Harmonic Phase MRI Research Articles

Systematic review and meta-analysis for the value of cardiac magnetic resonance strain to predict cardiac outcomes

Cardiac magnetic resonance (CMR) is the gold standard for the diagnostic classification and risk stratification in most patients with cardiac disorders. The aim of the present study was to investigate the ability of Strain-encoded MR (SENC) for the prediction of major adverse cardiovascular events (MACE). A systematic review and meta-analysis was performed according to the PRISMA Guidelines, including patients with or without cardiovascular disease and asymptomatic individuals. Myocardial strain by HARP were used as pulse sequences in 1.5 T scanners. Published literature in MEDLINE (PubMed) and Cochrane’s databases were explored before February 2023 for studies assessing the clinical utility of myocardial strain by Harmonic Phase Magnetic Resonance Imaging (HARP), Strain-encoded MR (SENC) or fast-SENC. In total, 8 clinical trials (4 studies conducted in asymptomatic individuals and 4 in patients with suspected or known cardiac disease) were included in this systematic review, while 3 studies were used for our meta-analysis, based on individual patient level data. Kaplan–Meier analysis and Cox proportional hazard models were used, testing the ability of myocardial strain by HARP and SENC/fast-SENC for the prediction of MACE. Strain enabled risk stratification in asymptomatic individuals, predicting MACE and the development of incident heart failure. Of 1332 patients who underwent clinically indicated CMR, including SENC or fast-SENC acquisitions, 19 patients died, 28 experienced non-fatal infarctions, 52 underwent coronary revascularization and 86 were hospitalized due to heart failure during median 22.4 (17.2–28.5) months of follow-up. SENC/fast-SENC, predicted both all-cause mortality and MACE with high accuracy (HR = 3.0, 95% CI = 1.2–7.6, p = 0.02 and HR = 4.1, 95% CI = 3.0–5.5, respectively, p < 0.001). Using hierarchical Cox-proportional hazard regression models, SENC/fast-SENC exhibited incremental value to clinical data and conventional CMR parameters. Reduced myocardial strain predicts of all-cause mortality and cardiac outcomes in symptomatic patients with a wide range of ischemic or non-ischemic cardiac diseases, whereas in asymptomatic individuals, reduced strain was a precursor of incident heart failure.

Mathematical Development and Computational Analysis of Harmonic Phase-Magnetic Resonance Imaging (HARP-MRI) Based on Bloch Nuclear Magnetic Resonance (NMR) Diffusion Model for Myocardial Motion.

Harmonic Phase-Magnetic Resonance Imaging (HARP-MRI) is a tagged image analysis method that can measure myocardial motion and strain in near real-time and is considered a potential candidate to make magnetic resonance tagging clinically viable. However, analytical expressions of radially tagged transverse magnetization in polar coordinates (which is required to appropriately describe the shape of the heart) have not been explored because the physics required to directly connect myocardial deformation of tagged Nuclear Magnetic Resonance (NMR) transverse magnetization in polar geometry and the appropriate harmonic phase parameters are not yet available. The analytical solution of Bloch NMR diffusion equation in spherical geometry with appropriate spherical wave tagging function is important for proper analysis and monitoring of heart systolic and diastolic deformation with relevant boundary conditions. In this study, we applied Harmonic Phase MRI method to compute the difference between tagged and untagged NMR transverse magnetization based on the Bloch NMR diffusion equation and obtained radial wave tagging function for analysis of myocardial motion. The analytical solution of the Bloch NMR equations and the computational simulation of myocardial motion as developed in this study are intended to significantly improve healthcare for accurate diagnosis, prognosis and treatment of cardiovascular related deceases at the lowest cost because MRI scan is still one of the most expensive anywhere. The analysis is fundamental and significant because all Magnetic Resonance Imaging techniques are based on the Bloch NMR flow equations.

