Resolution Spectral Domain Optical Coherence Tomography Research Articles

Shear flow-induced optical inhomogeneity of blood assessed in vivo and in vitro by spectral domain optical coherence tomography in the 1.3 μm wavelength range

The optical inhomogeneity of flowing blood, which appears as a waisted double fan-shaped intensity pattern inside vessels in cross-sectional optical coherence tomography (OCT) images, was investigated for the first time. High resolution spectral domain OCT in the 1.3 μm wavelength region is used to assess this inhomogeneous intravascular backscattering of light in an in vivo mouse model and flow phantom measurements. Based on a predicted alignment of the red blood cells toward laminar shear flow, an angular modulation of the corresponding backscattering cross-section inside the vessels is assumed. In combination with the signal attenuation in depth by absorption and scattering, a simple model of the intravascular intensity modulation is derived. The suitability of the model is successfully demonstrated in the in vivo experiments and confirmed by the in vitro measurements. The observed effect appears in flowing blood only and shows a strong dependency on the shear rate. In conclusion, the shear-induced red blood cell alignment in conjunction with the vessel geometry is responsible for the observed intensity distribution. This inherent effect of blood imaging has to be considered in attenuation measurements performed with OCT. Furthermore, the analysis of the intravascular intensity pattern might be useful to evaluate flow characteristics.

Heterogeneous Pattern of Retinal Nerve Fiber Layer in Multiple Sclerosis. High Resolution Optical Coherence Tomography: Potential and Limitations

BackgroundRecently the reduction of the retinal nerve fibre layer (RNFL) was suggested to be associated with diffuse axonal damage in the whole CNS of multiple sclerosis (MS) patients. However, several points are still under discussion. (1) Is high resolution optical coherence tomography (OCT) required to detect the partly very subtle RNFL changes seen in MS patients? (2) Can a reduction of RNFL be detected in all MS patients, even in early disease courses and in all MS subtypes? (3) Does an optic neuritis (ON) or focal lesions along the visual pathways, which are both very common in MS, limit the predication of diffuse axonal degeneration in the whole CNS? The purpose of our study was to determine the baseline characteristics of clinical definite relapsing-remitting (RRMS) and secondary progressive (SPMS) MS patients with high resolution OCT technique.MethodologyForty-two RRMS and 17 SPMS patients with and without history of uni- or bilateral ON, and 59 age- and sex-matched healthy controls were analysed prospectively with the high resolution spectral-domain OCT device (SD-OCT) using the Spectralis 3.5mm circle scan protocol with locked reference images and eye tracking mode. Furthermore we performed tests for visual and contrast acuity and sensitivity (ETDRS, Sloan and Pelli-Robson-charts), for color vision (Lanthony D-15), the Humphrey visual field and visual evoked potential testing (VEP).Principal FindingsAll 4 groups (RRMS and SPMS with or without ON) showed significantly reduced RNFL globally, or at least in one of the peripapillary sectors compared to age-/sex-matched healthy controls. In patients with previous ON additional RNFL reduction was found. However, in many RRMS patients the RNFL was found within normal range. We found no correlation between RNFL reduction and disease duration (range 9–540 months).ConclusionsRNFL baseline characteristics of RRMS and SPMS are heterogeneous (range from normal to markedly reduced levels).

Retinal Structure of Birds of Prey Revealed by Ultra-High Resolution Spectral-Domain Optical Coherence Tomography

To reveal three-dimensional (3-D) information about the retinal structures of birds of prey in vivo. An ultra-high resolution spectral-domain optical coherence tomography (SD-OCT) system was built for in vivo imaging of retinas of birds of prey. The calibrated imaging depth and axial resolution of the system were 3.1 mm and 2.8 μm (in tissue), respectively. 3-D segmentation was performed for calculation of the retinal nerve fiber layer (RNFL) map. High-resolution OCT images were obtained of the retinas of four species of birds of prey: two diurnal hawks (Buteo platypterus and Buteo brachyurus) and two nocturnal owls (Bubo virginianus and Strix varia). These images showed the detailed retinal anatomy, including the retinal layers and the structure of the deep and shallow foveae. The calculated thickness map showed the RNFL distribution. Traumatic injury to one bird's retina was also successfully imaged. Ultra-high resolution SD-OCT provides unprecedented high-quality 2-D and 3-D in vivo visualization of the retinal structures of birds of prey. SD-OCT is a powerful imaging tool for vision research in birds of prey.

Diagnostic and predictive methods for a Niemann‐Pick disease type B patient with ocular involvement

Fundus examination of a 37-year-old man with NiemannPick disease (NPD) type B revealed a central macular halo in both eyes (Fig. 1). Spectral domain optical coherence tomography (SD-OCT) revealed a focal thickening with high reflectivity in the ganglion cell layer of the foveal area except foveola (Fig. 1). Multifocal electroretinography (mfERG) showed decreased central peak amplitude in both eyes (Fig. 2). The ganglion cells of the retina form a single cell layer, except in the macula, where they are present in multiple layers, and in the foveola, where they are absent. If significant lipid accumulation occurs in the ganglion cells, a white ring of lipid-laden neurons encircling the red, ganglion cell-free fovea can be observed, hence this characteristic finding is termed “macular halo” or “cherry red macula” (McGovern et al. 2004; Sperl et al. 1994). These studies have relied entirely on the fundus examination. Histopathologic and microscopic studies have shown that deposits accumulate in the ganglion cell layer (Libert et al. 1975). We can confirm that lipid deposition occurs selectively in this layer using the high resolution SD-OCT, which may also enable optical biopsy. Although patients with macular halo usually have little or no visual impairment and our patient had normal visual acuity OS, mfERG revealed depressed, prolonged latency in the first concentric ring. In summary, SD-OCT and mfERG may be very useful methods for determining the extent and depth of lipid deposition and predictive functional evaluation in NiemannPick disease patients with ocular involvement.

