1. Articles from Jean Martial Mari

    1-13 of 13
    1. Dynamic Change in Optic Nerve After Intracranial Pressure Reduction in Children

      Dynamic Change in Optic Nerve After Intracranial Pressure Reduction in Children

      Advances in optical coherence tomography (OCT) have enabled researchers to obtain in vivo information regarding the lamina cribrosa (LC) in a noninvasive manner. We used swept-source OCT (SS-OCT) to investigate the dynamic changes in deep anterior optic nerve head (ONH) structures after surgical decompression for increased intracranial pressure (IICP) in pediatric patients.

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    2. Positional and Curvature Difference of Lamina Cribrosa According to the Baseline Intraocular Pressure in Primary Open-Angle Glaucoma: A Swept-Source Optical Coherence Tomography (SS-OCT) Study

      Positional and Curvature Difference of Lamina Cribrosa According to the Baseline Intraocular Pressure in Primary Open-Angle Glaucoma: A Swept-Source Optical Coherence Tomography (SS-OCT) Study

      Purpose To investigate the variation of lamina cribrosa (LC) structure based on the baseline intraocular pressure (IOP) in eyes with primary open-angle glaucoma (POAG) and healthy individuals using swept-source optical coherence tomography. Methods A total of 108 eyes with POAG and 61 healthy eyes were recruited. Based on the baseline IOP, the POAG eyes were divided into higher-baseline IOP (HTG; baseline IOP > 21 mmHg, n = 38 eyes) and lower-baseline IOP (NTG; baseline IOP ≤ 21 mmHg, n = 70 eyes). The anterior laminar insertion depth (ALID), mean LC depth (mLCD), and the LC curvature index (mLCD–ALID) were measured, and compared among ...

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    3. Enhancement of Corneal Visibility in Optical Coherence Tomography Images with Corneal Opacification

      Enhancement of Corneal Visibility in Optical Coherence Tomography Images with Corneal Opacification

      Purpose : To establish and to rank the performance of a corneal adaptive compensation (CAC) algorithm in enhancing corneal images with scars acquired from three commercially available anterior segment optical coherence tomography (ASOCT) devices. Methods : Horizontal B-scans of the cornea were acquired from 10 patients using three ASOCT devices (Spectralis, RTVue, and Cirrus). We compared ASOCT image quality (with and without CAC) by computing the intralayer contrast (a measure of shadow removal), the interlayer contrast (a measure of tissue boundary visibility), and the tissue/background contrast (a measure of overall corneal visibility). All six groups (Spectralis, RTVue, Cirrus, Spectralis+CAC, RTVue ...

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    4. In Vivo 3-Dimensional Strain Mapping of the Optic Nerve Head Following Intraocular Pressure Lowering by Trabeculectomy

      In Vivo 3-Dimensional Strain Mapping of the Optic Nerve Head Following Intraocular Pressure Lowering by Trabeculectomy

      Purpose To map the 3-dimensional (3D) strain of the optic nerve head (ONH) in vivo after intraocular pressure (IOP) lowering by trabeculectomy (TE) and to establish associations between ONH strain and retinal sensitivity. Design Observational case series. Participants Nine patients with primary open-angle glaucoma (POAG) and 3 normal controls. Methods The ONHs of 9 subjects with POAG (pre-TE IOP: 25.3±13.9 mmHg; post-TE IOP: 11.8±8.6 mmHg) were imaged (1 eye per subject) using optical coherence tomography (OCT) (Heidelberg Spectralis, Heidelberg Engineering GmbH, Heidelberg, Germany) before (<21 days) and after (<50 days) TE. The imaging protocol ...

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    5. Enhancement of Corneal Visibility in Optical Coherence Tomography Images Using Corneal Adaptive Compensation

      Enhancement of Corneal Visibility in Optical Coherence Tomography Images Using Corneal Adaptive Compensation

      Purpose: To improve the contrast of optical coherence tomography (OCT) images of the cornea (post processing). Methods: We have recently developed standard compensation (SC) algorithms to remove light attenuation artifacts. A more recent approach, namely adaptive compensation (AC), further limited noise overamplification within deep tissue regions. AC was shown to work efficiently when all A-scan signals were fully attenuated at high depth. But in many imaging applications (e.g., OCT imaging of the cornea), such an assumption is not satisfied, which can result in strong noise overamplification. A corneal adaptive compensation (CAC) algorithm was therefore developed to overcome such limitation ...

