title: Assessment of inflow and washout of indocyanine green in the adult human brain by monitoring of diffuse reflectance at large source-detector separation.
abstract: Recently, it was shown in measurements carried out on humans that time-resolved near-infrared reflectometry and fluorescence spectroscopy may allow for discrimination of information originating directly from the brain avoiding influence of contaminating signals related to the perfusion of extracerebral tissues. We report on continuation of these studies, showing that the near-infrared light can be detected noninvasively on the surface of the tissue at large interoptode distance. A multichannel time-resolved optical monitoring system was constructed for measurements of diffuse reflectance in optically turbid medium at very large source-detector separation up to 9 cm. The instrument was applied during intravenous injection of indocyanine green and the distributions of times of flight of photons were successfully acquired showing inflow and washout of the dye in the tissue. Time courses of the statistical moments of distributions of times of flight of photons are presented and compared to the results obtained simultaneously at shorter source-detector separations (3, 4, and 5 cm). We show in a series of experiments carried out on physical phantom and healthy volunteers that the time-resolved data acquisition in combination with very large source-detector separation may allow one to improve depth selectivity of perfusion assessment in the brain.
authors.affiliation: Polish Academy of Sciences, Nalecz Institute of Biocybernetics and Biomedical Engineering, Trojdena 4, 02-109 Warsaw, Poland. adam.liebert@ibib.waw.pl
authors.forename: Adam
authors.initials: A
authors.lastname: Liebert
authors.forename: Piotr
authors.initials: P
authors.lastname: Sawosz
authors.forename: Daniel
authors.initials: D
authors.lastname: Milej
authors.forename: Michał
authors.initials: M
authors.lastname: Kacprzak
authors.forename: Wojciech
authors.initials: W
authors.lastname: Weigl
authors.forename: Marcin
authors.initials: M
authors.lastname: Botwicz
authors.forename: Joanna
authors.initials: J
authors.lastname: Maczewska
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Fronczewska
authors.forename: Ewa
authors.initials: E
authors.lastname: Mayzner-Zawadzka
authors.forename: Leszek
authors.initials: L
authors.lastname: Królicki
authors.forename: Roman
authors.initials: R
authors.lastname: Maniewski
mesh_terms: D000328:Adult; D001921:Brain / Q000098:blood supply / Q000378:metabolism*; D002540:Cerebral Cortex / Q000098:blood supply / Q000378:metabolism*; D003952:Diagnostic Imaging / Q000379:methods*; D006801:Humans; D007208:Indocyanine Green / Q000737:chemistry* / Q000493:pharmacokinetics; D019047:Phantoms, Imaging; D012039:Regional Blood Flow / Q000502:physiology; D012815:Signal Processing, Computer-Assisted; D019265:Spectroscopy, Near-Infrared / Q000379:methods*
chemical_list: D007208:Indocyanine Green