Space-time segmentation using level set active contours applied to myocardial gated SPECT

This paper presents a new variational method for the segmentation of a moving object against a still background, over a sequence of (2-D or 3-D) image frames. The method is illustrated in application to myocardial gated SPECT data, and incorporates a level set framework to handle topological changes while providing closed boundaries.The key innovation is the introduction of a geometrical constraint into the derivation of the Euler-Lagrange equations, such that the segmentation of each individual frame can be interpreted as a closed boundary of an object (an isolevel of a set of hyper-surfaces) while integrating information over the entire sequence. This results in the definition of an evolution velocity normal to the object boundary. Applying this method to 3-D myocardial gated SPECT sequences, the left ventricle endocardial and epicardial limits can be computed in each frame.This space-time segmentation method was tested on simulated and clinical 3-D myocardial gated SPECT sequences and the corresponding ejection fractions were computed.