Search

Purpose To develop a method of averaging optical coherence tomography (OCT) angiography to improve visualization of choriocapillaris structure. Methods A stack of OCT angiographic data from vascular layers were placed into the red-green-blue channels of a conventional digital color image. The superficial plexus was placed in the blue channel, choriocapillaris in the green, and deep vascular plexus in the red channel. The red-green-blue images derived from nine separate OCT angiographic scans were registered using an automatic registration sequence and the images were averaged. The averaged red-green-blue image was then split into the three averaged component layers. The technique is flexible and any vascular layer, such as macular neovascularization, can be used as well. Results The utility of the imaging method was demonstrated by showing the imaging of two different diseases. A patient with a history of familial amyloidosis, hypertension, kidney failure, kidney transplantation, and prednisone use, followed by central serous chorioretinopathy treated by photodynamic therapy. She had alterations in retinal pigment epithelial pigmentation and widespread abnormalities of autofluorescence. She showed remarkably decreased vascular density and vessel configuration of her choriocapillaris. A patient with pseudoxanthoma elasticum with subretinal drusenoid deposits at an early age also showed marked decreased choriocapillaris density and vascular configuration. These findings were compared with healthy controls of similar age with no abnormalities. Conclusion The detailed method is capable of averaging choriocapillaris OCT angiographic images using a simple automatic method. Image averaging offers opportunity to improve the noisy OCT angiographic images such that actual vascular structure is visible.

Digital Image Correlation (DIC) is a camera-based method of measuring mechanical displacement and strain which is commonly used in high-temperature experiments due to its ability to take contactless measurements. High-temperature DIC is challenging due to light emitted from the sample which can saturate the camera sensor. Blue-DIC and UV-DIC have been developed to minimize this effect, but the maximum sample temperature range of DIC remains a function of the camera and camera settings. Bit depth, also referred to as color depth or number of bits, is an important camera setting which affects the dynamic range of an image, but which has received insufficient attention in DIC literature. In this work, the effect of bit depth on DIC measurements is investigated both analytically and experimentally. If image noise is sufficiently low, increasing bit depth reduces DIC random error. Using increased bit depth and reduced exposure time, the maximum sample temperature for DIC measurements was shown to increase without negative impact on measurement precision.

Purpose: To evaluate the mutual effect of widening the field of view and multiple en face image averaging on the quality of optical coherence tomography angiography (OCTA) images. Methods: This prospective, observational, cross-sectional case series included 20 eyes of 20 healthy volunteers with no history of ocular or systemic disease. OCTA imaging of a 3 × 3-mm, 6 × 6-mm, and 12 × 12-mm area centered on the fovea was performed nine times using the PLEX Elite 9000. We acquired averaged OCTA images generated from nine en face OCTA images. The corresponding areas in the three scan sizes were evaluated for the original single-scanned OCTA images and averaged OCTA images both qualitatively and quantitatively. Quantitative measurements included vessel density (VD), vessel length density (VLD), fractal dimension (FD), and contrast-to-noise ratio (CNR). Results: Significant differences in VD, VLD, FD, and CNR (P < 0.001) were observed due to the mutual effect of averaging and differences in scan size. Both qualitative and quantitative evaluations indicated that the quality of 6 × 6-mm averaged images was equal to or better than that of 3 × 3-mm single-scanned images. However, the quality of 12 × 12-mm averaged images did not reach that of 3 × 3-mm single-scanned images. Conclusions: To some extent, multiple en face OCTA image averaging can compensate for the deterioration in image quality caused by widening the field of view. Translational Relevance: Multiple en face OCTA image averaging can be a technique for acquiring wider field OCTA images with good quality.

Thyroid disease is a frequent occurrence in clinical practice and the computerized analysis of ultrasonography has been becoming the most prospective tool for thyroid disease automatic diagnosis. However, the accuracy of vision-based diagnostic analysis is often reduced because the quality of ultrasound image is easily corrupted by the speckle noise. Thus, noise suppression is imperative and significant for the thyroid ultrasonography image preprocessing to increase the reliability of subsequent analysis. In this paper, we propose a novel weighted image averaging method based on anisotropic diffusion filters combination to remove speckle noise and enhance the details of the image at the same time. The method first denoises the image separately by two filters with different performances. The speckle reducing anisotropic diffusion filter can enhance the details of the image, and the anisotropic diffusion filter can better suppress the speckle noise in the image. In order to integrate the advantages of the two filters and reduce the mutual interference meanwhile, an adaptive weighted image averaging method is further proposed to combine the pixels of the two denoised images. The experimental results indicate that the proposed method can achieve promising performance on the template images with various noise levels by considering PSNR and SSIM. What's more, it is not only superior to other methods in automatic segmentation, but also can obtain better visual effect for thyroid images.

