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Imaging three-dimensional myocardial mechanics using navigator-gated volumetric spiral cine DENSE MRI.

ABSTRACT: A navigator-gated 3D spiral cine displacement encoding with stimulated echoes (DENSE) pulse sequence for imaging 3D myocardial mechanics was developed. In addition, previously described 2D postprocessing algorithms including phase unwrapping, tissue tracking, and strain tensor calculation for the left ventricle (LV) were extended to 3D. These 3D methods were evaluated in five healthy volunteers, using 2D cine DENSE and historical 3D myocardial tagging as reference standards. With an average scan time of 20.5 ± 5.7 min, 3D data sets with a matrix size of 128 × 128 × 22, voxel size of 2.8 × 2.8 × 5.0 mm(3), and temporal resolution of 32 msec were obtained with displacement encoding in three orthogonal directions. Mean values for end-systolic mid-ventricular mid-wall radial, circumferential, and longitudinal strain were 0.33 ± 0.10, -0.17 ± 0.02, and -0.16 ± 0.02, respectively. Transmural strain gradients were detected in the radial and circumferential directions, reflecting high spatial resolution. Good agreement by linear correlation and Bland-Altman analysis was achieved when comparing normal strains measured by 2D and 3D cine DENSE. Also, the 3D strains, twist, and torsion results obtained by 3D cine DENSE were in good agreement with historical values measured by 3D myocardial tagging.

SUBMITTER: Zhong X

PROVIDER: S-EPMC2946451 | biostudies-literature | 2010 Oct

REPOSITORIES: biostudies-literature

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Imaging three-dimensional myocardial mechanics using navigator-gated volumetric spiral cine DENSE MRI.

Zhong Xiaodong X Spottiswoode Bruce S BS Meyer Craig H CH Kramer Christopher M CM Epstein Frederick H FH

Magnetic resonance in medicine 20101001 4

A navigator-gated 3D spiral cine displacement encoding with stimulated echoes (DENSE) pulse sequence for imaging 3D myocardial mechanics was developed. In addition, previously described 2D postprocessing algorithms including phase unwrapping, tissue tracking, and strain tensor calculation for the left ventricle (LV) were extended to 3D. These 3D methods were evaluated in five healthy volunteers, using 2D cine DENSE and historical 3D myocardial tagging as reference standards. With an average scan ...[more]

PMID: 20574967

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Project description:PURPOSE:To determine the optimal respiratory navigator gating configuration for the quantification of left ventricular strain using spiral cine displacement encoding with stimulated echoes (DENSE) MRI. MATERIALS AND METHODS:Two-dimensional spiral cine DENSE was performed on a 3 Tesla MRI using two single-navigator configurations (retrospective, prospective) and a combined "dual-navigator" configuration in 10 healthy adults and 20 healthy children. The adults also underwent breathhold DENSE as a reference standard for comparisons. Peak left ventricular strains, signal-to-noise ratio (SNR), and navigator efficiency were compared. Subjects also underwent dual-navigator gating with and without visual feedback to determine the effect on navigator efficiency. RESULTS:There were no differences in circumferential, radial, and longitudinal strains between navigator-gated and breathhold DENSE (P?=?0.09-0.95) (as confidence intervals, retrospective: [-1.0%-1.1%], [-7.4%-2.0%], [-1.0%-1.2%]; prospective: [-0.6%-2.7%], [-2.8%-8.3%], [-0.3%-2.9%]; dual: [-1.6%-0.5%], [-8.3%-3.2%], [-0.8%-1.9%], respectively). The dual configuration maintained SNR compared with breathhold acquisitions (16 versus 18, P?=?0.06). SNR for the prospective configuration was lower than for the dual navigator in adults (P?=?0.004) and children (P?<?0.001). Navigator efficiency was higher (P?<?0.001) for both retrospective (54%) and prospective (56%) configurations compared with the dual configuration (35%). Visual feedback improved the dual configuration navigator efficiency to 55% (P?<?0.001). CONCLUSION:When quantifying left ventricular strains using spiral cine DENSE MRI, a dual navigator configuration results in the highest SNR in adults and children. In adults, a retrospective configuration has good navigator efficiency without a substantial drop in SNR. Prospective gating should be avoided because it has the lowest SNR. Visual feedback represents an effective option to maintain navigator efficiency while using a dual navigator configuration. LEVEL OF EVIDENCE:2 J. Magn. Reson. Imaging 2017;45:786-794.

Project description:Defining myocardial contours is often the most time-consuming portion of dynamic cardiac MRI image analysis. Displacement encoding with stimulated echoes (DENSE) is a quantitative MRI technique that encodes tissue displacement into the phase of the complex MRI images. Cine DENSE provides a time series of these images, thus facilitating the non-invasive study of myocardial kinematics. Epicardial and endocardial contours need to be defined at each frame on cine DENSE images for the quantification of regional displacement and strain as a function of time. This work presents a reliable and effective two-dimensional semi-automated segmentation technique that uses the encoded motion to project a manually-defined region of interest through time. Contours can then easily be extracted for each cardiac phase. This method boasts several advantages, including, (1) parameters are based on practical physiological limits, (2) contours are calculated for the first few cardiac phases, where it is difficult to visually distinguish blood from myocardium, and (3) the method is independent of the shape of the tissue delineated and can be applied to short- or long-axis views, and on arbitrary regions of interest. Motion-guided contours were compared to manual contours for six conventional and six slice-followed mid-ventricular short-axis cine DENSE datasets. Using an area measure of segmentation error, the accuracy of the segmentation algorithm was shown to be similar to inter-observer variability. In addition, a radial segmentation error metric was introduced for short-axis data. The average radial epicardial segmentation error was 0.36+/-0.08 and 0.40+/-0.10 pixels for slice-followed and conventional cine DENSE, respectively, and the average radial endocardial segmentation error was 0.46+/-0.12 and 0.46+/-0.16 pixels for slice following and conventional cine DENSE, respectively. Motion-guided segmentation employs the displacement-encoded phase shifts intrinsic to DENSE MRI to accurately propagate a single set of pre-defined contours throughout the remaining cardiac phases.

