Abstract
Optical coherence tomography (OCT) has revolutionises the diagnosis of retinal disease based on the detection of microscopic rather than subcellular changes in retinal anatomy. However, currently the technique is limited to the detection of microscopic rather than subcellular changes in retinal anatomy. However, coherence based imaging is extremely sensitive to both changes in optical contrast and cellular events at the micrometer scale, and can generate subtle changes in the spectral content of the OCT image. Here we test the hypothesis that OCT image speckle (image texture) contains information regarding otherwise unresolvable features such as organelle changes arising in the early stages of neuronal degeneration. Using ultrahigh resolution (UHR) OCT imaging at 800 nm (spectral width 140 nm) we developed a robust method of OCT image analyses, based on spatial wavelet and texture-based parameterisation of the image speckle pattern. For the first time we show that this approach allows the non-invasive detection and quantification of early apoptotic changes in neurons within 30 min of neuronal trauma sufficient to result in apoptosis. We show a positive correlation between immunofluorescent labelling of mitochondria (a potential source of changes in cellular optical contrast) with changes in the texture of the OCT images of cultured neurons. Moreover, similar changes in optical contrast were also seen in the retinal ganglion cell- inner plexiform layer in retinal explants following optic nerve transection. The optical clarity of the explants was maintained throughout in the absence of histologically detectable change. Our data suggest that UHR OCT can be used for the non-invasive quantitative assessment of neuronal health, with a particular application to the assessment of early retinal disease.
Highlights
The quantification of cellular health is essential to allow accurate monitoring of responses to experimental or therapeutic interventions
Our study demonstrates that texture analysis of optical coherence tomography (OCT) images can be used to generate quantitative surrogate measures of cellular health in the early stages of neuronal degeneration
Automated texture analysis was able to detect cellular events leading to apoptosis within 30 minutes of the application of staurosporine
Summary
The quantification of cellular health is essential to allow accurate monitoring of responses to experimental or therapeutic interventions. Many of the available optical techniques to probe cellular health rely on either the use of fluorophores to tag molecules of interest [1,2] or are limited by the need for a high numerical aperture (NA) in microscopy or Raman spectroscopy [3]. Interference based imaging technology such as optical coherence tomography (OCT) is promising in this respect and has recently been used for quantification of cell death in vitro and in vivo [5]. Since the axial resolution in OCT is not constrained by the numerical aperture of the focusing optics [6] it has the potential to detect subcellular changes (such as organelle disruption) that are known to precede cell death [7,8], allowing the non-invasive characterization of early apoptotic events. The availability of broad spectral bandwidth light sources (spectral spread 140 nm and above) has increased the resolution of these devices to 1–2 mm which should, in principle, allow the detection of optical changes driven by organelle alterations at a subcellular scale, even when the identification of individual organelles is not possible
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