BACKGROUND AND OBJECTIVE: To describe a method for averaging ocular coherence tomography angiography (OCTA) images using a commercially available photo editing software: Adobe Photoshop CC 2017. PATIENTS AND METHODS: This single-center study assessed the feasibility of using Adobe Photoshop as an OCTA image averaging tool. Three 3.0 mm × 3.0 mm OCTA images from each eye were obtained using commercially available OCTA devices. Captured OCTA images were exported in high-resolution TIFF format, imported as an image stack, aligned using an automated function, and averaged by creating a Smart Object using Photoshop CC 2017 software. In conjunction with qualitative assessment, the main outcome of the study was image grader preferences with respect to clarity of the foveal avascular zone (FAZ), blood vessel delineation, and the ability to identify abnormal vasculature. RESULTS: After removing OCTA scans with significant image distortion, 25 sets of images were included in the analysis. Adobe Photoshop CC 2017 successfully aligned and averaged all images of the superficial and deep retinal plexuses that contained a minimum 40% overlap. Three independent retinal specialists found the averaged images to be slightly or definitely preferable to the original 87%, 89%, and 69% of the time with respect to clarity of the FAZ, clarity of blood vessel delineation, and the ability to identify abnormal vasculature, respectively. CONCLUSIONS: Adobe Photoshop CC 2017 is an excellent tool for image averaging, producing high-quality resulting OCTA images. As an easily accessible software, Photoshop has the potential for use in a diversity of pathological conditions. [ Ophthalmic Surg Lasers Imaging Retina . 2019;50:802–807.]

Laminin polymerization is a key step of basement membrane assembly that depends on the binding of α, β and γ N-terminal LN domains to form a polymer node. Nodal assembly can be divided into two steps consisting of β- and γ-LN dimerization followed by calcium-dependent addition of the α-LN domain. The assembly and structural organization of laminin-111 LN-LEa segments was examined by size-exclusion chromatography (SEC) and electron microscopy. Triskelion-like structures were observed in negatively-stained images of purified α1/β1/γ1 LN-LEa trimers. Image averaging of these revealed a heel-to-toe organization of the LN domains with angled outward projections of the LEa stem-like domains. A series of single-amino acid substitutions was introduced into the polymerization faces of the α1, β1 and γ1 LN domains followed by SEC analysis to distinguish between loss of β-γ mediated dimerization and loss of α-dependent trimerization (with intact β-γ dimers). Dimer-blocking mutations were confined to the γ1-toe and the β1-heel, whereas the trimer-only-blocking mutations mapped to the γ1-heel, β1-toe and the α1-toe and heel. Thus, in the polymer node the γ1-toe pairs with the β1-heel, the β1-toe pairs with the α1-heel, and the α1-toe pairs with the γ1-heel.

Purpose To analyze the structure of the choriocapillaris in healthy eyes by using averaged en face images acquired using swept source optical coherence tomography angiography and to examine the changes in the macular profile in relation to age, sex, axial length, and choroidal thickness. Methods This prospective, cross-sectional study included 81 eyes of 81 subjects without ophthalmologic or systemic diseases who underwent a full ophthalmologic examination, including 3 × 3-mm macular optical coherence tomography angiography. Four to nine choriocapillaris en face images were registered and averaged. The averaged images were then binarized and analyzed. Results The averaged choriocapillaris images showed a continuous capillary meshwork, whereas the unaveraged images had a granular appearance. The mean total area and size of flow voids were 0.99 ± 0.20 mm2 and 567.8 ± 201.5 μm2, respectively, and these values correlated positively with age (p = 0.002, R = 0.336 and p = 0.026, R = 0.247, respectively). Age-related gains in the mean total area and flow void size were 4.20 × 10−3 mm2 and 3.07 μm2 per year, respectively. However, the mean total area and flow void size had no significant correlation with axial length, subfoveal choroidal thickness, or sex. Conclusions Multiple averaged en face swept source optical coherence tomography angiography is more effective than a single optical coherence tomography angiography scan for better visualizing the choriocapillaris. The total area and size of flow voids within a 3 × 3-mm macular area positively correlated with age. This technique can be useful for investigating the changes arising in macular diseases.

Purpose To assess the repeatability of multiple automatic vessel density (VD) measurements and the effect of image averaging on vessel detection by optical coherence tomography angiography (OCTA). Methods An observational study was conducted in a series of healthy volunteers and patients with macular oedema. Five sequential OCTA images were acquired for each eye using the OptoVue HD device. The effect of the averaging of the 5 acquisitions on vessel detection was analysed quantitatively using a pixel-by-pixel automated analysis. In addition, two independent retina experts qualitatively assessed the change in vessel detection in averaged images segmented in 9 boxes and compared to the first non-averaged image. Results The automatic VD measurement in OCTA images showed a good repeatability with an overall mean intra-class correlation coefficient (ICC) of 0.924. The mean ICC was higher in healthy eyes compared to eyes with macular oedema (0.877 versus 0.960; p < 0.001) and in the superficial vascular plexus versus the deep vascular complex (0.967 versus 0.888; p = 0.001). The quantitative analysis of the effect of the averaging showed that averaged images had a mean gain of 790.4 pixels/box, located around or completing interruptions in the vessel walls, and a mean loss of 727.2 pixels/box. The qualitative analysis of the averaged images showed that 99.6% of boxes in the averaged images had a gain in vessel detection (i.e., vessels detected in the averaged image but not in the non-averaged image). The loss of pixels was due to a reduction in background noise and motion artifacts in all cases and no case of loss of vessel detection was observed. Conclusion The automatic VD measurement using the OptoVue HD device showed a good repeatability in 5 acquisitions in a row setting. Averaging images increased vessel detection, and in about a third of boxes, decreased the background noise, both in healthy eyes and, in a greater proportion, in eyes with macular oedema.

