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Strong light scattering and absorption limit observation of the internal structure of biological tissue. Only special tools
for turbid media imaging, such as optical diffuse tomography, enable noninvasive investigation of the internal biological
tissues, including visualization and intravital monitoring of deep tumors.
In this work the preliminary results of diffuse fluorescence tomography (DFT) of small animals are presented. Usage
of exogenous fluorophores, targeted specifically at tumor cells, and fluorescent proteins expressed endogenously can
significantly increase the contrast of obtained images. Fluorescent compounds of different nature, such as sulphonated
aluminium phthalocyanine (Photosens), red fluorescing proteins and CdTe/CdSe-core/shell nanocrystals (quantum dots)
were applied. We tested diffuse fluorescence tomography method at model media, in post mortem and in vivo
experiments. The animal was scanned in transilluminative configuration by low-frequency modulated light (1 kHz) from
Nd:YAG laser with second harmonic generation at wavelength of 532 nm or semiconductor laser at wavelength of 655
nm. Quantum dots or protein DsRed2 in glass capsules (inner diameter 2-3 mm) were placed post mortem inside the
esophagus of 7-day-old hairless rats to simulate marked tumors. Photosens was injected intravenously to linear mice with
metastazing Lewis lung carcinoma.
The reconstruction algorithm, based on Algebraic Reconstruction Technique, was created and tested numerically in
model experiments. High contrast images of tumor simulating capsules with DsRed2 concentrations about 10-6 M and
quantum dots about 5x10-11 M have been obtained. Organ distribution of Photosens and its accumulation in tumors and
surrounding tissues of animals has been examined. We have conducted the monitoring of tumors, exogenously labeled
by photosensitizer.
This work demonstrates potential capabilities of DFT method for intravital detection and monitoring of deep fluorescent-labeled
tumors in animal models. The comparative analysis of conventional photosensitizer, fluorescent proteins and
quantum dots has been carried out.
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