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Comprehensive cardiovascular magnetic resonance of myocardial mechanics in mice using three-dimensional cine DENSE.

Zhong X, Gibberman LB, Spottiswoode BS, Gilliam AD, Meyer CH, French BA, Epstein FH - J Cardiovasc Magn Reson (2011)

Bottom Line: Peak end-systolic values for the normal strains at the mid-ventricular level were 0.29 ± 0.17, -0.13 ± 0.03, and -0.18 ± 0.14 for E(rr), E(cc), and E(ll), respectively.Peak end-systolic values for the shear strains were 0.00 ± 0.08, 0.04 ± 0.12, and 0.03 ± 0.07 for E(rc), E(rl), and E(cl), respectively.The peak end-systolic normalized torsion was 5.6 ± 0.9°.

View Article: PubMed Central - HTML - PubMed

Affiliation: MR R&D Collaborations, Siemens Healthcare, Atlanta, USA.

ABSTRACT

Background: Quantitative noninvasive imaging of myocardial mechanics in mice enables studies of the roles of individual genes in cardiac function. We sought to develop comprehensive three-dimensional methods for imaging myocardial mechanics in mice.

Methods: A 3D cine DENSE pulse sequence was implemented on a 7T small-bore scanner. The sequence used three-point phase cycling for artifact suppression and a stack-of-spirals k-space trajectory for efficient data acquisition. A semi-automatic 2D method was adapted for 3D image segmentation, and automated 3D methods to calculate strain, twist, and torsion were employed. A scan protocol that covered the majority of the left ventricle in a scan time of less than 25 minutes was developed, and seven healthy C57Bl/6 mice were studied.

Results: Using these methods, multiphase normal and shear strains were measured, as were myocardial twist and torsion. Peak end-systolic values for the normal strains at the mid-ventricular level were 0.29 ± 0.17, -0.13 ± 0.03, and -0.18 ± 0.14 for E(rr), E(cc), and E(ll), respectively. Peak end-systolic values for the shear strains were 0.00 ± 0.08, 0.04 ± 0.12, and 0.03 ± 0.07 for E(rc), E(rl), and E(cl), respectively. The peak end-systolic normalized torsion was 5.6 ± 0.9°.

Conclusions: Using a 3D cine DENSE sequence tailored for cardiac imaging in mice at 7 T, a comprehensive assessment of 3D myocardial mechanics can be achieved with a scan time of less than 25 minutes and an image analysis time of approximately 1 hour.

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Example end-systolic short-axis Err, Ecc, and Ell strain maps. Example end-systolic short-axis Err, Ecc, and Ell strain maps at basal, mid-ventricular, and apical locations measured using 3D cine DENSE in a normal mouse. Fairly uniform shortening is observed for the circumferential and longitudinal strains, while fairly uniform lengthening is observed for radial strain.
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Figure 4: Example end-systolic short-axis Err, Ecc, and Ell strain maps. Example end-systolic short-axis Err, Ecc, and Ell strain maps at basal, mid-ventricular, and apical locations measured using 3D cine DENSE in a normal mouse. Fairly uniform shortening is observed for the circumferential and longitudinal strains, while fairly uniform lengthening is observed for radial strain.

Mentions: Image quality was routinely very good in the mid-ventricular region where off-resonance effects are usually minimal. An example demonstrating this image quality is shown in Figure 3, where a magnitude-reconstructed image is displayed as are phase-reconstructed images encoded for in-plane and through-plane displacement. Image blurring was more prevalent mainly toward the apex where off-resonance effects are greater. Nonetheless, image quality was adequate throughout most of the LV to achieve measurements of tissue displacement and myocardial mechanics. For example, maps of the end-systolic normal strains Err, Ecc, and Ell are shown in Figure 4 at basal, mid-ventricular, and apical slices. Figure 5 shows a bar chart of the average end-systolic strains at the basal, mid-ventricular, and apical levels. Heterogeneity in myocardial strains at different levels was observed (Figure 5), which is consistent with prior studies [22-25,32].


