Abstract
The nEUROPt protocol is one of two new protocols developed within the European project nEUROPt to characterize the performances of time-domain systems for optical imaging of the brain. It was applied in joint measurement campaigns to compare the various instruments and to assess the impact of technical improvements. This protocol addresses the characteristic of optical brain imaging to detect, localize, and quantify absorption changes in the brain. It was implemented with two types of inhomogeneous liquid phantoms based on Intralipid and India ink with well-defined optical properties. First, small black inclusions were used to mimic localized changes of the absorption coefficient. The position of the inclusions was varied in depth and lateral direction to investigate contrast and spatial resolution. 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 nEUROPt 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.
Highlights
In biomedical optics, the characterization of instrumentation with the help of appropriate tissue-simulating phantoms[1] plays an important role, ranging from proof-of-principle tests at early stages of the development to quality assurance during routine clinical application.[2]
We introduce the tests of the nEUROPt protocol and present examples of results obtained with different instruments and methods of data analysis
The results presented in this paper refer to this specific kind of measurement, it is worth noting that the nEUROPt protocol is not restricted to time-resolved measurements, but can be applied to continuous wave or frequency-domain instruments
Summary
The characterization of instrumentation with the help of appropriate tissue-simulating phantoms[1] plays an important role, ranging from proof-of-principle tests at early stages of the development to quality assurance during routine clinical application.[2] Numerous performance studies have been carried out by individual research groups; there are only a few multilaboratory efforts to characterize and to compare multiple instruments Such approaches are essential to provide a sound basis for achieving quantitatively comparable results in clinical studies. The nEUROPt protocol was developed to address the characteristic of instruments for optical brain imaging to detect, localize, and quantify changes in the optical properties of the brain and to strive to eliminate the influence of changes in extracerebral tissues on the measurement It is focused on the assessment of sensitivity, spatial resolution, and quantification of an absorption change Δμa in the cerebral cortex as the most relevant physical quantity related to neurological. A number of instruments which were assessed during the joint measurement campaigns within the nEUROPt project are introduced, and typical results are reported, which were obtained with the two types of phantoms and two different approaches for data analysis
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