Comparison of strain measurement from multimodality tissue tracking with strain-encoding MRI and harmonic phase MRI in pulmonary hypertension

BackgroundPixel-based multimodality tissue tracking (MTT) is a new noninvasive method for the quantification of cardiac deformation from cine image of MRI. The aim of this study is to validate bi-ventricular strain measurement by MTT compared to strain-encoding (SENC) MRI and harmonic phase (HARP) MRI in pulmonary hypertension (PH) patients. MethodsIn 45 subjects (30 PH patients and 15 normal subjects), RV and LV peak global longitudinal strains (Ell) were measured from long axis 4 chamber view using MTT. LV peak global circumferential strains (Ecc) by MTT were measured from short axis. For validation, RV and LV Ell by MTT were compared to measures by SENC-MRI from short axis, and LV Ecc by MTT was compared to measures by short axis tagged MRI analysis (HARP). Reproducibility of MTT was also determined. ResultsMTT quantified RV Ell correlated closely to those of SENC (r=0.72, p<0.001), with good limits of agreement. LV Ell quantified by MTT showed moderate correlation with SENC (r=0.57, p=0.001), and LV Ecc by MTT also showed moderate correlation with HARP (−16.9±4.1 vs −14.3±3.5, p<0.001 for all, r=0.60, p<0.001). RV Ell negatively correlated with RVEF (r=−0.53, p=0.001) and also positively correlated with mean PAP in PH patients (r=0.60, p=0.001). Strain measurement by MTT showed high reproducibility. ConclusionsWe demonstrate that MTT is a reproducible tool for quantification of cardiac deformation using cine images in PH patients. Hence, it could serve as a new rapid and comprehensive technique for clinical assessment of regional cardiac function.

Feature tracking strain is a promising functional analysis technique in single ventricle patients

Background Feature-tracking Strain (FT S) is a new technique that performs myocardial Strain evaluation on Steady State Free Precession (SSFP) cines without the need for myocardial tagging. As a pilot study to determine whether FT S may be useful in single ventricle patients, we applied this analysis to patients with hypoplastic left heart syndrome (HLHS) and tricuspid atresia (TA). Methods We retrospectively reviewed 22 patients with a history of Fontan palliation (median age 8.2, range 2 - 27.5 years) who had cardiac MRIs with a Siemens 1.5 Tesla Avanto (Siemens Medical Systems) scanner, 11 with TA, 11 with HLHS. All had steady-state free precession (SSFP) sequences of 4-chamber (4ch) cine and short axis (SAx) cine stacks from cardiac base to apex. Ejection fraction (EF) was calculated from the SAx stack on a Leonardo workstation (Siemens, Inc.). FT S analysis of the 4ch cine was performed off-line with TomTec 2D Cardiac Performance Analysis (version 1.0, TomTec Imaging Systems) following two tracking protocols: endocardial trace only (Endo), epicardial to endocardial trace (Endo-Epi) (Figure 1). Pearson correlation was used to test relationship between absolute global longitudinal Strain (GLSabs) and EF. Differences in GLS between tracking methods were tested with Bland Altman analysis. Results Mean EF was 60.2%, 95% CI 42.6% to 77.8%. Mean GLS was -15.7 (95% CI -6.8 to -24.7) by Endo., and -16.5 (95% CI -6.9 to -26.1) by Endo-Epi tracking methods. There was fair correlation (Figure 2) between GLSabs and EF using the Endo method (Pearson r = 0.67, p mean Endo GLS of 0.8, with a wide distribution in difference values, 95% CI 2.9 to -4.5. Morphologic ventricle type (single LV vs single RV) did not make a difference in GLS to EF correlations when compared to the mixed cohort. Mean GLS for single LVs was somewhat higher than single RVs, but this difference did not reach statistical significance. Conclusions There is fair correlation between GLS and EF in single ventricle patients with feature-tracking Strain analysis tracking the ventricular endocardium. Validation in a larger sample is warranted. Comparison of FT S with tagged harmonic phase MRI in single ventricle patients may further validate this promising technique in defining regional and global strain. Funding

