In vivo oximetry of human bulbar conjunctival and episcleral microvasculature using snapshot multispectral imaging

Mackenzie, Lewis E.; Choudhary, Tushar R.; McNaught, Andrew; Harvey, Andrew R.

doi:10.1016/j.exer.2016.06.008

Cited by 37 publications

(54 citation statements)

References 42 publications

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“…[27,28] In multispectral oximetry, snapshot imaging reduces artefacts in image quality and OS when compared to time-sequential imaging systems. [29] The IRIS has previously been applied to snapshot oximetry of retinal vessels, [30] snapshot oximetry of bulbar conjunctival and episcleral vessels, [31] and video-rate snapshot oximetry of individual red blood cells. [32] For best performance in conventional oximetry applications, the IRIS should be utilized in conjunction with a tiled spectral 'clean-up' filter plate to improve spectral purity, [28,32] but for BOMA, maximal light throughput is of greatest importance so as to maximize image-acquisition rate; therefore the clean-up filter plate was not used for this study.…”

Section: Retinal Imaging With a Video-rate Multispectral Fundus Cameramentioning

confidence: 99%

Dye-free retinal angiography using blood-oxygenation modulation

Mackenzie

Choudhary

Ramos

et al. 2018

Preprint

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Fluorescence angiography (FA) is widely used for studying and diagnosing abnormalities in the retinal blood circulation, but has associated risks of nausea, skin irritation, and even death. We describe a new non-invasive angiography technique: Blood Oxygenation Modulation Angiography, in which multispectral imaging of a transient perturbation in bloodoxygen saturation, yields angiography sequences similar to FA, including key features such as sequential filling of choroidal and retinal-vessels, which that underpin assessment of circulation health. This is the first non-invasive angiography technique capable of visualizing these circulation features.A These diffuse background characteristics of the "choroidal flush" arise because the light emitted from fluorescein within the choroidal vessels is multiply scattered by the retinal tissue. Further, melanin pigmentation in the retina acts to obscure the dense choroidal vasculature. However, in subjects with low levels of retinal pigmentation, the choroidal blood vessels can be directly observed. [57]

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Section: Retinal Imaging With a Video-rate Multispectral Fundus Cameramentioning

confidence: 99%

Dye-free retinal angiography using blood-oxygenation modulation

Mackenzie

Choudhary

Ramos

et al. 2018

Preprint

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“…[10][11][12] Various imaging techniques have been employed in the past to measure retinal oxygen saturation, [13][14][15][16][17][18][19][20][21][22] and recently emerging techniques have enabled oximetry to be applied in a variety of in vivo applications. [23][24][25] Nevertheless, the vast majority of retinal oximetry studies use a fundus camera-based approach, which has a limited spatial resolution and provides insufficient contrast to perform oximetry in retinal microvessels smaller than ∼100 μm. However, it is in the smaller microvessels that the oxygen saturation is expected to decrease in response to local increased metabolic demand or decreased oxygen delivery capacity.…”

Section: Introductionmentioning

confidence: 99%

In vivo subdiffuse scanning laser oximetry of the human retina

et al. 2019

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Scanning laser ophthalmoscopes (SLOs) have the potential to perform high speed, high contrast, functional imaging of the human retina for diagnosis and follow-up of retinal diseases. Commercial SLOs typically use a monochromatic laser source or a superluminescent diode for imaging. Multispectral SLOs using an array of laser sources for spectral imaging have been demonstrated in research settings, with applications mainly aiming at retinal oxygenation measurements. Previous SLO-based oximetry techniques are predominantly based on wavelengths that depend on laser source availability. We describe an SLO system based on a supercontinuum (SC) source and a double-clad fiber using the single-mode core for illumination and the larger inner cladding for quasi-confocal detection to increase throughput and signal-to-noise ratio. A balanced detection scheme was implemented to suppress the relative intensity noise of the SC source. The SLO produced dual wavelength, high-quality images at 10 frames∕s with a maximum 20 deg imaging field-of-view with any desired combination of wavelengths in the visible spectrum. We demonstrate SLO-based dual-wavelength oximetry in vessels down to 50 μm in diameter. Reproducibility was demonstrated by performing three different imaging sessions of the same volunteer, 8 min apart. Finally, by performing a wavelength sweep between 485 and 608 nm, we determined, for our SLO geometry, an approximately linear relationship between the effective path length of photons through the blood vessels and the vessel diameter.

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“…Methods with a finer sampling of the spectral response, such as multi-or hyperspectral imaging (MSI/HSI) systems (≈10 and 100 spectral color channels, respectively), 12,13 may enable quantitative assessment of functional tissue properties and more detailed statistical classification of the spectral changes that occur during disease. The use of reflectance-based MSI/HSI systems in biomedical applications has, for example, been shown to increase contrast in vascular conditions, 14 wound healing, [15][16][17] ophthalmology, 15,18,19 cancer diagnostics, 12,[20][21][22][23] and for the determination of tumor resection margins. 24 The application of a targeted fluorescent contrast agent is often referred to as optical molecular imaging (OMI) and has shown promise for endoscopic cancer detection in the GI tract.…”

Section: Introductionmentioning

confidence: 99%

Bimodal reflectance and fluorescence multispectral endoscopy based on spectrally resolving detector arrays

et al. 2018

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Emerging clinical interest in combining standard white light endoscopy with targeted near-infrared (NIR) fluorescent contrast agents for improved early cancer detection has created demand for multimodal imaging endoscopes. We used two spectrally resolving detector arrays (SRDAs) to realize a bimodal endoscope capable of simultaneous reflectance-based imaging in the visible spectral region and multiplexed fluorescencebased imaging in the NIR. The visible SRDA was composed of 16 spectral bands, with peak wavelengths in the range of 463 to 648 nm and full-width at half-maximum (FWHM) between 9 and 26 nm. The NIR SRDA was composed of 25 spectral bands, with peak wavelengths in the range 659 to 891 nm and FWHM 7 to 15 nm. The spectral endoscope design was based on a "babyscope" model using a commercially available imaging fiber bundle. We developed a spectral transmission model to select optical components and provide reference endmembers for linear spectral unmixing of the recorded image data. The technical characterization of the spectral endoscope is presented, including evaluation of the angular field-of-view, barrel distortion, spatial resolution and spectral fidelity, which showed encouraging performance. An agarose phantom containing oxygenated and deoxygenated blood with three fluorescent dyes was then imaged. After spectral unmixing, the different chemical components of the phantom could be successfully identified via majority decision with high signal-to-background ratio (>3). Imaging performance was further assessed in an ex vivo porcine esophagus model. Our preliminary imaging results demonstrate the capability to simultaneously resolve multiple biological components using a compact spectral endoscopy system.

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In vivo oximetry of human bulbar conjunctival and episcleral microvasculature using snapshot multispectral imaging

Cited by 37 publications

References 42 publications

Dye-free retinal angiography using blood-oxygenation modulation

Dye-free retinal angiography using blood-oxygenation modulation

In vivo subdiffuse scanning laser oximetry of the human retina

Bimodal reflectance and fluorescence multispectral endoscopy based on spectrally resolving detector arrays

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