title: A review on continuous wave functional near-infrared spectroscopy and imaging instrumentation and methodology.
abstract: This year marks the 20th anniversary of functional near-infrared spectroscopy and imaging (fNIRS/fNIRI). As the vast majority of commercial instruments developed until now are based on continuous wave technology, the aim of this publication is to review the current state of instrumentation and methodology of continuous wave fNIRI. For this purpose we provide an overview of the commercially available instruments and address instrumental aspects such as light sources, detectors and sensor arrangements. Methodological aspects, algorithms to calculate the concentrations of oxy- and deoxyhemoglobin and approaches for data analysis are also reviewed. From the single-location measurements of the early years, instrumentation has progressed to imaging initially in two dimensions (topography) and then three (tomography). The methods of analysis have also changed tremendously, from the simple modified Beer-Lambert law to sophisticated image reconstruction and data analysis methods used today. Due to these advances, fNIRI has become a modality that is widely used in neuroscience research and several manufacturers provide commercial instrumentation. It seems likely that fNIRI will become a clinical tool in the foreseeable future, which will enable diagnosis in single subjects.
authors.affiliation: Biomedical Optics Research Laboratory, Division of Neonatology, University Hospital Zurich, 8091 Zurich, Switzerland.
authors.forename: Felix
authors.initials: F
authors.lastname: Scholkmann
authors.forename: Stefan
authors.initials: S
authors.lastname: Kleiser
authors.forename: Andreas Jaakko
authors.initials: AJ
authors.lastname: Metz
authors.forename: Raphael
authors.initials: R
authors.lastname: Zimmermann
authors.forename: Juan
authors.initials: J
authors.lastname: Mata Pavia
authors.forename: Ursula
authors.initials: U
authors.lastname: Wolf
authors.forename: Martin
authors.initials: M
authors.lastname: Wolf
mesh_terms: D059907:Functional Neuroimaging / Q000295:instrumentation*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007259:Infrared Rays; D015233:Models, Statistical; D019265:Spectroscopy, Near-Infrared / Q000295:instrumentation*
keywords: Brain activity; Continuous wave; Functional near-infrared imaging (fNIRI); Functional near-infrared spectroscopy (fNIRS); Instrumentation; Near-infrared imaging (NIRI); Near-infrared spectroscopy (NIRS); Review