Emerging Star in Ophthalmic Imaging Technologies – OCT Angiography

2016 ◽  
Vol 10 (01) ◽  
pp. 27
Author(s):  
Lukas Reznicek ◽  
Keyword(s):  
Imaging Techniques ◽  
Three Dimensional ◽  
Oct Angiography ◽  
Non Invasive ◽  
Narrow Angle ◽  
Lack Of Information ◽  
Ophthalmic Imaging ◽  
High Resolution Images ◽  
Angle Of View ◽  
Areas Of Interest

Optical Coherence Tomography (OCT) angiography has recently been introduced as a novel non-invasive OCT based technique providing three-dimensional high resolution images of vascular and microvascular ocular structures without the need to use intravenous dyes. A relatively narrow angle of view and a lack of information along the timeline are outweighed by the huge advantages of non-invasiveness and three-dimensional information of the depicted areas of interest, as this technique emerges and becomes the new star among ophthalmic imaging techniques.

scholarly journals Deep vascular imaging in the eye with flow-enhanced ultrasound

2021 ◽  
Author(s):  
Christian Damsgaard ◽  
Henrik Lauridsen
Keyword(s):  
Imaging Techniques ◽  
Three Dimensional ◽  
The Body ◽  
High Frequency Ultrasound ◽  
Spatiotemporal Resolution ◽  
Ultrasound Technique ◽  
Non Invasive ◽  
Nucleated Red Blood Cells ◽  
Invasive Method ◽  
Flow Enhancement

The eye's retina is one of the most energy-demanding tissues in the body and thus requires high rates of oxygen delivery from a rich blood supply. The capillary lamina of the choroid lines the outer surface of the retina and is the dominating source of oxygen in most vertebrates, but this vascular bed is challenging to image with traditional optical techniques due to its position behind the highly light-absorbing retina. Here we describe a high-frequency ultrasound technique with flow-enhancement to image deep vascular beds (0.5 - 3 cm) of the eye with a high spatiotemporal resolution. This non-invasive method works well in species with nucleated red blood cells (non-mammalian and fetal animal models), and it generates non-invasive three-dimensional angiographies without the use of contrast agents that is independent of blood flow angles and with a higher sensitivity than Doppler based ultrasound imaging techniques.

Quantifying the Spatial Variation of Lower-Limb Soft Tissue Artefact During Functional Activity Using MR Imaging and X-Ray Fluoroscopy

2009 ◽  
Author(s):  
Massoud Akbarshahi ◽  
Justin W. Fernandez ◽  
Anthony Schache ◽  
Richard Baker ◽  
Scott Banks ◽  
...  
Keyword(s):  
Soft Tissue ◽  
Lower Limb ◽  
Imaging Techniques ◽  
Three Dimensional ◽  
X Ray ◽  
Non Invasive ◽  
3D Motion Analysis ◽  
X Ray Imaging ◽  
Tissue Interface ◽  
Soft Tissue Artifact

Non-rigid movement of the soft tissue interface between skin-mounted markers and the underlying bones, also known as soft tissue artifact (STA), poses a major limitation to the non-invasive estimation of joint kinematics using three-dimensional (3D) motion analysis systems. Thorough knowledge of the nature of this non-rigid behavior is essential for development of compensation algorithms to enhance the accuracy of these systems. The studies in the literature aimed at quantifying STA have implemented invasive measurement methods such as bone pins [1] and external fixator devices [2], or have used subjects with pathological conditions [3]. In the present study, we integrated Magnetic Resonance (MR) and X-ray imaging techniques to evaluate the non-rigid behavior of the lower-limb soft tissue of healthy adults for a number of different functional tasks.

scholarly journals Review of OCT Angiography Findings in Diabetic Retinopathy: Insights and Perspectives

2021 ◽  
Vol 1 (3) ◽  
pp. 286-305
Author(s):  
John Moir ◽  
Saira Khanna ◽  
Dimitra Skondra
Keyword(s):  
Diabetic Retinopathy ◽  
Optical Coherence Tomography Angiography ◽  
Imaging Modality ◽  
Imaging Techniques ◽  
Three Dimensional ◽  
Foveal Avascular Zone ◽  
Analysis Techniques ◽  
Non Invasive ◽  
Retinal Microvasculature ◽  
Avascular Zone

