Estimation and detection of myocardial tags in MR image without user-defined myocardial contours

Magnetic resonance (MR) tagging has been Shown to, be a useful technique fo r noninvasively measuring the deformation of an in vivo heart. An important step in analyzing tagged images is the identification of tag lines in each image of a cine sequence. Most existing tag identification algorithms requ ire user defined myocardial contours. Contour identification, however, is t ime consuming and requires a considerable amount of user intervention. In t his paper, a new method for identifying tag lines, which me call the ML/MAP method, is presented that does not require user defined myocardial contour s. The ML/MAP method is composed of three stages. First, a set of candidate tag line centers is estimated across the entire region-of-interest (ROI) w ith a snake algorithm based on a maximum-likelihood (ML) estimate of the ta g center. Next, a maximum a posteriori (MAP) hypothesis test is used to det ect the candidate tag centers that are actually part of a tag line. Finally , a pruning algorithm is used to remove any detected tag line centers that do not meet a spatio-temporal continuity criterion. The ML/MAP method is de monstrated on data from ten in vivo human hearts.