Function tfi 

pub fn tfi(
    total_field: &[f64],
    mask: &[u8],
    magnitude: EchoMagnitudes<'_>,
    grid: &Grid,
    bdir: (f64, f64, f64),
    params: &TfiParams,
    progress: impl FnMut(usize, usize),
) -> Vec<f64>

Preconditioned total field inversion (2024 MEDI_L1.m with a preconditioner)

Arguments

• total_field - Total field in ppm, before background removal (nx * ny * nz)
• mask - Binary mask (nx * ny * nz), 1 = brain: P = 1 and the data are fitted here
• magnitude - Echo magnitudes, or a combined magnitude (see module docs)
• grid - Volume grid (dimensions and voxel sizes)
• bdir - B0 field direction
• params - TFI parameters, including field strength and echo spacing
• progress - Progress callback (current_step, total_steps) over CG iterations

Returns

Susceptibility P·y in ppm, zero outside the mask