Radial Scanning Research Articles

Swept-source optical coherence tomography assessment of iris–trabecular contact after phacoemulsification with or without goniosynechialysis in eyes with primary angle closure glaucoma

AimsTo compare the change in iris–trabecular contact (ITC) area using swept-source optical coherence tomography (SS-OCT) in eyes with primary angle closure glaucoma (PACG) and cataract that underwent phacoemulsification (PE) with...

New possibilities of accurate particle characterisation by applying direct boundary models to analytical centrifugation.

Analytical centrifugation (AC) is a powerful technique for the characterisation of nanoparticles in colloidal systems. As a direct and absolute technique it requires no calibration or measurements of standards. Moreover, it offers simple experimental design and handling, high sample throughput as well as moderate investment costs. However, the full potential of AC for nanoparticle size analysis requires the development of powerful data analysis techniques. In this study we show how the application of direct boundary models to AC data opens up new possibilities in particle characterisation. An accurate analysis method, successfully applied to sedimentation data obtained by analytical ultracentrifugation (AUC) in the past, was used for the first time in analysing AC data. Unlike traditional data evaluation routines for AC using a designated number of radial positions or scans, direct boundary models consider the complete sedimentation boundary, which results in significantly better statistics. We demonstrate that meniscus fitting, as well as the correction of radius and time invariant noise significantly improves the signal-to-noise ratio and prevents the occurrence of false positives due to optical artefacts. Moreover, hydrodynamic non-ideality can be assessed by the residuals obtained from the analysis. The sedimentation coefficient distributions obtained by AC are in excellent agreement with the results from AUC. Brownian dynamics simulations were used to generate numerical sedimentation data to study the influence of diffusion on the obtained distributions. Our approach is further validated using polystyrene and silica nanoparticles. In particular, we demonstrate the strength of AC for analysing multimodal distributions by means of gold nanoparticles.

Une nouvelle analyse de l’anneau neuro-rétinien en tomographie par cohérence optique en domaine spectral, Spectralis (Heidelberg Engineering, Germany). Étude préliminaire

Clinical determination of the outer limits of the optic disk (OD) doesn't always correspond to the true anatomic limits of the optic nerve head (ONH) defined by the Bruch's membrane opening (BMO). A new index analyzing the OD with optical coherence tomography (OCT), "minimal rim width" (BMO-MRW), evaluates the smallest thickness of the neuroretinal rim between the BMO and the internal limiting membrane. The purpose of this study was to evaluate new software for automatic measurement of the BMO-MRW. This study investigated 95 eyes: 40 control eyes and 55 eyes followed and treated for primary open angle glaucoma (42 early glaucoma, 7 moderate glaucoma and 6 advanced glaucoma). After a precise localization of the OD center, 24 radial scans of the ONH are taken with the Spectralis OCT (Heidelberg Engineering, Germany). From the 48 measurements of BMO-MRW, the mean thickness as well as that in each of the 6 papillary sectors of this new index are calculated. ROC curves analysis (receiver operating characteristic) was used to assess the diagnostic capabilities of the various parameters. Thicknesses of all parameters were statistically lower in glaucoma than in controls. The mean value and inferotemporal sector (IT) had the best diagnostic capabilities without significant difference between them (BMO-MRW-average = 0.890 ± 0.062, BMO-MRW-IT = 0.881 ± 0.066, P = 0.59). The area under the curve was lowest in the temporal sector (0.820 ± 086 statistically lower than the average value, P = 0.04). This preliminary study of a new automated analysis of the neuroretinal rim highlights the diagnostic value of the BMO-MRW index. This evaluation appears to be best correlated with the anatomy of the ONH with good diagnostic sensitivity.

Foveal contour changes following surgery for idiopathic epiretinal membrane.

