Synthtic OCT Data for image processing performance testing

The use of synthetic images is needed for testing the performance of image processing methods in order to establish a ground truth to test performance metrics. However, these synthetic images do not represent real applications. The aim of this paper is to build a mathematical model to obtain a synthetic noise-free image mimicking a real Optical Coherence Tomography (OCT) B-scan or volume from the human retina, in order to establish a ground truth for filtering performance metrics in this context. Moreover we also suggest a method to add speckle noise to this image based on the speckle noise of the given OCT volume. In this way we establish a replicable method to obtain a ground truth for image processing performance metrics that actually mimics a real case.FCTFEDERProgram COMPET

Effect of laser heat treatments on the hardness of tool steels

The application of laser heat treatments (LHT) has been growing attention in the last years, due to the effectiveness of localized hardening that can improve the tribological properties of steels. AISI P20 mod. steel is commonly used for plastic injection moulds applications and can be heat-treated to achieve high hardness values. This work presents an experimental investigation on the laser local heat treatments effect on the hardness of AISI P20 mod. steel parts, using a high-power diode laser. Different heat treatments at 1060 ºC and 1100 ºC using a feed rate of 10 mm·s-1 and 15 mm·s-1 were applied on the steel. The LHT were assessed through the hardness mapping trough depth and width. The results showed that the hardness of asreceived P20 mod. tool steel is approximately 300 HV, and after LHT occurred an increment to around 625 HV with a fair hardness distribution. LHT had a minimum of 0.8mm and a maximum of 1.0mm depth.publishe

Optical coherence tomography: automatic retina classification through support vector machines

Optical coherence tomography (OCT) is becoming one of the most important imaging modalities in ophthalmology due to its non-invasiveness and by allowing the visualisation the human retina structure in detail. It was recently proposed that OCT data embeds functional information from the human retina. Specifically, it was proposed that blood–retinal barrier status information is present within OCT data from the human retina. Besides this ability, the authors present data supporting the idea of having the OCT data encoding the ageing of the retina in addition to the disease (diabetes) condition from the healthy status. The methodology followed makes use of a supervised classification procedure, the support vector machine (SVM) classifier – based solely on the statistics of the distribution of OCT data from the human retina (i.e. OCT data between the inner limiting membrane and the retinal pigment epithelium). Results achieved suggest that information on both the healthy status of the blood–retinal barrier and on the ageing process co-exist encoded within the optical properties of the human retina

A conversion model for OCTA vessel density metrics in diabetic eyes: AngioVue vs Angioplex

To understand measurements variability between 2 different OCTA devices and to develop a conversion model that translate vascular metrics into a standardized and comparable value in patients with different stages of DR.info:eu-repo/semantics/publishedVersio

The influence of surface finishing on laser heat treatments of a tool steel

Laser heat treatments (LHT) has received growing attention in the last years because of highly localized precision and manufacturing efficiency related to laser processing of moulds steel. Due of its strong resistance and ability to maintain hardness and strength at high temperatures, AISI P20 steel is one of the most widely used tool steel in the plastics injection mould industry. This work presents an experimental investigation on LHT using P20 mod. steel produced with different surface finishes. After mechanical surface finishing, the diode laser beam with 15 mm width was applied to the P20 specimens at 1060 °C using a feed rate of 8.8 mms-1in an air and argon ambient. The influence of different LHT atmosphere conditions and specimen initial surface finishing on characteristics such as final roughness, microhardness and microstructure were comprehensively analyzed. The use of a controlled atmosphere during processing showed an increment in depth and hardness values of samples. Through 3D profilometer, it was possible to determine the samples roughness. Results showed that lower average roughness leads to higher hardness values close to the surface, while higher average roughness lead to a deeper heat-treated zone. Macroscopical analysis revealed the depth and width afftected by LHT. The microhardness results showed an increment from 300 HV to around 750 HV on laser heat-treated zone using a controlled environment. Optical microscopy analysed the microstructural changes into martensite between LHT and non LHT zones for all samplespublishe

Characterization of initial stages of diabetic macular edema

This study is aimed at characterizing the type of retinal edema in the initial stages of retinopathy in type 2 diabetes. In this retrospective cross-sectional study, spectral domain optical coherence tomography (OCT) layer by layer analysis of the retina in association with OCT-Leakage, an algorithm to detect sites of low optical reflectivity, were used to examine eyes with minimal, mild, and moderate diabetic retinopathy (DR). A total of 142 eyes from 142 patients (28% women) aged 52–88 years were imaged. Macular edema, either subclinical (SCME) or central-involved macular edema (CIME), was present in 43% of eyes in group 10–20, 41% of eyes in group 35, and 38% of eyes in group 43–47. The inner nuclear layer (INL) was the layer showing higher and most frequent increases in retinal thickness (79%). The edema was predominantly intracellular in group 10–20 (65%) and extracellular in groups 35 (77%) and 43–47 (69%). Eyes from diabetic patients in the initial stages of DR with different Early Treatment Diabetic Retinopathy Study gradings show similar prevalence of SCME and CIME, independent of the severity of the retinopathy. Retinal edema is located mainly in the INL and appears to be mostly extracellular except in the earliest stages of diabetic retinal disease where intracellular edema predominates.info:eu-repo/semantics/publishedVersio

