{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,29]],"date-time":"2026-04-29T20:35:29Z","timestamp":1777494929010,"version":"3.51.4"},"reference-count":56,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2012,12,24]],"date-time":"2012-12-24T00:00:00Z","timestamp":1356307200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/3.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Detection limits of the changes in absorption and reduced scattering coefficients were investigated using a frequency-domain near-infrared system in a realistic head phantom. The results were quantified in terms of the maximum detectable depth for different activation volumes in the range of 0.8\u201320 microliters. The non-linear relation between the maximum detectable depth and the magnitude of changes in the absorption coefficient conform well with the Born approximation to the diffusion equation. The minimal detectable changes in the reduced scattering coefficient measured in terms of the phase signal were found to be approximately twice as large as that of the absorption coefficient using the AC signal for the same volume and at the same depth. The phase delay, which can be used to quantify the fast neuronal optical response in the human brain, showed a linear dependence on the reciprocal of the reduced scattering coefficient, as predicted by the Rytov approximation.<\/jats:p>","DOI":"10.3390\/s130100152","type":"journal-article","created":{"date-parts":[[2012,12,24]],"date-time":"2012-12-24T07:41:06Z","timestamp":1356334866000},"page":"152-164","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["Detectability of Absorption and Reduced Scattering Coefficients in Frequency-Domain Measurements Using a Realistic Head Phantom"],"prefix":"10.3390","volume":"13","author":[{"given":"Xiaofeng","family":"Zhang","sequence":"first","affiliation":[{"name":"Department of Radiology, Duke University Medical Center, DUMC 3808, Durham, NC 27710, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Andrew","family":"Webb","sequence":"additional","affiliation":[{"name":"Department of Radiology, Leiden University Medical Center, Albinusdreef 2, 2333 ZA Leiden, The Netherlands"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2012,12,24]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"707","DOI":"10.1098\/rstb.1997.0053","article-title":"Optical investigations of physiology: A study of intrinsic and extrinsic biomedical contrast","volume":"352","author":"Chance","year":"1997","journal-title":"Philos. Trans. Roy. Soc. Lond B Biol. Sci."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1097\/01.WCB.0000043472.45775.29","article-title":"Beyond the visible\u2014Imaging the human brain with light","volume":"23","author":"Obrig","year":"2003","journal-title":"J. Cereb Blood Flow Metab"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"1521","DOI":"10.1016\/S1053-8119(03)00152-6","article-title":"The roles of changes in deoxyhemoglobin concentration and regional cerebral blood volume in the fMRI BOLD signal","volume":"19","author":"Toronov","year":"2003","journal-title":"Neuroimage"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"11008","DOI":"10.1117\/1.1854673","article-title":"Measurement of brain activity by near-infrared light","volume":"10","author":"Gratton","year":"2005","journal-title":"J. Biomed. Opt."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"054007","DOI":"10.1117\/1.2363365","article-title":"Diffuse optical imaging of the whole head","volume":"11","author":"Franceschini","year":"2006","journal-title":"J. Biomed. Opt."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"505","DOI":"10.1016\/j.neuroimage.2006.07.006","article-title":"Spatially weighted BOLD signal for comparison of functional magnetic resonance imaging and near-infrared imaging of the brain","volume":"33","author":"Sassaroli","year":"2006","journal-title":"Neuroimage"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"2919","DOI":"10.1158\/0008-5472.CAN-08-3370","article-title":"Quantitative optical spectroscopy: A robust tool for direct measurement of breast cancer vascular oxygenation and total hemoglobin content in vivo","volume":"69","author":"Brown","year":"2009","journal-title":"Cancer Res."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"12630","DOI":"10.1364\/OE.18.012630","article-title":"A low-cost, portable, and quantitative spectral imaging system for application to biological tissues","volume":"18","author":"Fu","year":"2010","journal-title":"Opt. Express"},{"key":"ref_9","first-page":"4558","article-title":"Methods in diffuse optical imaging","volume":"369","author":"Arridge","year":"2011","journal-title":"Philos. Trans. A Math. Phys. Eng. Sci."