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

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34 Chapter 2. Extraction <strong>of</strong> <strong>Tubular</strong> <strong>Structures</strong><br />

represents a slightly curved surface path.<br />

(a) 3d volume render<strong>in</strong>g.<br />

(b) 2d cross sections <strong>of</strong> 3d objects.<br />

1000<br />

100<br />

500<br />

0<br />

0<br />

0 200 400 600 800 1000 1200 1400 1600 18000 200 400 600 800 1000 1200 1400 1600 1800<br />

(c) 1d cross sections <strong>of</strong> 3d objects.<br />

(d) Response <strong>of</strong> Frangi’s method [44].<br />

50<br />

50<br />

0<br />

0<br />

0 200 400 600 800 1000 1200 1400 1600 18000 200 400 600 800 1000 1200 1400 1600 1800<br />

(e) Response <strong>of</strong> Krissian’s method [70].<br />

(f) Response <strong>of</strong> Pock’s method [114] us<strong>in</strong>g<br />

typical parameter η = 0.5. For variations<br />

<strong>of</strong> η see Fig. 2.8.<br />

20<br />

10<br />

500<br />

0<br />

0<br />

0 200 400 600 800 1000 1200 1400 1600 18000 200 400 600 800 1000 1200 1400 1600 1800<br />

(g) Response <strong>of</strong> GVF-based tube detection<br />

with central medialness (Section 2.3.1).<br />

(h) Response <strong>of</strong> GVF-based tube detection<br />

with <strong>of</strong>fset medialness (Section 2.3.2).<br />

Figure 2.7: <strong>Tubular</strong> structures with vary<strong>in</strong>g cross section pr<strong>of</strong>ile represent<strong>in</strong>g situations<br />

found <strong>in</strong> typical CT datasets and responses <strong>of</strong> different TDFs. The x-axis <strong>in</strong>dicates the<br />

location and the y-axis the contrast/response.<br />

Fig. 2.7(d)-(h) show the responses <strong>of</strong> the different TDFs. With all the approaches<br />

the responses descreases with <strong>in</strong>creas<strong>in</strong>g deviation from the expected cross section pr<strong>of</strong>iles<br />

(ellipse) or <strong>in</strong> case <strong>of</strong> other nearby image structures (e.g. another closely tangent<strong>in</strong>g<br />

tube). In case <strong>of</strong> the TDFs <strong>of</strong> Krissian and Pock the response is also correlated with<br />

the edge-type (blurred edges, or Gaussian cross section pr<strong>of</strong>ile), while with the method<br />

<strong>of</strong> Frangi and the GVF-based approaches the responses do not decrease <strong>in</strong> these cases.<br />

The TDFs <strong>of</strong> Frangi and Krissian also produced quite strong responses for the surface<br />

patch like structure and between the closely tangent<strong>in</strong>g tubular objects. The GVF-based<br />

approaches do not produce responses between the closely tangent<strong>in</strong>g tubular objects as<br />

we have already seen <strong>in</strong> the experiments <strong>of</strong> the vary<strong>in</strong>g tube configurations (see Fig. 2.6).

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