Mesoscopic early-photon fluorescence molecular lifetime tomography: first experimental results
Alexander B. Konovalov,1,2 Vitaly V. Vlasov,1,2 Sergei I. Samarin,1 Ilya D. Soloviev,2 Alexander P. Savitsky2, Valery V. Tuchin,2,3,4,5
1 Federal State Unitary Enterprise “Russian Federal Nuclear Center – Zababakhin All-Russia Research Institute of Technical Physics,” Snezhinsk, Russia 2 Bach Institute of Biochemistry, Research Center of Biotechnology of the Russian Academy of Science, Moscow, Russia 3 Saratov State University, Saratov, Russia 4 Tomsk State University, Tomsk, Russia 5 Institute of Precision Mechanics and Control of the Russian Academy of Sciences, Saratov, Russia
Abstract
The paper is devoted to an original approach to time-domain fluorescence molecular lifetime tomography based on the use of early arriving diffuse photons and asymptotic approximation to the fluorescence source function. Such an approximation gives us an opportunity to solve the tomographic inverse problem with respect to the fluorescence parameter distribution function of a simple form and then to separate the distributions of the fluorophore absorption coefficient and fluorescence lifetime in the time domain. The paper presents the theoretical foundation of the method and describes an experiment on the reconstruction of a tissue-like phantom with fluorophore. The time-resolved measurement data are registered in mesoscopic regime with the use of a three-channel fiber probe for 3D reflectance geometry that is typical of small animal imaging. Sensitivity functions are simulated via the Monte Carlo method. For solving the inverse problem we use the compressed-sensing-like hybrid algorithm that combines algebraic reconstruction, fast iterative shrinkage thresholding, and total variation regularization. Fluorescence parameter separation is performed via the known QR-factorization least square algorithm. We show that our method is capable of giving quite adequate fluorescence lifetime reconstructions but their quality depends on the number of source-receiver links, the strategy we use for generating measurement data arrays and sensitivity matrices, as well as a priori information that is available for reconstruction.
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Alexander B. Konovalov
Federal State Unitary Enterprise “Russian Federal Nuclear Center – Zababakhin All-Russia Research Institute of Technical Physics”
Russia
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