Antibody binding to cell surface proteins plays a crucial role in immunity and the location of an epitope can altogether determine the immunological outcome of a host-target interaction. Techniques available today for epitope identification are costly, time-consuming, and unsuited for high-throughput analysis. Fast and efficient screening of epitope location can be useful for the development of therapeutic monoclonal antibodies and vaccines. In the present work, we have developed a method for imaging-based localization of binding sites on cellular surface proteins. The cellular morphology typically varies, and antibodies often bind in a non-homogenous manner, making traditional particle-averaging strategies challenging for accurate native antibody localization. Nanometer-scale resolution is achieved through localization in one dimension, namely the distance from a bound ligand to a reference surface, by using topological image averaging. Our results show that this method is well suited for antibody binding site measurements on native cell surface morphology.

PRéCIS:: Averaging triplicate en face angiograms of the radial peripapillary capillary (RPC) plexus with optical coherence tomography angiography (OCTA) improves vessel visualization, reduces vessel density parameters, and increases the diagnostic accuracy for glaucoma of one such parameter.The purpose of this study was to test the hypothesis that triplicate averaging of the RPC layer improves visualization and diagnostic accuracy of OCTA for glaucoma.This is a cross-sectional study involving 63 primary open-angle glaucoma patients and 70 age-matched glaucoma suspects. Triplicate 6×6 mm OCTA scans of the optic nerve head were acquired, and the RPC layer was extracted. RPC en face images were registered and averaged. Parameters of global entropy, global standard deviation, local texture correlation, local homogeneity, signal-to-noise ratio, and intercapillary distance were used to measure the change in visualization with averaging. Vessel area density (VAD), vessel skeleton density (VSD), and flux parameters were calculated in a 2.8 mm annulus excluding the optic disc. The diagnostic accuracy of these parameters for glaucoma was assessed by calculating the area under the receiver operating curve (AUC) values.Three-frame averaging resulted in decreased global entropy and global standard deviation (Ps0.001), and increased local texture correlation, local homogeneity, signal-to-noise ratio, and intercapillary distance (Ps0.001). Averaged images also had reduced VAD, VSD, and flux (Ps0.001). AUC was significantly increased for VSD after image averaging (P=0.018), while no significant change in AUC was observed for VAD (P=0.229) or flux (P=0.193).Triplicate averaging improves visualization of the RPC layer and the diagnostic accuracy of VSD for glaucoma. The impact of image averaging on OCTA diagnostic performance and other potential applications warrants further exploration.

Background To estimate choriocapillaris flow deficits beyond normal intercapillary distance with swept source optical coherence tomography angiography (SS-OCTA). Methods Subjects were enrolled and repeated SS-OCTA scans were performed using the 3 mm × 3 mm scan pattern. Blood flow was identified using the complex optical microangiography (OMAGc) algorithm. The choriocapillaris (CC) was defined as a 20 µm slab of the flow volume beneath the outer boundary of Bruch's membrane (BM) and was compensated with the corresponding structural image for flow deficits measurement. Flow deficits were segmented based on one mean standard deviation from a normal database. A histogram based thresholding method was developed to remove small flow deficits that were determined by examining intercapillary spacing within normal CC networks. A registration method based on affine and B-spline transformation was utilized for the CC angiogram averaging. Four repeated scans were averaged, and results were compared with and without removal of small flow deficits after averaging a different number of scans (N=1, group 1; N=2, group 2; N=3, group 3 and N=4, group 4). Results Seven normal subjects were enrolled. Intercapillary distance was found to be 24 µm for the CC networks under OCTA, which was used as the threshold to exclude small flow deficits for CC quantification. After averaging, significant reduction in background noise and improvement in continuity of blood vessel networks were observed both on retinal and choriocapillaris angiograms. Flow deficit percentages of the choriocapillaris were significantly reduced with averaging (group 1 vs. group 2: P

Purpose To investigate the effect of multiple enface image averaging on image quality of the optical coherence tomography angiography (OCTA). Methods Twenty-one normal volunteers were enrolled in this study. For each subject, one eye was imaged with 3 × 3 mm scan protocol, and another eye was imaged with the 6 × 6 mm scan protocol centred on the fovea using the ZEISS Angioplex™ spectral-domain OCTA device. Eyes were repeatedly imaged to obtain nine OCTA cube scan sets, and nine superficial capillary plexus (SCP) and deep capillary plexus (DCP) were individually averaged after registration. Results Eighteen eyes with a 3 × 3 mm scan field and 14 eyes with a 6 × 6 mm scan field were studied. Averaged images showed more continuous vessels and less background noise in both the SCP and the DCP as the number of frames used for averaging increased, with both 3 × 3 and 6 × 6 mm scan protocols. The intensity histogram of the vessels dramatically changed after averaging. Contrast-to-noise ratio (CNR) and subjectively assessed image quality scores also increased as the number of frames used for averaging increased in all image types. However, the additional benefit in quality diminished when averaging more than five frames. Averaging only three frames achieved significant improvement in CNR and the score assigned by certified grades. Conclusion Use of multiple image averaging in OCTA enface images was found to be both objectively and subjectively effective for enhancing image quality. These findings may of value for developing optimal OCTA imaging protocols for future studies.

