in eyes with non-neovascular age-related macular degeneration (AMD) were analyzed and compared to those seen in two eyes with the "onion sign," an OCT signature previously shown to represent cholesterol crystals (CC) in the sub-retinal pigment epithelium-basal laminar space of eyes with neovascular AMD. A third eye with the "onion sign" was imaged with dense B-scan (DB)-OCTA. Ten eyes of ten patients (77.4 ± 8.7years) with HCD were analyzed. On SS-OCTA, HCD produced linear artifacts of high signal intensity passing through the HCD and spanning the entire scan depth. On SD-OCT, HCD produced planar artifacts located anterior to both the retina and a hyporeflective space representing normal vitreous signal. The horizontal extent of the artifact did not differ significantly from the corresponding HCD on OCT B-scans (P = 0.62). The OCT artifacts produced by the "onion sign" appeared similar to those of HCD. The additional eye with neovascular AMD imaged with DB-OCTA was characterized by a single, vertical, linear false-flow signal crossing retinal layers. To the authors' knowledge, this is the first description of SD- and SS-OCT/OCTA artifacts corresponding to both HCD and the "onion sign." These artifacts are likely due to highly reflective CC previously shown on histology to correspond to both of these OCT signatures.

Artifacts of optical coherence tomography

Purpose. To study and classify artifacts of spectral-domain optical coherence tomography (OCT). Material and methods. The retrospective study included OCT data of 112 patients (112 eyes) examined on two Cirrus HD-OCTs (Carl Zeiss Meditec) sequentially for three days (macular area examinations, 67 patients) and five days (examination of the optic disc region, 62 people), including 17 people who underwent both types of examination. Both the original scanning data (B-scans) and the results of their subsequent analysis were evaluated for the presence of artifacts. Results. The criteria of OCT artifacts were suggested and their practical classification was proposed, which distinguishes three types of artifacts: segmentation errors/errors in delineation of the optic disc borders, "out-of-register" artifacts and displacement/fallout of B-scans, and eight main causes of artifacts. The frequency of artifacts ranged from 19 % (analysis of the optic disc area) to 37 % (analysis of the macular area) and 65 % (evaluation of the ganglion cell-inner plexiform layer). The most common were segmentation errors in patients with pronounced pathology or epiretinal membranes (fibrosis). Conclusion. Clinically significant OCT artifacts occur in 19–65 % of cases, depending on the analyzed eye fundus structures. The most common artifacts are segmentation errors in patients with pronounced pathology and epiretinal membranes (fibrosis). A practical classification of OCT artifacts is proposed, which distinguishes three main types and the most important causes of their presence.

TCT-570 Uncertain detection of stent fracture by three-dimensional intravascular optical coherence tomography

Three-dimensional (3D) intravascular optical coherence tomography (OCT) is available for online guiding during percutaneous coronary intervention and could be of particular value in detection of acute stent fracture (SF). OCT artifacts mimicking fractured stent struts are a limitation for this

Involuntary eye motion correction in retinal optical coherence tomography: Hardware or software solution?

In this paper, we review state-of-the-art techniques to correct eye motion artifacts in Optical Coherence Tomography (OCT) imaging. The methods for eye motion artifact reduction can be categorized into two major classes: (1) hardware-based techniques and (2) software-based techniques. In the first class, additional hardware is mounted onto the OCT scanner to gather information about the eye motion patterns during OCT data acquisition. This information is later processed and applied to the OCT data for creating an anatomically correct representation of the retina, either in an offline or online manner. In software based techniques, the motion patterns are approximated either by comparing the acquired data to a reference image, or by considering some prior assumptions about the nature of the eye motion. Careful investigations done on the most common methods in the field provides invaluable insight regarding future directions of the research in this area. The challenge in hardware-based techniques lies in the implementation aspects of particular devices. However, the results of these techniques are superior to those obtained from software-based techniques because they are capable of capturing secondary data related to eye motion during OCT acquisition. Software-based techniques on the other hand, achieve moderate success and their performance is highly dependent on the quality of the OCT data in terms of the amount of motion artifacts contained in them. However, they are still relevant to the field since they are the sole class of techniques with the ability to be applied to legacy data acquired using systems that do not have extra hardware to track eye motion.

Guidewire shadow artifacts in optical coherence tomography.

