ConcentrationsToOpticalDensity¶
Infer NIRS (delta-)optical density from chormophore (HbO, HbR) concentration changes.
This node implements the reverse process of the EstimateConcentrations node, and is therefore less frequently used. One use case is to work backwards from concentration data to optical density at different wavelengths in order to then image the optical density using tomographic imaging methods such as HD-DOT. This node uses the modified Beer-Lambert Law (MBLL) which relies on the fact that the different chromophores have different light absorption spectra. The calculation depends on a number of parameters, notably the differential pathlength factor and the partial volume correction, which can be looked up from textbooks. Both of these are configurable as parameters to this node. Incorrect assumptions will mostly result in incorrect scaling of the estimated optical density changes. Version 0.5.0
Ports/Properties¶
data¶
Data to process.
dpf¶
Differential Pathlength Factor (DPF). This is a factor, often between 4-9, which relates optical pathlength through some tissue (e.g., bone, skin, brain) to the distance between optodes.
pvc¶
Partial Volume Correction (PVC). A correction term that quantifies what fraction of the optical path is subject to concentration changes -- for fNIRS this is typically on the other of 40-90. The DPF is divided by the PVC to yield the Partial Pathlength Factor (PPF), which is often loosely around 0.1.
wavelengths¶
List of NIRS wavelengths at which to estimate concentrations. Given in nanometers.
coords_unit¶
Unit of the channel positions. Typically this would be m for meters, but some data may have it wrong.
set_breakpoint¶
Set a breakpoint on this node. If this is enabled, your debugger (if one is attached) will trigger a breakpoint.
metadata¶
User-definable meta-data associated with the node. Usually reserved for technical purposes.