Project description:We sought to assess the effectiveness of automated mechanical dyssynchrony (MD) parameters based on regional heterogeneity of strain (circumferential [CURE], longitudinal [LURE], and radial uniformity ratio estimates) relative to parameters based on regional time to peak contraction with cardiac magnetic resonance (CMR) cine DENSE (Displacement Encoding with Stimulated Echoes) validated with myocardial tissue tagging (MTT) strain data.Dyssynchrony measures based on the Fourier transformation (FT) of regional strain, such as CURE (previously evaluated in cardiac resynchronization therapy candidates), directly assess MD and yield straightforward global dyssynchrony indexes; however, performance relative to the 12-segment standard deviation of time to peak strain (SD12) or maximal regional delay in time to peak strain is unknown.Cine DENSE and MTT were obtained with CMR (1.5-T Siemens Avanto, Siemens, Erlangen, Germany) in 13 canines: 3 normal control subjects, 5 with tachycardia pacing-induced heart failure (HF) and left bundle branch ablation (LBBB-HF), and 5 with HF and narrow QRS (NQRS-HF). Strain and dyssynchrony parameters were determined with both CMR methods.Both HF groups had reduced peak strains and left ventricular ejection fraction compared with normal cases. There was strong agreement between cine DENSE and MTT on the basis of intraclass correlation coefficients (CURE: 0.99, 95% CI: 0.96 to 1.00; LURE: 0.92, 95% CI: 0.77 to 0.98; circumferential strain [E(CC)]: 0.95, 95% CI: 0.72 to 0.99; longitudinal strain [E(LL)]: 0.82, 95% CI: 0.42 to 0.97). The FT-based metrics (scale 0 to 1), in particular CURE, discriminated highly between LBBB-HF and NQRS-HF groups (median difference): CURE: 0.60, 95% CI: 0.43 to 0.76; LURE: 0.39, 95% CI: 0.19 to 0.58; radial uniformity ratio estimate: 0.22, 95% CI: 0.04 to 0.40). In contrast, relative confidence intervals for group differences in time-to-peak parameters were wide, indicating less consistent discrimination (median difference): SD12-E(CC): 52.5, 95% CI: -4.0 to 109.2; SD12-E(LL): 40.9, 95% CI: -5.3 to 87.1; SD12-radial strain: 42.0, 95% CI: 0.4 to 83.6). Correlations between FT-based and time-to-peak parameters were significant (CURE/SD12-E(CC): r = -0.62, p = 0.03; LURE/SD12-E(LL): r = -0.76, p = 0.005) but not as tight as correlations between time-to-peak parameters.Automated FT-based circumferential, radial, and longitudinal dyssynchrony measures compare favorably with time-to-peak parameters. Cine DENSE was effective for this application and validated with MTT. Further clinical evaluation in cardiac resynchronization therapy candidates with CMR or other imaging modalities is warranted.

Project description:INTRODUCTION:Displacement encoding with stimulated echoes (DENSE) is a phase contrast technique that encodes tissue displacement into phase images, which are typically processed into measures of cardiac function such as strains. For improved signal to noise ratio and spatiotemporal resolution, DENSE is often acquired with a spiral readout using an 11.1?ms readout duration. However, long spiral readout durations are prone to blurring due to common phenomena such as off-resonance and T2* decay, which may alter the resulting quantifications of strain. We hypothesized that longer readout durations would reduce image quality and underestimate cardiac strains at both 3.0?T and 1.5?T and that using short readout durations could overcome these limitations. MATERIAL AND METHODS:Computational simulations were performed to investigate the relationship between off-resonance and T2* decay, the spiral cine DENSE readout duration, and measured radial and circumferential strain. Five healthy participants subsequently underwent 2D spiral cine DENSE at both 3.0?T and 1.5?T with several different readout durations 11.1?ms and shorter. Pearson correlations were used to assess the relationship between cardiac strains and the spiral readout duration. RESULTS:Simulations demonstrated that long readout durations combined with off-resonance and T2* decay yield blurred images and underestimate strains. With the typical 11.1?ms DENSE readout, blurring was present in the anterior and lateral left ventricular segments of participants and was markedly improved with shorter readout durations. Radial and circumferential strains from those segments were significantly correlated with the readout duration. Compared to the 1.9?ms readout, the 11.1?ms readout underestimated radial and circumferential strains in those segments at both field strengths by up to 19.6% and 1.5% (absolute), or 42% and 7% (relative), respectively. CONCLUSIONS:Blurring is present in spiral cine DENSE images acquired at both 3.0?T and 1.5?T using the typical 11.1?ms readout duration, which yielded substantially reduced radial strains and mildly reduced circumferential strains. Clinical studies using spiral cine DENSE should consider these limitations, while future technical advances may need to leverage accelerated techniques to improve the robustness and accuracy of the DENSE acquisition rather than focusing solely on reduced acquisition time.

Dataset Information

Imaging three-dimensional myocardial mechanics using navigator-gated volumetric spiral cine DENSE MRI.

Publications

Imaging three-dimensional myocardial mechanics using navigator-gated volumetric spiral cine DENSE MRI.

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