Because of the high resolution made possible by optical coherence tomography (OCT), previously indistinguishable guidewire artifacts are recognized during coronary imaging, and these affect image interpretation. This study aimed to assess the effect of guidewire size and structure on the artifacts produced and to introduce a novel guidewire specifically for OCT imaging that produces fewer artifacts. Elimination or minimization of guidewire artifacts supports optimal OCT imaging. Silicon tubes simulating the coronary arteries were used to assess guidewire shadow artifacts in OCT imaging. The angles of artifacts produced by 4 types of guidewires were evaluated, including our newly designed guidewire. Clinical data of guidewire artifacts were also obtained from 20 patients with coronary artery disease who underwent OCT examination with these guidewires before stenting. The angles of the guidewire artifacts decreased with a reduction in the wire diameter. Wires with the dipping polymer structure produced unique artifacts brought about by a combination of the sparse spring coil structure, wire core, and polymer, and these affected image interpretation. The guidewire designed in this study could be used in clinical settings and produced fewer artifacts than the other examined guidewires. Our novel guidewire, which had a small diameter, lacked the dipping polymer structure, and was easy to handle, was successfully used for OCT imaging. Guidewire artifacts are affected by guidewire size and structure. We developed a specialized guidewire for optimal OCT imaging that effectively produced fewer shadow artifacts than its generally used counterparts.

Artifacts in optical coherence tomography

Optical coherence tomography (OCT) is now an integral part of management for numerous retinal diseases for diagnosis, treatment planning and follow up. OCT interpretation must involve the understanding of the associated artifacts. These artifacts can mislead physicians to wrong diagnosis or inappropriate management. This review article discusses the various types of artifacts in OCT scans obtained from various devices in various retinal diseases. This article would help to improve the understanding about the various artifacts and their clinical importance.

Real-time eye motion compensation for OCT imaging with tracking SLO

Fixational eye movements remain a major cause of artifacts in optical coherence tomography (OCT) images despite the increases in acquisition speeds. One approach to eliminate the eye motion is to stabilize the ophthalmic imaging system in real-time. This paper describes and quantifies the performance of a tracking OCT system, which combines a phase-stabilized optical frequency domain imaging (OFDI) system and an eye tracking scanning laser ophthalmoscope (TSLO). We show that active eye tracking minimizes artifacts caused by eye drift and micro saccades. The remaining tracking lock failures caused by blinks and large saccades generate a trigger signal which signals the OCT system to rescan corrupted B-scans. Residual motion artifacts in the OCT B-scans are reduced to 0.32 minutes of arc (~1.6 µm) in an in vivo human eye enabling acquisition of high quality images from the optic nerve head and lamina cribrosa pore structure.

Reduction of image artifacts in three-dimensional optical coherence tomography of skin in vivo

This paper presents results of in vivo studies on the effect of refractive index-matching media on image artifacts in optical coherence tomography (OCT) images of human skin. These artifacts present as streaks of artificially low backscatter and displacement or distortion of features. They are primarily caused by refraction and scattering of the OCT light beam at the skin surface. The impact of the application of glycerol and ultrasound gel is assessed on both novel skin-mimicking phantoms and in vivo human skin, including assessment of the epidermal thickening caused by the media. Based on our findings, recommendations are given for optimal OCT imaging of skin in vivo.

Correction of coherence gate curvature in high numerical aperture optical coherence imaging

We present a method for correcting coherence gate curvature caused by scanning-induced path length variations in spectral-domain high-NA optical coherence imaging systems. These variations cause curvature artifacts in optical coherence tomography and effectively restrict the field of view in optical coherence microscopy (OCM). Here we show that the coherence gate curvature can be measured and corrected by recovering the phase of the analytic signal from a calibration image. This phase information can be used directly to process OCM images allowing the coherence gate curvature, as well as any order of system dispersion, to be corrected in a computationally efficient manner. We also discuss the use of various image quality metrics that can be used to adjust the calibrated phase in order to keep the coherence and confocal gates aligned in tissue.

Autocorrelation artifacts in optical coherence tomography and interferometric synthetic aperture microscopy

Interferometric synthetic aperture microscopy processing of optical coherence tomography data has been shown to allow computational focusing of en face planes that have traditionally been regarded as out of focus. It is shown that this focusing of the image also produces a defocusing effect in autocorrelation artifacts resulting from Fourier-domain data collection. This effect is verified experimentally and through simulation.