We evaluated the change in foveal contour in eyes with idiopathic epiretinal membrane (ERM) before and four months following pars plana vitrectomy with internal limiting and epiretinal membrane peeling, and correlated foveal contour with best corrected visual acuity (BCVA) and optical coherence tomography (OCT) parameters. Retrospective chart review of consecutive patients undergoing surgery with pre- and postoperative OCT. Foveal contour grading was devised according to the thickness of the fovea relative to the surrounding macula from OCT radial line scans: Grade 0, foveal depression relative to surrounding macula; Grade 1, relative flatness; and Grade 2, fovea thicker than surrounding macula. Baseline and follow-up grades were compared for change and correlated with BCVA, central retinal thickness (CRT), central subfield thickness (CST), central subfield volume (CSV), and integrity of the ellipsoid zone (EZ). Among 41 eyes of 41 patients, mean follow-up was 125 days. No eyes were Grade 0 at baseline; 7 of 41 eyes were Grade 0 at follow-up. Baseline Grade 1 eyes improved CRT (P < 0.001), CST (P < 0.001), CSV (P = 0.002), and BCVA (P = 0.022). Baseline Grade 2 eyes improved CRT (P < 0.001), CST (P < 0.001), and CSV (P < 0.001), but not BCVA (P = 0.369). We developed a novel foveal contour grading method to assess retinal contour in ERM eyes before and after surgery. In eyes with ERM and no foveal depression, the majority did not regain foveal depression following surgery even though retinal thickness improved.

Analysis of fundus shape in highly myopic eyes by using curvature maps constructed from optical coherence tomography.

PurposeTo evaluate fundus shape in highly myopic eyes using color maps created through optical coherence tomography (OCT) image analysis.MethodsWe retrospectively evaluated 182 highly myopic eyes from 113 patients. After obtaining 12 lines of 9-mm radial OCT scans with the fovea at the center, the Bruch’s membrane line was plotted and its curvature was measured at 1-µm intervals in each image, which was reflected as a color topography map. For the quantitative analysis of the eye shape, mean absolute curvature and variance of curvature were calculated.ResultsThe color maps allowed staphyloma visualization as a ring of green color at the edge and as that of orange-red color at the bottom. Analyses of mean and variance of curvature revealed that eyes with myopic choroidal neovascularization tended to have relatively flat posterior poles with smooth surfaces, while eyes with chorioretinal atrophy exhibited a steep, curved shape with an undulated surface (P<0.001). Furthermore, eyes with staphylomas and those without clearly differed in terms of mean curvature and the variance of curvature: 98.4% of eyes with staphylomas had mean curvature ≥7.8×10−5 [1/µm] and variance of curvature ≥0.26×10−8 [1/µm].ConclusionsWe established a novel method to analyze posterior pole shape by using OCT images to construct curvature maps. Our quantitative analysis revealed that fundus shape is associated with myopic complications. These values were also effective in distinguishing eyes with staphylomas from those without. This tool for the quantitative evaluation of eye shape should facilitate future research of myopic complications.

Isotropic diffusion weighting for measurement of a high-resolution apparent diffusion coefficient map using a single radial scan in MRI

This work proposes an isotropic diffusion weighting method for a high-resolution diffusion-weighted image and for a high-resolution apparent diffusion coefficient (ADC) map using a single radial scan in MRI. By using a conventional radial imaging technique, a high-resolution diffusion-weighted (DW) image can be obtained at the cost of a long imaging time. To reduce the imaging time, the proposed method acquires a DW image by altering the diffusion gradient directions for each radial spoke. The acquisition order and directions of the diffusion gradients for an accurate DW image and an ADC map are also proposed by modifying the golden angle ratio in 3D space. In addition, an individual-direction diffusion-weighted (id-DW) image can also be obtained by a diffusion gradient direction, which is one of the multiple directions used in isotropic diffusion weighting. Computer simulations and experiment results show that the proposed method is more accurate and faster than the conventional radial diffusion-weighted imaging. This study suggests that the proposed isotropic diffusion-weighted imaging can be used to obtain a DW image and a high-resolution ADC map accurately in a single radial scan, while reducing the artifacts caused by the diffusion anisotropy, compared to the diffusion-weighted echo-planar-imaging.

The relation between peripapillary and macular thickness with refractive errors

AbstractPurpose To determine the correlation of the peripapillary retinal nerve fiber layer thickness (RNFLT) and macular thickness (MT) with type and degree of refractive errors.Methods Seventy‐four (37 myopic and 37 hyperopic) subjects with the mean age of 26.47 ± 0.75 years were participated in this study. Visual acuity (VA), Refractive errors (RE), axial length (AL), Intra ocular pressure (IOP) and corneal power (CP) were determined. RNFLT were measured by cirrus OCT using circular scan with diameter 3.4mm around optic disc, and MT was captured using radial scan in a 200 × 200mm area, Independent student T‐test was performed to compare the CP, RNFLT, MT and AL between groups. The correlation of the AL with RNFLT and MT were assessed using the Pearson correlation.Results There was a significant difference in AL between myopic and hyperopic eyes (p&lt;0.05). In myopic eyes, the AL significantly correlated with RNFLT (p&lt;0.001) and MT (p&lt;0.05). Notwithstanding, axial length had no significant correlations with RNFLT and MT in hyperopic eyes. Also there is statistically significant relationship between MT and RNFLT with degree of the refractive errors in myopic eyes (p&lt;0.05).Conclusion The results of this investigation indicated that myopes have thinner RNFLT and MT than hyperopes. These results could help clinicians in diagnosis and management of the patients with glaucoma.

