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A. Gerega



Recent publications
1.  Gerega A., Milej D., Weigl W., Botwicz M., Żołek N., Kacprzak M., Wierzejski W., Toczyłowska B., Mayzner-Zawadzka E., Maniewski R., Lieberta A., Multiwavelength time-resolved detection of fluorescence during the inflow of indocyanine green into the adult’s brain, JOURNAL OF BIOMEDICAL OPTICS, ISSN: 1083-3668, DOI: 10.1117/1.JBO.17.8.087001, Vol.17, No.8, pp.087001-1-9, 2012

Abstract:
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

Keywords:
indocyanine green bolus, near-infrared spectroscopy, fluorescence, time-resolved spectra, multiwavelength detection

Affiliations:
Gerega A. - other affiliation
Milej D. - Nałęcz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences (PL)
Weigl W. - other affiliation
Botwicz M. - Nałęcz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences (PL)
Żołek N. - other affiliation
Kacprzak M. - Nałęcz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences (PL)
Wierzejski W. - other affiliation
Toczyłowska B. - other affiliation
Mayzner-Zawadzka E. - other affiliation
Maniewski R. - other affiliation
Lieberta A. - other affiliation
2.  Milej D., Gerega A., Żołek N., Weigl W., Kacprzak M., Sawosz P., Mączewska J., Fronczewska K., Mayzner-Zawadzka E., Królicki L., Maniewski R., Liebert A., Time-resolved detection of fluorescent light during inflow of ICG to the brain - a methodological study, PHYSICS IN MEDICINE AND BIOLOGY, ISSN: 0031-9155, DOI: 10.1088/0031-9155/57/20/6725, Vol.57, pp.6725-6742, 2012

Abstract:
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 (0.025 mg 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.

Affiliations:
Milej D. - Nałęcz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences (PL)
Gerega A. - other affiliation
Żołek N. - other affiliation
Weigl W. - other affiliation
Kacprzak M. - Nałęcz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences (PL)
Sawosz P. - Nałęcz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences (PL)
Mączewska J. - other affiliation
Fronczewska K. - other affiliation
Mayzner-Zawadzka E. - other affiliation
Królicki L. - other affiliation
Maniewski R. - other affiliation
Liebert A. - Nałęcz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences (PL)

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