Deep learning-based inpainting of saturation artifacts in optical coherence tomography images

Limited by the dynamic range of the detector,saturation artifacts usually occur in optical coherence tomography(OCT)imaging for high scattering media.The available methods are difficult to remove saturation artifacts and restore texture completely in OCT images.We proposed a deep learning-based inpainting method of saturation artifacts in this paper.The generation mechanism of saturation artifacts was analyzed,and experimental and simulated datasets were built based on the mechanism.Enhanced super-resolution generative adversarial networks were trained by the clear–saturated phantom image pairs.The perfect reconstructed results of experimental zebrafish and thyroid OCT images proved its feasibility,strong generalization,and robustness.

Intravascular photoacoustic and optical coherence tomography imaging dual-mode system for detecting spontaneous coronary artery dissection: A feasibility study

In this work,we present an intravascular dual-mode endoscopic system capable of both intravascular photoacoustic imaging(IVPAI)and intravascular optical coherence tomography(IVOCT)for recognizing spontaneous coronary artery dissection(SCAD)phantoms.IVPAI provides high-resolution and high-penetration images of intramural hematoma(IMH)at different depths,so it is especially useful for imaging deep blood clots associated with imaging phantoms.IVOCT can readily visualize the double-lumen morphology of blood vessel walls to identify intimal tears.We also demonstrate the capability of this dual-mode endoscopic system using mimicking phantoms and biological samples of blood clots in ex vivo porcine arteries.The results of the experiments indicate that the combined IVPAI and IVOCT technique has the potential to provide a more accurate SCAD assessment method for clinical applications.

Automatic diagnosis of diabetic retinopathy using vision transformer based on wide-field optical coherence tomography angiography

Diabetic retinopathy(DR)is one of the major causes of visual impairment in adults with diabetes.Optical coherence tomography angiography(OCTA)is nowadays widely used as the golden criterion for diagnosing DR.Recently,wide-field OCTA(WF-OCTA)provided more abundant information including that of the peripheral retinal degenerative changes and it can contribute in accurately diagnosing DR.The need for an automatic DR diagnostic system based on WF-OCTA pictures attracts more and more attention due to the large diabetic population and the prevalence of retinopathy cases.In this study,automatic diagnosis of DR using vision transformer was performed using WF-OCTA images(12 mm×12 mm single-scan)centered on the fovea as the dataset.WF-OCTA images were automatically classified into four classes:No DR,mild nonproliferative diabetic retinopathy(NPDR),moderate to severe NPDR,and proliferative diabetic retinopathy(PDR).The proposed method for detecting DR on the test set achieves accuracy of 99.55%,sensitivity of 99.49%,and specificity of 99.57%.The accuracy of the method for DR staging reaches up to 99.20%,which has been proven to be higher than that attained by classical convolutional neural network models.Results show that the automatic diagnosis of DR based on vision transformer and WF-OCTA pictures is more effective for detecting and staging DR.

Detecting early changes in choroidal vascularity and thickness using optical coherence tomography in patients with corneal crosslinking for keratoconus

AIM:To investigate changes in choroidal thickness and vascularity in keratoconus patients treated with corneal crosslinking.METHODS:This study evaluated 28 eyes of 22 patients with keratoconus who underwent corneal crosslinking.The choroidal thicknesses were evaluated on enhanced depth imaging optical coherence tomography at the preoperative and postoperative 3d,1,and 3mo.Choroidal thickness in the four cardinal quadrants and the fovea were evaluated.The choroidal vascularity index was also calculated.RESULTS:There was no significant difference in central choroidal thickness between the preoperative and postoperative 3d,1mo(P>0.05).There was a significant increase in the 3mo(P=0.034)and a significant decrease in the horizontal choroidal vascularity index on the postoperative 3d(P=0.014),there was no statistically significant change in vertical axes and other visits in horizontal sections(P>0.05).CONCLUSION:This study sheds light on choroidal changes in postoperative corneal crosslinking for keratoconus.While it suggests the procedure’s relative safety for submacular choroid,more extensive research is necessary to confirm these findings and their clinical significance.

