This paper describesamethod based onanautomatic segmentation process to coregister carpal bones of the same patient imaged at\ndifferent time points. A rigid registration was chosen to avoid artificial bone deformations and to allow finding eventual differences\nin the bone shape due to erosion, disease regression, or other eventual pathological signs. The actual registration step is performed\non the basis of principal inertial axes of each carpal bone volume, as estimated from the inertia matrix. In contrast to already\npublished approaches, the proposed method suggests splitting the 3D rotation into successive rotations about one axis at a time\n(the so-called basic or elemental rotations). In such a way, singularity and ambiguity drawbacks affecting other classical methods,\nfor instance, the Euler angles method, are addressed.The proposed method was quantitatively evaluated using a set of real magnetic\nresonance imaging (MRI) sequences acquired at two different times from healthy wrists and by choosing a direct volumetric\ncomparison as a cost function. Both the segmentation and registration steps are not based on a priori models, and they are therefore\nable to obtain good results even in pathological cases, as proven by the visual evaluation of actual pathological cases
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