We introduce an improved approach in the 3D localization of discrete fluorescent inclusions in a thick scattering
medium. Previously our approach provided accurate localization of a single inclusion, showing the potential for
direct time-of-flight fluorescence diffuse optical tomography. Here, we localize various combinations of multiple
fluorescent inclusions. We resort to time-domain (TD) detection of emitted fluorescence pulses after short pulse
laser excitation. Our approach relies on a signal processing technique, dubbed numerical constant fraction
discrimination (NCFD), for extracting in a stable manner the arrival time of early photons emitted by one or
many fluorescent inclusions from measured time-of-flight (TOF) distributions. Our experimental set-up allows
multi-view tomographic optical TD measurements over 360 degrees without contact with the medium. It uses an ultra-short pulse laser and ultra-fast time-correlated single photon counting (TCSPC) detection. Fluorescence time point-spread functions (FTPSFs) are acquired all around the phantom after laser excitation. From measured
FTPSFs, the arrival time of a fluorescent wavefront at a detector position is extracted with our NCFD technique.
Indocyanine green (ICG; absorption peak = 780nm, emission peak = 830nm) is used for the inclusions. Various
experiments were conducted with this set-up in a stepwise fashion. First, single inclusion experiments are
presented to provide background information. Second, we present results using two inclusions in a plane. Then,
we move on with two inclusions located in different planes. Finally, we show results with a plurality of inclusions
(>2) distributed at arbitrary positions in the medium. Using an algorithm we have developed and tested on the
acquired data, we successfully achieve to locate the inclusions. Here, results are obtained for discrete inclusions.
In a close future, we expect to extend our method to continuous fluorescence distributions.