Made available in DSpace on 2018-12-11T17:19:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-09-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Objectives: In order to enable less experienced physicians to reliably detect early signs of stroke, A novel approach was proposed to enhance the visual perception of ischemic stroke in non-enhanced CT. Methods: A set of 39 retrospective CT scans were used, divided into 23 cases of acute ischemic stroke and 16 normal patients. Stroke cases were obtained within 4.5 h of symptom onset and with a mean NIHSS of 12.9±7.4. After selection of adjunct slices from the CT exam, image averaging was performed to reduce the noise and redundant information. This was followed by a variational decomposition model to keep the relevant component of the image. The expectation maximization method was applied to generate enhanced images. Results: We determined a test to evaluate the performance of observers in a clinical environment with and without the aid of enhanced images. The overall sensitivity of the observer’s analysis was 64.5 % and increased to 89.6 % and specificity was 83.3 % and increased to 91.7 %. Conclusion: These results show the importance of a computational tool to assist neuroradiology decisions, especially in critical situations such as the diagnosis of ischemic stroke. Key Points: • Diagnosing patients with stroke requires high efficiency to avoid irreversible cerebral damage. • A computational algorithm was proposed to enhance the visual perception of stroke. • Observers’ performance was increased with the aid of enhanced images. Instituto de Biociências de Botucatu Departamento de Física e Biofísica UNESP—Universidade Estadual Paulista, P.O. BOX 510, Distrito de Rubião Junior S/N Laboratory I3MTO – University of Orleans, 5 Rue de Chartres, BP 6744 Departamento de Neurologia Psicologia e Psiquiatria Faculdade de Medicina de Botucatu UNESP—Universidade Estadual Paulista, Distrito de Rubião Junior S/N Departamento de Diagnóstico por Imagem Escola Paulista de Medicina – UNIFESP, Rua Napoleão de Barros, 800 Departamento de Doenças Tropicais e Diagnóstico por Imagem Faculdade de Medicina de Botucatu UNESP—Universidade Estadual Paulista, Distrito de Rubião Junior S/N Instituto de Biociências de Botucatu Departamento de Física e Biofísica UNESP—Universidade Estadual Paulista, P.O. BOX 510, Distrito de Rubião Junior S/N Departamento de Neurologia Psicologia e Psiquiatria Faculdade de Medicina de Botucatu UNESP—Universidade Estadual Paulista, Distrito de Rubião Junior S/N Departamento de Doenças Tropicais e Diagnóstico por Imagem Faculdade de Medicina de Botucatu UNESP—Universidade Estadual Paulista, Distrito de Rubião Junior S/N FAPESP: 2014/22296-1

The genus Mycoplasma is made up of the smallest parasitic and sometimes commensal bacteria; Mycoplasma pneumoniae, which causes human “walking pneumonia,” is representative. More than ten Mycoplasma species glide on host tissues by novel mechanisms, always in the direction of the distal side of the machinery. Mycoplasma mobile, the fastest species in the genus, catches, pulls, and releases sialylated oligosaccharides (SOs), the carbohydrate molecules also targeted by influenza viruses, by means of a specific receptor and using ATP hydrolysis for energy. Here, the architecture of the gliding machinery was visualized three dimensionally by electron cryotomography (ECT), and changes in the structure and binding activity coupled to ATP hydrolysis were discovered. Based on the results, a refined mechanism was proposed for this unique motility., Mycoplasma mobile, a fish pathogen, glides on solid surfaces by repeated catch, pull, and release of sialylated oligosaccharides by a unique mechanism based on ATP energy. The gliding machinery is composed of huge surface proteins and an internal “jellyfish”-like structure. Here, we elucidated the detailed three-dimensional structures of the machinery by electron cryotomography. The internal “tentacle”-like structure hydrolyzed ATP, which was consistent with the fact that the paralogs of the α- and β-subunits of F1-ATPase are at the tentacle structure. The electron microscopy suggested conformational changes of the tentacle structure depending on the presence of ATP analogs. The gliding machinery was isolated and showed that the binding activity to sialylated oligosaccharide was higher in the presence of ADP than in the presence of ATP. Based on these results, we proposed a model to explain the mechanism of M. mobile gliding.

Aims Plaque burden (PB) measurement using intravascular optical coherence tomography (IVOCT) is currently thought to be inferior to intravascular ultrasound (IVUS). We developed an automated IVOCT image processing algorithm to enhance the external elastic lamina (EEL) contour. Thus, we investigated the accuracies of standard IVOCT and an IVOCT enhancement algorithm for measuring PB using IVUS as the reference standard. Methods and results The EEL-enhancement algorithm combined adaptive attenuation compensation, exponentiation, angular registration, and image averaging using three sequential frames. In two different laboratories with intravascular imaging expertise, PB was quantified on 200 randomized, matched IVOCT and IVUS images by four independent observers. Fibroatheroma, fibrocalcific plaque, fibrous plaque, pathological intimal thickening (PIT), and mixed plaque were included in each set. Pearson’s correlation coefficients between IVUS and standard IVOCT measurements of PB were 0.61, 0.67, 0.76, 0.78, and 0.87 for fibroatheromas, mixed plaques, fibrocalcific plaques, fibrous plaques, and PIT plaques, respectively. Pearson’s correlation coefficients increased to 0.81, 0.83, 0.83, 0.84, and 0.90 when using the EEL-enhanced images (P = 0.003, P = 0.004, P = 0.08, P = 0.12, and P = 0.23, respectively). EEL-enhanced IVOCT analysis was associated with a lower EEL-area measurement absolute error for fibroatheromas, mixed plaques, and all pooled plaques (P = 0.006, P = 0.02, and P Conclusion EEL-enhanced IVOCT can be used to reliably measure PB in all types of coronary atherosclerotic lesions, including fibroatheromas and mixed plaques.

