Optical coherence tomography

About: Optical coherence tomography is a research topic. Over the lifetime, 19051 publications have been published within this topic receiving 477433 citations. The topic is also known as: optical coherent tomography.

Primary retinal pathology in multiple sclerosis as detected by optical coherence tomography

Abstract: Optical coherence tomography studies in multiple sclerosis have primarily focused on evaluation of the retinal nerve fibre layer. The aetiology of retinal changes in multiple sclerosis is thought to be secondary to optic nerve demyelination. The objective of this study was to use optical coherence tomography to determine if a subset of patients with multiple sclerosis exhibit primary retinal neuronopathy, in the absence of retrograde degeneration of the retinal nerve fibre layer and to ascertain if such patients may have any distinguishing clinical characteristics. We identified 50 patients with multiple sclerosis with predominantly macular thinning (normal retinal nerve fibre-layer thickness with average macular thickness < 5th percentile), a previously undescribed optical coherence tomography defined phenotype in multiple sclerosis, and compared them with 48 patients with multiple sclerosis with normal optical coherence tomography findings, 48 patients with multiple sclerosis with abnormal optical coherence tomography findings (typical for multiple sclerosis) and 86 healthy controls. Utilizing a novel retinal segmentation protocol, we found that those with predominant macular thinning had significant thinning of both the inner and outer nuclear layers, when compared with other patients with multiple sclerosis (P < 0.001 for both), with relative sparing of the ganglion cell layer. Inner and outer nuclear layer thicknesses in patients with non-macular thinning predominant multiple sclerosis were not different from healthy controls. Segmentation analyses thereby demonstrated extensive deeper disruption of retinal architecture in this subtype than may be expected due to retrograde degeneration from either typical clinical or sub-clinical optic neuropathy. Functional corroboration of retinal dysfunction was provided through multi-focal electroretinography in a subset of such patients. These findings support the possibility of primary retinal pathology in a subset of patients with multiple sclerosis. Multiple sclerosis-severity scores were also significantly increased in patients with the macular thinning predominant phenotype, compared with those without this phenotype (n = 96, P=0.006). We have identified a unique subset of patients with multiple sclerosis in whom there appears to be disproportionate thinning of the inner and outer nuclear layers, which may be occurring as a primary process independent of optic nerve pathology. In vivo analyses of retinal layers in multiple sclerosis have not been previously performed, and structural demonstration of pathology in the deeper retinal layers, such as the outer nuclear layer, has not been previously described in multiple sclerosis. Patients with inner and outer nuclear layer pathology have more rapid disability progression and thus retinal neuronal pathology may be a harbinger of a more aggressive form of multiple sclerosis.

Optimal interferometer designs for optical coherence tomography

Abstract: We introduce a family of power-conserving fiber-optic interferometer designs for low-coherence reflectometry that use optical circulators, unbalanced couplers, and (or) balanced heterodyne detection. Simple design equations for optimization of the signal-to-noise ratio of the interferometers are expressed in terms of relevant signal and noise sources and measurable system parameters. We use the equations to evaluate the expected performance of the new configurations compared with that of the standard Michelson interferometer that is commonly used in optical coherence tomography (OCT) systems. The analysis indicates that improved sensitivity is expected for all the new interferometer designs, compared with the sensitivity of the standard OCT interferometer, under high-speed imaging conditions.

Optical coherence tomography: a window into the mechanisms of multiple sclerosis.

Abstract: Multiple sclerosis is characterized by both demyelination and neurodegeneration. The lack of myelin in the retina makes this an ideal structure in which to visualize the latter process. In this Review, Frohman et al. describe the novel use of retinal imaging technology, and in particular optical coherence tomography (OCT), to model the disease process in multiple sclerosis. They suggest that OCT could ultimately be used to identify strategies aimed at neuroprotection in the CNS. The pathophysiology of multiple sclerosis (MS) is characterized by demyelination, which culminates in a reduction in axonal transmission. Axonal and neuronal degeneration seem to be concomitant features of MS and are probably the pathological processes responsible for permanent disability in this disease. The retina is unique within the CNS in that it contains axons and glia but no myelin, and it is, therefore, an ideal structure within which to visualize the processes of neurodegeneration, neuroprotection, and potentially even neurorestoration. In particular, the retina enables us to investigate a specific compartment of the CNS that is targeted by the disease process. Optical coherence tomography (OCT) can provide high-resolution reconstructions of retinal anatomy in a rapid and reproducible fashion and, we believe, is ideal for precisely modeling the disease process in MS. In this Review, we provide a broad overview of the physics of OCT, the unique properties of this method with respect to imaging retinal architecture, and the applications that are being developed for OCT to understand mechanisms of tissue injury within the brain.

Ultrahigh-resolution optical coherence tomography by broadband continuum generation from a photonic crystal fiber

Abstract: We have developed an ultrahigh-resolution optical coherence tomographic system in which broadband continuum generation from a photonic crystal fiber is used to produce high longitudinal resolution. Longitudinal resolution of 1.3-microm has been achieved in a biological tissue by use of continuum light from 800 to 1400 nm. The system employed a dynamic-focusing tracking method to maintain high lateral resolution over a large imaging depth. Subcellular imaging is demonstrated.

Image enhancement in optical coherence tomography using deconvolution

Abstract: The present invention provides an improved optical coherence tomography system and involves estimating the impulse response (which is indicative of the actual reflecting and scattering sites within a tissue sample) from the output interferometric signal of an interferometer according to the following steps: (a) acquiring auto-correlation data from the interferometer system; (b) acquiring cross-correlation data from the interferometer system having the biological tissue sample in the sample arm; and (c) processing the auto-correlation data and the cross correlation data to produce an optical impulse response of the tissue The impulse response may be obtained from the cross-correlation and auto-correlation data by: (d) obtaining an auto-power spectrum from the auto-correlation data by performing a Fourier transform on the auto-correlation data; (e) obtaining a cross-power spectrum from the cross-correlation data by performing a Fourier transform on the cross-correlation data; (f) obtaining a transfer function of the LSI system by taking a ratio of the cross-power spectrum to the auto-power spectrum; and (g) obtaining the optical impulse response of the LSI system by performing an inverse-Fourier transform on the transfer function Preferably, coherent demodulation is used in combination with the above deconvolution technique to resolve closely-spaced reflecting sites in the sample By utilizing both the magnitude and phase data of the demodulated interferometric signals, the OCT system of the present invention is able to distinguish between closely spaced reflecting sites within the sample