Optical coherence tomography enhanced depth imaging of chorioretinal folds in patients with orbital tumors

AIM:To characterize spectral-domain optical coherence tomography(SD-OCT)features of chorioretinal folds in orbital mass imaged using enhanced depth imaging(EDI).METHODS:Prospective observational case-control study was conducted in 20 eyes of 20 patients,the uninvolved eye served as a control.All the patients underwent clinical fundus photography,computed tomography,EDI SDOCT imaging before and after surgery.Two patients with cavernous hemangiomas underwent intratumoral injection of bleomycin A5;the remaining patients underwent tumor excision.Patients were followed 1 to 14mo following surgery(average follow up,5.8mo).RESULTS:Visual acuity prior to surgery ranged from 20/20 to 20/200.Following surgery,5 patients’visual acuity remained unchanged while the remaining 15 patients had a mean letter improvement of 10(range 4 to 26 letters).Photoreceptor inner/outer segment defects were found in 10 of 15 patients prior to surgery.Following surgical excision,photoreceptor inner/outer segment defects fully resolved in 8 of these 10 patients.CONCLUSION:Persistence of photoreceptor inner/outer segment defects caused by compression of the globe by an orbital mass can be associated with reduced visual prognosis.Our findings suggest that photoreceptor inner/outer segment defects on EDI SD-OCT could be an indicator for immediate surgical excision of an orbital mass causing choroidal compression.

Bibliometric analysis of artificial intelligence and optical coherence tomography images:research hotspots and frontiers

AIM:To explore the latest application of artificial intelligence(AI)in optical coherence tomography(OCT)images,and to analyze the current research status of AI in OCT,and discuss the future research trend.METHODS:On June 1,2023,a bibliometric analysis of the Web of Science Core Collection was performed in order to explore the utilization of AI in OCT imagery.Key parameters such as papers,countries/regions,citations,databases,organizations,keywords,journal names,and research hotspots were extracted and then visualized employing the VOSviewer and CiteSpace V bibliometric platforms.RESULTS:Fifty-five nations reported studies on AI biotechnology and its application in analyzing OCT images.The United States was the country with the largest number of published papers.Furthermore,197 institutions worldwide provided published articles,where University of London had more publications than the rest.The reference clusters from the study could be divided into four categories:thickness and eyes,diabetic retinopathy(DR),images and segmentation,and OCT classification.CONCLUSION:The latest hot topics and future directions in this field are identified,and the dynamic evolution of AIbased OCT imaging are outlined.AI-based OCT imaging holds great potential for revolutionizing clinical care.

Microstructural morphology and visual acuity outcome in eyes with epiretinal membrane before,during,and after membrane peeling in intraoperative optical coherence tomography assisted macular surgery

AIM:To measure the difference of intraoperative central macular thickness(CMT)before,during,and after membrane peeling and investigate the influence of intraoperative macular stretching on postoperative best corrected visual acuity(BCVA)outcome and postoperative CMT development.METHODS:A total of 59 eyes of 59 patients who underwent vitreoretinal surgery for epiretinal membrane was analyzed.Videos with intraoperative optical coherence tomography(OCT)were recorded.Difference of intraoperative CMT before,during,and after peeling was measured.Pre-and postoperatively obtained BCVA and spectral-domain OCT images were analyzed.RESULTS:Mean age of the patients was 70±8.13y(range 46-86y).Mean baseline BCVA was 0.49±0.27 log MAR(range 0.1-1.3).Three and six months postoperatively the mean BCVA was 0.36±0.25(P=0.01 vs baseline)and 0.38±0.35(P=0.08 vs baseline)log MAR respectively.Mean stretch of the macula during surgery was 29%from baseline(range 2%-159%).Intraoperative findings of macular stretching did not correlate with visual acuity outcome within 6mo after surgery(r=-0.06,P=0.72).However,extent of macular stretching during surgery significantly correlated with less reduction of CMT at the fovea centralis(r=-0.43,P<0.01)and 1 mm nasal and temporal from the fovea(r=-0.37,P=0.02 and r=-0.50,P<0.01 respectively)3mo postoperatively.CONCLUSION:The extent of retinal stretching during membrane peeling may predict the development of postoperative central retinal thickness,though there is no correlation with visual acuity development within the first 6mo postoperatively.

Intraoperative imaging of oral-maxillofacial lesions using optical coherence tomography

Histopathological examination is still the gold standard for diagnoses of oral-maxillofacial lesions,but it is invasive and time-consuming.Optical coherence tomography(OCT)provides a kind of noninvasive,label-free,real-time and high-resolution imaging technology.In this study,in order to assess the feasibility of OCT in oral clinical application,fresh excised tissue specimens from 59 patients undergoing oral-maxillofacial surgery were imaged in detail by using a benchtop sweptsource OCT system.It is shown that different lesions or tissues can be obviously distinguished based on their different microstructural features in OCT images,and the features are similar to those of their corresponding histopathological images.It is proven that OCT has great feasibility and potential as a diagnostic aid for surgeons in oral medicine.

