Algorithm 2: 2D-to-3D framework for edge detection
Input: Projections with detected edges $\left\{edge\left(V,\theta \right)|\theta \in \Theta \right\}$, threshold T
Initialization: $B=zeros\left(\left|\Theta \right|,L,W,H\right)$
Procedure Backward projection
for each $\theta \in \Theta$ do
$B\left(\theta \right)=BP\left(edge\left(V,\theta \right)\right)$
end
Refine B for m iterations;
return tomogram with detected edges $E_{3D}=1\left(\left[{\sum }_{\theta \in \Theta }B\left(\theta \right)\right]>T\right)$