Summary: Multi-object Segmentation with Coupled Deformable Models
Dagmar Kainmuellera, Hans Lameckera, Stefan Zachowa, Markus Hellerb, Hans-Christian Hegea
aZuse Institute Berlin, Takustr. 7, 14195 Berlin, Germany
bJulius Wolff Institut and Center for Musculoskeletal Surgery, Charit´e - Universit¨atsmedizin Berlin, Germany
Abstract. For biomechanical simulations, the segmentation of multiple adjacent anatomical structures from medical
image data is often required. If adjacent structures are hardly distinguishable in image data, automatic segmentation
methods for single structures in general do not yield sufficiently accurate results. To improve segmentation accuracy
in these cases, knowledge about adjacent structures must be exploited. Optimal graph searching based on deformable
surface models allows for a simultaneous segmentation of multiple adjacent objects. However, this method requires
a correspondence relation between vertices of adjacent surface meshes. Line segments, each containing two corre-
sponding vertices, may then serve as shared displacement directions in the segmentation process. In this paper we
propose a scheme for constructing a correspondence relation in adjacent regions of two arbitrary surfaces. When
applying the thus generated shared displacement directions in segmentation with deformable surfaces, overlap of the
surfaces is guaranteed not to occur. We show correspondence relations for regions on a femoral head and acetabulum
and other adjacent structures, as well as preliminary segmentation results obtained by a graph cut algorithm.
For patient-specific biomechanical simulations, e.g. of the human lower limb, an accurate reconstruction of the bony
anatomy from medical image data is required. This particularly applies to joint regions, as simulation results heavily
depend on the location of joints . In CT data, bony tissue can usually be reconstructed by simple thresholding.
However, in joint regions, thresholding is often not sufficient for separating adjacent individual bones from each other.