A principal components analysis of tongue motion patterns in normal and glossectomy speakers

This study determines whether a small excision of the tongue, due to removal of a lateral T1 tumor, will cause a change in tongue motion patterns during speech. Principal components analysis (PCA) compared the motion patterns of ten control subjects to those of three glossectomy patients. The patients were 7–39 months post-glossectomy removal of T1N0M0 tumors and had primary closures. Cine- and tagged- magnetic resonance imaging (MRI) data included three sagittal slices, which were used to compare the midsagittal and bi-lateral motions of the tongue during speech. The data were internal tissue point motions extracted from the tagged MRI images using harmonic phase MRI (HARP-MRI) (NessAiver and Prince, 2003). The motion patterns of the tongue (velocity field) were observed during the motion from “ee” to “s” which may be difficult for glossectomy patients as it requires subtle changes in the tongue tip. The results demonstrated normal variability across the control subjects. The three patients retained some components of normal tongue motion; however, there were also notable differences from the controls. The glossectomy patients plotted at the extremes of the PC loadings, and the details revealed how they differed from the controls, from each other, and used individual compensatory strategies. [Work supported by NIH-R01CA133015.]

Systematic method for cleaning circumferential strain from raw harmonic phase magnetic resonance imaging (HARP) analyzed data

Methods Spatial Modulation of Magnetization tissue tags were placed on the myocardium at 3 T in 400 participants in the Dallas Heart Study. Short-axis tagged slices were analyzed by the harmonic phase (HARP) method (Diagnosoft, Palo Alto, California) to assess circumferential strain. The raw segmental data at each phase (24 points per wall/ phase) was evaluated by the Shapiro-Wilk test for normality. If the strain at a given phase was not normally distributed (Shapiro-Wilk test p 5 or < -5% strain at the end of diastole in clean vs. raw data was compared.

MRI of myocardial infarction with tissue tagging

Myocardial tagging with MRI has been available for three decades as a method for direct noninvasive quantification of regional myocardial motion for assessing the impact of ischemia, electrical asynchrony, and heart failure, among other conditions. In recent years, new developments in imaging sequences, hybrid techniques, and automated postprocessing have brought tagging closer to clinical application. Improvements in acquisition strategies have increased tag-tissue contrast and persistence, making automated tag detection easier and more robust. Imaging techniques such as harmonic phase MRI and displacement encoding with stimulated echoes that quantify pixel-by-pixel myocardial motion have simplified postprocessing. Parallel imaging and the increased signal-to-noise ratio available at the higher field strengths of new clinical scanners have moved the assessment of cardiac function into the real-time imaging domain. All of these developments have made myocardial motion mapping with tagged MRI a gold standard for the quantification of regional function within the research world, with potential to become an extremely valuable clinical technique.

Feasibility and Accuracy of Different Techniques of Two-Dimensional Speckle Based Strain and Validation With Harmonic Phase Magnetic Resonance Imaging

Different 2-dimensional speckle-based strain techniques have been developed to overcome the problem of angle dependency with Doppler-based strain. However, their relative accuracy has not been assessed. The aim of this study was to determine the feasibility and accuracy of 2 such techniques (velocity vector imaging [VVI] and automated function imaging [AFI]), using tagged harmonic phase (HARP) magnetic resonance imaging (MRI) as a reference standard. Thirty patients with known or suspected ischemic heart disease underwent measurement of peak systolic longitudinal, radial, and circumferential Lagrangian strain with all 3 techniques using a 16-segment model. The extent of scar tissue in each segment was determined using contrast-enhanced MRI. The measurement of myocardial strain in all 3 directions was highly feasible with both VVI and AFI. Longitudinal strain was underestimated by both VVI (-11 +/- 8%; P < .01) and AFI (-12 +/- 6%; P < .01) in comparison with HARP MRI (-14 +/- 5%), and radial strain was underestimated by VVI (14 +/- 18% vs 23 +/- 7%; P < .01). All strain measurements with AFI showed better correlation and agreement with HARP MRI compared with VVI. Circumferential strain with AFI had the greatest accuracy (area under the receiver operating characteristic curve = 0.74, P < .001) for the prediction of scar tissue on MRI. Two-dimensional strain measured with AFI has significantly better accuracy than VVI. Circumferential strain with AFI has the best discriminative ability for the detection of regional myocardial dysfunction.