Diabetes mellitus (DM), a disorder rapidly growing in prevalence, is linked to the retinal microvasculature complication diabetic retinopathy (DR). As one of the leading global causes of vision impairment and loss, imaging techniques to detect and monitor DR must continue to improve in order to address this growing burden. Optical coherence tomography angiography (OCTA) is a nascent imaging modality that generates three-dimensional visualizations of the retinal and choroidal microvasculature. Compared to fluorescein angiography, the gold-standard imaging modality for retinal vessels, OCTA offers the advantages of being non-invasive, quick, and able to resolve the multiple plexuses within the retina. Quantitative OCTA studies have explored parameters such as vessel density (VD), foveal avascular zone (FAZ), acircularity index, vessel tortuosity (VT), and fractal dimension (FD) amongst DR patients. This review synthesizes the main trends emerging from quantitative OCTA-based studies of DR and interrogates them within the context of DR pathophysiology. We offer a glimpse into how analysis techniques have shifted in the years since OCTA came into existence, while speculating on its future role in clinical practice.

scholarly journals Anatomy of Mitral Valve Complex as Revealed by Non-Invasive Imaging: Pathological, Surgical and Interventional Implications

2020 ◽  
Vol 7 (4) ◽  
pp. 49
Author(s):  
Laura Anna Leo ◽  
Vera Lucia Paiocchi ◽  
Susanne Anna Schlossbauer ◽  
Elisa Gherbesi ◽  
Francesco F. Faletra
Keyword(s):  
Mitral Valve ◽  
Heart Surgery ◽  
Wide Spectrum ◽  
Imaging Techniques ◽  
Open Heart Surgery ◽  
Three Dimensional ◽  
Correct Interpretation ◽  
Anatomical Features ◽  
Non Invasive ◽  
Direct Inspection

Knowledge of mitral valve (MV) anatomy has been accrued from anatomic specimens derived by cadavers, or from direct inspection during open heart surgery. However, today two-dimensional and three-dimensional transthoracic (2D/3D TTE) and transesophageal echocardiography (2D/3D TEE), computed tomography (CT) and cardiac magnetic resonance (CMR) provide images of the beating heart of unprecedented quality in both two and three-dimensional format. Indeed, over the last few years these non-invasive imaging techniques have been used for describing dynamic cardiac anatomy. Differently from the “dead” anatomy of anatomic specimens and the “static” anatomy observed during surgery, they have the unique ability of showing “dynamic” images from beating hearts. The “dynamic” anatomy gives us a better awareness, as any single anatomic arrangement corresponds perfectly to a specific function. Understanding normal anatomical aspects of MV apparatus is of a paramount importance for a correct interpretation of the wide spectrum of patho-morphological MV diseases. This review illustrates the anatomy of MV as revealed by non-invasive imaging describing physiological, pathological, surgical and interventional implications related to specific anatomical features of the MV complex.

Broad application of non-invasive imaging techniques to echinoids and other echinoderm taxa*

Zoosymposia ◽  
2012 ◽  
Vol 7 (1) ◽  
pp. 53-70 ◽  
Author(s):  
ALEXANDER ZIEGLER
Keyword(s):  
Sea Urchin ◽  
Large Scale ◽  
Sea Urchins ◽  
Imaging Techniques ◽  
Three Dimensional ◽  
Image Data ◽  
Micro Computed Tomography ◽  
Non Invasive ◽  
Mri Scans ◽  
Three Dimensional Models

Tomographic imaging techniques such as micro-computed tomography (μCT) and magnetic resonance imaging (MRI) permit the gathering of digital anatomical data from whole animal specimens non-invasively. The resulting datasets can be used for direct observation of the two-dimensional tomographic image data as well as for manual and semi-automated three-dimensional modelling. Freshly fixed specimens as well as preserved museum material can be successfully ana­lyzed using this approach, giving the zoomorphologist a powerful tool for large-scale comparative studies. In order to demonstrate the principle suitability of non-invasive imaging in echinoderm research, μCT scans of 199 and MRI scans of 92 sea urchin (Echinodermata: Echinoidea) species were acquired, resulting in a total of 203 analyzed echinoid species. The taxa selected represent 50 of the currently recognized 60 extant sea urchin families. The present article lists all spe­cies that have been analyzed so far and provides information about the scanning parameters employed for each dataset. Furthermore, the workflow established to generate three-dimensional models of sea urchins is outlined. Using a number of examples from μCT as well as MRI scans performed on echinoids, the potential of the systematic approach described here is highlighted. Finally, the suitability of non-invasive imaging techniques for the study of other echinoderm taxa is assessed based on multimodal datasets of representative species.

