Noninvasive detection of functional brain activity with near-infrared diffusing-wave spectroscopy

Abstract

Abstract. We use near-infrared dynamic multiple scattering of light ͓diffusing-wave spectroscopy ͑DWS͔͒ to detect the activation of the somato-motor cortex in 11 right-handed volunteers performing a finger opposition task separately with their right and left hands. Temporal autocorrelation functions g ͑1͒ ͑r , ͒ of the scattered light field are measured during 100-s periods of motor task alternating with 100-s resting baseline periods. From an analysis of the experimental data with an analytical theory for g ͑1͒ ͑r , ͒ from a three-layer geometry with optical and dynamical heterogeneity representing scalp, skull, and cortex, we obtain quantitative estimates of the diffusion coefficient in cortical regions. Consistent with earlier results, the measured cortical diffusion coefficient is found to be increased during the motor task, with a strong contralateral and a weaker ipsilateral increase consistent with the known brain hemispheric asymmetry for right-handed subjects. Our results support the interpretation of the increase of the cortical diffusion coefficient during finger opposition being due to the functional increase in cortical blood flow rate related to vasodilation.

Task complexity relates to activation of cortical motor areas during uni- and bimanual performance: A functional NIRS study

“…Previous studies using fNIRS confirmed results from traditional methods demonstrating functional oxygenation changes in response to simple motor activation tasks (Kleinschmidt et al, 1996, Maki et al, 1996, Franceschini et al, 2003, Koeneke et al, 2004, Li et al, 2005, Sato et al, 2007, Grefkes et al, 2008, Mackert et al, 2008, Shibuya et al, 2008. It is unknown, however, whether fNIRS can also detect changes in response to tasks with increasing complexity.…”

Measurements of human motor and visual activities with diffusing-wave spectroscopy

“…Both contra-and ipsilateral stimulations show enhanced cortical dynamics. We find that the contralateral response (approximately 39%) is stronger than the ipsilateral (20%) [13] …”

Near-infrared diffuse correlation spectroscopy in cancer diagnosis and therapy monitoring

“…Output from the laser can be delivered to the tissue through a multimode optical fiber. Single-mode 23 (or few-mode 20,49 ) fibers should be used to collect photons from a single (or a few) speckle(s) emitted from the tissue surface. Fast photon-counting avalanche photodiodes (APDs) (e.g., SPCM-AQR-12, Perkin Elmer, CA) are generally used as detectors.…”

“…Endogenous tumor-to-normal contrasts available to NIRS include: tissue absorption; scattering; concentrations of oxy-, deoxy-, and total-hemoglobin, water and lipids; and blood oxygen saturation. [7][8][9][10][11][12][13][14][15] A relatively new dynamic NIR technique, namely diffuse correlation spectroscopy (DCS) 16,17 or diffuse wave spectroscopy (DWS), [18][19][20] has been developed which can directly measure the motions of red blood cells in biological tissues while also maintaining all the advantages of NIRS. DCS flow measurements are accomplished by monitoring speckle fluctuations of photons induced by the moving scatterers in tissues.…”

“…Intuitively, the random ballistic flow model might be considered the best model with which to fit DCS data. In practice, however, the diffusion model, i.e., hΔr 2 ðτÞi ¼ 6D B τ, fits the autocorrelation curves rather well over a broad range of tissue types, ranging from rat brain, 43,45 and mouse tumor, 5,35 to piglet brain, 39 adult human skeletal muscle, 23,26 premature brain, 34,38 adult brain, 20,27,33,41 and adult tumors. 21,29,30 Here D B is the effective Brownian diffusion coefficient.…”