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Segmentation of 3D Tubular Tree Structures in Medical Images ...

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62 Chapter 3. Group<strong>in</strong>g and L<strong>in</strong>kage <strong>in</strong>to Connected Networks<br />

Quantitative Results: The quantitative comparison <strong>of</strong> the centerl<strong>in</strong>e accuracy is based<br />

on the average centerl<strong>in</strong>e distances between the different methods. To make the CSs<br />

comparable, the skeletons obta<strong>in</strong>ed with the methods <strong>of</strong> Bouix and Palagyi were pruned<br />

and only branches detected by all methods (the segmentation methods and the TDF<br />

methods) were considered. Tables 3.1 and 3.2 summarize the average centerl<strong>in</strong>e distances<br />

between the different methods for the two datasets. All the methods are quite comparable<br />

(except the results achieved with the comb<strong>in</strong>ed approach <strong>of</strong> Krissian and Bullitt). Our two<br />

group<strong>in</strong>g/l<strong>in</strong>kage methods utilized the same tubular structures, thus only show<strong>in</strong>g small<br />

differences. But also notable is the small difference between our GVF-based method and<br />

Hassouna’s approach on the airway tree, but this may be expla<strong>in</strong>ed s<strong>in</strong>ce this method is<br />

also based on the GVF. As these results show, the achieved centerl<strong>in</strong>e accuracy <strong>of</strong> our GVFbased<br />

tube detection and group<strong>in</strong>g/l<strong>in</strong>kage method is comparable to the variation found<br />

between different skeletonization approaches. Note that all the skeletonization approaches<br />

use the same b<strong>in</strong>ary segmentations while our method does not know this gold standard.<br />

This shows that our approach is able to extract CSs <strong>of</strong> comparable quality directly from<br />

the gray value images.<br />

Table 3.1: Average centerl<strong>in</strong>e distances <strong>in</strong> voxels (aorta).<br />

M1 M2 M3 M4 M5 M6<br />

GVF TDF + GVF l<strong>in</strong>kage M1 – 0.01 0.66 0.62 0.79 1.49<br />

GVF TDF + structure l<strong>in</strong>kage M2 0.03 – 0.69 0.58 0.81 1.38<br />

Hassouna M3 0.63 0.68 – 0.60 0.72 1.14<br />

Bouix M4 0.59 0.58 0.63 – 0.78 1.58<br />

Palagyi M5 0.78 0.81 0.75 0.80 – 1.53<br />

Krissian + Bullitt M6 1.61 1.45 1.17 1.70 1.60 –<br />

Table 3.2: Average centerl<strong>in</strong>e distances <strong>in</strong> voxels (bronchial tree).<br />

M1 M2 M3 M4 M5 M6<br />

GVF TDF + GVF l<strong>in</strong>kage M1 – 0.08 0.24 0.41 0.40 0.58<br />

GVF TDF + structure l<strong>in</strong>kage M2 0.04 – 0.24 0.44 0.40 0.66<br />

Hassouna M3 0.22 0.23 – 0.37 0.34 0.72<br />

Bouix M4 0.47 0.42 0.36 – 0.45 0.67<br />

Palagyi M5 0.44 0.47 0.33 0.44 – 0.70<br />

Krissian M6 0.59 0.67 0.53 0.57 0.66 –

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