Warsaw Praski Hospital

Warsaw, Poland

Warsaw Praski Hospital

Warsaw, Poland
SEARCH FILTERS
Time filter
Source Type

Milej D.,Nalecz Institute of Biocybernetics and Biomedical Engineering | Gerega A.,Nalecz Institute of Biocybernetics and Biomedical Engineering | Zolek N.,Nalecz Institute of Biocybernetics and Biomedical Engineering | Zolek N.,Polish Academy of Sciences | And 11 more authors.
Physics in Medicine and Biology | Year: 2012

It was reported that time-resolved reflectance measurements carried out during inflow and washout of an optical contrast agent may provide information on the blood supply to the brain cortex of human adults. It was also shown that a measurement of fluorescence excited in the dye circulating in the brain is feasible. Unfortunately, patterns of time-resolved fluorescence signals observed during in vivo measurements are difficult to interpret. The aim of this study was to analyze the influence of several factors on the fluorescence signals measured during in vivo experiments. A laboratory instrument for recording the distributions of arrival of fluorescence photons was constructed and optimized for measurements on humans. Monte Carlo simulations and laboratory measurements on liquid phantoms as well as in vivo measurements on healthy volunteers were carried out. An influence of source-detector separation, position of the source-detector pair on the head, as well as a dose of the injected indocyanine green (ICG) on the fluorescence signals were studied in detail. It was shown that even for a small dose of ICG (0.025mg kg 1) the time-resolved signals can be successfully detected on the surface of the head. Strong influence of the studied factors on the fluorescence signals was observed. It was also noted that the changes in moments of distributions of arrival times of fluorescence photons depend on the anatomical structure of the tissues located between the source and the detector. © 2012 Institute of Physics and Engineering in Medicine.


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.


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).


Gerega A.,Nalecz Institute of Biocybernetics and Biomedical Engineering | Milej D.,Nalecz Institute of Biocybernetics and Biomedical Engineering | Weigl W.,Medical University of Warsaw | Weigl W.,Warsaw Praski Hospital | And 9 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).


PubMed | Uppsala University Hospital, Nalecz Institute of Biocybernetics and Biomedical Engineering and Warsaw Praski Hospital
Type: Journal Article | Journal: 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.

Loading Warsaw Praski Hospital collaborators
Loading Warsaw Praski Hospital collaborators