Abstract
A multi-modal optical imaging system for quantitative 3D bioluminescence and functional diffuse imaging is presented, which has no moving parts and uses mirrors to provide multi-view tomographic data for image reconstruction. It is demonstrated that through the use of trans-illuminated spectral near-infrared measurements and spectrally constrained tomographic reconstruction, recovered concentrations of absorbing agents can be used as prior knowledge for bioluminescence imaging within the visible spectrum. Additionally, the first use of a recently developed multi-view optical surface capture technique is shown and its application to model-based image reconstruction and free-space light modelling is demonstrated. The benefits of model-based tomographic image recovery as compared to two-dimensional (2D) planar imaging are highlighted in a number of scenarios where the internal luminescence source is not visible or is confounding in 2D images. The results presented show that the luminescence tomographic imaging method produces 3D reconstructions of individual light sources within a mouse-sized solid phantom that are accurately localized to within 1.5 mm for a range of target locations and depths, indicating sensitivity and accurate imaging throughout the phantom volume. Additionally the total reconstructed luminescence source intensity is consistent to within 15%, which is a dramatic improvement upon standard bioluminescence imaging. Finally, results from a heterogeneous phantom with an absorbing anomaly are presented, demonstrating the use and benefits of a multi-view, spectrally constrained coupled imaging system that provides accurate 3D luminescence images.
Highlights
Bioluminescence imaging (BLI) is widely used for in vivo pre-clinical biomedical studies where the aim is to image distributed biological light sources, such as luciferase-tagged cancer cells, located inside a living animal
We provide an overview of current developments of non-contact small animal imaging systems, mostly limited to 3D bioluminescence-based imaging but with some discussion of systems designed for fluorescence molecular tomography‡ (FMT) which are conceptually closely related[4]
In order to test the concept of utilising diffuse optical tomography (DOT) results as a priori data to aid bioluminescence tomography (BLT) image reconstruction, the Trigalight luminescent-like source was placed in the lower tunnel between background-matching rods, whilst the absorption anomaly remained in place in the upper rod
Summary
Bioluminescence imaging (BLI) is widely used for in vivo pre-clinical biomedical studies where the aim is to image distributed biological light sources, such as luciferase-tagged cancer cells, located inside a living animal. The quantitative accuracy is limited by the unknown, highly attenuating and scattering properties of biological tissue This leads to ambiguous data and inaccurate analyses derived directly from captured twodimensional images, for deep sources[1]. In comparison with 2D BLI, 3D bioluminescence tomography (BLT) studies have shown that in some cases, most often when imaging optically homogeneous phantoms, individual luminescent sources can be reconstructed from surface fluence data with high accuracy in terms of spatial displacement, size and/or photon counting metrics improving upon BLI in terms of quantitative accuracy[2]. The system provides information regarding the optical properties - the spectrally and spatially varying optical absorption and reduced scattering coefficients - of the domain being imaged, providing a detailed understanding of the behaviour of light travelling through the medium, allowing compensation for light attenuation in BLT reconstruction and providing accurate analysis in terms of parameters of interest, such as cell count and activity. The multi-modal system represents a novel combination of optical imaging modalities providing a fundamentally new methodology and resultant 3D imaging data set
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