Algorithm

Let θ*=[θ1*,θ2*,θ3*] be the estimated parameter vector at β=β*.

Calculate K1, k2+k3, k4 and Vb from Eqs [A6]–[A9].

If K1≤0 or k2+k3≤0:

Discard voxel.

Else if Vb<0:

Set θ3=Vb=0 in Eq [A2] and re-estimate θ*=[θ1*,θ2*].

Calculate K1, k2+k3, k4 from Eqs [A6]–[A8].

If k4<0:

Set θ2=θ3=0 in Eq [A2] and re-estimate θ*=[θ1*].

Set k4=0 and calculate K1, k2+k3 from Eqs [A6]–[A7].

If K1≤0 or k2+k3≤0 discard voxel; otherwise retain voxel.

Else if k4<0:

Set θ2=0 in Eq [A2] and re-estimate θ*=[θ1*,θ3*].

Set k4=0 and calculate K1, k2+k3, Vb from Eqs [A6], [A7], [A9].

If Vb<0:

Set θ2=θ3=0 in Eq [A2] and re-estimate θ*=[θ1*].

Set Vb=0 and calculate K1, k2+k3 from Eqs [A6]–[A7].

If K1≤0 or k2+k3≤0 discard voxel; otherwise retain voxel.

Else

Retain voxel.

End