Segmentation of retinal fluid based on deep learning:application of three-dimensional fully convolutional neural networks in optical coherence tomography images

AIM: To explore a segmentation algorithm based on deep learning to achieve accurate diagnosis and treatment of patients with retinal fluid.METHODS: A two-dimensional(2D) fully convolutional network for retinal segmentation was employed. In order to solve the category imbalance in retinal optical coherence tomography(OCT) images, the network parameters and loss function based on the 2D fully convolutional network were modified. For this network, the correlations of corresponding positions among adjacent images in space are ignored. Thus, we proposed a three-dimensional(3D) fully convolutional network for segmentation in the retinal OCT images.RESULTS: The algorithm was evaluated according to segmentation accuracy, Kappa coefficient, and F1 score. For the 3D fully convolutional network proposed in this paper, the overall segmentation accuracy rate is 99.56%, Kappa coefficient is 98.47%, and F1 score of retinal fluid is 95.50%. CONCLUSION: The OCT image segmentation algorithm based on deep learning is primarily founded on the 2D convolutional network. The 3D network architecture proposed in this paper reduces the influence of category imbalance, realizes end-to-end segmentation of volume images, and achieves optimal segmentation results. The segmentation maps are practically the same as the manual annotations of doctors, and can provide doctors with more accurate diagnostic data.

Parallel Spectral-Domain Optical Coherence Tomography for Non-Scattering Object Imaging

The parallel spectral-domain optical coherence tomography（PSDOCT） is described for highspeed optical coherence tomography（OCT） without lateral scanning. In this setup, the self-elimination of auto-correlation（AC） interference algorithm was used for eradicating the AC interference and ghost images. However, when performed in free space OCT, this algorithm still generated a weak DC component. The algorithm was improved by adding the background intensity part to compensate for the mutual interference between object and reference arms. The results demonstrate that the DC component can be eradicated. Compared with conventional QCT and complex Fourier-domain optical coherence to- mography, the advantages of PSDOCT with the improved algorithm in free space are that it has no moving parts to generate consecutive phase shift, the structure of the object can be reconstructed immediately and automatically, and the speed is approximately 16 times faster than those of the other two in the same case.

Optical coherence tomography with or without enhanced depth imaging for peripapillary retinal nerve fiber layer and choroidal thickness

AIM：To assess peripapillary retinal nerve fiber layer（RNFL）and choroidal thickness obtained with enhanced depth imaging（EDI）mode compared with those obtained without EDI mode using Heidelberg Spectralis optical coherence tomography（OCT）.METHODS：Fifty eyes of 25 normal healthy subjects and32 eyes of 20 patients with different eye diseases were included in the study.All subjects underwent 3.4 mm diameter peripapillary circular OCT scan centered on the optic disc using both the conventional and the EDI OCT protocols.The visualization of RNFL and choroidoscleral junction was assessed using an ordinal scoring scale.The paired t-test,intraclass correlation coefficient（ICC）,95%limits of agreement（LoA）,and Bland and Altman plots were used to test the agreement of measurements.RESULTS：The visibility score of RNFL obtained with and without EDI was of no significant difference（P=0.532）,the visualization of choroidoscleral junction was better using EDI protocol than conventional protocol（P〈0.001）.Peripapillary RNFL thickness obtained with EDI was slightly thicker than that obtained without EDI（103.25±9.42μm vs 101.87±8.78μm,P=0.010）.The ICC of the two protocols was excellent with the value of 0.867 to 0.924,the 95%LoA of global RNFL thickness was between-10.0 to 7.4μm.Peripapillary choroidal thickness obtained with EDI was slightly thinner than that obtained without EDI（147.23±51.04μm vs 150.90±51.84μm,P〈0.001）.The ICC was also excellent with the value of 0.960 to 0.987,the 95%LoA of global choroidal thickness was between-12.5 to 19.8μm.CONCLUSION：Peripapillary circular OCT scan with or without EDI mode shows comparable results in the measurement of peripapillary RNFL and choroidal thickness.

Automatic quantification of superficial foveal avascular zone in optical coherence tomography angiography implemented with deep learning

