Cerebral hemodynamics evaluation by near-infrared time-resolved spectroscopy: Correlation with simultaneous positron emission tomography measurements

Trends in research related to “Shinrin-yoku” (taking in the forest atmosphere or forest bathing) in Japan

“…The most recent feature of this method that makes it interesting is the possibility of measuring absolute hemoglobin concentration by using the time-resolved spectroscopy (TRS) technique [5,6]. In earlier studies, NIRS could only be applied to measure relative changes in hemoglobin concentration from a certain baseline.…”

Comparison of a layered slab and an atlas head model for Monte Carlo fitting of time-domain near-infrared spectroscopy data of the adult head

“…Various continuous-wave (CW), [1][2][3][4][5] frequency-domain (FD), [6][7][8][9][10][11][12][13][14] and time-domain (TD) [15][16][17][18][19] near-infrared spectroscopy (NIRS) approaches offer the ability to determine the absolute absorption and scattering coefficients of biological tissue. The retrieved optical absorption measured at multiple wavelengths allows quantification of different chromophores' concentrations within the tissue.…”

“…For brain imaging, the robust assessment of cerebral blood volume (CBV) and oxygenation, derived from the measure of hemoglobin concentrations in the brain, is essential for reliable cross-sectional and longitudinal studies of health, disease, and disease progression. 8,9,[19][20][21][22] Continuous-wave methods, such as broadband or hyperspectral approaches originally proposed more than 15 years ago, 2 require spatially 1 or spectrally [2][3][4][5] resolved information in order to disentangle the contributions from tissue absorption and scattering. The frequency-domain multidistance (FDMD) approach based on a homogeneous model 6 has been extensively validated with Monte Carlo simulations, 14 phantoms, 6,12 and animal models.…”

“…21 Most of the in vivo studies mentioned above have relied on a simple head model described as a homogeneous semi-infinite medium. 1,[6][7][8][9][10]16,[19][20][21][22]25,26 This model has shown promising results in piglets and infants, 5,8,9,11,20,22,27 but it is widely recognized that, in the case of the adult head, its oversimplification causes strong contamination of the brain optical properties by those of the extracerebral tissue. For the FDMD approach, Franceschini et al 12 have shown, with simulations and phantom measurements in a slab geometry, that when a superficial layer thicker than ∼1 cm is present, the error on the retrieved absorption of the second layer can exceed 50%.…”

Near-Infrared Spectroscopy

“…Cerebral NIRS devices measure mean tissue oxygen saturation and, as such, reflect hemoglobin saturation in venous, capillary, and arterial blood comprising the sampling volume. For cerebral cortex, average tissue hemoglobin is distributed in a proportion of 70% venous and 30% arterial (McCormick et al, 1991), based on correlations between position emission tomography (PET) and NIRS (Ohmae et al, 2006). However, clinical studies have demonstrated that there can be considerable biological variation in individual cerebral arterial/venous (A/V) ratios between patients, further underscoring that the use of a fixed ratio can produce significant divergence from actual in vivo tissue oxygen saturation, thus confounding even 'absolute' measures of changes in cerebral oxygenation (Watzman et al, 2000).…”