Near-Infrared Light Propagation in an Adult Head Model. II. Effect of Superficial Tissue Thickness on the Sensitivity of the Near-Infrared Spectroscopy Signal

Department of Electronics and Electrical Engineering, Keio University, Edo, Tōkyō, Japan
Applied Optics (Impact Factor: 1.78). 07/2003; 42(16):2915-22. DOI: 10.1364/AO.42.002915
Source: PubMed


It is important for near-infrared spectroscopy (NIRS) and imaging to estimate the sensitivity of the detected signal to the change in hemoglobin that results from brain activation and the volume of tissue interrogated for a specific source-detector fiber spacing. In this study light propagation in adult head models is predicted by Monte Carlo simulation to investigate the effect of the superficial tissue thickness on the partial optical path length in the brain and on the spatial sensitivity profile. In the case of source-detector spacing of 30 mm, the partial optical path length depends mainly on the depth of the inner skull surface whereas the spatial sensitivity profile is significantly affected by the thickness of the cerebrospinal fluid layer. The mean optical path length that can be measured by time-resolved experiments increases when the skull thickness increases whereas the partial mean optical path length in the brain decreases when the skull thickness increases. These results indicate that it is not appropriate to use the mean optical path length as an alternative to the partial optical path length to compensate the NIRS signal for the difference in sensitivity caused by variation of the superficial tissue thickness.

Full-text preview

Available from:
  • Source
    • "The distance between pairs of emitter and detector probes was set at 3.0 cm, and each measuring area between pairs of emitter and detector probes was defined as a " channel. " The NIRS machine measures the region at 2–3 cm depth from the scalp, which is approximately the surface of the cerebral cortex (Toronov et al., 2001; Okada and Delpy, 2003). Probes were placed on participants' prefrontal and temporal regions. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Patients with affective disorders exhibit changes in regional brain function and show abnormal social adaptation. However, to our knowledge, no near-infrared spectroscopy (NIRS) study has examined the relationship between these two phenomena longitudinally. This study examined the region-specific functional abnormality associated with bipolar disorder (BD) and major depressive disorder (MDD), and the association between particular longitudinal changes in regional activation and social adaptation. We evaluated frontotemporal functioning during a verbal fluency test (VFT) for patients with BD (N=18), those with MDD (N=10), and healthy controls (HCs; N=14) using NIRS. NIRS measurements and the Social Adaptation Self-evaluation Scale (SASS) were administered twice with an interval of approximately 6 months. The BD and MDD groups showed lesser activation than the HCs in the bilateral ventro-lateral prefrontal cortex and the anterior part of the temporal cortex (VLPFC/aTC). Longitudinal changes in SASS scores were positively associated with the extent of change in left VLPFC/aTC activation in the BD group and with right VLPFC/aTC activation in the MDD group. Our small sample size limited statistical power, and the effect of medication and multiple comparisons cannot be excluded, although these effects were considered in the interpretation of the present results. Longitudinal increases of VLPFC/aTC activation were associated with improvement in social adaptation in patients with BD and those with MDD. NIRS measurement could be a useful tool for objective evaluation of changes in social adaptation in BD and MDD. Copyright © 2015 Elsevier B.V. All rights reserved.
    Full-text · Article · Jan 2015 · Journal of Affective Disorders
  • Source
    • "The near-infrared light sources, which are laser-emitting diodes, are placed directly onto a participant's scalp and are sent—in a “banana-shaped” form (Okada and Delpy, 2003)—to the detectors, called optodes. The depth and exactness of measurement depends on the distance between the source and the detector. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Over the last decade, the application of neuroscience to economic research has gained in importance and the number of neuroeconomic studies has grown extensively. The most common method for these investigations is fMRI. However, fMRI has limitations (particularly concerning situational factors) that should be countered with other methods. This review elaborates on the use of functional Near-Infrared Spectroscopy (fNIRS) as a new and promising tool for investigating economic decision making both in field experiments and outside the laboratory. We describe results of studies investigating the reliability of prototype NIRS studies, as well as detailing experiments using conventional and stationary fNIRS devices to analyze this potential. This review article shows that further research using mobile fNIRS for studies on economic decision making outside the laboratory could be a fruitful avenue helping to develop the potential of a new method for field experiments outside the laboratory.
    Full-text · Article · Aug 2014 · Frontiers in Human Neuroscience
  • Source
    • "Considering this aim, we hypothesized that the PFC would be the most suitable measurement location, since it is easier accessible using fNIRS as compared to S2 (due to coverage by hair) or ACC (due to too high cortical depth) (Haeussinger et al., 2011; Huppert et al., 2007; Okada & Delpy, 2003). "
    [Show abstract] [Hide abstract]
    ABSTRACT: The aim was to investigate the effect of mechanical pain stimulation at the lower back on hemodynamic and oxygenation changes in the prefrontal cortex (PFC) assessed by functional near-infrared spectroscopy (fNIRS) and on the partial pressure of end-tidal carbon dioxide ( PetCO 2) measured by capnography. 13 healthy subjects underwent three measurements (M) during pain stimulation using pressure pain threshold (PPT) at three locations, i.e., the processus spinosus at the level of L4 (M1) and the lumbar paravertebral muscles at the level of L1 on the left (M2) and the right (M3) side. Results showed that only in the M2 condition the pain stimulation elicited characteristic patterns consisting of (1) a fNIRS-derived decrease in oxy- and total hemoglobin concentration and tissue oxygen saturation, an increase in deoxy-hemoglobin concentration, (2) a decrease in the PetCO 2 response and (3) a decrease in coherence between fNIRS parameters and PetCO 2 responses in the respiratory frequency band (0.2-0.5 Hz). We discuss the comparison between M2 vs. M1 and M3, suggesting that the non-significant findings in the two latter measurements were most likely subject to effects of the different stimulated tissues, the stimulated locations and the stimulation order. We highlight that PetCO 2 is a crucial parameter for proper interpretation of fNIRS data in experimental protocols involving pain stimulation. Together, our data suggest that the combined fNIRS-capnography approach has potential for further development as pain monitoring method, such as for evaluating clinical pain treatment.
    Full-text · Article · Mar 2014 · Journal of Integrative Neuroscience
Show more