A full time-resolved scheme that has been previously applied in diffuse optical tomography is extended to time-domain
fluorescence diffuse optical tomography regime, based on a finite-element-finite-time-difference photon diffusion
modeling and a Newton-Raphson inversion framework. The merits of using full time-resolved data are twofold: it helps
evaluate the intrinsic performance of time-domain mode for improvement of image quality and set up a 'gold standard'
for the development of computationally efficient featured-data-based algorithms, and provides a self-normalized
implementation to preclude the necessary for the scaling-factor calibration and spectroscopic-feature assessments of the
system as well as to overcome the adversity of system instability. We validate the proposed methodology using simulated
data, and evaluate its performances in simultaneously recovering the fluorescent yield and lifetime as well as its
superiority to the featured-data one in the fidelity of image reconstruction.
In this study, time-domain fluorescence diffuse optical tomography (FDOT) in biological tissue is investigated by solving
the inverse problem using a convolution and deconvolution of the zero-lifetime emission light intensity and the exponential
function for a finite lifetime, respectively. We firstly formulate the fundamental equations in time-domain assuming that
the fluorescence lifetime is equal to zero, and then the solution including the lifetime is obtained by convolving
the emission light intensity and the lifetime function. The model is a 2-D 10 mm-radius circle with the optical properties
simulating biological tissue for the near infrared light, and contains some regions with fluorophores.
Temporal and spatial profiles of excitation and emission light intensities are calculated and discussed for several models.
The inverse problem of fluorescence diffuse optical tomography is solved using simulated measurement emission intensities
for reconstructing fluorophore concentration. A time-domain measurement system uses ultra-short pulsed laser for excitation
and measures the temporal and spatial distributions of fluorescence emitting from the tissue surface.
To improve image quality, we propose implementation of a FDOT algorithm using full time-resolved (TR) data.