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. Author manuscript; available in PMC: 2017 Aug 3.
Published in final edited form as: IEEE Trans Med Imaging. 2014 Jul 8;33(12):2293–2310. doi: 10.1109/TMI.2014.2337057

Algorithm 1.

Automatic trachea extraction algorithm

Require: 𝒯 MinRadius, MaxRadius. {𝒯 = Empirically determined thresh-old on the rate of change of volume per unit step. MinRadius/ MaxRa dius = Empirically determined minimum/maximum expected radius of the trachea region along the axial axis.}
1: for i = 1 to # of slices along axial plane do
2:   circles=HoughTranform(slice(i))
3:   for j = 1 to # of circles do
4:     if radius(circles(j))>MinRadius and radius(circles(j))<MaxRadius then
5:       TracheaRegion = circles(j)
6:       BREAK
7:     end if
8:   end for
9: end for
10: FCMap = DoFC(TracheaRegion)
11: τ=max(FCMap)
12: repeat
13:   TracheaSeg=Threshold(FCMap, τ)
14:   if Volume(TracheaSeg)> 30cm3 or (Volume(TracheaSeg)-Volume(PrevTracheaSeg))> 𝒯 then
15:     return PrevTracheaSeg
16:   else
17:     PrevTracheaSeg = TracheaSeg
18:     τ––
19:   end if
20: until τ > 0