Function r2prime 

pub fn r2prime(r2star: &[f64], r2: &[f64], mask: &[u8]) -> Vec<f64>

Compute R2’ = R2* − R2, clamped at zero, within the mask.

R2* (from a gradient-echo acquisition) captures reversible + irreversible dephasing; R2 (from a spin-echo acquisition) captures only the irreversible part. Their difference R2’ is the reversible dephasing that chi-separation uses to constrain the paramagnetic/diamagnetic split. Noise can make R2* < R2 in some voxels, so negative values are clamped to zero.

Arguments

• r2star - R2* map in Hz [nx*ny*nz]
• r2 - R2 map in Hz [nx*ny*nz] (co-registered to r2star)
• mask - Binary brain mask [nx*ny*nz]

Returns

R2’ map in Hz [nx*ny*nz].