Converting NIRO-200NX data to snirf

[JonteP]

I posed this question at Neurostars (https://neurostars.org/t/convert-to-snirf-format/24855) and was recommended to post an issue here as well. I copy my question here:

am looking into BIDS formatting our fNIRS data. We have used a more clinically oriented device, NIRO-200NX, which provides the following measurements: Tissue oxygenation index, TOI (%) Normalized tissue hemoglobin index, nTHI (absolute value in arbitrary unit) Oxygenated hemoglobin change, ∆O2Hb (μmol/L) Deoxygenated hemoglobin change, ∆HHb (μmol/L) Total hemoglobin change, ∆cHb (μmol/L)

Looking at the format spec of Snirf, I cannot find any correspondence among dataTypeLabels to the first two (TOI and nTHI). Am I missing something or are they simply outside of the scope of the format?

A related question: We recorded the 3d coordinates of the optode placements in subject space using neuronavigation equipment + a t1w image. I define this space as 'individual' now, but how do I link this to the t1 image used?

[samuelpowell]

In a meeting of 17/04/2024

• it was agreed that StO2 should be added to list of valid entries in the dataTypeLabel field
• it is acceptable and intended that changes in HbO, HbR, and HbT be stored using the associated dataTypeLabel despite the lack of the delta annotation (see #126 for a proposal about absolute values)

• more obscure values such as nTHI might best be stored in an auxiliary field, @Horschig to provide further details.

  The latter question is outside of the scope of the SNIRF specification.