Phantom for standardization in functional near-infrared spectroscopy, part 1: implementation and usage

Significance: The use of functional near-infrared spectroscopy (fNIRS) is expanding, including examples of devices approved for routine clinical use for specific indications. Instrument standardization is a critical element to facilitate clinical adoption. Currently, there is no published description of a phantom that meets the requirements of IEC 80601-2-71, the IEC/ISO standard for fNIRS equipment. Aim: We report an example of the implementation of the fNIRS standard phantom described in IEC 80601-2-71. We further report results from measurement campaigns with this phantom prototype in Japan and Europe. Approach: A phantom prototype was built and circulated among multiple academic and commercial fNIRS groups with diverse instrumentation. The phantom prototype was characterized by wavelength-dependent measurements of its diffuse optical features and utilized in a test for fNIRS signal magnitude as described in IEC 80601-2-71. Results: The optical loss of this phantom prototype as well as its change by varying an internal aperture were found to be ∼40dB and between 3.5 and 3.6 dB, respectively. The test for fNIRS signal magnitude based on this phantom was successfully carried out on various commercial fNIRS devices. Conclusions: The characteristics of the phantom prototype agreed with the specifications in the standard. The phantom prototype proved suitable for the related test in IEC 80601-2-71.