pub const DR_SHIN_2021: f64 = 137.0;Expand description
χ-separation’s relaxometric constant D_r, in Hz/ppm, as published by Shin et al. 2021.
The forward model is R2' = D_r,pos·|χ+| + D_r,neg·|χ−|, and both published derivations give
the two sources the same relaxivity — neither paper fits them separately. 137 Hz/ppm comes
from linear regression of R2’ against single-orientation QSM in iron-rich deep grey matter
(Shin et al. 2021, NeuroImage 240:118371), which is the reconstruction every analytic method
in this module is given, so it is their default.
DR_KIM_2025_COSMOS is the same quantity re-measured against COSMOS. Which is correct for a
given dataset is an open question in the field; what is not open is that a value measured
against one kind of QSM belongs with that kind of QSM. Changing one method’s default without
the others makes two variants of the same method incomparable on the same data — which is the
state QSM.rs#130 was filed about — so these are shared constants rather than four literals.