Detection of motion artifacts in optical coherence tomography using the fundus enhancement system

HINTERGRUND: Bei Untersuchungen mit der optischen Koharenztomographie (OCT) sind ausgepragte Bewegungsartefakte erkennbar, Haufigkeit und Auspragung geringer Bewegungen sind aber bislang nicht untersucht worden. ZIEL DER STUDIE war es, Haufigkeit und Ausmas von durch Augenbewegungen wahrend des Untersuchungsprozesses hervorgerufenen Artefakten und Fehlmessungen bei OCT zu untersuchen. METHODEN: Mit Hilfe eines zur Integration von OCT-Bildern in fluoreszenzangiographische Aufnahmen entwickelten Fundusbildsystems (Fundus-Enhancement-System, FES) kann der Scanning-Prozess bei einem konventionellen Zeiss-Stratus-OCT aufgenommen und als Videosequenz verlangsamt wiedergegeben werden. Wir untersuchten mit Hilfe dieses Systems 40 Augen bei 20 gesunden Probanden mit einem Visus von mindestens 1,0; untersucht wurde das Vorhandensein von Bewegungen (Fixationsverlusten) wahrend des Ablaufes des Scans bei je einem 5 mm langen horizontalen und vertikalen Scan durch die Fovea. Gemessene Parameter: Vorhandensein oder Abwesenheit von Augenbewegungen wahrend der Aufnahme und mittlere Abweichung von der geplanten Scanposition in horizontaler oder vertikaler Richtung in Millimeter. ERGEBNISSE: Sieben von 20 gesunden Probanden zeigten uberhaupt keine Bewegung wahrend der Untersuchung. Von den ubrigen 13 Patienten zeigten vier Bewegungen nur auf einer Seite. Die mittlere Abweichung von der gewunschten Position betrug 0,2 mm bei den horizontalen und 0,28 mm bei den vertikalen Scans. SCHLUSSFOLGERUNG: Konventionelle OCT-Systeme konnen erweitert werden, um geringe Augenbewegungen wahrend der Untersuchung zu erfassen. In dieser ersten Serie gesunder Probanden mit voller Sehscharfe traten durch Fixationsverlust bedingte Augenbewegungen bei uber der Halfte der Untersuchungen auf. Auch wenn die Abweichungen von der intendierten Scanposition bei Gesunden gering erscheinen, sind weitere Untersuchungen dieses Phanomens notwendig. OCT wird bei Makulaerkrankungen in zunehmendem Mase als Therapiekontrolle verwendet und das Ausmas bewegungsbedingter Fehler ist bislang nicht untersucht worden.

Alignment Artifacts in Optical Coherence Tomography Analyzed Images

To compare retinal thickness and retinal height of the original scanned optical coherence tomography (OCT) images with those of the same images after automated retinal thickness analysis. Cross-sectional study. Thirty normal eyes, 20 eyes with neovascular age-related macular degeneration (AMD), 20 with central serous chorioretinopathy (CSC), 20 with macular holes, and 20 with non-AMD related macular edema from 110 subjects were selected randomly from an OCT database. One of the 6 macular scans in each eye was chosen randomly for analysis. Two sets of OCT images--original images and analyzed images (after retinal thickness [single eye] analysis)--in each eye were exported for retinal thickness or retinal height measurement. Comparisons of retinal thickness or retinal height at selected locations were performed. Retinal thickness (defined as the distance between the anterior boundary of the retinal nerve fiber layer [RNFL] and posterior boundary of the photoreceptor layer) and retinal height (defined as the distance between the anterior boundary of the RNFL and baseline level of the anterior boundary of the retinal pigment epithelium [RPE]). Retinal height was measured when there was detachment of neurosensory retina or RPE. No significant difference in retinal thickness was observed between the original and the analyzed OCT images in normal eyes and in eyes with macular holes or non-AMD related macular edema. However, OCT-analyzed images demonstrated retinal thickness or retinal height measurements in eyes with CSC or neovascular AMD significantly lower than the corresponding measurements in the original images (all with Ps< or =0.001, Wilcoxon signed rank test). In the groups of neovascular AMD and CSC, Bland-Altman plots revealed mean differences of 124 mum (95% limits of agreement between -65.5 and 313.6) and 84.4 mum (95% limits of agreement between -178.0 and 346.8), respectively, between the original and analyzed retinal measurements. Retinal thickness and retinal height could be underestimated in patients with CSC or neovascular AMD after retinal thickness analysis in Stratus OCT when either automatic measurements or manual caliper-assisted measurements are performed on the analyzed images. We recommend exporting the original scanned OCT images for retinal thickness and retinal height measurement in patients with CSC or neovascular AMD.