},{"key":"ref_10","first-page":"075010","article-title":"Noninvasive optical quantification of absolute blood flow, blood oxygenation, and oxygen consumption rate in exercising skeletal muscle","volume":"17","author":"Gurley","year":"2012","journal-title":"J. Biomed. Opt."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"817","DOI":"10.1097\/00004647-199609000-00006","article-title":"Simultaneous recording of cerebral blood oxygenation changes during human brain activation by magnetic resonance imaging and near-infrared spectroscopy","volume":"16","author":"Kleinschmidt","year":"1996","journal-title":"J. Cereb. Blood Flow Metab."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"14","DOI":"10.1002\/hbm.10026","article-title":"Simultaneous measurements of cerebral oxygenation changes during brain activation by near-infrared spectroscopy and functional magnetic resonance imaging in healthy young and elderly subjects","volume":"16","author":"Colier","year":"2002","journal-title":"Human Brain Map."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"719","DOI":"10.1006\/nimg.2002.1227","article-title":"A quantitative comparison of simultaneous BOLD fMRI and NIRS recordings during functional brain activation","volume":"17","author":"Strangman","year":"2002","journal-title":"Neuroimage"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"1275","DOI":"10.1016\/j.neuroimage.2003.12.003","article-title":"Multimodal assessment of cortical activation during apple peeling by NIRS and fMRI","volume":"21","author":"Okamoto","year":"2004","journal-title":"Neuroimage"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"351","DOI":"10.1177\/153303460600500407","article-title":"Combined diffuse optical tomography (DOT) and MRI system for cancer imaging in small animals","volume":"5","author":"Gulsen","year":"2006","journal-title":"Technol. Cancer Res. Treat."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"349","DOI":"10.1016\/j.neuroimage.2005.09.048","article-title":"Investigating the post-stimulus undershoot of the BOLD signal\u2014A simultaneous fMRI and fNIRS study","volume":"30","author":"Schroeter","year":"2006","journal-title":"Neuroimage"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"1136","DOI":"10.1016\/j.neuroimage.2006.08.048","article-title":"A spatial and temporal comparison of hemodynamic signals measured using optical and functional magnetic resonance imaging during activation in the human primary visual cortex","volume":"34","author":"Toronov","year":"2007","journal-title":"Neuroimage"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"561","DOI":"10.1111\/1469-8986.00058","article-title":"The event-related optical signal (EROS) in visual cortex: Replicability, consistency, localization, and resolution","volume":"40","author":"Gratton","year":"2003","journal-title":"Psychophysiology"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"061702","DOI":"10.1117\/1.3505007","article-title":"\u201cSeeing\u201d electroencephalogram through the skull: Imaging prefrontal cortex with fast optical signal","volume":"15","author":"Medvedev","year":"2010","journal-title":"J. Biomed. Opt."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"105","DOI":"10.1016\/S0304-3940(00)01395-1","article-title":"Somatosensory evoked fast optical intensity changes detected non-invasively in the adult human head","volume":"291","author":"Steinbrink","year":"2000","journal-title":"Neurosci. Lett."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"1868","DOI":"10.1006\/nimg.2002.1261","article-title":"Functional frequency-domain near-infrared spectroscopy detects fast neuronal signal in the motor cortex","volume":"17","author":"Wolf","year":"2002","journal-title":"Neuroimage"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"044014","DOI":"10.1117\/1.2234319","article-title":"Fast optical signals in the peripheral nervous system","volume":"11","author":"Tong","year":"2006","journal-title":"J. Biomed. Opt."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"314","DOI":"10.1016\/j.neuroimage.2005.07.013","article-title":"Event-related optical imaging reveals the temporal dynamics of right temporal and frontal cortex activation in pre-attentive change detection","volume":"29","author":"Tse","year":"2006","journal-title":"Neuroimage"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"1707","DOI":"10.1152\/jn.1997.78.3.1707","article-title":"Light scattering changes follow evoked potentials from hippocampal Schaeffer collateral stimulation","volume":"78","author":"Rector","year":"1997","journal-title":"J. Neurophysiol."