Spectral domain optical coherence tomography in a murine retinal detachment model

Spectral domain optical coherence tomography (SD-OCT) was used to image retinal detachments in vivo, in a murine model of retinal detachment (RD). Subretinal injections of hyaluronic acid (Healon) were delivered to the right eye of seventeen 10–20 week-old C57Bl6 mice. Evaluation of the fundus with an operating microscope and fundus photography were performed. In vivo, non-contact, ultra high resolution SD-OCT imaging was performed on day 0, day 1–2, day 5–6 and day 15–16. The retinal morphology at the edge and in the area of maximal RD was evaluated. Eyes were enucleated for histologic analysis. The retinal detachment was confirmed by microscopy in all mice. The extent of the retinal detachment was evaluated by measuring the height of the retinal detachment. The retinal layers, including the photoreceptor layer, were evaluated. Retinal layers appeared indistinct soon after RD (day 1, 5), particularly over areas of maximal detachment. By day 5 and 15 the external limiting membrane was no longer visible and there was increased reflectivity of the photoreceptor layer and undulation of the outer retina in areas of RD on both SD-OCT and histology. The thickness of the outer nuclear layer and photoreceptor outer segments decreased on day 5 and 15. SD-OCT is a promising technology to follow retinal detachment and outer retinal abnormalities in a murine model.

Retinal tumor imaging and volume quantification in mouse model using spectral-domain optical coherence tomography

We have successfully imaged the retinal tumor in a mouse model using an ultra-high resolution spectral-domain optical coherence tomography (SD-OCT) designed for small animal retinal imaging. For segmentation of the tumor boundaries and calculation of the tumor volume, we developed a novel segmentation algorithm. The algorithm is based on parametric deformable models (active contours) and is driven by machine learning-based region classification, namely a Conditional Random Field. With this algorithm we are able to obtain the tumor boundaries automatically, while the user can specify additional constraints (points on the boundary) to correct the segmentation result, if needed. The system and algorithm were successfully applied to studies on retinal tumor progression and monitoring treatment effects quantitatively in a mouse model of retinoblastoma.

QUANTITATIVE EVALUATION OF RETINAL TUMOR VOLUME IN MOUSE MODEL OF RETINOBLASTOMA BY USING ULTRA HIGH-RESOLUTION OPTICAL COHERENCE TOMOGRAPHY

An ultra high resolution spectral-domain optical coherence tomography (SD-OCT) together with an advanced animal restraint and positioning system was built for noninvasive non-contact in vivo three-dimensional imaging of rodent models of ocular diseases. The animal positioning system allowed the operator to rapidly locate and switch the areas of interest on the retina. This function together with the capability of precise spatial registration provided by the generated OCT fundus image allows the system to locate and compare the same lesion (retinal tumor in the current study) at different time point throughout the entire course of the disease progression. An algorithm for fully automatic segmentation of the tumor boundaries and calculation of tumor volume was developed. The system and algorithm were successfully applied to monitoring retinal tumor growth quantitatively over time in the LHBETATAG mouse model of retinoblastoma.

In vivo tests of thyroid function.

<h3>ABSTRACT</h3> <h3>Background</h3> To assess the pediatric anterior segment characteristics in ocular pathology, using spectral domain optical coherence tomography (SD-OCT). <h3>Methods</h3> Our case series follows 115 eyes of 78 children aged 2–17 years of age with anterior segment pathology in an academic facility. A thorough eye examination and investigations were performed for each child. The anterior segment optical coherence tomography (AS-OCT) analysis was done using the Optopol Revo 80^® high resolution SD-OCT (840 nm, axial resolution of 5 µm) using an imaging adapter. All pathological features visible on imaging were observed, studied, tabulated, and analyzed. <h3>Results</h3> 115 eyes of 78 children with anterior segment pathology were imaged. The average age was 11.84 years, with 44 males and 34 females. The primary clinical diagnosis was <i>cataract</i> (congenital and acquired) in 40 (34.8%) eyes, followed by <i>corneal disease</i> (congenital, inflammatory, and traumatic) in 28 (24.3%) eyes, <i>glaucoma</i> (juvenile and secondary) in 18 (15.7%) and <i>trauma</i> in 15 (13%) eyes. Systemic diseases were associated in 20.9%. The commonest imaging pathology observed was <i>lens opacification</i> (any morphology/location) in 43 (37.4%), <i>increased reflectivity of the cornea</i> in 31 (28.2<i>%), corneal stromal thinning</i> in 34 (29.6%), increased corneal thickness in 28 (24.3%), <i>shallow anterior chamber</i> in 17 (14.8%), and <i>cells in anterior chamber</i> in18 (15.7%) eyes, along with a multitude of other findings. <h3>Conclusions</h3> Our study demonstrates that anterior segment optical coherence tomography is a useful non-contact technique used without sedation for the detailed anatomic and pathologic assessment, imaging, diagnosis, and monitoring of pediatric ocular diseases.