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 dataTypeLabel spec for "absolute" moments (TD data) #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.