X-ray microtomography

1988 ◽  
Vol 46 ◽  
pp. 998-999
Author(s):  
H.W. Deckman ◽  
B.F. Flannery ◽  
J.H. Dunsmuir ◽  
K.D' Amico
Keyword(s):  
Computed Tomography ◽  
Internal Structure ◽  
Imaging Technique ◽  
Three Dimensional ◽  
Tissue Structure ◽  
Individual Element ◽  
X Ray ◽  
Non Invasive ◽  
Panoramic Imaging ◽  
Three Dimensional Images

We have developed a new X-ray microscope which produces complete three dimensional images of samples. The microscope operates by performing X-ray tomography with unprecedented resolution. Tomography is a non-invasive imaging technique that creates maps of the internal structure of samples from measurement of the attenuation of penetrating radiation. As conventionally practiced in medical Computed Tomography (CT), radiologists produce maps of bone and tissue structure in several planar sections that reveal features with 1mm resolution and 1% contrast. Microtomography extends the capability of CT in several ways. First, the resolution which approaches one micron, is one thousand times higher than that of the medical CT. Second, our approach acquires and analyses the data in a panoramic imaging format that directly produces three-dimensional maps in a series of contiguous stacked planes. Typical maps available today consist of three hundred planar sections each containing 512x512 pixels. Finally, and perhaps of most import scientifically, microtomography using a synchrotron X-ray source, allows us to generate maps of individual element.

Mitochondrial Reconstructions Based on Serial Thick Sections and HVEM

1975 ◽  
Vol 33 ◽  
pp. 286-287
Author(s):  
Jerome J. Paulin
Keyword(s):  
Imaging Techniques ◽  
Three Dimensional ◽  
Posterior Pole ◽  
Dimensional Structure ◽  
Stereo Imaging ◽  
Thin Sections ◽  
Anatomical Features ◽  
The Past ◽  
Cellular Components ◽  
Mitochondrial Reticulum

Within the past decade it has become apparent that HVEM offers the biologist a means to explore the three-dimensional structure of cells and/or organelles. Stereo-imaging of thick sections (e.g. 0.25-10 μm) not only reveals anatomical features of cellular components, but also reduces errors of interpretation associated with overlap of structures seen in thick sections. Concomitant with stereo-imaging techniques conventional serial Sectioning methods developed with thin sections have been adopted to serial thick sections (≥ 0.25 μm). Three-dimensional reconstructions of the chondriome of several species of trypanosomatid flagellates have been made from tracings of mitochondrial profiles on cellulose acetate sheets. The sheets are flooded with acetone, gluing them together, and the model sawed from the composite and redrawn.The extensive mitochondrial reticulum can be seen in consecutive thick sections of (0.25 μm thick) Crithidia fasciculata (Figs. 1-2). Profiles of the mitochondrion are distinguishable from the anterior apex of the cell (small arrow, Fig. 1) to the posterior pole (small arrow, Fig. 2).

Electron crystallographic determination of the 3-D structure of staurolite at atomic resolution

1991 ◽  
Vol 49 ◽  
pp. 540-541
Author(s):  
Kenneth H. Downing ◽  
Hu Meisheng ◽  
Hans-Rudolf Went ◽  
Michael A. O'Keefe
Keyword(s):  
High Resolution ◽  
Three Dimensional ◽  
High Resolution Electron Microscopy ◽  
Atomic Resolution ◽  
Dimensional Structure ◽  
Structure Information ◽  
Resolution Electron ◽  
Scattering Effects ◽  
High Resolution Images ◽  
Effects Of Radiation

With current advances in electron microscope design, high resolution electron microscopy has become routine, and point resolutions of better than 2Å have been obtained in images of many inorganic crystals. Although this resolution is sufficient to resolve interatomic spacings, interpretation generally requires comparison of experimental images with calculations. Since the images are two-dimensional representations of projections of the full three-dimensional structure, information is invariably lost in the overlapping images of atoms at various heights. The technique of electron crystallography, in which information from several views of a crystal is combined, has been developed to obtain three-dimensional information on proteins. The resolution in images of proteins is severely limited by effects of radiation damage. In principle, atomic-resolution, 3D reconstructions should be obtainable from specimens that are resistant to damage. The most serious problem would appear to be in obtaining high-resolution images from areas that are thin enough that dynamical scattering effects can be ignored.