An accurate segmentation and quantification of the superficial foveal avascular zone(sFAZ)is important to facilitate the diagnosis and treatment of many retinal diseases,such as diabetic retinopathy and retinal vein occlusion.We proposed a method based on deep learning for the automatic segmentation and quantification of the sFAZ in optical coherence tomography angiography(OCTA)images with robustness to brightness and contrast(B/C)variations.A dataset of 405 OCTA images from 45 participants was acquired with Zeiss Cirrus HD-OCT 5000 and the ground truth(GT)was manually segmented subsequently.A deep learning network with an encoder–decoder architecture was created to classify each pixel into an sFAZ or non-sFAZ class.Subsequently,we applied largestconnected-region extraction and hole-filling to fine-tune the automatic segmentation results.A maximum mean dice similarity coefficient(DSC)of 0.976±0.011 was obtained when the automatic segmentation results were compared against the GT.The correlation coefficient between the area calculated from the automatic segmentation results and that calculated from the GT was 0.997.In all nine parameter groups with various brightness/contrast,all the DSCs of the proposed method were higher than 0.96.The proposed method achieved better performance in the sFAZ segmentation and quantification compared to two previously reported methods.In conclusion,we proposed and successfully verified an automatic sFAZ segmentation and quantification method based on deep learning with robustness to B/C variations.For clinical applications,this is an important progress in creating an automated segmentation and quantification applicable to clinical analysis.

Standardization of choroidal thickness measurements using enhanced depth imaging optical coherence tomography

AIM: To describe and evaluate a standardized protocol for measuring the choroidal thickness(Ch T) using enhanced depth imaging optical coherence tomography(EDI OCT).METHODS: Single 9 mm EDI OCT line scans across the fovea were used for this study. The protocol used in this study classified the EDI OCT images into four groups based on the appearance of the choroidal-scleral interface and suprachoroidal space. Two evaluation iterations of experiments were performed: first, the protocol was validated in a pilot study of 12 healthy eyes. Afterwards, the applicability of the protocol was tested in 82 eyes of patients with diabetes. Inter-observer and intra-observer agreements on image classifications were performed using Cohen’s kappa coefficient(κ). Intraclass correlation coefficient(ICC) and Bland-Altman’s methodology were used for the measurement of the Ch T.RESULTS: There was a moderate(κ=0.42) and perfect(κ =1) inter- and intra-observer agreements on image classifications from healthy eyes images and substantial(κ =0.66) and almost perfect(κ =0.86) agreements from diabetic eyes images. The proposed protocol showed excellent inter- and intra-observer agreements for the Ch T measurements on both, healthy eyes and diabetic eyes(ICC 】0.90 in all image categories). The Bland-Altman plot showed a relatively large Ch T measurement agreement in the scans that contained less visible choroidal outer boundary. CONCLUSION: A protocol to standardize Ch T measurements in EDI OCT images has been developed;the results obtained using this protocol show that the technique is accurate and reliable for routine clinical practice and research.

Peripapillary choroidal thickness in Chinese children using enhanced depth imaging optical coherence tomography

AIM：To evaluate the peripapillary choroidal thickness（PPCT） in Chinese children,and to analyze the influencing factors.METHODS： PPCT was measured with enhanced depth imaging optical coherence tomography（EDI-OCT） in 70children（53 myopes and 17 non-myopes） aged 7 to 18 y,with spherical equivalent refractive errors between 0.50and-5.87 diopters（D）.Peripapillary choroidal imaging was performed using circular scans of a diameter of 3.4 mm around the optic disc.PPCT was measured by EDI-OCT in six sectors： nasal（N）,superonasal（SN）,superotemporal（ST）,temporal（T）,inferotemporal（IT）and inferonasal（IN）,as well as global RNFL thickness（G）.RESULTS： The mean global PPCT was 165.49±33.76 μm.The temporal,inferonasal,inferotemporal PPCT were significantly thinner than the nasal,superonasal,superotemporal segments PPCT were significantly thinner in the myopic group at temporal,superotemporal and inferotemporal segments.The axial length was significantly associated with the average global（β=-0.419,P =0.014）,superonasal（β=-2.009,P=0.049） and inferonasal（β=-2.000,P=0.049） PPCT.The other factors（gender,age,SE） were not significantly associated with PPCT.CONCLUSION： PPCT was thinner in the myopic group at temporal,superotemporal and inferotemporal segments.The axial length was found to be negatively correlated to PPCT.We need more further studies about the relationship between PPCT and myopia.

Imaging of arterial plaque by quadrature swept-source optical coherence tomography with signal to noise ratio enhancements

Arterial plaque from a myocardial infarction-prone Watanabe heritable hyperlipidemic (WHHLMI) rabbit is visualized and characterized using a signal to noise ratio enhanced swept-source optical coherence tomography system with a quadrature interferometer (QSS-OCT). A semiconductor optical amplifier is used in the sample arm to amplify the weak signal scattered from arterial plague. Signal to noise ratio improvement are demonstrated in our QSS-OCT system. This finding results into an increase of the penetration depth possible in OCT images, from 1 mm to 2 mm. Preliminary results show that vulnerable plaque with fibrous cap, macrophage accumulations and calcification in the arterial tissue are measurable with our QSS-OCT system.