Age-associated changes in the retinal nerve fiber layer and optic nerve head.

Optical coherence tomography (OCT) measures of the retinal nerve fiber layer (RNFL) thickness and neuroretinal rim (NRR) parameters are often used as a surrogate for retinal ganglion cell content. The purpose of this study was to investigate the relationship between these morphological measures and the aging effects on these structures. One hundred thirteen healthy individuals, aged 19 to 76 years, with no prior history of retinal of optic nerve head pathology were recruited. A circumpapillary and radial OCT scan centered on the optic nerve head (ONH) was used for data analysis. Transverse scaling was calculated for each subject using measures from optical biometry. Custom algorithms were used for morphological analysis of the ONH NRR and RNFL that included quantification of major retinal vascular contribution. There was a significant age-related loss of RNFL thickness (-0.23 μm/y, R(2) = 0.24, P < 0.01), major retinal vascular contribution (-0.03 μm/y, R(2) = 0.07, P = 0.01, neural rim volume (NRV, -0.004 mm(3)/y, R(2) = 0.15, P < 0.01), and minimum rim width (MRW, -1.77 μm/y, R(2) = 0.23, P < 0.01) before, and after, incorporating the Bruch's membrane opening size (sMRW, -1.86 μm/y, R(2) = 0.22, P < 0.01). When normalized, the rates of change for ONH NRR parameters (NRV, 0.69%/y and sMRW, 0.50%/y) exceeded that of RNFL thickness (0.19%/y, P < 0.01). Although both RNFL and ONH NRR parameters contain axons of retinal ganglion cells, there are differences in age-related changes in these measures that should be considered in clinical application.

Prospective, randomized, comparative study of delineation capability of radial scanning and curved linear array endoscopic ultrasound for the pancreaticobiliary region.

Background and study aims: There are two types of endoscopic ultrasound (EUS) endoscope, the radial scanning (RS) and the curved linear array (CL). The type of EUS endoscope used at a first intent depends on local expertise, local habits and sometimes on how the examination is reimbursed. In Japan, RS is mainly used for observation, whereas CL is primarily used for histopathological diagnosis and treatment. We compared the imaging capabilities of RS and CL in evaluating the pancreaticobiliary region, a study which has not been performed previously.Patients and methods: This prospective and randomized trial included 200 patients undergoing endoscopic ultrasonography of the pancreaticobiliary region by RS (n = 99) or CL (n = 101). The primary end point was the basal imaging capability of each technique. Eleven pancreaticobiliary areas were assessed and scored (range, 0 – 2). Endoscopists evaluated each criterion, and a transcriber recorded the decisions in real time. Results: The mean imaging scores in the RS and CL groups were 18.39 and 19.62, respectively (significantly higher in CL, 95 %CI: 0.82 – 1.64). Although no significant difference in imaging capability for the pancreatic head, body, or tail was observed between CL and RS, the imaging capability of CL for the pancreatic head – body transition region was superior to that of RS. Although no significant difference in imaging capability for the middle and inferior bile duct or the cystic duct was observed between CL and RS, the imaging capability of RS for the major duodenal papilla and gallbladder was superior to that of CL. For the area from the hepatic portal region to the superior bile duct, the imaging capability of CL was superior. In the delineation of the branch area of the celiac and superior mesenteric arteries, CL was also superior to RS. Conclusions: The non-inferiority of the overall imaging capability of CL to that of RS was demonstrated. CL was superior in the delineation of the pancreatic head – body transition region, the area from the hepatic portal region to the superior bile duct, and the vascular bifurcation, whereas RS was superior in the delineation of the major duodenal papilla and gallbladder. Thus, for detailed evaluations of specific areas, the choice of scope should probably be considered.

Diabetic macular oedema quantified with spectral-domain optical coherence tomography--evaluation of boundary line artefacts and the effect on retinal thickness.