Images of defects in a plate-like structure can be obtained from amplitude distributions measured using the scanning laser source technique. This paper discusses high-speed non-contact imaging for defects in a plate. Fundamental experiments conducted using a contact piezoelectric transducer as a receiving device revealed the effect of the generated wave shape and measurement speed on the defect images. Generating tone-burst waves consisting of multiple frequency components and averaging the images obtained in multiple frequency bands (frequency image averaging, FIA) gave clearer defect images in which noisy effects due to low signal-to-noise ratio and spurious images due to multiple reflections in high-speed imaging were reduced. Moreover, FIA was shown to be effective for high-speed non-contact imaging using a laser Doppler vibrometer.

Hydroxyapatite (HA) is one of the most common natural biomaterials widely used in medical applications. Full-field optical coherence tomography can be used to characterise the internal structures of this material by detection of multiple fringe envelope signals. However, the semi-translucent nature of HA and complex spongy aspect is a challenge. We propose here the “IMPROVE-Protocol”, combining a hybrid high dynamic range technique, image averaging and dark and flat corrections to study HA. The resulting increase in the SNR and improvement in the power of detection of the system allows normally unmeasured features to be observed, down to sub-µm in size.

To study the capabilities of high-speed spectral-domain optical coherence tomography angiography (SD-OCTA) with image averaging in the evaluation of choriocapillaries in healthy individuals and patients with central serous chorioretinopathy (CSC).All participants underwent OCTA examination on the SOLIX tomograph (Optovue, USA) using quadruplicate 3×3 mm scan with image averaging. Image analysis was performed in 9-µm custom slab with Phansalkar auto local threshold algorithm and calculation of flow voids larger than 5000 µmThe study included 18 eyes of 18 healthy volunteers (40.4±6.0 years old) and 18 fellow eyes of 18 unilateral CSC patients (37.4±10.7 years old). The slab 12 µm below the Bruch's membrane showed the minimal number of flow voids (23.1±7.0 of5000 µmThe optimal settings for choriocapillaris imaging on the SOLIX tomograph include 9-µm slab 9 to 18 µm below the Bruch's membrane. Using a 9-µm slab 12 µm below the Bruch's membrane, a substantial difference was found in choriocapillaris perfusion between eyes of healthy individuals and CSC patients.Изучить возможности высокоскоростной спектральной оптической когерентной томографии ангиографии (ОКТА) с технологией усреднения изображений в оценке статуса хориокапилляров в норме и у пациентов с острой центральной серозной хориоретинопатией (ЦСХ).Всем участникам была выполнена ОКТА на томографе SOLIX (Optovue, США) сканом 3×3 мм с четырехкратным повторением и усреднением изображений. Анализ изображений выполняли в пласте Custom толщиной 9 мкм путем определения аутолокального порога яркости по методу Phansalkar и подсчета зон потери сосудистого сигнала (войдов) площадью5000 мкмВ исследование включили 18 глаз 18 здоровых добровольцев (средний возраст — 40,4±6,0 года) и 18 здоровых глаз 18 пациентов с односторонней острой ЦСХ (средний возраст — 37,4±10,7 года). Пласт толщиной 9 мкм на глубине 12 мкм показал наименьшее количество войдов площадью5000 мкмПри использовании томографа SOLIX оптимальными настройками пласта для визуализации хориокапилляриса являются толщина пласта 9 мкм и глубина залегания 12 мкм под мембраной Бруха. Анализ данного пласта подтверждает существенные различия перфузии хориокапилляриса между здоровыми добровольцами и пациентами с ЦСХ.

Objectives The fluorescent dye, 5-aminolevulinic acid (5-ALA), is currently applied for fluorescence-guided resections of high-grade gliomas. Present limitations of this technique are qualitative and subjective analyses, which show little of the background structures. This paper describes the intraoperative quantitative analysis of fluorescence intensity, hot-spot enhancement by frame averaging, and observation of surrounding structures by using 1000-nm lighting in real time. Patients and methods A sample of diluted protoporphyrin IX (PpIX) in a bottle and 37 samples from nine patients with brain lesions were involved in this study. In this preliminary study, we determined appropriate conditions for image averaging and filters and selected the most sensitive spectrometer. In addition, we utilized a 1000-nm lighting system to visualize surrounding structures with no interference from PpIX fluorescence. Results The novel system permitted the real-time quantitative analysis of PpIX fluorescence in operative fields by illuminating structures with 1000-nm-lighting. The real-time quantification provided subjective evaluations for surgical decision-making. We found good correlations between the fluorescence and PpIX contents in brain tissue. Furthermore, 1000-nm lighting visualized the anatomical structures and PpIX fluorescence simultaneously. Conclusion The combination of spectroscopy and a 1000-nm lighting system could enable surgeons to create a spectrogram of targets of interest while observing background structures. The spectrometer that we selected is highly sensitive to PpIX fluorescence and enables us to perform intraoperative real-time tissue mapping. By using a real-time system, we can perform quantitative and objective evaluations to achieve maximal tumor resection.