From structural to functional imaging:the developments of clinical ophthalmology optical coherence tomography

Starting with introduction of basic concept of optical coherence tomography(OCT) techniques,this paper focuses on a detailed review of ophthalmic OCT instruments and their clinical applications. As one of the most important inventions of ophthalmology instruments,OCT has become a standard imaging tool for daily ophthalmic diagnosis. The imaging capability has been significantly improved during the past ~ 30 years. In this article,several representing systems which have made significant contributions to OCT developments will be reviewed in details. For each system,the system configuration will be discussed first,follow ed by a brief introduction of their clinical applications. The review concludes with discussions on potential directions of OCT developments and expectations for further improvements of OCT imaging capabilities.

Pencil-beam scanning catheter for intracoronary optical coherence tomography

Current gradient-index(GRIN)lens based proximal-driven intracoronary optical coherence tomography(ICOCT)probes consist of a spacer and a GRIN lens with large gradient constant.This design provides great flexibility to control beam profiles,but the spacer length should be well controlled to obtain desired beam profiles and thus it sets an obstacle in mass catheter fabrication.Besides,although GRIN lens with large gradient constant can provide tight focus spot,it has short depth of focus and fast-expanded beam which leads to poor lateral resolution for deep tissue.In this paper,a type of spacer-removed probe is demonstrated with a small gradient constant GRIN lens.This design simplifies the fabrica-tion process and is suitable for mass production.The output beam of the catheter is a narrow nearly collimated light beam,referred to as pencil beam here.The full width at half maximum beam size varies from 35.1μm to 75.3μm in air over 3-mm range.Probe design principles are elaborated with probe/catheter fabrication and performance test.The in vivo imaging of the catheter was verified by a clinical ICOCT system.Those results prove that this novel pencil-beam scanning catheter is potentially a good choice for ICOCT systems.

All-optically integrated photoacoustic and optical coherence tomography:A review

All-optically integrated photoacoustic(PA)and optical coherence tomography(OCT)dualmode imaging technology that could o®er comprehensive pathological information for accurate diagnosis in clinic has gradually become a promising imaging technology in the aspect of biomedical imaging during the recent years.This review refers to the technology aspects of alloptical PA detection and system evolution of optically integrated PA and OCT,including Michelson interferometer dual-mode imaging system,Fabry–Perot(FP)interferometer dualmode imaging system and Mach–Zehnder interferometer dual-mode imaging system.It is believed that the optically integrated PA and OCT has great potential applications in biomedical imaging.

APPLICATION OF DOPPLER OPTICAL COHERENCE TOMOGRAPHY IN RHEOLOGICAL STUDIES:BLOOD FLOW AND VESSELS MECHANICAL PROPERTIES EVALUATION

Doppler Optical Coherence Tomography(DOCT)is a noninvasive optical diagnostic technique,which is well suited for the quantitative mapping of microflow velocity profiles and the analysis of flow-vessel interactions.The noninvasive imaging and quantitative analysis of blood flow in the complex-structured vascular bed is required in many biomedical applications,including those where the determination of mechanical properties of vessels or the knowledge of the mechanic interactions between the flow and the housing medium plays a key role.The change of microvessel wall elasticity could be a potential indicator of cardiovascular disease at the very early stage,whilst monitoring the blood flow dynamics and associated temporal and spatial variations in vessel’s wall shear stress could help predicting the possible rupture of atherosclerotic plaques.The results of feasibility studies of application of DOCT for the evaluation of mechanical properties of elastic vessel model are presented.The technique has also been applied for imaging of sub-cranial rat blood flow in vivo.

In vivo evaluation of laser-induced choroidal neovascularization in rats simultaneously using optical coherence tomography and photoacoustic microscopy

Determination of the precise location and the degree of the Choroidal neovascularization(CNV)lesion is essential for diagnosation Neovascular age-related macular degeneration(AMD)and evaluation the efficacy of treatment.Noninvasive imaging techniques with specific contrast for CNV evaluation are demanded.In this paper,two noninvasive imaging techniques,namely Optical coherence tomography(OCT)and Photoacoustic microscopy(PAM),are combined to provide specific detection of CNV for their complimentary contrast mechanisms.In vivo time-serial evaluation of Laser-induced CNV in rats is present at days 1,3,5,7,14,21 after laser photocoagulation is applied to the rat fundus.Both OCT and PAM show that the CNV increases to its maximum at day 7 and decreases at day 14.Quantification of CNV area and CNV thickness is given.The dual-modal information of CNV is consistent with the histologic evaluation by hematoxylin and eosin(H&E)staining.