To characterize frequency, morphological cause and time-dependent change of boundary line artefacts in optical coherence tomography (OCT) examinations of centre-involved diabetic macular oedema (ciDME) patients who underwent ranibizumab treatment with 1-year follow-up and to evaluate the impact of artefacts on retinal thickness. One hundred and fourteen patients were examined with radial scan protocol by Topcon 3D OCT at baseline, 3 and 12 months. All B scans from all visits were examined for boundary line artefacts (artefacts) and were stratified by morphological element causing artefacts including hard exudates (HE), epiretinal membranes (ERM), optical opacities and serous detachments. Boundary line artefacts were manually corrected and the corrected central subfield thickness (CST) and macular volume were compared with automated values. Data were compared with a repeatability coefficient of 25 μm. Boundary line artefacts were found in 51.8% of the total 342 OCT examinations and in 25.5% of the total 2052 B scans. Morphological elements that caused artefacts in the total 2052 B scans were HE (10.6%), ERM (10.3%), optical opacities (4.4%), serous detachments (1.7%) and others (1.2%). The number of artefacts due to HE decreased significantly (p = 0.0005), and the number of artefacts due to ERM were unchanged (p = 0.087) during 12 months. In OCT examinations with artefacts caused by HE, manually corrected CST was statistically significant higher than automated value at baseline and 3 months. For ERM, manually corrected CST was statistically significant lower than automated value at baseline and 12 months. Boundary line artefacts in OCT examinations of ciDME patients using Topcon 3D OCT occur in 51.8%. In situation of boundary line artefacts in centre 1-mm area every fourth OCT examination has a change in CST beyond 25 μm.

Swelling of ion-irradiated 3C–SiC characterized by synchrotron radiation based XRD and TEM

An experimental technique was established to characterize irradiation-induced volume swelling through a combined utilization of synchrotron radiation-based X-ray diffraction (XRD) and transmission electron microscopy (TEM). 3C–SiC specimens were irradiated by Si2+ ions (5MeV) with fluences up to 5×1017ion/cm2 at 1000°C. In order to avoid the accumulation of implanted Si ions in the SiC layer, specific thicknesses of the epitaxy layer and implanted ion energy were chosen. Unresolvable black spot defects were studied by TEM, and the average size and density were calculated. XRD radial scan results of surface (002), (111), (022), (113), and (200) including peak shift and asymmetry peak broadening were observed. Different interplanar spacing information of single crystal SiC can be obtained from this XRD measurement method, making it possible to investigate the lattice expansion and volume swelling more precisely. While TEM provided a direct visualization of the microstructures and the interplanar spacing was measured from HRTEM images. It is suggested that irradiation induced point defects and compressive stress from the Si substrate were the cause of anisotropic (a=b<c) volume swelling of irradiated 3C–SiC in this study.

Can False Profile View Radiographs of the Hip accurately identify CAM lesions? A retrospective radiographic analysis with computed tomography comparison

Dunn, Frog Leg Lateral, and AP radiographic views have been verified to accurately correlate with three-dimensional imaging while assessing for CAM lesions of the hip. The false profile radiographic view of the hip has traditionally been used to measure acetabular coverage in the setting of femoroacetabular impingement but some believe it can also be useful in assessing the morphology of the femoral head-neck junction. The objective of this study was to examine the accuracy of using a false profile radiograph of the hip to identify CAM lesions as compared to three-dimensional CT scan findings. An a prior power analysis using the results from a previous study showed we needed 45 patients to have (1-β>0.80. Patients undergoing hip arthroscopy between January 2011 and September 2012 were reviewed. Patients were included if they had a CT scan performed at our institution and if they had adequate screening radiographs in our PACs system(AP pelvis, 90-degree Dunn lateral and false profile). Alpha-angle measurements were performed on radial oblique CT scans and plain radiographs as previously described by Notzli. 2 physicians measured each x-ray and then re-measured 3 months later. An alpha angle > 50° was used as a cut-off for abnormal. SPSS was used to perform all statistics. 45 patients were reviewed, 24 females and 21 males, 32 right hips and 13 left hips. The average age was 35 yo (17-53 yo). 32 hips had a cam lesion on reformatted CT (α-angle > 50°). 31 hips had a cam lesion present about the 2 o'clock position of the femoral head-neck junction and 19 hips had a cam lesion present about the 3 o'clock position. The false profile view was found to be 60% sensitive and 89% specific at identifying cam lesions. When combined with the AP pelvis and 90-degree Dunn lateral views, this series was found to be 86% sensitive and 90% specific. The false profile view had a strong correlation to both the 2 o'clock and 3 o'clock views (r = 0.75 and 0.70 respectively). The False Profile view has a 76% agreement with the 2 o'clock view and an 83% agreement with the 3 o'clock view. Inter and Intra-Observer Correlation Coefficients were 0.81 & 0.88 respectively. This is the first study to suggest that the false profile view can be effectively used to assess the femoral head-neck junction. This has important implications for diagnostic and treatment purposes, as the false profile view has traditionally only been used to only assess for anterior acetabular coverage (pincer-type impingement). We have found that the false profile view effectively characterizes CAM lesions about the anterior portion of the femoral head-neck junction from 2 o'clock to 3 o'clock. Measuring the alpha angle on this view appears to be a reproducible with a significant ICC. In combination with the AP and 90-degree Dunn lateral views the false profile view allows for a physician to fully assess for CAM-lesions about the anterosuperior head neck junction.

