The present invention relates to an image processing device (10) comprising a data input (11) for receiving spectral computed tomography volumetric image data organized in voxels, comprising multispectral information for each voxel. The device further comprises a calcium surface feature analyzer (12) for estimating, for each voxel, based on said multispectral information, a first value indicative of a maximum probability that a local neighborhood around the voxel corresponds to a calcium surface structure and a second value indicative of an orientation of the calcium structure surface. The device also comprises a probability processor (13) for calculating a probability map indicative of a probability, for each voxel, that the voxel represents a bone or hard plaque structure, taking at least the first and second value and the multispectral information into account. The device also comprises a segmentation unit (14) for segmenting bone and/or hard plaque structures in the volumetric image data based on the probability map.
