This article introduces a new image processing technique for rapid analysis of tagged cardiac magnetic resonance image sequences. The method uses isolated spectral peaks in SPAMMtagged magnetic resonance images, which contain information about cardiac motion. The inverse Fourier transform of a spectral peak is a complex image whose calculated angle is called a harmonic phase (HARP) image. It is shown how two HARP image sequences can be used to automatically and accurately track material points through time. A rapid, semiautomated procedure to calculate circumferential and radial Lagrangian strain from tracked points is described. This new computational approach permits rapid analysis and visualization of myocardial strain within 5-10 min after the scan is complete. Its performance is demonstrated on MR image sequences reflecting both normal and abnormal cardiac motion. Results from the new method are shown to compare very well with a previously validated tracking algorithm. Magn Reson Med 42:1048-1060,

Abstract-This paper describes a new image processing technique for rapid analysis and visualization of tagged cardiac magnetic resonance (MR) images. The method is based on the use of isolated spectral peaks in spatial modulation of magnetization (SPAMM)-tagged magnetic resonance images. We call the calculated angle of the complex image corresponding to one of these peaks a harmonic phase (HARP) image and show that HARP images can be used to synthesize conventional tag lines, reconstruct displacement fields for small motions, and calculate two-dimensional (2-D) strain. The performance of this new approach is demonstrated using both real and simulated tagged MR images. Potential for use of HARP images in fast imaging techniques and three-dimensional (3-D) analyses are discussed.

This article presents a new method for measuring longitudinal strain in a short-axis section of the heart using harmonic phase magnetic resonance imaging (HARP-MRI). The heart is tagged using 1-1 SPAMM at end-diastole with tag surfaces parallel to a short-axis imaging plane. Two or more images are acquired such that the images have different phase encodings in a direction orthogonal to the image plane. A dense map of the longitudinal strain can be computed from these images using a simple, fast computation.

This article introduces a new image processing technique for rapid analysis of tagged cardiac magnetic resonance image sequences. The method uses isolated spectral peaks in SPAMM-tagged magnetic resonance images, which contain information about cardiac motion. The inverse Fourier transform of a spectral peak is a complex image whose calculated angle is called a harmonic phase (HARP) image. It is shown how two HARP image sequences can be used to automatically and accurately track material points through time. A rapid, semiautomated procedure to calculate circumferential and radial Lagrangian strain from tracked points is described. This new computational approach permits rapid analysis and visualization of myocardial strain within 5-10 min after the scan is complete. Its performance is demonstrated on MR image sequences reflecting both normal and abnormal cardiac motion. Results from the new method are shown to compare very well with a previously validated tracking algorithm. Keywords cardiac motion; harmonic phase; magnetic resonance tagging; myocardial strain Major developments over the past decade in tagged cardiac magnetic resonance imaging (1-6) have made it possible to measure the detailed strain patterns of the myocardium in vivo (7-11). MR tagging uses a special pulse sequence to spatially modulate the longitudinal magnetization of the subject to create temporary features, called tags, in the myocardium. Fast spoiled gradient echo imaging techniques are used to create CINE sequences that show the motion of both the anatomy of the heart and the tag features that move with the heart. Analysis of the motion of the tag features in many images taken from different orientations and at different times can be used to track material points in 3D, leading to detailed maps of the strain patterns within the myocardium (11,12). Tagged MRI has figured prominently in many recent medical research and scientific investigations. It has been used to develop and refine models of normal and abnormal myocardial motion (7,8,12-14) to better understand the correlation of coronary artery disease with myocardial motion abnormalities (15), to analyze cardiac activation patterns using pacemakers (16), to understand the effects of treatment after myocardial infarction (17), and in combination with stress testing for the early detection of myocardial ischemia (18). Despite

Background-Tagged MRI of the heart is difficult to implement clinically because of the lack of fast analytical techniques.We investigated the accuracy of harmonic phase (HARP) imaging for rapid quantification of myocardial strains and for detailed analysis of left ventricular (LV) function during dobutamine stimulation. Methods and Results-Tagged MRI was performed in 10 volunteers at rest and during 5 to 20 g Ϫ1 ⅐ kg Ϫ1 ⅐ min

Cardiovascular magnetic resonance (CMR) is currently the gold standard for assessing both global and regional myocardial function. New tools for quantifying regional function have been recently developed to characterize early myocardial dysfunction in order to improve the identification and management of individuals at risk for heart failure. Of particular interest is CMR myocardial tagging, a non-invasive technique for assessing regional function that provides a detailed and comprehensive examination of intra-myocardial motion and deformation. Given the current advances in gradient technology, image reconstruction techniques, and data analysis algorithms, CMR myocardial tagging has become the reference modality for evaluating multidimensional strain evolution in the human heart. This review presents an in depth discussion on the current clinical applications of CMR myocardial tagging and the increasingly important role of this technique for assessing subclinical myocardial dysfunction in the setting of a wide variety of myocardial disease processes.

Abstract. Harmonic phase magnetic resonance imaging (HARP) is a new technique for measuring the motion of the left ventricle of the heart. HARP uses magnetic resonance tagging, Fourier filtering and special processing algorithms to calculate key indices of myocardial motion including Eulerian and Lagrangian strain. This paper presents several new methods for visualizing myocardial motion based on HARP. Quantities that are computed and visualized include motion grids, velocity fields, strain rates, pathlines, tracked Eulerian strain, and contraction angle. The computations are fast and fully automated and have the potential for clinical application.

Background-The efficacy of cardiac resynchronization therapy (CRT) depends on placement of the left ventricular lead within the late-activated territory. The geographic extent and 3-dimensional distribution of left ventricular (LV) locations yielding optimal CRT remain unknown. Methods and Results-Normal or tachypacing-induced failing canine hearts made dyssynchronous by right ventricular free wall pacing or chronic left bundle-branch ablation were acutely instrumented with a nonconstraining epicardial elastic sock containing 128 electrodes interfaced with a computer-controlled stimulation/recording system. Biventricular CRT was performed using a fixed right ventricular site and randomly selected LV sites covering the entire free wall. For each LV site, global cardiac function (conductance catheter) and mechanical synchrony (magnetic resonance imaging tagging) were determined to yield 3-dimensional maps reflecting CRT impact. Optimal CRT was achieved from LV lateral wall sites, slightly more anterior than posterior and more apical than basal. LV sites yielding Ն70% of the maximal dP/dtmax increase covered Ϸ43% of the LV free wall. This distribution and size were similar in both normal and failing hearts. The region was similar for various systolic and diastolic parameters and correlated with 3-dimensional maps based on mechanical synchrony from magnetic resonance imaging strain analysis. Conclusions-In hearts with delayed lateral contraction, optimized CRT is achieved over a fairly broad area of LV lateral wall in both nonfailing and failing hearts, with modest anterior or posterior deviation still capable of providing effective CRT. Sites selected to achieve the most mechanical synchrony are generally similar to those that most improve global function, confirming a key assumption underlying the use of wall motion analysis to optimize CRT.