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Warsaw, Poland

Milej D.,Nalecz Institute of Biocybernetics and Biomedical Engineering | Gerega A.,Nalecz Institute of Biocybernetics and Biomedical Engineering | Kacprzak M.,Nalecz Institute of Biocybernetics and Biomedical Engineering | Sawosz P.,Nalecz Institute of Biocybernetics and Biomedical Engineering | And 3 more authors.
Opto-electronics Review | Year: 2014

Time-resolved near-infrared spectroscopy is an optical technique which can be applied in tissue oxygenation assessment. In the last decade this method is extensively tested as a potential clinical tool for noninvasive human brain function monitoring and imaging. In the present paper we show construction of an instrument which allows for: (i) estimation of changes in brain tissue oxygenation using two-wavelength spectroscopy approach and (ii) brain perfusion assessment with the use of single-wavelength reflectometry or fluorescence measurements combined with ICG-bolus tracking. A signal processing algorithm based on statistical moments of measured distributions of times of flight of photons is implemented. This data analysis method allows for separation of signals originating from extra- and intracerebral tissue compartments. In this paper we present compact and easily reconfigurable system which can be applied in different types of time-resolved experiments: two-wavelength measurements at 687 and 832 nm, single wavelength reflectance measurements at 760 nm (which is at maximum of ICG absorption spectrum) or fluorescence measurements with excitation at 760 nm. Details of the instrument construction and results of its technical tests are shown. Furthermore, results of in-vivo measurements obtained for various modes of operation of the system are presented. © 2014 Versita Warsaw and Springer-Verlag Wien. Source


Gerega A.,Nalecz Institute of Biocybernetics and Biomedical Engineering | Milej D.,Nalecz Institute of Biocybernetics and Biomedical Engineering | Weigl W.,Medical University of Warsaw | Botwicz M.,Nalecz Institute of Biocybernetics and Biomedical Engineering | And 8 more authors.
Journal of Biomedical Optics | Year: 2012

Optical technique based on diffuse reflectance measurement combined with indocyanine green (ICG) bolus tracking is extensively tested as a method for clinical assessment of brain perfusion in adults at the bedside. Methodology of multiwavelength and time-resolved detection of fluorescence light excited in the ICG is presented and advantages of measurements at multiple wavelengths are discussed. Measurements were carried out: 1. on a physical homogeneous phantom to study the concentration dependence of the fluorescence signal, 2. on the phantom to simulate the dynamic inflow of ICG at different depths, and 3. in vivo on surface of the human head. Pattern of inflow and washout of ICG in the head of healthy volunteers after intravenous injection of the dye was observed for the first time with time-resolved instrumentation at multiple emission wavelengths. The multiwavelength detection of fluorescence signal confirms that at longer emission wavelengths, probability of reabsorption of the fluorescence light by the dye itself is reduced. Considering different light penetration depths at different wavelengths, and the pronounced reabsorption at longer wavelengths, the time-resolved multiwavelength technique may be useful in signal decomposition, leading to evaluation of extra- and intracerebral components of the measured signals. © 2012 Society of Photo-Optical Instrumentation Engineers (SPIE). Source


Milej D.,Nalecz Institute of Biocybernetics and Biomedical Engineering | Janusek D.,Nalecz Institute of Biocybernetics and Biomedical Engineering | Gerega A.,Nalecz Institute of Biocybernetics and Biomedical Engineering | Wojtkiewicz S.,Nalecz Institute of Biocybernetics and Biomedical Engineering | And 5 more authors.
Journal of Biomedical Optics | Year: 2015

The aim of the study was to determine optimal measurement conditions for assessment of brain perfusion with the use of optical contrast agent and time-resolved diffuse reflectometry in the near-infrared wavelength range. The source-detector separation at which the distribution of time of flights (DTOF) of photons provided useful information on the inflow of the contrast agent to the intracerebral brain tissue compartments was determined. Series of Monte Carlo simulations was performed in which the inflow and washout of the dye in extra- and intracerebral tissue compartments was modeled and the DTOFs were obtained at different source-detector separations. Furthermore, tests on diffuse phantoms were carried out using a time-resolved setup allowing the measurement of DTOFs at 16 source-detector separations. Finally, the setup was applied in experiments carried out on the heads of adult volunteers during intravenous injection of indocyanine green. Analysis of statistical moments of the measured DTOFs showed that the source-detector separation of 6 cm is recommended for monitoring of inflow of optical contrast to the intracerebral brain tissue compartments with the use of continuous wave reflectometry, whereas the separation of 4 cm is enough when the higher-order moments of DTOFs are available. © 2015 Society of Photo-Optical Instrumentation Engineers (SPIE). Source

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