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    6. Lamina Cribrosa Visibility using Optical Coherence Tomography: Comparison of Devices and Effects of Image Enhancement Techniques

      Lamina Cribrosa Visibility using Optical Coherence Tomography: Comparison of Devices and Effects of Image Enhancement Techniques

      Purpose: To compare the visibility of the lamina cribrosa (LC) in optic disc images acquired from 60 glaucoma and 60 control subjects using three optical coherence tomography (OCT) devices, with and without enhanced depth imaging (EDI) and adaptive compensation (AC). Methods: A horizontal B-scan was acquired through the centre of the disc using two spectral-domain (Spectralis and Cirrus; with and without EDI) and a swept-source (DRI) OCT. AC was applied post-acquisition to improve image quality. To assess LC visibility, four masked observers graded the 1,200 images in a randomised sequence. The anterior LC was graded from 0 to 4 ...

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    7. A Simplified Method to Measure Choroidal Thickness Using Adaptive Compensation in Enhanced Depth Imaging Optical Coherence Tomography

      A Simplified Method to Measure Choroidal Thickness Using Adaptive Compensation in Enhanced Depth Imaging Optical Coherence Tomography

      Purpose To evaluate a simplified method to measure choroidal thickness (CT) using commercially available enhanced depth imaging (EDI) spectral domain optical coherence tomography (SD-OCT). Methods We measured CT in 31 subjects without ocular diseases using Spectralis EDI SD-OCT. The choroid-scleral interface of the acquired images was first enhanced using a post-processing compensation algorithm. The enhanced images were then analysed using Photoshop. Two graders independently graded the images to assess inter-grader reliability. One grader re-graded the images after 2 weeks to determine intra-grader reliability. Statistical analysis was performed using intra-class correlation coefficient (ICC) and Bland-Altman plot analyses. Results Using adaptive compensation ...

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    8. In vivo optic nerve head biomechanics: performance testing of a three-dimensional tracking algorithm

      In vivo optic nerve head biomechanics: performance testing of a three-dimensional tracking algorithm

      Measurement of optic nerve head (ONH) deformations could be useful in the clinical management of glaucoma. Here, we propose a novel three-dimensional tissue-tracking algorithm designed to be used in vivo . We carry out preliminary verification of the algorithm by testing its accuracy and its robustness. An algorithm based on digital volume correlation was developed to extract ONH tissue displacements from two optical coherence tomography (OCT) volumes of the ONH (undeformed and deformed). The algorithm was tested by applying artificial deformations to a baseline OCT scan while manipulating speckle noise, illumination and contrast enhancement. Tissue deformations determined by our algorithm were ...

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    9. Intracoronary imaging using attenuation-compensated optical coherence tomography allows better visualisation of coronary artery diseases

      Intracoronary imaging using attenuation-compensated optical coherence tomography allows better visualisation of coronary artery diseases

      Purpose To allow an accurate diagnosis of coronary artery diseases by enhancing optical coherence tomography (OCT) images of atheromatous plaques using a novel automated attenuation compensation technique. Background One of the major drawbacks of coronary OCT imaging is the rapid attenuation of the OCT signal, limiting penetration in tissue to only few millimetres. Visualisation of deeper anatomy is however critical for accurate assessment of plaque burden in-vivo. Methods A compensation algorithm, previously developed to correct for light attenuation in soft tissues and to enhance contrast in ophthalmic OCT images, was applied to intracoronary plaque imaging using spectral-domain OCT. Results Application ...

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    10. Enhancement of Lamina Cribrosa Visibility in Optical Coherence Tomography Images using Adaptive Compensation

      Enhancement of Lamina Cribrosa Visibility in Optical Coherence Tomography Images using Adaptive Compensation

      Purpose. To improve the visibility of the lamina cribrosa (LC), including its posterior boundary, in optical coherence tomography (OCT) images of the human optic nerve head (ONH). Methods. An adaptive compensation algorithm was developed to overcome a limitation of our standard compensation algorithm, that is the over-amplification of noise at high depth. Such limitation currently hampers our ability to distinguish the posterior LC boundary. In adaptive compensation, standard compensation operations are performed until an energy threshold is reached, at which stage the compensation process is stopped to limit noise over-amplification in the deeper portion of the OCT image.The performance ...

