Biomedical Engineering Reference
In-Depth Information
hypothalamus, caudate nucleus and putamen). The filled WM volume was then
binarized via thresholding of the fuzzy values at 0.5. This binary volume was fur-
ther processed for topology correction with a multiscale graph-based algorithm
[99]. The CCMC was then used to extract the WM surface of the volume. At this
point, the WM surface was used as the initial level zero of the level set segmenta-
tion to extract three cortical surfaces: WM/GM surface, central cortical surface,
and pial (CM/CSF) surface.
Segmentation accuracy was assessed through error measurements at 10 land-
mark points manually selected on major sulci and gyri on six MRI cases. Land-
mark error was measured as the minimum distance between the landmark points
and the segmented surfaces. The overall average error was 0.87 mm (std 0.5 mm)
outperforming a previous method from the same group based on a parametric de-
formable model that produced an average error of 1.22 mm (std 1.01 mm) [100].
Visual inspection of the segmented data did not reveal any self-intersection on
the extracted surfaces. The algorithm computational time was about 40 min-
utes on a SGI O2 workstation for reconstruction of the three surfaces. This
performance compares favorably to typical deformable model algorithms with
arbitrary initialization as claimed by the authors.
Limitations:
The main limitation of this algorithm is the involvement of
the preprocessing for initialization of the WM that make the process difficult to
reproduce.
2.4.3.3
Segmentation and Measurement of the Cortex from 3D
MR Images using Coupled-Surfaces Propagation
This research was published by Zeng
et al.
in [33].
Method:
The authors proposed the segmentation and measurement of the
cortical GM thickness from brain MRI data with a level set method using coupled-
surfaces propagation. As stated by the authors, coupling surfaces can prevent
two problems:
The inner cortical surface can collapse with the CSF due to higher contrast
at the CSF/GM interface than at the WM/GM interface.
The presence of eye sockets with no CSF signal can drive the outer cortical
surface to expend outward from the brain.
