The invention relates to system (100) for segmenting an image dataset based on a deformable model for modeling an object in the image dataset, utilizing a coarse mesh for adapting to the image dataset and a fine mesh for extracting detailed information from the image dataset, the system comprising an initialization unit (110) for initializing the coarse mesh in an image dataset space, a construction unit (120) for constructing the fine mesh in the image dataset space based on the initialized coarse mesh, a computation unit (130) for computing an internal force field on the coarse mesh and an external force field on the coarse mesh, wherein the external force is computed based on the constructed fine mesh and the scalar field of intensities, and an adaptation unit (140) for adapting the coarse mesh to the object in the image dataset, using the computed internal force field and the computed external force field, thereby segmenting the image dataset. Since only the coarse mesh is adapted to the image dataset, keeping the modeled object surface smooth does not require a smoothing of the surface over large neighboring areas, and therefore the adaptation of the coarse mesh is much faster than the adaptation of the fine mesh. Advantageously, the proposed technique can be easily integrated into existing frameworks of model-based image segmentation.