Near-ir light (700-900 nm) penetrates several centimeters into tissues and passes through bony structures and fat layers. The major contribution to light absorption in this spectral region arises from hemoglobin. In response to tissue metabolism, the hemoglobi oxygenation and its spectral properties change and the hemoglobin concentratio increases. During the previous granting period, we developed frequency domain methods that allowed us to precisely quantify tissue oxygenation changes, in conjunction with measurements at different locations on the tissue surface. High-frequency (~100 MHz) modulated light is applied to a part of the tissue using optical fibers and then collected at different locations, generally 3-4 cm from the source, after the light has diffused deep into the tissue. The determination of the tissue optical properties was very fast and suggested the possibility of performing functional studies in the brain and the muscles that were not available before. One apparent limitation of the use of the diffusive part of the light that propagates in tissues is the relatively low spatial resolution (about 1 cm). However, the applicants reported research showing tha if they observe changes of tissue optical parameters, then the spatial and temporal resolution can be greatly improved with respect to steady-state measurements. The applicants proposed to develop a new detector for the study of rapid changes (1 to 10 ms time scale) of optical parameters deep (1 to 2 cm in tissues. The new detector can localize changes occurring in a small volume (3 mm in radius). It has low noise and relatively high bandwidth. Using this new detector, the applicants proposed to study the dynamics of tissues, particularly the muscle and the brain in the frequency bandwidth up to about 100 Hz. Their approach signals a significant advance with respect to current methodologies and this method could provide physiologists with a new tool for functional studies of the brain and other tissues.

Agency
National Institute of Health (NIH)
Institute
National Center for Research Resources (NCRR)
Type
Research Project (R01)
Project #
5R01RR010966-05
Application #
6056719
Study Section
Diagnostic Imaging Study Section (DMG)
Project Start
1995-09-01
Project End
2001-08-31
Budget Start
1999-09-01
Budget End
2000-08-31
Support Year
5
Fiscal Year
1999
Total Cost
Indirect Cost
Name
University of Illinois Urbana-Champaign
Department
Physics
Type
Schools of Engineering
DUNS #
041544081
City
Champaign
State
IL
Country
United States
Zip Code
61820
Wolf, Ursula; Wolf, Martin; Choi, Jee H et al. (2007) Regional differences of hemodynamics and oxygenation in the human calf muscle detected with near-infrared spectrophotometry. J Vasc Interv Radiol 18:1094-101
Safonova, Larisa P; Michalos, Antonios; Wolf, Ursula et al. (2004) Age-correlated changes in cerebral hemodynamics assessed by near-infrared spectroscopy. Arch Gerontol Geriatr 39:207-25
Toronov, Vlad; Walker, Scott; Gupta, Rajarsi et al. (2003) The roles of changes in deoxyhemoglobin concentration and regional cerebral blood volume in the fMRI BOLD signal. Neuroimage 19:1521-31
Wolf, Ursula; Wolf, Martin; Choi, Jee H et al. (2003) Localized irregularities in hemoglobin flow and oxygenation in calf muscle in patients with peripheral vascular disease detected with near-infrared spectrophotometry. J Vasc Surg 37:1017-26
Wolf, Martin; Franceschini, Maria A; Paunescu, Lelia A et al. (2003) Absolute frequency-domain pulse oximetry of the brain: methodology and measurements. Adv Exp Med Biol 530:61-73
Wolf, Ursula; Wolf, Martin; Choi, Jee H et al. (2003) Mapping of hemodynamics on the human calf with near infrared spectroscopy and the influence of the adipose tissue thickness. Adv Exp Med Biol 510:225-30
Wolf, Martin; Wolf, Ursula; Choi, Jee H et al. (2003) Detection of the fast neuronal signal on the motor cortex using functional frequency domain near infrared spectroscopy. Adv Exp Med Biol 510:193-7
Wolf, Martin; Wolf, Ursula; Toronov, Vlad et al. (2002) Different time evolution of oxyhemoglobin and deoxyhemoglobin concentration changes in the visual and motor cortices during functional stimulation: a near-infrared spectroscopy study. Neuroimage 16:704-12
Toronov, V; Webb, A; Choi, J H et al. (2001) Investigation of human brain hemodynamics by simultaneous near-infrared spectroscopy and functional magnetic resonance imaging. Med Phys 28:521-7
Toronov, V; Franceschini, M A; Filiaci, M et al. (2000) Near-infrared study of fluctuations in cerebral hemodynamics during rest and motor stimulation: temporal analysis and spatial mapping. Med Phys 27:801-15

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