Radial Versus Raster Spectral-Domain Optical Coherence Tomography Scan Patterns for Detection of Macular Pathology

To compare the 6-line radial vs the 25-line raster spectral-domain optical coherence tomography (SD OCT) acquisition patterns at detecting intraretinal fluid, subretinal fluid, vitreomacular traction, and full-thickness macular hole (MH). Retrospective cross-sectional analysis. Series of 365 eyes with neovascular age-related macular degeneration (AMD), diabetic macular edema (DME), central and branch retinal vein occlusion (CRVO/BRVO), central serous chorioretinopathy, vitreomacular traction, and full-thickness MH. Sequential 6-line radial and 25-line raster scans were evaluated for intraretinal/subretinal fluid and, when applicable, vitreomacular traction and MH. For neovascular AMD (133 scans), 7 25-line raster scans confirmed subretinal/intraretinal fluid not identified by the 6-line radial (P=.02). For DME (140 scans) and central serous chorioretinopathy (91 scans), 25-line raster confirmed fluid in 4 scans (P=.13) and 1 scan (P=.32), respectively, that was not observed with the 6-line radial. For CRVO (123 scans) and BRVO (126 scans), 25-line raster confirmed fluid on 2 (P=.25) and 4 scans (P=.13), respectively, that was not detected by the 6-line radial. Conversely, for focal vitreomacular traction (70 scans) and full-thickness MH (82 scans), 25-line raster missed focal traction (<1500 μm) and MH in 5 scans (P=.07) and 7 scans (P=.02), respectively, that were identified using the 6-line radial. The 6-line radial scan is statistically comparable to the 25-line raster at detecting fluid in DME, BRVO/CRVO, and central serous chorioretinopathy, but not neovascular AMD. Furthermore, it is superior to the 25-line raster pattern at detecting early MH formation, while demonstrating a positive trend in identifying focal vitreomacular traction.

Smoking and choroidal thickness in patients over 65 with early-atrophic age-related macular degeneration and normals.

To compare macular choroidal thickness between cigarette smokers, those with a history of smoking, and nonsmokers in patients over 65 years of age with early-atrophic age-related macular degeneration (AMD) and normals. Prospective, consecutive, observational case series. Enhanced depth imaging spectral domain optical coherence tomography 12-line radial scans were performed and choroidal thickness manually quantified at 84 points in the central 3 mm of the macula. Data of normals, soft drusen alone, and soft drusen with additional features of early AMD were compared. A multivariate analysis of variance (MANOVA) model, controlling for age, was constructed to evaluate the effect of smoking history and AMD features on choroidal thickness. A history of smoking was significantly associated with a thinner choroid across all patients via logistic regression (P=0.004; O.R.=12.4). Mean macular choroidal thickness was thinner for smokers (148±63 μm) than for nonsmokers (181±65 μm) among all diagnosis categories (P=0.003). Subgroup analysis of patients with AMD features revealed a similar decreased choroidal thickness in smokers (121±41 μm) compared with nonsmokers (146±46 μm, P=0.006). Bivariate analysis revealed an association between increased pack-years of smoking and a thin choroid across all patients (P<0.001) and among patients with features of early AMD (P<0.001). Both the presence of features of macular degeneration (P<0.001) and a history of smoking (P=0.024) were associated with decreased choroidal thickness in a MANOVA model. Chronic cigarette smoke exposure may be associated with decreased choroidal thickness. There may be an anatomic sequelae to chronic tobacco smoke exposure that underlies previously reported AMD risk.

