1,955,137 research outputs found
Master slave en-face OCT/SLO
Full text linkMaster Slave optical coherence tomography (MS-OCT) is an OCT method that does not require resampling of data and can be used to deliver en-face images from several depths simultaneously. As the MS-OCT method requires important computational resources, the number of multiple depth en-face images that can be produced in real-time is limited. Here, we demonstrate progress in taking advantage of the parallel processing feature of the MS-OCT technology. Harnessing the capabilities of graphics processing units (GPU)s, information from 384 depth positions is acquired in one raster with real time display of up to 40 en-face OCT images. These exhibit comparable resolution and sensitivity to the images produced using the conventional Fourier domain based method. The GPU facilitates versatile real time selection of parameters, such as the depth positions of the 40 images out of the set of 384 depth locations, as well as their axial resolution. In each updated displayed frame, in parallel with the 40 en-face OCT images, a scanning laser ophthalmoscopy (SLO) lookalike image is presented together with two B-scan OCT images oriented along rectangular directions. The thickness of the SLO lookalike image is dynamically determined by the choice of number of en-face OCT images displayed in the frame and the choice of differential axial distance between them
A comparison of bone-patellar tendon-bone and bone-hamstring tendon-bone autografts for anterior cruciate ligament reconstruction
No full textOptimization of dental OCT imaging
No full textDental caries is the most common chronic disease in the world. An early diagnosis is required in order to initiate prompt treatment strategies. Radiographic imaging (X-Ray) is the most common detection method, but uses ionization radiation and isn’t ideally used during pregnancy or in early childhood development. Optical coherence tomography (OCT) imaging uses no ionising radiation and may be used in place of X-rays in some clinical settings. We present development of a Convolutional Neural Network (CNN) for quantification of caries lesions in human dental tissues imaged by OCT. Using high definition high contrast time delay integration x-ray microtomography (XMT) as a gold standard for mineralization measurements, we are training the CNNs to apply weightings derived from XMT to OCT data. We show results using Local Laplacian, Wiener, BM3D denoising and sharpening, to clean low SNR OCT data followed by automatic identification of normal structure and pathology
Implementation of polarization sensitive OCT
Full text linkopenwe will cover the basic physical mechanisms used by OCT technologies to produce signals from which we can recover the information required to produce an image. we will then show How we implemented a polarization sensitive OCT covering the set up and discussing the implementations of the functionalities required to correctly filter and elaborate the signal in order to produce B-scanswe will cover the basic physical mechanisms used by OCT technologies to produce signals from which we can recover the information required to produce an image. we will then show How we implemented a polarization sensitive OCT covering the set up and discussing the implementations of the functionalities required to correctly filter and elaborate the signal in order to produce B-scan
Passive OCT probe head for 3D duct inspection
Full text linkA passive, endoscopic optical coherence tomography (OCT) probe has been demonstrated, incorporating an imaging fibre bundle and 45° conical mirror, and with no electromechanical components at the probe tip. Circular scanning, of the beam projected onto the proximal face of the imaging bundle, produces a corresponding circular scan at the distal end of the bundle. The beam is turned through 90° by the conical mirror and converted into a radially-scanned sample beam, permitting circumferential OCT scanning in quasi-cylindrical ducts. OCT images, displayed as polar plots and as 3D reconstructions, are presented, showing the internal profile of a metallic test sample containing a 660µm step in the internal wall. Results have been acquired using two methods: one that makes use of multiple beam-circle diameters, and a mechanical 'pull-back' technique. The effects of the convex surface of the conical mirror on spatial resolution are discussed, with suggested working distances given for different application regimes
Coherent fibre bundles in full-field swept-source OCT
Full text linkEndoscopic OCT probes deliver light to the measurement region via a single
optical fibre mounted in a probe head. The output beam is focused onto the
sample, providing a single point measurement. The beam is translated, using
mechanical scanning at the probe tip, to address a line or area of sampling
points and produce an image. We are investigating a swept-source OCT system
incorporating coherent fibre bundles, to allow many measurement points to be
addressed, within an area of the sample, without the need for mechanical motion
within the endoscope probe. Scanning components are still present at the input
of our system, but are no longer required within the flexible ndoscope section.
This allows a small-diameter, electrically passive probe to be engineered using
off-the-shelf scanning components. A common-path probe design is proposed, in
which the bundle is external to the OCT interferometer. This eliminates contrast
variations caused by non-controllable differences in the state of polarisation
between fibres. Imaging bundle fibres are typically few-moded, which can lead to
ghost features and reduced SNR in OCT images, but the common-path configuration
also removes cross-mode interference problems, and reduces dispersion artefacts.
