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Developing validating performance assessment tasks concepts geometrical optics

Common protocols were developed to provide guidelines for the assessment and comparison of instruments in coordinated measurement campaigns, for the estimation of the impact of technological and methodological advances on their performances, and for supporting quality assurance by routine tests, in particular, during clinical studies.

Thus, the performance assessment is directed toward the final results of the measurement related to the clinical application, mimicked by appropriate phantom measurements.

The results of these measurements are influenced by instrumental features and settings as well as by the analysis procedure.

Such approaches are essential to provide a sound basis for achieving quantitatively comparable results in clinical studies.

They require the development of standardized guidelines to perform the same measurements on phantoms with the same properties in different laboratories.

Second, two-layered liquid phantoms with variable absorption coefficients were employed to study the quantification of layer-wide changes and, in particular, to determine depth selectivity, i.e., the ratio of sensitivities for deep and superficial absorption changes.

We introduce the tests of the n EUROPt protocol and present examples of results obtained with different instruments and methods of data analysis.This protocol could be a useful step toward performance tests for future standards in diffuse optical imaging.Wabnitz, Jelzow, Mazurenka, Steinkellner, Macdonald, Milej, Żołek, Kacprzak, Sawosz, Maniewski, Liebert, Magazov, Hebden, Martelli, Di Ninni, Zaccanti, Torricelli, Contini, Re, Zucchelli, Spinelli, Cubeddu, and Pifferi: Performance assessment of time-domain optical brain imagers, part 2: n EUROPt protocol Numerous performance studies have been carried out by individual research groups; however, there are only a few multilaboratory efforts to characterize and to compare multiple instruments.To model localized absorption changes related to a localized brain activation, solid black inclusions were used.This choice was supported by the derivation of an equivalence relation between a realistic absorption change in a finite volume and the perturbation produced by a small black object.Heidrun Wabnitz; Alexander Jelzow; Mikhail Mazurenka; Oliver Steinkellner; Rainer Macdonald; Daniel Milej; Norbert Żołek; Michał Kacprzak; Piotr Sawosz; Roman Maniewski; Adam Liebert; Salavat Magazov; Jeremy C.Hebden; Fabrizio Martelli; Paola Di Ninni; Giovanni Zaccanti; Alessandro Torricelli; Davide Contini; Rebecca Re; Lucia M.The protocol consists of a total of six tests which address three main features that are of direct relevance for the performance of optical brain imaging in clinical applications, namely (1) sensitivity, (2) spatial resolution, and (3) quantitation of absorption changes in the brain. In particular, the sensitivity is described by contrast and contrast-to-noise ratio, the spatial resolution by depth sensitivity and lateral resolution, and the quantitation by accuracy and linearity.The n EUROPt protocol was developed in the context of time-domain brain imaging, which relies on the measurement of time-resolved diffuse reflectance, most commonly by time-correlated single photon counting (TCSPC).We defined and applied tests and measurands, such as contrast, contrast-to-noise ratio, spatial resolution, and depth selectivity.The explicit specification of the operational parameters for the implementation of the protocol was another prerequisite to ensure the comparability of results across various laboratories. First the measurands and individual tests are introduced, followed by the description of the liquid phantoms and the measurement conditions relevant for the implementation of the protocol.

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