FREQUENCY-BASED NONRIGID MOTION ANALYSIS - APPLICATION TO 4-DIMENSIONAL MEDICAL IMAGES

We present a method for nonrigid motion analysis in time sequences of volume images (4D data). In this method, nonrigid motion of the deform ing object contour is dynamically approximated by a physically-based d eformable surface. In order to reduce the number of parameters describ ing the deformation, we make use of a modal analysis which provides a spatial smoothing of the surface. The deformation spectrum, which outl ines the main excited modes, can be efficiently used for deformation c omparison. Fourier analysis on time signals of the main deformation sp ectrum components provides a temporal smoothing of the data. Thus a co mplex nonrigid deformation is described by only a few parameters: the main excited modes and the main Fourier harmonics. Therefore, 4D data can be analyzed in a very concise manner. The power and robustness of the approach is illustrated by various results on medical data. We bel ieve that our method has important applications in automatic diagnosis of heart diseases and in motion compression.