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.

Time-resolved diffuse optical tomography using fast-gated single-photon avalanche diodes

“…This capability was already explored using both single [30] and multi-distance measurements [31]. Time gated instruments can improve this intrinsic features of time-domain techniques [32,33].…”

Time-resolved multi-channel optical system for assessment of brain oxygenation and perfusion by monitoring of diffuse reflectance and fluorescence

“…The instrument was validated in experiments on liquid phantom and in−vivo studies on healthy subjects and on patients [41,45,48]. In this paper we show only examples of signals which can be obtained with the use of the instrument and provided results of two in−vivo experiments on the human head in healthy subjects.…”

“…The system can be used for acquisition of distributions of times of arrival (DTA) of fluorescence photons and distribu− tions of times of flight (DTOF) of diffusely reflected pho− tons. Its construction is based on our earlier methodological studies in which we used trNIRS [41,[48][49][50]. Most impor− tant advantage of the presented instrument is its compact design and ability to switch between different modes of operation in less than 5 min.…”

“…In this respect indocyanine green (ICG) is considered as a va− luable contrast agent revealing high absorption in near infra− red wavelength region [34] which can be safely [35] used in clinical studies [36][37][38]. In some of these studies the time− −resolved optical systems were applied in order to eliminate influence of changes in extracerebral tissue perfusion and oxygenation during recording of signals related to the inflow of the dye to the brain [39][40][41]. Moreover, it was reported that fluorescence light excited in the fluorophore circulating in the brain can be detected on the surface of the head [42][43][44][45][46][47].…”

Multi-channel medical device for time domain functional near infrared spectroscopy based on wavelength space multiplexing

“…It is worth mentioning that European research groups located in academic or public research centers have designed and built most of the existing TD fNIRS systems effectively employed in the clinics. In particular the most active in the field are the research groups at Physikalisch-Technische Bundesanstalt, Berlin, Germany [9][10][11][12][13][14][15], at the Institute of Biocybernetics and Biomedical Engineering, Warsaw, Poland [16][17][18], and at the the Department of Medical Physics and Bioengineering, University College London [19][20][21][22][23]. In the US we can mention the group at the Massachusetts General Hospital, Athinoula A. Martinos Center, Charlestown, Massachusetts [6,[24][25][26].…”