Conformational Transitions in Escherichia coli Ribosomal RNAs as Visualized by Dedicated STEM

1988 ◽  
Vol 46 ◽  
pp. 176-177
Author(s):  
J.S. Wall ◽  
V. Maridiyan ◽  
S. Tumminia ◽  
J. Hairifeld ◽  
M. Boublik
Keyword(s):  
Ionic Strength ◽  
Three Dimensional ◽  
Conformational Transitions ◽  
Dark Field ◽  
Dimensional Structure ◽  
Ribosomal Rnas ◽  
Field Mode ◽  
Freeze Dried ◽  
High Resolution Images ◽  
Low Ionic Strength

The high contrast in the dark-field mode of dedicated STEM, specimen deposition by the wet film technique and low radiation dose (1 e/Å2) at -160°C make it possible to obtain high resolution images of unstained freeze-dried macromolecules with minimal structural distortion. Since the image intensity is directly related to the local projected mass of the specimen it became feasible to determine the molecular mass and mass distribution within individual macromolecules and from these data to calculate the linear density (M/L) and the radii of gyration.2 This parameter (RQ), reflecting the three-dimensional structure of the macromolecular particles in solution, has been applied to monitor the conformational transitions in E. coli 16S and 23S ribosomal RNAs in solutions of various ionic strength.In spite of the differences in mass (550 kD and 1050 kD, respectively), both 16S and 23S RNA appear equally sensitive to changes in buffer conditions. In deionized water or conditions of extremely low ionic strength both appear as filamentous structures (Fig. la and 2a, respectively) possessing a major backbone with protruding branches which are more frequent and more complex in 23S RNA (Fig. 2a).

Recent applications of TEM to the study of interfaces

1990 ◽  
Vol 48 (4) ◽  
pp. 308-309
Author(s):  
C. Barry Carter
Keyword(s):  
High Resolution ◽  
Sample Preparation ◽  
Grain Boundaries ◽  
Diffuse Scattering ◽  
Imaging Techniques ◽  
Amorphous Material ◽  
Contrast Imaging ◽  
Current State ◽  
Actual Nature ◽  
High Resolution Images

This paper will review the current state of understanding of interface structure and highlight some of the future needs and problems which must be overcome. The study of this subject can be separated into three different topics: 1) the fundamental electron microscopy aspects, 2) material-specific features of the study and 3) the characteristics of the particular interfaces. The two topics which are relevant to most studies are the choice of imaging techniques and sample preparation. The techniques used to study interfaces in the TEM include high-resolution imaging, conventional diffraction-contrast imaging, and phase-contrast imaging (Fresnel fringe images, diffuse scattering). The material studied affects not only the characteristics of the interfaces (through changes in bonding, etc.) but also the method used for sample preparation which may in turn have a significant affect on the resulting image. Finally, the actual nature and geometry of the interface must be considered. For example, it has become increasingly clear that the plane of the interface is particularly important whenever at least one of the adjoining grains is crystalline.A particularly productive approach to the study of interfaces is to combine different imaging techniques as illustrated in the study of grain boundaries in alumina. In this case, the conventional imaging approach showed that most grain boundaries in ion-thinned samples are grooved at the grain boundary although the extent of this grooving clearly depends on the crystallography of the surface. The use of diffuse scattering (from amorphous regions) gives invaluable information here since it can be used to confirm directly that surface grooving does occur and that the grooves can fill with amorphous material during sample preparation (see Fig. 1). Extensive use of image simulation has shown that, although information concerning the interface can be obtained from Fresnel-fringe images, the introduction of artifacts through sample preparation cannot be lightly ignored. The Fresnel-fringe simulation has been carried out using a commercial multislice program (TEMPAS) which was intended for simulation of high-resolution images.

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