Trajectory correction for free-breathing radial cine MRI

Radial acquisitions can suffer from trajectory errors leading to reduced image quality. Here we present a new method of trajectory correction that uses all spokes of a radial acquisition and compare it to an existing method that uses a two-spoke pre-scan calibration. For both methods, estimates of the necessary shifts were made using magnitude or phase data and the performances were compared. The additional effect of B0 correction was considered in all cases. Mouse cardiac scans were used for the comparisons and we also compared the quality of navigator signals obtained from the radial data with each technique.The proposed method gave improved image quality over the existing method, as assessed by visual inspection and quantitative evaluation of artifacts. The typical shading artifacts seen in radial scans were significantly reduced with both approaches, with phase-based corrections generally outperforming magnitude-based methods. B0 correction gave further improvements in each case. Furthermore, modulation of navigator signals due to the acquisition angle was significantly reduced with the new technique. We show that our proposed method works well to reduce artifacts seen in mouse cardiac imaging that can make faster imaging feasible.

Automated Segmentation of Optic Nerve Head Structures With Optical Coherence Tomography

To quantify and characterize the difference between automated and manual segmentation of optic nerve head structures with spectral-domain optical coherence tomography (SD-OCT). Optic nerve head radial scans in 107 glaucoma patients and 48 healthy controls were conducted with SD-OCT. Independent segmentations of the internal limiting membrane (ILM) and Bruch's membrane opening (BMO) were performed manually with custom software and with an automated algorithm in each radial scan. The minimum distance between BMO and ILM, termed BMO-minimum rim width (BMO-MRW) was calculated with each segmentation method. Absolute differences between automated and manual segmentations of ILM (ΔILM) and BMO (ΔBMO), and the resulting computation of BMO-MRW (ΔBMO-MRW) were computed. Finally, the relationship between image quality score and ΔILM and ΔBMO was explored. The median (interquartile range, IQR) ΔILM was 8.9 (6.5, 13.4) μm in patients and 7.3 (5.3, 9.9) μm in controls. The corresponding values for ΔBMO were 11.5 (6.6, 22.1) μm and 12.4 (6.8, 25.4) μm. Subject-averaged ΔILM was higher in patients than controls (P < 0.01); however, mean ΔBMO was not (P = 0.09). The median (IQR) subject-averaged absolute ΔBMO-MRW was 13.4 (10.6, 16.8) μm in patients and 12.1 (10.0, 16.8) μm in controls and not statistically different (P = 0.21). Mean image quality score was statistically higher in controls than patients (P = 0.03) but not related to subject-averaged ΔILM or ΔBMO. In individual scans, the median difference in ILM and BMO segmentations was <2 and <3 image pixels, respectively. There were no differences between patients and controls in ΔBMO-MRW.

Evaluation of Retinal and Choroidal Thickness by Swept-Source Optical Coherence Tomography: Repeatability and Assessment of Artifacts

To determine the repeatability of automated retinal and choroidal thickness measurements with swept-source optical coherence tomography (SS OCT) and the frequency and type of scan artifacts. Prospective evaluation of new diagnostic technology. Thirty healthy subjects were recruited prospectively and underwent imaging with a prototype SS OCT instrument. Undilated scans of 54 eyes of 27 subjects (mean age, 35.1 ± 9.3 years) were obtained. Each subject had 4 SS OCT protocols repeated 3 times: 3-dimensional (3D) 6× 6-mm raster scan of the optic disc and macula, radial, and line scan. Automated measurements were obtained through segmentation software. Interscan repeatability was assessed by intraclass correlation coefficients (ICCs). ICCs for choroidal measurements were 0.92, 0.98, 0.80, and 0.91, respectively, for 3D macula, 3D optic disc, radial, and line scans. ICCs for retinal measurements were 0.39, 0.49, 0.71, and 0.69, respectively. Artifacts were present in up to 9% scans. Signal loss because of blinking was the most common artifact on 3D scans (optic disc scan, 7%; macula scan, 9%), whereas segmentation failure occurred in 4% of radial and 3% of line scans. When scans with image artifacts were excluded, ICCs for choroidal thickness increased to 0.95, 0.99, 0.87, and 0.93 for 3D macula, 3D optic disc, radial, and line scans, respectively. ICCs for retinal thickness increased to 0.88, 0.83, 0.89, and 0.76, respectively. Improved repeatability of automated choroidal and retinal thickness measurements was found with the SS OCT after correction of scan artifacts. Recognition of scan artifacts is important for correct interpretation of SS OCT measurements.

