Start:4 start iterations
Start:5 For each projection angle
Start:6 For each ray

Compute the numerical projection (Equation 21)

Close:6
Start:7 For each ray

Calculate the correction as:

Calculate the average of correction as:

Close:7
Start:8 For each ray
Start: 9 For each cell
If is non –zero then

where is a relaxation factor.
Close:9
Close:8
Close:5
Check for convergence as:
If

(where is the prescribed convergence, say
STOP:
Else: continue
close:4