The Estimation Of Left Ventricular Twist Based On PAC Registration For B Mode Ultrasound Images

The left ventricular torsion is defined as the left ventricular apex rotate counterclockwise and the base rotate clockwise at the direction of the long axis of the ventricle,and the movement caused by the opposite rotation of two parts.Changes in myofibril fibrous structure and function,and whether the systolic and diastolic movements of the heart and septum of the heart are normal is a very important reference for evaluating cardiac function.Cardiac torsion exercise can be more sensitive to reflect the changes in the movement parameters of the heart,early diagnosis of heart disease has a significant significance.The advantages of ultrasound examination are non-invasive and non-radioactive.Real-time,intuitive images provide a simple and convenient evaluation model for clinical diagnosis.In the previous study,it has been proposed to use the B-signal-based speckle tracking method for the evaluation of cardiac left ventricular torsion.Select the region of interest(ROI)in the myocardial wall,which is distributed on different echo spots.And then use the best pattern matching technique to identify and track the location of the region of interest in each frame image,compare it with the position analysis of the spot in the previous frame and get the motion vector.So we can draw the motion trajectory of the region of interest and get the motion parameters of the heart.When we use this method to calculate the motion vector,we need to compare the current frame spot position with the reference frame,so the process is complex.Besides the occurrence of transverse or axial translation of the myocardial tissue will make error result and it has poor robustness.In this paper,a new method of estimating left ventricular torsional motion based on B-scan of principle axes and centroid registration is proposed.Calculate the angle of intersection of the center of mass,the angle between the principal and the coordinate system which called the deflection angle for each frame of the left ventricular apex and the basal part of a cardiac cycle.The first image frame of the cardiac cycle(the end of the diastolic period of the last cardiac cycle)is used as the reference frame.The difference between the deflection angle of the residual image frame and the reference frame deflection angle is the relative deflection angle.And then calculate the deflection angle for each frame B-image in the cardiac cycle.The first image frame of one cardiac cycle is used as the reference frame,and the difference between the deflection angle of the residual image frame and the reference frame deflection angle is the relative deflection angle.Then get all the relative deflection angles of all the image frames in one cycle.Finally plotting the trajectory curve of the apex and the base of the left ventricular in one cardiac cycle according to the torsion angle.In the experiment,the MRI images of the brain without speckle were experimentally rotated.It was verified that the error was not more than 0.1 degree when the spindle centroid method was used to calculate the rotation angle of the image(mainly symmetrical and not containing speckle).The mean error and the standard deviation of the rotation angle of the B-scan images of the basal part of the left ventricle and the apex of the left ventricle were 0.013 ±0.005 and 0.013 ±0.004 respectively.The results showed that there was no significant effectComparing the twist angle curves obtained by the two methods,we find that the trajectory is consistent and prove the method of this article is effective.The method has the advantages of simple method,easy operation,good reproducibility,small computation and high accuracy on this basis.The radial and axial deformation of myocardial tissue has no effect on the result,and it has good robustness;The calculation process of each frame image deflection angle is independent,without producing cumulative error.This method provides a new idea for the evaluation of left ventricular torsional motion,which has some theoretical and practical significance and is ready for further research.