In Search of a Holy Grail

“It came out of nowhere and captured the cardiology community by storm.” The cliche seems very appropriate when describing the impact of cardiac resynchronization therapy (CRT) on the treatment of heart failure. CRT improves survival rate in symptomatic patients 1 and is the only nonsurgical technique that provides substantial and stable reverse remodeling in both symptomatic and asymptomatic patients.2,3 The most surprising fact is that this is accomplished through mechanisms that are still unclear and that are not fully elucidated in experimental models. CRT is the only heart failure therapy with a potential to improve survival rate that is not based on neurohormonal modulation. Finally, it represents a challenge to the imaging community, as it establishes a need to measure something that was previously overlooked—dyssynchrony. Article see p 14 Unfortunately, CRT is not universally successful. One third of CRT patients do not feel better,4 and close to 40% of patients do not experience reverse remodeling, which is important because it predicts survival rate.5 This should not be a surprise—treatment of chronic diseases is rarely homogenously beneficial to all the patients. Nevertheless, in the case of CRT, some extra precautions are necessary. CRT is expensive; placement of electrodes may be difficult; and, even in experienced centers, a significant number of patients may require surgical placement. Finally, it is an expensive, healthcare-intensive therapy with extensive follow-up and occasional complications. Thus, there is an ongoing search for practical methods to predict the outcome of CRT and guide its use. Current guidelines use QRS duration (and symptoms) as the principal determinants for implantation, and as noted, this is fairly successful, with two thirds of such patients demonstrating improvement. The real challenge for clinicians comes in two situations: identifying those patients with narrow QRS who are …

Measuring tongue motion from tagged cine-MRI using harmonic phase (HARP) processing

A cine series of tagged magnetic resonance (MR) images of the tongue is used to measure tongue motion and its internal deformation during speech. Tagged images are collected in three slice orientations (sagittal, coronal, and axial) during repetitions of the utterance "disouk" (/disuk/). A new technique called harmonic phase MRI (HARP-MRI) is used to process the tagged MR images to measure the internal deformation of the tongue. The measurements include displacement and velocity of tissue points, principal strains, and strain in the line-of-action of specific muscles. These measurements are not restricted to tag intersections, but can be calculated at every pixel in the image. The different motion measurements complement each other in understanding the tongue kinematics and in hypothesizing the internal muscle activity of the tongue.

Automatic 3D tracking of cardiac material markers using slice-following and harmonic-phase MRI

A method to track a grid of cardiac material points in three dimensions using slice-following (SF) tagged magnetic resonance imaging (MRI) and harmonic-phase MRI is presented. A three-dimensional grid of material points on the lines of intersections of short-axis (SA) and long-axis (LA) planes is automatically tracked by combining two-dimensional pathlines that are computed on both SA and LA image planes. This process yields the true three-dimensional motion of points originating on the image plane intersections. Experimental data from normal volunteers, each obtained in four short breath-holds using the SF harmonic phase MRI pulse sequence, is presented. A validation of two-dimensional in-plane tracks using this pulse sequence on a moving phantom is also presented.

