Research On Left Ventricular Motion In Tagged Magnetic Resonance Images

The Tagged Magnatic Resonance (TMR) sequence provides an effective way for theanalysis of complex cardiac motion. Current clinical diagnoses mainly rely on naked eyeobservation or manual calibration, which means heavy workload and imprecise evaluationcriteria. Therefore, it’s necessary to do qualitative and quantitative analysis on cardiacmotion by means of computer image processing method, and then provides reference datafor doctors to diagnose.First of all, dividing the left ventricular internal and external wall using thresholdmethod and bilinear Snake model method, so that finding out the interested myocardialregion, and then getting the cardiac image sequence for next steps. Then, enhancingcardiac markers by Gabor filtering method according to the periodic characteristics ofmark of TMR images. Above based, designing a movement grid energy model in order toextract and trace the tag line intersections of cardiac motion image. The initial position ofthe movement grid nodes (The intersection of the tag line) is decided by using grayprojection method on the first frame, and the process of minimizing the Energy of GridMesh (EGM) determines the subsequent state of grid. EGM includes the structure energyof maintaining topology and mutual positional relationship, the characteristic energy ofgradation grayscale trait of tagged intersection and the limited energy of motionrelationship between adjacent frames. Choosing greedy algorithm to solve minimum valueof the total energy so as to obtain the final position of tagged intersection. Finally, gettingthe dense displacement field of left ventricular myocardial area by computing the motiondisplacement of tagged intersection between the left ventricular internal and externalwalls.In the experiment, using image sequences with complete cardiac period from15cases as data, which are provided by Tongji Medical College of Huazhong University of Science and Technology, and make the doctors’ manual calibration as standard. The resultshow that: the result of dividing left ventricular internal and external wall is good, theenhancement of tag line is effect and the result of extracting and tracing taggedintersection is precise.