Noninvasive determination of the optical properties of adult brain: near-infrared spectroscopy approach.
The basic parameters for physiological measurements provided by near-infrared spectroscopy are the local absorption and scattering coefficients. For the adult human head, they have been difficult to measure noninvasively because of the layered structure of the head. The results of measurements of absorption and reduced scattering coefficients through the forehead on 30 adult volunteers using a multidistance frequency domain method are reported. The optode separation distance ranged from 10 to 80 mm and measurements were recorded at 758 and 830 nm. The measured absorption and reduced scattering coefficients of the forehead were used to evaluate the hemoglobin content in the scalp and brain as well as cerebral oxygen saturation. We found that cerebral oxygenation was relatively narrowly distributed within the subject group (the standard deviation was about 3% for scalp and 6% for brain, respectively), whereas hemoglobin concentrations had a relatively broader distribution. We found that as the optode distance increased, the absorption coefficients increased and the scattering coefficients decreased, retrieving the optical values of scalp and brain for shorter and longer optode distances, respectively. We present the transition curves of the absorption and reduced scattering coefficients as functions of the optode distance. In order to verify the values for each layer, a comparison between the experimental data and a prediction based on the two-layer model of the adult head was carried out. The thicknesses of scalp and skull for the two-layer model were obtained by magnetic resonance imaging of a subject's head. The optical parameters obtained from the two-layer model agreed very well with those measured by the multidistance method.
Choi
JeeHyun
J
Laboratory for Fluorescence Dynamics, Department of Physics, University of Illinois at Urbana-Champaign, 1110 W. Green Street, Urbana, IL 61801-3080, USA. jeechoi@uiuc.edu
Wolf
Martin
M
Toronov
Vladislav
V
Wolf
Ursula
U
Polzonetti
Chiara
C
Hueber
Dennis
D
Safonova
Larisa P
LP
Gupta
Rajarsi
R
Michalos
Antonios
A
Mantulin
William
W
Gratton
Enrico
E
D000328:Adult; D000465:Algorithms; D001921:Brain / Q000502:physiology*; D001923:Brain Chemistry; D001931:Brain Mapping / Q000295:instrumentation* / Q000379:methods*; D003198:Computer Simulation; D005260:Female; D006257:Head / Q000502:physiology; D006454:Hemoglobins / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D010100:Oxygen / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D019265:Spectroscopy, Near-Infrared / Q000295:instrumentation* / Q000379:methods*; D014159:Transducers
D006454:Hemoglobins; D010100:Oxygen