Comparison of Two-Dimensional Speckle and Tissue Velocity Based Strain and Validation With Harmonic Phase Magnetic Resonance Imaging

Two-dimensional (2-D) strain (epsilon2-D) on the basis of speckle tracking is a new technique for strain measurement. This study sought to validate epsilon2-D and tissue velocity imaging (TVI)-based strain (epsilonTVI) with tagged harmonic-phase (HARP) magnetic resonance imaging (MRI). Thirty patients (mean age 62 +/- 11 years) with known or suspected ischemic heart disease were evaluated. Wall motion (wall motion score index 1.55 +/- 0.46) was assessed by an expert observer. Three apical images were obtained for longitudinal strain (16 segments) and 3 short-axis images for radial and circumferential strain (18 segments). Radial epsilonTVI was obtained in the posterior wall. HARP MRI was used to measure principal strain, expressed as maximal length change in each direction. Values for epsilon2-D, epsilonTVI, and HARP MRI were comparable for all 3 strain directions and were reduced in dysfunctional segments. The mean difference and correlation between longitudinal epsilon2-D and HARP MRI (2.1 +/- 5.5%, r = 0.51, p <0.001) were similar to those between longitudinal epsilonTVI and HARP MRI (1.1 +/- 6.7%, r = 0.40, p <0.001). The mean difference and correlation were more favorable between radial epsilon2-D and HARP MRI (0.4 +/- 10.2%, r = 0.60, p <0.001) than between radial epsilonTVI and HARP MRI (3.4 +/- 10.5%, r = 0.47, p <0.001). For circumferential strain, the mean difference and correlation between epsilon2-D and HARP MRI were 0.7 +/- 5.4% and r = 0.51 (p <0.001), respectively. In conclusion, the modest correlations of echocardiographic and HARP MRI strain reflect the technical challenges of the 2 techniques. Nonetheless, epsilon2-D provides a reliable tool to quantify regional function, with radial measurements being more accurate and feasible than with TVI. Unlike epsilonTVI, epsilon2-D provides circumferential measurements.

Imaging longitudinal cardiac strain on short-axis images using strain-encoded MRI.

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. Simulations are conducted to study the effect of noise and the choice of out-of-plane phase encoding values. Longitudinal strains acquired from a normal human male are shown.

Visualizing myocardial function using HARP MRI

Harmonic phase magnetic resonance imaging (HARP) is a new technique formeasuring the motion of the left ventricle of the heart. HARP usesmagnetic resonance tagging, Fourier filtering and special processingalgorithms to calculate key indices of myocardial motion includingEulerian and Lagrangian strain. This paper presents several new methodsfor visualizing myocardial motion based on HARP. Quantities that arecomputed and visualized include motion grids, velocity fields, strainrates, pathlines, tracked Eulerian strain, and contraction angle. Thecomputations are fast and fully automated and have the potential forclinical application.

Fast Determination of Regional Myocardial Strain Fields From Tagged Cardiac Images Using Harmonic Phase MRI

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. Tagged MRI was performed in 10 volunteers at rest and during 5 to 20 microg(-1). kg(-1). min(-1) dobutamine and in 9 postinfarct patients at rest. We compared 2D myocardial strains (circumferential shortening, Ecc; maximal shortening, E(2); and E(2), direction) as assessed by a conventional technique and by HARP. Full quantitative analysis of the data was 10 times faster with HARP. For pooled data, the regression coefficient was r=0.93 for each strain (P<0.001). In volunteers, Ecc and E(2) were greater in the free wall than in the septum (P<0.01), but recruitable myocardial strain at peak dobutamine was greater in the LV septum (P<0.01). E(2) orientation shifted away from the circumferential direction at peak dobutamine (P<0.01). HARP accurately detected subtle changes in myocardial strain fields under increasing doses of dobutamine. In patients, HARP-determined Ecc and E(2) values were dramatically reduced in the asynergic segments as compared with remote (P<0.001), and E(2) direction shifted away from the circumferential direction (P<0.001). HARP MRI provides fast, accurate assessment of myocardial strains from tagged MR images in normal subjects and in patients with coronary artery disease with wall motion abnormalities. HARP correctly indexes dobutamine-induced changes in strains and has the potential for on-line quantitative monitoring of LV function during stress testing.