To determine the effects of averaging five en face optical coherence tomography angiographic (OCTA) images on the quality of the images in eyes with a choroidal neovascularization (CNV).Twenty-seven eyes of 25 patients (18 men, 7 women; average age 71.0 years) with a CNV were examined by OCTA (OCT HS-100, Canon. Japan). A 3 × 3-mm image including the CNV was recorded and automatically segmented between the retinal outer layers. Analyses were performed on a single image (S-image) and the average of five single images of the same area (A-images). The region of the CNV was selected by ImageJ, and the peak signal-to-noise ratio (PSNR), the vascular density (VD), fractal dimension (FD), and the noise component using band pass filter (BPF) processing of the S- and A-images of each case were compared.The average PSNR for the A-images was 14.0 which was significantly higher than the 12.2 for the S-images (P 0.01). However, the average VD was 33.6% for the S-images and 34.8% for the A-images (P 0.1). The average FD was 1.67 for the S-images and 1.54 for the A-images (P 0.01). The mean luminance difference obtained by subtracting the luminance of the A-image from the S-image after BPF processing was 10.41 ± 14.66 db which was positive for all eyes.The better quality of the A-images of a CNV and absence of a significant difference in the vascular density indicates that the improvement was due to the removal of the same signal levels of the noise component and blood vessels.

Background: The aim of this study was to examine the influence of B-scan averaging on choroidal thickness using wide-field enhanced-depth imaging optical coherence tomography. Methods: Six high-resolution trans-foveal horizontal enhanced-depth imaging line scans (spanning a 60° field) were acquired consecutively from the right eye of 10 healthy adults (mean age 30 ± 5 years), with each line scan an average of 10, 20, 30, 40, 50 or 100 B-scans, using the automated real-time image averaging and follow-up features of a Spectralis device. The impact of B-scan averaging on regional measures of wide-field choroidal thickness (across macular and peripheral regions) and their accuracy was investigated, assuming that averaging 100 B-scans would provide the most accurate estimate of choroidal thickness. Results: Regional estimates of wide-field choroidal thickness did not vary across the different B-scan averaging conditions (all p > 0.05). The mean choroidal thickness averaged across the full wide-field area exhibited the closest agreement to measures obtained with 100 averaged B-scans, when frame averaging exceeded 30 B-scans (95 per cent limits of agreement +10 to −7, +7 to −7 and +6 to −3 μm for 30, 40 and 50 averaged B-scans, respectively), compared to 10 and 20 averaged B-scans (95 per cent limits of agreement +13 to −8 and +13 to −6 μm, respectively; p < 0.01 and p < 0.02 compared to the accuracy of 50 averaged B-scans). Conclusion: Averaging 30 B-scans for an individual enhanced-depth imaging optical coherence tomography line scan provided accurate measures of choroidal thickness across a wide-field (60°) area in young healthy eyes. This information can assist in designing the volumetric scan protocols required for detailed examination of the macular and peripheral choroid.

Stroke is a cardio-vascular disease that currently ranks in the fifth position among all causes of death worldwide. Computed tomography is the first radiologic examination performed in emergency decisions to diagnose stroke. The earliest signs of ischemic stroke are quite subtle in CT, thus image-processing tools can be used to enhance ischemic areas and to aid physicians during diagnosis. This study aimed to enhance the ischemic stroke visual perception in computed tomography examinations. A cohort of 45 exams were used during this study, with 28 patients previously diagnosed with ischemic stroke and 17 control patients. Stroke cases were obtained within 4.5 h of symptom onset and with mean NIHSS of 13.6 ± 5.5. The complete series of non-enhanced images were obtained in DICOM format and all processing was performed in Matlab software R2017a. The main steps of the computed algorithm were as follows: an image averaging was performed to reduce the noise and redundant information within each slice; then a variational decomposition model was applied to keep the relevant component for our analysis; then three different segmentation methods were used to enhance the ischemic stroke area. The segmentation methods used were expectation maximization method, K-means and mean-shift. We determined a test to evaluate the performance of six observers (physicians) in a clinical environment with and without the aid of enhanced images. According to the opinion of the observers who participated in this study the enhanced images were particularly useful when displayed together with the original images. The overall sensitivity of the observer’s analysis changed after the evaluation of the enhanced images with the expectation maximization method. The overall specificity also increased. The improvement was even more remarkable for the three least experienced physicians.

