title: Performance assessment of time-domain optical brain imagers, part 1: basic instrumental performance protocol.
abstract: Performance assessment of instruments devised for clinical applications is of key importance for validation and quality assurance. Two new protocols were developed and applied to facilitate the design and optimization of instruments for time-domain optical brain imaging within the European project nEUROPt. Here, we present the "Basic Instrumental Performance" protocol for direct measurement of relevant characteristics. Two tests are discussed in detail. First, the responsivity of the detection system is a measure of the overall efficiency to detect light emerging from tissue. For the related test, dedicated solid slab phantoms were developed and quantitatively spectrally characterized to provide sources of known radiance with nearly Lambertian angular characteristics. The responsivity of four time-domain optical brain imagers was found to be of the order of 0.1 m² sr. The relevance of the responsivity measure is demonstrated by simulations of diffuse reflectance as a function of source-detector separation and optical properties. Second, the temporal instrument response function (IRF) is a critically important factor in determining the performance of time-domain systems. Measurements of the IRF for various instruments were combined with simulations to illustrate the impact of the width and shape of the IRF on contrast for a deep absorption change mimicking brain activation.
authors.affiliation: Physikalisch-Technische Bundesanstalt (PTB), Abbestraße 2-12, 10587 Berlin, Germany.
authors.forename: Heidrun
authors.initials: H
authors.lastname: Wabnitz
authors.affiliation: Physikalisch-Technische Bundesanstalt (PTB), Abbestraße 2-12, 10587 Berlin, Germany.
authors.forename: Dieter Richard
authors.initials: DR
authors.lastname: Taubert
authors.affiliation: Physikalisch-Technische Bundesanstalt (PTB), Abbestraße 2-12, 10587 Berlin, Germany.
authors.forename: Mikhail
authors.initials: M
authors.lastname: Mazurenka
authors.affiliation: Physikalisch-Technische Bundesanstalt (PTB), Abbestraße 2-12, 10587 Berlin, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Steinkellner
authors.affiliation: Physikalisch-Technische Bundesanstalt (PTB), Abbestraße 2-12, 10587 Berlin, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Jelzow
authors.affiliation: Physikalisch-Technische Bundesanstalt (PTB), Abbestraße 2-12, 10587 Berlin, Germany.
authors.forename: Rainer
authors.initials: R
authors.lastname: Macdonald
authors.affiliation: Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, ul. Trojdena 4, 02-109 Warsaw, Poland.
authors.forename: Daniel
authors.initials: D
authors.lastname: Milej
authors.affiliation: Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, ul. Trojdena 4, 02-109 Warsaw, Poland.
authors.forename: Piotr
authors.initials: P
authors.lastname: Sawosz
authors.affiliation: Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, ul. Trojdena 4, 02-109 Warsaw, Poland.
authors.forename: Michał
authors.initials: M
authors.lastname: Kacprzak
authors.affiliation: Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, ul. Trojdena 4, 02-109 Warsaw, Poland.
authors.forename: Adam
authors.initials: A
authors.lastname: Liebert
authors.affiliation: University College London, Department of Medical Physics and Biomedical Engineering, Gower Street, London WC1E 6BT, United Kingdom.
authors.forename: Robert
authors.initials: R
authors.lastname: Cooper
authors.affiliation: University College London, Department of Medical Physics and Biomedical Engineering, Gower Street, London WC1E 6BT, United Kingdom.
authors.forename: Jeremy
authors.initials: J
authors.lastname: Hebden
authors.affiliation: Politecnico di Milano, Dipartimento di Fisica, Piazza Leonardo da Vinci 32, 20133 Milano, ItalyeIstituto di Fotonica e Nanotecnologie, CNR, Piazza Leonardo da Vinci 32, 20133 Milano, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Pifferi
authors.affiliation: Istituto di Fotonica e Nanotecnologie, CNR, Piazza Leonardo da Vinci 32, 20133 Milano, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Farina
authors.affiliation: Istituto Italiano di Tecnologia, Center for Nano Science and Technology @ PoliMi, via Pascoli 70/3, 20133 Milano, Italy.
authors.forename: Ilaria
authors.initials: I
authors.lastname: Bargigia
authors.affiliation: Politecnico di Milano, Dipartimento di Fisica, Piazza Leonardo da Vinci 32, 20133 Milano, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Contini
authors.affiliation: Politecnico di Milano, Dipartimento di Fisica, Piazza Leonardo da Vinci 32, 20133 Milano, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Caffini
authors.affiliation: Politecnico di Milano, Dipartimento di Fisica, Piazza Leonardo da Vinci 32, 20133 Milano, Italy.
authors.forename: Lucia
authors.initials: L
authors.lastname: Zucchelli
authors.affiliation: Istituto di Fotonica e Nanotecnologie, CNR, Piazza Leonardo da Vinci 32, 20133 Milano, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Spinelli
authors.affiliation: Politecnico di Milano, Dipartimento di Fisica, Piazza Leonardo da Vinci 32, 20133 Milano, ItalyeIstituto di Fotonica e Nanotecnologie, CNR, Piazza Leonardo da Vinci 32, 20133 Milano, Italy.
authors.forename: Rinaldo
authors.initials: R
authors.lastname: Cubeddu
authors.affiliation: Politecnico di Milano, Dipartimento di Fisica, Piazza Leonardo da Vinci 32, 20133 Milano, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Torricelli
mesh_terms: D000465:Algorithms; D000818:Animals; D001921:Brain / Q000166:cytology*; D004867:Equipment Design; D019544:Equipment Failure Analysis / Q000379:methods*; D005060:Europe; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D051379:Mice; D008853:Microscopy / Q000295:instrumentation*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D041622:Tomography, Optical / Q000295:instrumentation*