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"619","DOI":"10.1016\/j.neuroimage.2005.02.030","article-title":"Spatio-temporal mapping of rat whisker barrels with fast scattered light signals","volume":"26","author":"Rector","year":"2005","journal-title":"Neuroimage"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"66","DOI":"10.1016\/j.neuroimage.2005.11.030","article-title":"Blood volume and hemoglobin oxygenation response following electrical stimulation of human cortex","volume":"31","author":"Suh","year":"2006","journal-title":"Neuroimage"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"996","DOI":"10.1016\/j.neuroimage.2005.03.006","article-title":"The fast optical signal\u2014Robust or elusive when non-invasively measured in the human adult?","volume":"26","author":"Steinbrink","year":"2005","journal-title":"Neuroimage"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"33001","DOI":"10.1117\/1.2209908","article-title":"Image analysis methods for diffuse optical tomography","volume":"11","author":"Pogue","year":"2006","journal-title":"J. Biomed. Opt."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"3109","DOI":"10.1364\/AO.42.003109","article-title":"Optical tomography of a realistic neonatal head phantom","volume":"42","author":"Gibson","year":"2003","journal-title":"Appl. Opt."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"051801","DOI":"10.1117\/1.2085172","article-title":"Two-dimensional phased arrays of sources and detectors for depth discrimination in diffuse optical imaging","volume":"10","author":"Liu","year":"2005","journal-title":"J. Biomed. Opt."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"064036","DOI":"10.1117\/1.2139971","article-title":"Tissue phantom for optical diagnostics based on a suspension of microspheres with a fractal size distribution","volume":"10","author":"Passos","year":"2005","journal-title":"J. Biomed. Opt."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"041102","DOI":"10.1117\/1.2335429","article-title":"Review of tissue simulating phantoms for optical spectroscopy, imaging and dosimetry","volume":"11","author":"Pogue","year":"2006","journal-title":"J. Biomed. Opt."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"433","DOI":"10.1007\/s00221-005-0242-4","article-title":"Brain tissue phantoms for optical near infrared imaging","volume":"170","author":"Rao","year":"2006","journal-title":"Exper. Brain Res. Exper. Hirnforsch. Exper. Cereb."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"5581","DOI":"10.1088\/0031-9155\/51\/21\/013","article-title":"A soft deformable tissue-equivalent phantom for diffuse optical tomography","volume":"51","author":"Hebden","year":"2006","journal-title":"Phys. Med. Biol."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"3925","DOI":"10.1364\/AO.44.003925","article-title":"Linear and nonlinear reconstruction for optical tomography of phantoms with nonscattering regions","volume":"44","author":"Gibson","year":"2005","journal-title":"Appl. Opt."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"779","DOI":"10.1364\/AO.37.000779","article-title":"Noninvasive determination of the optical properties of two-layered turbid media","volume":"37","author":"Kienle","year":"1998","journal-title":"Appl. Opt."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"5204","DOI":"10.1364\/AO.33.005204","article-title":"Quantitative determination of the absorption spectra of chromophores in strongly scattering media: A light-emitting-diode based technique","volume":"33","author":"Fantini","year":"1994","journal-title":"Appl. Opt."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"161","DOI":"10.1002\/mrm.1910300204","article-title":"Processing strategies for time-course data sets in functional MRI of the human brain","volume":"30","author":"Bandettini","year":"1993","journal-title":"Magn. Resona. Med."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"49","DOI":"10.1364\/OE.6.000049","article-title":"On-line optical imaging of the human brain with 160-ms temporal resolution","volume":"6","author":"Franceschini","year":"2000","journal-title":"Opt. Express"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"801","DOI":"10.1118\/1.598943","article-title":"Near-infrared study of fluctuations in cerebral hemodynamics during rest and motor stimulation: temporal analysis and spatial mapping","volume":"27","author":"Toronov","year":"2000","journal-title":"Med. Phys."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"93","DOI":"10.1117\/1.429973","article-title":"Activation of the visual cortex imaged by 24-channel near-infrared spectroscopy","volume":"5","author":"Takahashi","year":"2000","journal-title":"J. Biomed. Opt."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"791","DOI":"10.1002\/mrm.1107","article-title":"Relative changes of cerebral arterial and venous blood volumes during increased cerebral blood flow: Implications for BOLD fMRI","volume":"45","author":"Lee","year":"2001","journal-title":"Magn. Resona. Med."