Imaging of the choriocapillaris in vivo is challenging with existing technology. Optical coherence tomography angiography (OCTA), if optimized, could make the imaging less challenging.To investigate multiple en face image averaging on OCTA images of the choriocapillaris.Observational, cross-sectional case series at a referral institutional practice in Los Angeles, California. From the original cohort of 21 healthy individuals, 17 normal eyes of 17 participants were included in the study. The study dates were August to September 2016.All participants underwent OCTA imaging of the macula covering a 3 × 3-mm area using OCTA software (Cirrus 5000 with AngioPlex; Carl Zeiss Meditec). One eye per participant was repeatedly imaged to obtain 9 OCTA cube scan sets. Registration was first performed using superficial capillary plexus images, and this transformation was then applied to the choriocapillaris images. The 9 registered choriocapillaris images were then averaged. Quantitative parameters were measured on binarized OCTA images and compared with the unaveraged OCTA images.Vessel caliber measurement.Seventeen eyes of 17 participants (mean [SD] age, 35.1 [6.0] years; 9 [53%] female; and 9 [53%] of white race/ethnicity) with sufficient image quality were included in this analysis. The single unaveraged images demonstrated a granular appearance, and the vascular pattern was difficult to discern. After averaging, en face choriocapillaris images showed a meshwork appearance. The mean (SD) diameter of the vessels was 22.8 (5.8) µm (range, 9.6-40.2 µm). Compared with the single unaveraged images, the averaged images showed more flow voids (1423 flow voids [95% CI, 967-1909] vs 1254 flow voids [95% CI, 825-1683], P .001), smaller average size of the flow voids (911 [95% CI, 301-1521] µm2 vs 1364 [95% CI, 645-2083] µm2, P .001), and greater vessel density (70.7% [95% CI, 61.9%-79.5%] vs 61.9% [95% CI, 56.0%-67.8%], P .001). The distribution of the number vs sizes of the flow voids was skewed in both unaveraged and averaged images. A linear log-log plot of the distribution showed a more homogeneous distribution in the averaged images compared with the unaveraged images.Multiple en face averaging can improve visualization of the choriocapillaris on OCTA images, transforming the images from a granular appearance to a level where the intervascular spaces can be resolved in healthy volunteers.

This cross-sectional case series investigates multiple en face image averaging for optical coherence tomography angiography images of the choriocapillaris.

To investigate the impact of multiple en face image averaging on quantitative measurements of the retinal microvasculature using optical coherence tomography angiography (OCTA).Prospective, observational, cross-sectional case series.Twenty-one healthy individuals with normal eyes.Macular OCTA images were acquired from all participants using the Zeiss Cirrus 5000 with Angioplex OCTA software (Carl Zeiss Meditec, Dublin, CA). Nine OCTA cube scans per eye were obtained and 9 superficial retinal layer (SRL) and deep retinal layer (DRL) en face OCTA image slabs were averaged individually after registration. Quantitative parameters from the retinal microvasculature were measured on binarized and skeletonized OCTA images and compared with single OCTA images without averaging.Vessel density (VD), vessel length density (VLD), vessel diameter index (VDI), and fractal dimension (FD).Participants with artifact or poor image quality were excluded, leaving 18 eyes for the analysis. After averaging, qualitatively there was apparent reduction in background noise, and fragmented vessels in the images before averaging became continuous with smoother walls and showed sharper contrast in both the SRL and DRL. Binarized and skeletonized derivates of these averaged images also showed fewer line fragments and dots in nonvascular areas and more continuous vessel images than those of images without averaging. In both SRL and DRL, VD (P = 0.0010 and P = 0.0003, respectively), VLD (P0.0001 for both), and FD (P0.0001 for both) significantly decreased and VDI significantly increased after averaging (P0.0001 for both).Averaging of multiple en face OCTA images improves image quality and also significantly impacts quantitative measurements. Reducing noise that could be misinterpreted as flow and annealing discontinuous vessel segments seem to be major mechanisms by which averaging may be of benefit.

A common problem for imaging in the atmosphere is fog and atmospheric turbulence. Over the years, many researchers have provided insight into the physics of either the fog or turbulence but not both. Most recently, researchers have proposed methods to remove fog in images fast enough for real-time processing. Additionally, methods have been proposed by other researchers that address the atmospheric turbulence problem. In this paper, we provide an analysis that incorporates both physics models: 1) fog and 2) turbulence. We observe how contrast enhancements (fog removal) can affect image alignment and image averaging. We present in this paper, a new joint contrast enhancement and turbulence mitigation (CETM) method that utilizes estimations from the contrast enhancement algorithm to improve the turbulence removal algorithm. We provide a new turbulent mitigation object metric that measures temporal consistency. Finally, we design the CETM to be efficient such that it can operate in fractions of a second for near real-time applications.

Background and Objective. To determine optimal image averaging settings for Spectralis optical coherence tomography (OCT) in patients with and without cataract. Study Design/Material and Methods. In a prospective study, the eyes were imaged before and after cataract surgery using seven different image averaging settings. Image quality was quantitatively evaluated using signal-to-noise ratio, distinction between retinal layer image intensity distributions, and retinal layer segmentation performance. Measures were compared pre- and postoperatively across different degrees of averaging. Results. 13 eyes of 13 patients were included and 1092 layer boundaries analyzed. Preoperatively, increasing image averaging led to a logarithmic growth in all image quality measures up to 96 frames. Postoperatively, increasing averaging beyond 16 images resulted in a plateau without further benefits to image quality. Averaging 16 frames postoperatively provided comparable image quality to 96 frames preoperatively. Conclusion. In patients with clear media, averaging 16 images provided optimal signal quality. A further increase in averaging was only beneficial in the eyes with senile cataract. However, prolonged acquisition time and possible loss of details have to be taken into account.