Optical Coherence Tomography (OCT) Device Independent Intraretinal Layer Segmentation.

To develop and test an algorithm to segment intraretinal layers irrespectively of the actual Optical Coherence Tomography (OCT) device used. The developed algorithm is based on the graph theory optimization. The algorithm's performance was evaluated against that of three expert graders for unsigned boundary position difference and thickness measurement of a retinal layer group in 50 and 41 B-scans, respectively. Reproducibility of the algorithm was tested in 30 C-scans of 10 healthy subjects each with the Spectralis and the Stratus OCT. Comparability between different devices was evaluated in 84 C-scans (volume or radial scans) obtained from 21 healthy subjects, two scans per subject with the Spectralis OCT, and one scan per subject each with the Stratus OCT and the RTVue-100 OCT. Each C-scan was segmented and the mean thickness for each retinal layer in sections of the early treatment of diabetic retinopathy study (ETDRS) grid was measured. The algorithm was able to segment up to 11 intraretinal layers. Measurements with the algorithm were within the 95% confidence interval of a single grader and the difference was smaller than the interindividual difference between the expert graders themselves. The cross-device examination of ETDRS-grid related layer thicknesses highly agreed between the three OCT devices. The algorithm correctly segmented a C-scan of a patient with X-linked retinitis pigmentosa. The segmentation software provides device-independent, reliable, and reproducible analysis of intraretinal layers, similar to what is obtained from expert graders. Potential application of the software includes routine clinical practice and multicenter clinical trials.

Effect of Optical Coherence Tomography Scan Pattern and Density on the Detection of Full-Thickness Macular Holes

To evaluate the impact of different scan patterns and scan densities on small full-thickness macular hole (MH) detection. Retrospective cross-sectional analysis. Analysis was performed on 25 eyes from 24 patients with full-thickness MHs imaged with the Heidelberg Spectralis HRA+OCT. Included eyes underwent concurrent imaging with a standard (61-line) raster volume and a 24-line radial pattern. A 6-line radial scan pattern was extrapolated from the higher-density radial pattern. Comparisons of the missed hole rate as well as the proportion of individual B-scans demonstrating a full-thickness defect (termed "full-thickness detection index") were carried out for the 3 scan patterns. Additionally, qualitative and quantitative hole parameters were evaluated to identify factors associated with "missed" holes. Full-thickness defects were missed at substantially higher rates using both standard raster volume (20.0%, 90% confidence interval [CI] 8.2%-37.5%) and 6-line radial scanning (12.0%, 90% CI 3.7%-30.4%) when compared to 24-line radial scanning (0% for both comparisons). Full-thickness detection indices were significantly higher for both radial scan patterns when compared to raster scanning (P < .001 for both comparisons). Missed holes were smaller and commonly associated with prehole flaps. High-density radial scanning demonstrated superior detection rates of small full-thickness MHs compared to standard raster volume scanning. This finding may be attributable to the greater foveolar scan density attained with radial scan patterns. Failure to utilize radial scanning in the setting of suspected macular holes may lead to a delay in surgical treatment, with attendant worse anatomic and visual outcomes.

Exchange bias and crystal structure of epitaxial (111) FePt/BiFeO3 sputtered thin films

Crystallographic structure and magnetic properties of the epitaxial FePt (10 nm)/BiFeO3 (BFO) (10 nm) bilayer films grown on (111) SrTiO3 (STO) substrates with different deposition temperatures of FePt layers (Td) have been investigated using magnetron sputtering. Out-of-plane radial scan along (111) direction and off-normal (002) azimuthal scan, determined by synchrotron radiation x-ray diffractometry, evidence that the FePt layers were well epitaxially grown on the (111) epitaxial BFO layers for the samples with Td = 300 and 700 °C. On the contrary, for the bilayer films with Td = 500 °C, the FePt and BFO layers exhibit low epitaxial quality. Large in-plane exchange bias field (Heb) values of 45–412 Oe are obtained for the L10-FePt/BFO bilayer films measured with applied field of 12 kOe at room temperature. The change of effective interfacial area, observed by scanning electron microscopy, between FePt island-like particles and BFO continuous layers, and epitaxiality of the bilayer were correlated with the evolution of Heb.