Comparison of feature tracking, fast-SENC, and myocardial tagging for global and segmental left ventricular strain.

AIMS: A multitude of cardiac magnetic resonance (CMR) techniques are used for myocardial strain assessment; however, studies comparing them are limited. We sought to compare global longitudinal (GLS), circumferential (GCS), segmental longitudinal (SLS), and segmental circumferential (SCS) strain values, as well as reproducibility between CMR feature tracking (FT), tagging (TAG), and fast-strain-encoded (fast-SENC) CMR techniques. METHODS AND RESULTS: Eighteen subjects (11 healthy volunteers and seven patients with heart failure) underwent two CMR scans (1.5T, Philips) with identical parameters. Global and segmental strain values were measured using FT (Medis), TAG (Medviso), and fast-SENC (Myocardial Solutions). Friedman's test, linear regression, Pearson's correlation coefficient, and Bland-Altman analyses were used to assess differences and correlation in measured GLS and GCS between the techniques. Two-way mixed intra-class correlation coefficient (ICC), coefficient of variance (COV), and Bland-Altman analysis were used for reproducibility assessment. All techniques correlated closely for GLS (Pearson's r: 0.86-0.92) and GCS (Pearson's r: 0.85-0.94). Intra-observer and inter-observer reproducibility was excellent in all techniques for both GLS (ICC 0.92-0.99, CoV 2.6-10.1%) and GCS (ICC 0.89-0.99, CoV 4.3-10.1%). Inter-study reproducibility was similar for all techniques for GLS (ICC 0.91-0.96, CoV 9.1-10.8%) and GCS (ICC 0.95-0.97, CoV 7.6-10.4%). Combined segmental intra-observer reproducibility was good in all techniques for SLS (ICC 0.914-0.953, CoV 12.35-24.73%) and SCS (ICC 0.885-0.978, CoV 10.76-19.66%). Combined inter-study SLS reproducibility was the worst in FT (ICC 0.329, CoV 42.99%), while fast-SENC performed the best (ICC 0.844, CoV 21.92%). TAG had the best reproducibility for combined inter-study SCS (ICC 0.902, CoV 19.08%), while FT performed the worst (ICC 0.766, CoV 32.35%). Bland-Altman analysis revealed considerable inter-technique biases for GLS (FT vs. fast-SENC 3.71%; FT vs. TAG 8.35%; and TAG vs. fast-SENC 4.54%) and GCS (FT vs. fast-SENC 2.15%; FT vs. TAG 6.92%; and TAG vs. fast-SENC 2.15%). Limits of agreement for GLS ranged from ±3.1 (TAG vs. fast-SENC) to ±4.85 (FT vs. TAG) for GLS and ±2.98 (TAG vs. fast-SENC) to ±5.85 (FT vs. TAG) for GCS. CONCLUSIONS: We found significant differences in measured GLS and GCS between FT, TAG, and fast-SENC. Global strain reproducibility was excellent for all techniques. Acquisition-based techniques had better reproducibility than FT for segmental strain.

Strain-encoded cardiac magnetic resonance imaging: a new approach for fast estimation of left ventricular function.

BACKGROUND: Recently introduced fast strain-encoded (SENC) cardiac magnetic resonance (CMR) imaging (fast-SENC) provides real-time acquisition of myocardial performance in a single heartbeat. We aimed to test the ability and accuracy of real-time strain-encoded CMR imaging to estimate left ventricular volumes, ejection fraction and mass. METHODS: Thirty-five subjects (12 healthy volunteers and 23 patients with known or suspected coronary artery disease) were investigated. All study participants were imaged at 1.5 Tesla MRI scanner (Achieva, Philips) using an advanced CMR study protocol which included conventional cine and fast-SENC imaging. A newly developed real-time free-breathing SENC imaging technique based on the acquisition of two images with different frequency modulation was employed. RESULTS: All parameters were successfully derived from fast-SENC images with total study time of 105 s (a 15 s scan time and a 90 s post-processing time). There was no significant difference between fast-SENC and cine imaging in the estimation of LV volumes and EF, whereas fast-SENC underestimated LV end-diastolic mass by 7%. CONCLUSION: The single heartbeat fast-SENC technique can be used as a good alternative to cine imaging for the precise calculation of LV volumes and ejection fraction while the technique significantly underestimates LV end-diastolic mass.

Fourier phase analysis can be used to objectively analyze real-time myocardial contrast echocardiograms.

BACKGROUND: Real-time myocardial contrast echocardiography (MCE) is increasingly used to assess myocardial perfusion. However, objective methods for evaluating MCE are not yet widely available. We sought to validate the ability of Fourier analysis applied to MCE to assess serial changes in microvascular perfusion during coronary occlusion and reperfusion. METHODS: Six pigs underwent 45 min of left anterior descending coronary artery (LAD) occlusion followed by 120 min of reperfusion. Real time MCE was performed at baseline, during coronary occlusion, and at 5, 30, 60 and 120 min of reperfusion. Signal intensities from replenishment curves were fitted to an exponential function to obtain plateau SI (A) and the rate of SI rise (b). MCE images were mathematically transformed using a first-harmonic Fourier algorithm displaying the sequence of myocardial intensity changes as phase angles in parametric images. The phase angle difference (PD) of posterior vs. anterior region was calculated as an index of myocardial opacification heterogeneity and compared to MCE index of myocardial blood flow A x b. RESULTS: After initial hyperemia, a progressive reduction in flow was observed during reperfusion. During LAD occlusion signal intensities were significantly reduced in anterior regions (A x b = 0.02+/-0.01) compared to baseline (1.2+/-0.34, p < 0.01) defining risk areas and approached higher levels postrecanalization (A x b = 1.48+/-0.6) but gradually decreased during 120 min of reperfusion (A = 0.51+/-0.3, p < 0.01). Similarly, profiles of phase angles in LAD perfusion territorities were consistently modified during reperfusion. The mean PD at baseline was 18 degrees+/-15 degrees. PD decreased during coronary occlusion to -108 degrees+/-38 degrees, increased to 29 degrees+/-19 degrees postrecanalization but decreased to -61 degrees+/-35 degrees after 120 min of reperfusion. PD significantly correlated with A (r = 0.8, p < 0.0001) and b (r = 0.73, p < 0.0001). CONCLUSIONS: The progressive reduction in post-ischemic microvascular perfusion was accurately detected by real-time MCE. Fourier phase imaging is feasible to quantify dynamics of myocardial opacification in a simple and objective format and is a promising approach for the interpretation of contrast echocardiograms.