Being able to recognize the faces of our friends and family members no matter where we see them represents a substantial challenge for the visual system because the retinal image of a face can be degraded by both changes in the person (age, expression, pose, hairstyle, etc.) and changes in the viewing conditions (direction and degree of illumination). Yet most of us are able to recognize familiar people effortlessly. A popular theory for how face recognition is achieved has argued that the brain stabilizes facial appearance by building average representations that enhance diagnostic features that reliably vary between people while diluting features that vary between instances of the same person. This explains why people find it easier to recognize average images of people, created by averaging multiple images of the same person together, than single instances (i.e. photographs). Although this theory is gathering momentum in the psychological and computer sciences, there is no evidence of whether this mechanism represents a unique specialization for individual recognition in humans. Here we tested two species, chimpanzees (Pan troglodytes) and rhesus monkeys (Macaca mulatta), to determine whether average images of different familiar individuals were easier to discriminate than photographs of familiar individuals. Using a two-alternative forced-choice, match-to-sample procedure, we report a behaviour response profile that suggests chimpanzees encode the faces of conspecifics differently than rhesus monkeys and in a manner similar to humans.

Knowledge of the atomic resolution structures of viruses can be a powerful tool for vaccine discovery and design. X-ray crystallography has long served as an invaluable method for virus structure determination at high resolution, but over the past decade, cryo-electron microscopy (cryo-EM) has begun to emerge as a complementary method that can also provide this kind of information. Crystallographic approaches require significant amounts of purified virus that is structurally homogeneous. In instances where production of adequate amounts of purified virus can be challenging, or where homogeneity is difficult to achieve, the use of cryo-EM and image averaging may be the only way to obtain structural information at high resolution. In PNAS, Rossmann and co-workers (1) use cryo-EM techniques to present elegant results on the structure determination of rhinovirus C, a strain of rhinovirus that is associated with severe disease in children with asthma (2). Rhinoviruses of A, B, and C categories are the leading cause of common colds; there are well over 100 of these types of viruses. Efforts to understand the molecular mechanism of cell receptor binding and differences between rhinovirus strains have been hampered by the lack of structural information, especially for those strains that are difficult to propagate in cell culture (3). It was almost two decades ago that the first breakthroughs were made in the use of cryo-EM for virus structure determination, with the report of structures at ∼7 A resolution of the hepatitis B capsid (4, 5). A decade later, the first near-atomic resolution maps of icosahedral viruses, derived solely from cryo-EM, were published (6, 7). Since that time, as methods for high-resolution cryo-EM have become more widely used, dozens of near-atomic resolution structures of icosahedral viruses have been deposited in the Electron Microscopy Data Bank … [↵][1]1To whom correspondence should be addressed. Email: ss1{at}nih.gov. [1]: #xref-corresp-1-1

International audience; Full-field optical coherence tomography (FF-OCT) based on white-light interference microscopy, is an emerging noninvasive imaging technique for characterizing biological tissue or optical scattering media with micrometer resolution. Tomographic images can be obtained by analyzing a sequence of interferograms acquired with a camera. This is achieved by scanning an interferometric microscope objectives along the optical axis and performing appropriate signal processing for fringe envelope extraction, leading to three-dimensional imaging over depth. However, noise contained in the images can hide some important details or induce errors in the size of these details. To firstly reduce temporal and spatial noise from the camera, it is possible to apply basic image post processing methods such as image averaging, dark frame subtraction or flat field division. It has been demonstrate that this can improve the quality of microscopy images by enhancing the signal to noise ratio. In addition, the dynamic range of images can be enhanced to improve the contrast by combining images acquired with different exposure times or light intensity. This can be made possible by applying a hybrid high dynamic range (HDR) technique, which is proposed in this paper. High resolution tomographic analysis is thus performed using a combination of the above-mentioned image processing techniques. As a result, the lateral resolution of the system can be improved so as to approach the diffraction limit of the microscope as well as to increase the power of detection, thus enabling new sub-diffraction sized structures contained in a transparent layer, initially hidden by the noise, to be detected.

Facial stereotypes are cognitive representations of the facial characteristics of members of social groups. In this study, we examined the extent to which facial stereotypes for occupational groups were based on physiognomic cues to stereotypical social characteristics. In Experiment 1, participants rated the occupational stereotypicality of naturalistic face images. These ratings were then regressed onto independent ratings of the faces on 16 separate traits. These traits, particularly those relevant to the occupational stereotype, explained the majority of variance in occupational stereotypicality ratings. In Experiments 2 and 3, we used trait ratings to reconstruct stereotypical occupation faces from a separate set of images, using face averaging techniques. These reconstructed facial stereotypes were validated by separate groups of participants as conforming to the occupational stereotype. These results indicate that facial cues and group stereotypes are integrated through shared semantic content in the cognitive representations of groups.

Although X-ray microscopic computed tomography is widely used to assess the structural properties of polymeric tissue scaffolds its validity is dependent on the quality of the images obtained. Here, the role of resolution, integration time, image averaging, and X-ray power on the accurate determination of scaffold porosity, while aiming to minimize imaging time, was investigated. This work identified key parameters for optimization and a methodology to vary them to improve results. Based on this, guidelines were developed to assist in the selection of image acquisition parameters to allow rapid and accurate scaffold imaging as required for mass manufacture. © 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 100B: 360–367, 2012.