title: Comparison of light intensity on the brain surface due to laser exposure during optical topography and solar irradiation.
abstract: Optical topography (OT), which is based on the near-infrared spectroscopy, is a powerful tool for observing brain activity noninvasively. To estimate the effect of laser exposure on the brain, photon-distribution profiles in bald heads of adults and neonates during the OT were calculated using the photon-diffusion equation. These calculations showed that although the absolute values of the intensity depend on details of the head model, the relative values of OT exposure to sunlight exposure were less sensitive to the model details. As an example, the light intensities on the brain surface during OT obtained by using a commercially available system were about 2% for adults and 3% for neonates of those values obtained under midday sunlight on a sunny day in midsummer. These values were obtained under the reasonable assumptions with a large safety factor.
authors.affiliation: Hitachi, Ltd., Advanced Research Laboratory, Hatoyama, Saitama 350-0395, Japan. masashi.kiguchi.py@hitachi.com
authors.forename: Masashi
authors.initials: M
authors.lastname: Kiguchi
authors.forename: Noriyoshi
authors.initials: N
authors.lastname: Ichikawa
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Atsumori
authors.forename: Fumio
authors.initials: F
authors.lastname: Kawaguchi
authors.forename: Hiroki
authors.initials: H
authors.lastname: Sato
authors.forename: Atsushi
authors.initials: A
authors.lastname: Maki
authors.forename: Hideaki
authors.initials: H
authors.lastname: Koizumi
mesh_terms: D000328:Adult; D001921:Brain / Q000033:anatomy & histology / Q000502:physiology* / Q000528:radiation effects*; D006801:Humans; D007231:Infant, Newborn; D007834:Lasers / Q000009:adverse effects*; D008953:Models, Anatomic; D008959:Models, Neurological; D017785:Photons; D012449:Safety; D013472:Sunlight / Q000009:adverse effects*; D041622:Tomography, Optical / Q000379:methods*