Journal ArticleDOI
Near-infrared light propagation in an adult head model. I. Modeling of low-level scattering in the cerebrospinal fluid layer
Eiji Okada,David T. Delpy +1 more
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TLDR
Light propagation in an adult head model with discrete scatterers distributed within theCSF layer has been predicted by Monte Carlo simulation to investigate the effect of the small amount of scattering caused by the arachnoid trabeculae in the CSF layer.Abstract:
Adequate modeling of light propagation in a human head is important for quantitative near-infrared spectroscopy and optical imaging. The presence of a nonscattering cerebrospinal fluid (CSF) that surrounds the brain has been previously shown to have a strong effect on light propagation in the head. However, in reality, a small amount of scattering is caused by the arachnoid trabeculae in the CSF layer. In this study, light propagation in an adult head model with discrete scatterers distributed within the CSF layer has been predicted by Monte Carlo simulation to investigate the effect of the small amount of scattering caused by the arachnoid trabeculae in the CSF layer. This low scattering in the CSF layer is found to have little effect on the mean optical path length, a parameter that can be directly measured by a time-resolved experiment. However, the partial optical path length in brain tissue that relates the sensitivity of the detected signal to absorption changes in the brain is strongly affected by the presence of scattering within the CSF layer. The sensitivity of the near-infrared signal to hemoglobin changes induced by brain activation is improved by the effect of a low-scattering CSF layer.read more
Citations
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A brief review on the history of human functional near-infrared spectroscopy (fNIRS) development and fields of application.
TL;DR: A brief historical overview of the events that have shaped the present status of fNIRS is presented, including the introduction of the commercial multi-channel systems, recent commercial wireless instrumentation and more advanced prototypes.
Journal ArticleDOI
Recent advances in diffuse optical imaging.
TL;DR: The current state-of-the-art of diffuse optical imaging is reviewed, which is an emerging technique for functional imaging of biological tissue and recent work on in vivo applications including imaging the breast and brain is reviewed.
Journal ArticleDOI
HomER: a review of time-series analysis methods for near-infrared spectroscopy of the brain.
TL;DR: The practical implementation of various signal processing techniques for removing physiological, instrumental, and motion-artifact noise from optical data are described within the context of the MATLAB-based graphical user interface program, HomER, which is developed and distributed to facilitate the processing of optical functional brain data.
Journal ArticleDOI
Diffuse optics for tissue monitoring and tomography
TL;DR: The theoretical basis for near-infrared or diffuse optical spectroscopy (NIRS or DOS) is developed, and the basic elements of diffuse optical tomography (DOT) are outlined.
Journal ArticleDOI
A quantitative comparison of NIRS and fMRI across multiple cognitive tasks.
TL;DR: NIRS can be an appropriate substitute for fMRI for studying brain activity related to cognitive tasks, but care should be taken to ensure that the spatial resolution is adequate for answering the question of interest and the design accounts for weaker SNR, especially in brain regions more distal from the scalp.
References
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Journal ArticleDOI
Estimation of optical pathlength through tissue from direct time of flight measurement
TL;DR: Monte Carlo modelling of light pulses in tissue has shown that the mean value of the time dispersed light pulse correlates with the pathlength used in quantitative spectroscopic calculations, and this result has been verified in a phantom material.
Journal ArticleDOI
Near-infrared optical properties of ex vivo human skin and subcutaneous tissues measured using the Monte Carlo inversion technique
TL;DR: The absorption and transport scattering coefficients of c Caucasian and negroid dermis, subdermal fat and muscle have been measured for all wavelengths between 620 and 1000 nm and the optical properties of caucasian dermis were found to be approximately twice those of the underlying fat layer.
Journal ArticleDOI
A Monte Carlo model for the absorption and flux distributions of light in tissue
Brian C. Wilson,Gerhard Adam +1 more
TL;DR: A Monte Carlo computer model has been used to predict the distribution of absorbed dose in homogeneous tissues of different absorption/scattering ratios, for illumination both by external light beams and via implanted optical fibers.
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Performance comparison of several published tissue near-infrared spectroscopy algorithms
TL;DR: Multiwavelength near-infrared attenuation spectra on human forearm muscle, the adult rat head, and newborn piglet head are collected to compare the changes in chromophore concentration derived from these data using published algorithms from four groups, finding differences between the results from the algorithms on each data set.
Journal ArticleDOI
Theoretical and experimental investigation of near-infrared light propagation in a model of the adult head
TL;DR: Near-infrared light propagation in various models of the adult head is analyzed by both time-of-flight measurements and mathematical prediction, and both the optical path length and the spatial sensitivity profile of the models with aCSF layer are quite different from those without the CSF layer.