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    11. Feature Of The Week 9/9/12: Imaging of Coronary Artery Plaques Using Contrast Enhanced Optical Coherence Tomography

      Feature Of The Week 9/9/12: Imaging of Coronary Artery Plaques Using Contrast Enhanced Optical Coherence Tomography

      Optical Coherence Tomography (OCT) has recently emerged as a promising technology for intravascular guidance of interventions. With a resolution on the order of 10 microns, Intravascular OCT surpasses Intravascular Ultrasounds, and allows for precise measurement of cap thickness and identification of lipid rich Thin-Cap Fibroatheroma (TCFA). The diagnostic accuracy and assessment of atherosclerotic plaque morphology with OCT remains however limited by the rapid attenuation of OCT signal in tissue, limiting contrast on deep plaque structure and accurate assessment of plaque burden.A contrast enhancement algorithm, previously developed to compensate for light attenuation in spectral-domain OCT images of the human optic ...

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    12. Imaging of coronary artery plaques using contrast-enhanced optical coherence tomography

      Imaging of coronary artery plaques using contrast-enhanced optical coherence tomography

      Optical coherence tomography (OCT) has recently emerged as a promising technology for intravascular guidance of interventions. With a resolution on the order of 10µm, intravascular OCT surpasses intravascular ultrasounds, and allows for precise measurement of cap thickness and identification of lipid-rich thin-cap fibroatheroma. The diagnostic accuracy and assessment of atherosclerotic plaque

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    13. Shadow removal and contrast enhancement in optical coherence tomography images of the human optic nerve head

      Shadow removal and contrast enhancement in optical coherence tomography images of the human optic nerve head

      Purpose.To improve the quality of optical coherence tomography (OCT) images of the optic nerve head (ONH). Methods.Two algorithms were developed, one to compensate for light attenuation and the other to enhance contrast in OCT images. The former was borrowed from developments in ultrasound imaging and proven suitable with either time- or spectral-domain OCT. The latter was based on direct application of pixel intensity exponentiation. The performances of these two algorithms were tested using spectral-domain OCT images of 4 adult ONHs. Results.Application of the compensation algorithm significantly reduced the intra-layer contrast (from 0.74 ± 0.16 to 0 ...

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    1-13 of 13
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  2. Topics in the News

    1. (12 articles) Michaël J. A. Girard
    2. (11 articles) National University of Singapore
    3. (6 articles) Singapore Eye Research Institute
    4. (5 articles) Imperial College London
    5. (5 articles) University College London
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    Shadow removal and contrast enhancement in optical coherence tomography images of the human optic nerve head Imaging of coronary artery plaques using contrast-enhanced optical coherence tomography Feature Of The Week 9/9/12: Imaging of Coronary Artery Plaques Using Contrast Enhanced Optical Coherence Tomography Enhancement of Lamina Cribrosa Visibility in Optical Coherence Tomography Images using Adaptive Compensation Intracoronary imaging using attenuation-compensated optical coherence tomography allows better visualisation of coronary artery diseases In vivo optic nerve head biomechanics: performance testing of a three-dimensional tracking algorithm A Simplified Method to Measure Choroidal Thickness Using Adaptive Compensation in Enhanced Depth Imaging Optical Coherence Tomography Lamina Cribrosa Visibility using Optical Coherence Tomography: Comparison of Devices and Effects of Image Enhancement Techniques Enhancement of Corneal Visibility in Optical Coherence Tomography Images Using Corneal Adaptive Compensation In Vivo 3-Dimensional Strain Mapping of the Optic Nerve Head Following Intraocular Pressure Lowering by Trabeculectomy Perimeter Medical Imaging Closes Oversubscribed $C4.4M Financing Time-domain optical coherence tomography system based on moving-optical-wedge interferometer