Molecular imaging true-colour spectroscopic optical coherence tomography

Department of Biomedical Engineering and Fitzpatrick Institute for Photonics, Duke University, Durham, North Carolina 27708, USA
Nature Photonics (Impact Factor: 32.39). 12/2011; 5(12):744-747. DOI: 10.1038/nphoton.2011.257
Source: PubMed


Molecular imaging holds a pivotal role in medicine due to its ability to provide invaluable insight into disease mechanisms at molecular and cellular levels. To this end, various techniques have been developed for molecular imaging, each with its own advantages and disadvantages(1-4). For example, fluorescence imaging achieves micrometre-scale resolution, but has low penetration depths and is mostly limited to exogenous agents. Here, we demonstrate molecular imaging of endogenous and exogenous chromophores using a novel form of spectroscopic optical coherence tomography. Our approach consists of using a wide spectral bandwidth laser source centred in the visible spectrum, thereby allowing facile assessment of haemoglobin oxygen levels, providing contrast from readily available absorbers, and enabling true-colour representation of samples. This approach provides high spectral fidelity while imaging at the micrometre scale in three dimensions. Molecular imaging true-colour spectroscopic optical coherence tomography (METRiCS OCT) has significant implications for many biomedical applications including ophthalmology, early cancer detection, and understanding fundamental disease mechanisms such as hypoxia and angiogenesis.

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    • "The only technique that is reported to have comparable performance to our sdLCS system in terms of localized measurements of optical properties, is dual window sOCT that was developed by Robles et al. [8,14]. Whereas Robles et al. report that their method achieves higher resolution in both the spectral and the spatial domain by avoiding the inherent tradeoff between the two, their system may suffer from the effects of the sensitivity roll-off of the detecting spectrograph and the absence of focus tracking, which influence measurement depth. "
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    ABSTRACT: Low-coherence spectroscopy (LCS) offers the valuable possibility to measure quantitative and wavelength resolved optical property spectra within a tissue volume of choice that is controllable both in size and in depth. Until now, only time domain detection was investigated for LCS (tdLCS), but spectral domain detection offers a theoretical speed/sensitivity advantage over tdLCS. In this article, we introduce a method for spectral domain detection in LCS (sdLCS), with optimal sensitivity as a function of measurement depth. We validate our method computationally in a simulation and experimentally on a phantom with known optical properties. The attenuation, absorption and scattering coefficient spectra from the phantom that were measured by sdLCS agree well with the expected optical properties and the measured optical properties by tdLCS.
    Full-text · Article · Sep 2012 · Biomedical Optics Express
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    • "An alternative to these techniques is molecular imaging true-color spectroscopic (METRiCS) OCT which uses a wide spectral bandwidth laser source centered in the visible spectrum and the dual window (DW) processing method [5], which reveals spatially resolved spectroscopic information with high resolution in both the spatial domain and the spectral domain. This approach has been demonstrated to provide contrast from endogenous absorbers, such as oxygenated and deoxygenated hemoglobin [4], as well as exogenous absorbers in vivo [5]. In addition, the wide bandwidth in METRiCS OCT enables high depth resolution, greater than that seen with most OCT systems operating in the infrared region of the spectrum. "
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    ABSTRACT: We have recently developed a novel dual window scheme for processing spectroscopic OCT images to provide spatially resolved true color imaging of chromophores in scattering samples. Here we apply this method to measure the extinction spectra of plasmonic nanoparticles at various concentrations for potential in vivo applications. We experimentally demonstrate sub-nanomolar sensitivity in the measurement of nanoparticle concentrations, and show that colorimetric imaging with multiple species of nanoparticles produces enhanced contrast for spectroscopic OCT in both tissue phantom and cell studies.
    Full-text · Article · Aug 2012 · Biomedical Optics Express
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    ABSTRACT: Nonlinear phase dispersion spectroscopy is introduced as a means to retrieve wideband, high spectral resolution profiles of the wavelength-dependent real part of the refractive index. The method is based on detecting dispersion effects imparted to a light field with low coherence transmitted through a thin sample and detected interferometrically in the spectral domain. The same sampled signal is also processed to yield quantitative phase maps and spectral information regarding the total attenuation coefficient using spectral-domain phase microscopy and spectroscopic optical coherence tomography (SOCT), respectively. Proof-of-concept experiments using fluorescent and nonfluorescent polystyrene beads and another using a red blood cell demonstrate the ability of the method to quantify various absorptive/dispersive features. The increased sensitivity of this method, novel to our knowledge, is compared to intensity-based spectroscopy (e.g., SOCT), and potential applications are discussed.
    Full-text · Article · Dec 2011 · Optics Letters
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