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Towards in-vivo assessment of fluorescence lifetime: imaging using time-gated intensified CCD camera

Sawosz P., Wojtkiewicz S., Kacprzak M., Zieminska E., Morawiec M., Maniewski R., Liebert A.

Biocybernetics and Biomedical Engineering

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2018

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Vol. 38, no. 4

966--974

EN

A novel technique for imaging of a small animal with application of time-gated intensified CCD camera was proposed. The time-resolved method based on emission of picosecond light pulses and detection of the light penetrating in tissues was applied. In this technique, the fluorescence photons, excited in the dye circulating in the tissue, that diffusely penetrate in the optically turbid medium are detected. The data acquired during measurements carried out on a rat was analyzed in order to estimate fluorescence life time which depends strongly on the environment in which the dye is distributed. In the life time estimation a special emphasis was put on compensation of influence of the instrumental response function of the setup on the measured quantity. The proposed optical system was validated in series of phantom experiments, in which estimates of fluorescence lifetime of inclusions containing indocyanine green (ICG) were obtained. ICG is a dye revealing florescence properties in near-infrared wavelength region. Images of the estimate of fluorescence lifetime of the ICG accumulated in tissues of a rat were successfully acquired around six circular spots of illumination of the diameter of 6mm. Larger lifetime values were observed in lung/heart region of the animal. Aspect of sampling rate of the fluorescence lifetime images optimization was finally discussed.

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Functional brain imaging by multi-wavelength time-resolved near infrared spectroscopy

Torricelli A., Contini D., Pifferi A., Spinelli L., Cubeddu R.

Opto-Electronics Review

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2008

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Vol. 16, No. 2

131-135

EN

We present a description of evolution of time-resolved systems developed at the Department of Physics, Politecnico di Milano for tissue oximetry and functional brain imaging. From a single source and 4-channel set-up we have upgraded to a potentially 18-sources and 64-channel device. An example of sensitivity of the latest set-up is reported for a motor task experiment. A short discussion on the next generation time-resolved instrumentation for functional studies is also presented.

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Time-resolved reflectometry and spectroscopy for assessment of brain perfusion and oxygenation

Liebert A., Kacprzak M., Maniewski R.

Biocybernetics and Biomedical Engineering

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2007

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Vol. 27, no. 1-2

217-225

EN

Time-resolved optical methods and instrumentation for non-invasive assessment of the cerebral cortex perfusion and oxygenation are presented. The oxygenation can be calculated using the moments of the distributions of times of flight of photons measured at two wavelengths in the near infrared region. For assessment of the brain perfusion, the kinetics of the inflow and washout of an exogenous dye injected intravenously is analyzed. The instrument developed at the Institute of Biocybernetics and Biomedical Engineering PAS is equipped with picosecond diode lasers, fast photodetectors and time correlated single photon counting electronics for acquisition of the distributions of times of flight of photons. This technique allows for a depth-resolved estimation of the changes of absorption and, in consequence, for an assessment of the changes occurring in the cerebral cortex. Combination of the data from multiple sources and detectors placed on the surface of the head with the depth-resolved analysis based on the moments enables to obtain images of the cortex perfusion and/or oxygenation. Potential applications of the instrument and its limitations are also discussed.

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Time-resolved optical spectroscopy and imaging of breast

Taroni P., Pifferi A., Torricelli A., Cubeddu R.

Opto-Electronics Review

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2004

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Vol. 12, No. 2

249-253

EN

A fully automated system for time-resolved reflectance and transmittance spectroscopy from 610 to 1010 nm was developed and applied to the optical (absorption and scattering) characterization of breast tissue in vivo. From absorption spectra, information is derived on tissue content of oxy-, deoxyhemoglobin, water and lipids, while scattering spectra provide knowledge on tissue structure. A portable system for breast imaging at four wavelengths (683, 785, 912, and 975 nm) was also developed and is being tested in clinics for the detection and characterization of breast lesions (optical mammography).