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"521","DOI":"10.1111\/1469-8986.00054","article-title":"Fast cerebral functional signal in the 100-ms range detected in the visual cortex by frequency-domain near-infrared spectrophotometry","volume":"40","author":"Wolf","year":"2003","journal-title":"Psychophysiology"},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"S220","DOI":"10.1016\/j.neuroimage.2004.07.013","article-title":"Modeling the hemodynamic response to brain activation","volume":"23","author":"Buxton","year":"2004","journal-title":"Neuroimage"},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"701","DOI":"10.1016\/j.neuroimage.2004.12.032","article-title":"Simultaneous recording of task-induced changes in blood oxygenation, volume, and flow using diffuse optical imaging and arterial spin-labeling MRI","volume":"25","author":"Hoge","year":"2005","journal-title":"Neuroimage"},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"11013","DOI":"10.1117\/1.1852553","article-title":"Improved sensitivity to cerebral hemodynamics during brain activation with a time-gated optical system: analytical model and experimental validation","volume":"10","author":"Selb","year":"2005","journal-title":"J. Biomed. Opt."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"274","DOI":"10.1016\/j.jneumeth.2006.04.013","article-title":"Frequency domain near-infrared spectroscopy technique in the assessment of brain oxygenation: A validation study in live subjects and cadavers","volume":"157","author":"Gatto","year":"2006","journal-title":"J. Neurosci. Methods"},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"2753","DOI":"10.1088\/0031-9155\/49\/12\/019","article-title":"Theoretical evaluation of accuracy in position and size of brain activity obtained by near-infrared topography","volume":"49","author":"Kawaguchi","year":"2004","journal-title":"Phys. Med. Biol."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"1161","DOI":"10.1117\/1.1803545","article-title":"Improved quantification of small objects in near-infrared diffuse optical tomography","volume":"9","author":"Srinivasan","year":"2004","journal-title":"J. Biomed. Opt."},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"N155","DOI":"10.1088\/0031-9155\/49\/12\/N01","article-title":"Diffuse optical tomography with physiological and spatial a priori constraints","volume":"49","author":"Intes","year":"2004","journal-title":"Phys. Med. Biol."},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"4625","DOI":"10.1088\/0031-9155\/50\/19\/014","article-title":"A haemodynamic response function model in spatio-temporal diffuse optical tomography","volume":"50","author":"Zhang","year":"2005","journal-title":"Phys. Med. Biol."},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"2082","DOI":"10.1364\/AO.44.002082","article-title":"Diffuse optical tomography with spectral constraints and wavelength optimization","volume":"44","author":"Corlu","year":"2005","journal-title":"Appl. Opt."},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"1531","DOI":"10.1088\/0031-9155\/37\/7\/005","article-title":"The theoretical basis for the determination of optical pathlengths in tissue: Temporal and frequency analysis","volume":"37","author":"Arridge","year":"1992","journal-title":"Phys. Med. Biol."},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"114301","DOI":"10.1063\/1.2364138","article-title":"An integrated measurement system for simultaneous functional magnetic resonance imaging and diffuse optical tomography in human brain mapping","volume":"77","author":"Zhang","year":"2006","journal-title":"Rev. Sci. Instrum."},{"key":"ref_55","doi-asserted-by":"crossref","first-page":"2128","DOI":"10.1364\/JOSAB.11.002128","article-title":"Semi-infinite-geometry boundary problem for light migration in highly scattering media: A frequency-domain study in the diffusion approximation","volume":"11","author":"Fantini","year":"1994","journal-title":"J. Opt. Soc. Am. B"},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"882","DOI":"10.1364\/OL.23.000882","article-title":"Nonuniqueness in diffusion-based optical tomography","volume":"23","author":"Arridge","year":"1998","journal-title":"Opt. Lett."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/13\/1\/152\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T21:54:27Z","timestamp":1760219667000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/13\/1\/152"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2012,12,24]]},"references-count":56,"journal-issue":{"issue":"1","published-online":{"date-parts":[[2013,1]]}},"alternative-id":["s130100152"],"URL":"https:\/\/doi.org\/10.3390\/s130100152","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2012,12,24]]}}}