Two-dimensional segmentation of the retinal vascular network from optical coherence tomography

The automatic segmentation of the retinal vascular network from ocular fundus images has been performed by several research groups. Although different approaches have been proposed for traditional imaging modalities, only a few have addressed this problem for optical coherence tomography (OCT). Furthermore, these approaches were focused on the optic nerve head region. Compared to color fundus photography and fluorescein angiography, two-dimensional ocular fundus reference images computed from three-dimensional OCT data present additional problems related to system lateral resolution, image contrast, and noise. Specifically, the combination of system lateral resolution and vessel diameter in the macular region renders the process particularly complex, which might partly explain the focus on the optic disc region. In this report, we describe a set of features computed from standard OCT data of the human macula that are used by a supervised-learning process (support vector machines) to automatically segment the vascular network. For a set of macular OCT scans of healthy subjects and diabetic patients, the proposed method achieves 98% accuracy, 99% specificity, and 83% sensitivity. This method was also tested on OCT data of the optic nerve head region achieving similar results

Progression of Ganglion Cell-Inner Plexiform layer thickness in the initial stages of diabetic retinopathy in type 2 diabetic patients: a 5-year longitudinal study

Diabetic Retinopathy (DR)is a frequent complication of DiabetesMellitus (DM) andthe main cause of vision loss in the working population in western countries. Diabetic Retinopathy has always been considered a microvascular disease, but it has been suggested that neurodegeneration is also associated with this complex pathology[1], although there is evidence indicating that the neurodegenerative process may progress independently[2]. To evaluate this potential association, we have examined the progression of neurodegeneration over a 5-year period of follow-up (considering thinning of ganglion cell + inner plexiform retinal layers (GCL+IPL) in individuals with type 2 diabetes (T2D) and nonproliferative DR) and explored whetheritis associated with microaneurysmturnover (MAT), diseaselevel at baseline and severity progression.info:eu-repo/semantics/publishedVersio

Two-dimensional segmentation of the retinal vascular network from optical coherence tomography

The automatic segmentation of the retinal vascular network from ocular fundus images has been performed by several research groups. Although different approaches have been proposed for traditional imaging modalities, only a few have addressed this problem for optical coherence tomography (OCT). Furthermore, these approaches were focused on the optic nerve head region. Compared to color fundus photography and fluorescein angiography, two-dimensional ocular fundus reference images computed from three-dimensional OCT data present additional problems related to system lateral resolution, image contrast, and noise. Specifically, the combination of system lateral resolution and vessel diameter in the macular region renders the process particularly complex, which might partly explain the focus on the optic disc region. In this report, we describe a set of features computed from standard OCT data of the human macula that are used by a supervised-learning process (support vector machines) to automatically segment the vascular network. For a set of macular OCT scans of healthy subjects and diabetic patients, the proposed method achieves 98% accuracy, 99% specificity, and 83% sensitivity. This method was also tested on OCT data of the optic nerve head region achieving similar results

Characterization of 2-year progression of different phenotypes of nonproliferative diabetic retinopathy

The aim of the study was to characterize the 2-year progression of risk phenotypes of nonproliferative diabetic retinopathy (NPDR) in type 2 diabetes (T2D) phenotype C, or ischemic phenotype, identified by decreased skeletonized retinal vessel density (VD), ≥2 SD over normal values, and phenotype B, or edema phenotype, identified by increased retinal thickness, i.e., subclinical macular edema, and no significant decrease in VD. A prospective longitudinal cohort study (CORDIS, NCT03696810) was conducted with 4 visits (baseline, 6 months, 1 year, and 2 years). Ophthalmological examinations included best-corrected visual acuity, color fundus photography (CFP), and optical coherence tomography (OCT) and OCT angiography. Early Treatment Diabetic Retinopathy Study grading was performed at the baseline and last visits based on 7-field CFP. Results: One hundred and twenty-two eyes from T2D individuals with NPDR fitted in the categories of phenotypes B and C and completed the 2-year follow-up. Sixty-five (53%) of the eyes were classified as phenotype B and 57 (47%) eyes as phenotype C. Neurodegeneration represented by thinning of the ganglion cell layer and inner plexiform layer was present in both phenotypes and showed significant progression over the 2-year period (p < 0.001). In phenotype C, significant progression in the 2-year period was identified in decreased skeletonized VD (p = 0.01), whereas in phenotype B microvascular changes involved preferentially decrease in perfusion density (PD, p = 0.012). Phenotype B with changes in VD and PD (flow) and preferential involvement of the deep capillary plexus (p < 0.001) is associated with development of center-involved macular edema. In the 2-year period of follow-up, both phenotypes B and C showed progression in retinal neurodegeneration, with changes at the microvascular level characterized by decreases in PD in phenotype B and decreases in VD in phenotype C.info:eu-repo/semantics/publishedVersio