OCT images of a microscope cover-slip and a sample of spring onion, acquired
using the swept-source, bundle-based OCT system are presented. Features peculiar
to the inclusion of the fibre bundle are discussed, and directions for future
development of the system are outlined
Swept-source OCT with coherent imaging fibre bundles
Full text linkOCT probes for endoscopy typically use a single optical fibre to deliver light
to the measurement region. 2D imaging is achieved using mechanical scanning
components at the probe tip. We are investigating an OCT system in which fibre
imaging bundles replace the single probe fibre, allowing many thousand
measurement points to be addressed without any mechanical scanning at the probe
tip, over a region measuring a few millimetres in each dimension. This allows a
small-diameter, electrically passive probe to be engineered using offthe- shelf
scanning optics. Images from a single-fibre, conventionally- scanned probe and
from a bundle-based probe are presented, using swept-source processing centred
at 1330 nm
OCT-A 3D Vessel Segmentation .mp4
No full textThis video presents several qualitative results of 3D OCT-A vessel segmentation. We obtain those results using a network trained on 2D maximum intensity projections of OCT-A, which we use to segment every axial slice of the 3D volume, without any training on 3D data. The per-slice segmentations are then aggregated to form the final 3D segmentations. We also note that while our 2D network was trained on geometrically flattened and projected OCT-A, the 3D segmentations shown in the video are obtained using the same network applied on slices of the raw 3D OCT-A scan that contains significantly less vessels per slice
Optical coherence tomography (OCT) in multiple system atrophy: a comparative study towards Parkinson's disease and multiple sclerosis
Full text linkopenPresupposti: la diagnosi delle α-sinucleinopatie, malattie neurodegenerative come l’atrofia multisistemica (MSA) e la malattia di Parkinson (PD), è prettamente clinica; date le frequenti sovrapposizioni tra gli aspetti clinici, la diagnosi differenziale può essere gravata da errori. Emerge quindi la necessità di trovare nuovi e precisi markers di malattia che possano coadiuvare nella diagnosi.
Inoltre, recenti studi hanno constatato che la neuroinfiammazione potrebbe avere un ruolo importante nella patogenesi della MSA, fatto che permette di accomunarla alla sclerosi multipla (SM), di cui da tempo è nota la patogenesi infiammatoria.
Scopo dello studio: definire il possibile ruolo della tomografia a coerenza ottica (OCT) nella MSA, identificandone i parametri che possano fungere da biomarkers ai fini della diagnosi e nel follow-up. Valutare le possibili correlazioni tra i parametri OCT e dati clinici e di imaging disponibili nei pazienti MSA. Comparare i dati OCT dei pazienti MSA con quelli raccolti in pazienti PD e SM.
Materiali e metodi: soggetti con MSA, PD, SM e controlli sani (HC) sono stati sottoposti a scansioni OCT peripapillari e maculari. I pazienti MSA e PD sono stati valutati clinicamente tramite la scala COMPASS31 per i sintomi disautonomici e tramite le scale UMSARS e MDS-UPDRS, rispettivamente, per stimare il grado di severità della malattia. Il gruppo MSA è stato inoltre valutato
tramite esami di imaging.
Risultati: analizzando le scansioni OCT di 9 soggetti con diagnosi di MSA, 10 di PD, 9 di SM e 10 controlli (HC), il volume totale dello strato plessiforme esterno (OPL) della retina è risultato significativamente maggiore nei PD rispetto a MSA, HC e SM, e nel gruppo SM rispetto a MSA; lo spessore dell’inner ring (IR) dell’OPL è significativamente ridotto nella MSA rispetto a PD e SM, e lo spessore dell’outer ring (OR) è significativamente maggiore nei PD rispetto a MSA e HC. La MSA presenta quindi indici OPL ridotti rispetto a PD. Lo spessore dell’IR mostra una lieve correlazione lineare con la durata di malattia nella MSA. Non sono state trovate analogie significative in OCT tra MSA e PD, né tra MSA e SM.Il numero degli spots iperreflettenti retinici (HRF), segno di attivazione microgliale locale, è risultato significativamente maggiore in tutti i gruppi patologici rispetto ai controlli sani.
Conclusioni: gli indici dello strato OPL variano significativamente tra MSA, PD, SM e controlli sani. Lo studio pone le basi per l’uso della OCT nella valutazione delle patologie neurodegenerative, che è auspicabile venga indagato ulteriormente in futuro
OCT-defined microcalcification.
No full textAn OCT-defined microcalcification with a calcium arc<22.5° is marked with a white arrow. Scale bar in the right lower corner.</p
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