Continuous spectrum near-infrared spectroscopy approach in functional activation studies in the human adult

摘要

Abstract: In contrast to the conventional approaches using singlewavelengths the whole spectrum approach monitorsoptical changes across a continuous spectrum in thenear infrared. By fitting the spectra of oxygenated anddeoxygenated haemoglobin into the spectrum the changesin the concentration of these parameters can becalculated in an extension of the known near-infraredspectroscopy (NIRS) algorithms. By twicedifferentiating both chromophore and recordedattenuation spectra the offset and wavelength dependentinfluence of scattering (assumed to be linear) cancelsout. Since oxygenated haemoglobin (oxy-Hb) andcytochrome oxidase (Cyt-02) spectra have essentiallyfeatureless second differentials a fitting procedureusing the second differentials of water anddeoxygenated haemoglobin (deoxy-Hb) result in a ratioof the compounds' contribution to the spectrum. Thiscorresponds to the ratio of their concentrations in thetissue. Assuming a known and constant concentration ofwater (deoxy-Hb) can be quantified. On the basis ofthis theory previously described the paper shows thatthe response to a motor stimulation paradigm isconsistent with data reported with a conventional NIRSmonitor (n equals 8ss). Data suggest that signal tonoise is greater for the new approach. A concentrationof 10.5 muM is found for the adult human brain (nequals 6ss). Exploring the temporal resolution of themethod the contribution of the different compounds tothe optical changes evoked by the heart beat areexamined (n equals 5ss). !17