Comprehensive cardiovascular magnetic resonance of myocardial mechanics in mice using three-dimensional cine DENSE.

Zhong X, Gibberman LB, Spottiswoode BS, Gilliam AD, Meyer CH, French BA, Epstein FH - J Cardiovasc Magn Reson (2011)

Example end-systolic short-axis Err, Ecc, and Ell strain maps. Example end-systolic short-axis Err, Ecc, and Ell strain maps at basal, mid-ventricular, and apical locations measured using 3D cine DENSE in a normal mouse. Fairly uniform shortening is observed for the circumferential and longitudinal strains, while fairly uniform lengthening is observed for radial strain.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3278394&req=5

Figure 4: Example end-systolic short-axis Err, Ecc, and Ell strain maps. Example end-systolic short-axis Err, Ecc, and Ell strain maps at basal, mid-ventricular, and apical locations measured using 3D cine DENSE in a normal mouse. Fairly uniform shortening is observed for the circumferential and longitudinal strains, while fairly uniform lengthening is observed for radial strain.
Mentions: Image quality was routinely very good in the mid-ventricular region where off-resonance effects are usually minimal. An example demonstrating this image quality is shown in Figure 3, where a magnitude-reconstructed image is displayed as are phase-reconstructed images encoded for in-plane and through-plane displacement. Image blurring was more prevalent mainly toward the apex where off-resonance effects are greater. Nonetheless, image quality was adequate throughout most of the LV to achieve measurements of tissue displacement and myocardial mechanics. For example, maps of the end-systolic normal strains Err, Ecc, and Ell are shown in Figure 4 at basal, mid-ventricular, and apical slices. Figure 5 shows a bar chart of the average end-systolic strains at the basal, mid-ventricular, and apical levels. Heterogeneity in myocardial strains at different levels was observed (Figure 5), which is consistent with prior studies [22-25,32].

Bottom Line: Peak end-systolic values for the normal strains at the mid-ventricular level were 0.29 ± 0.17, -0.13 ± 0.03, and -0.18 ± 0.14 for E(rr), E(cc), and E(ll), respectively.Peak end-systolic values for the shear strains were 0.00 ± 0.08, 0.04 ± 0.12, and 0.03 ± 0.07 for E(rc), E(rl), and E(cl), respectively.The peak end-systolic normalized torsion was 5.6 ± 0.9°.

View Article: PubMed Central - HTML - PubMed

Affiliation: MR R&D Collaborations, Siemens Healthcare, Atlanta, USA.

ABSTRACT

Background: Quantitative noninvasive imaging of myocardial mechanics in mice enables studies of the roles of individual genes in cardiac function. We sought to develop comprehensive three-dimensional methods for imaging myocardial mechanics in mice.

Methods: A 3D cine DENSE pulse sequence was implemented on a 7T small-bore scanner. The sequence used three-point phase cycling for artifact suppression and a stack-of-spirals k-space trajectory for efficient data acquisition. A semi-automatic 2D method was adapted for 3D image segmentation, and automated 3D methods to calculate strain, twist, and torsion were employed. A scan protocol that covered the majority of the left ventricle in a scan time of less than 25 minutes was developed, and seven healthy C57Bl/6 mice were studied.

Results: Using these methods, multiphase normal and shear strains were measured, as were myocardial twist and torsion. Peak end-systolic values for the normal strains at the mid-ventricular level were 0.29 ± 0.17, -0.13 ± 0.03, and -0.18 ± 0.14 for E(rr), E(cc), and E(ll), respectively. Peak end-systolic values for the shear strains were 0.00 ± 0.08, 0.04 ± 0.12, and 0.03 ± 0.07 for E(rc), E(rl), and E(cl), respectively. The peak end-systolic normalized torsion was 5.6 ± 0.9°.

Conclusions: Using a 3D cine DENSE sequence tailored for cardiac imaging in mice at 7 T, a comprehensive assessment of 3D myocardial mechanics can be achieved with a scan time of less than 25 minutes and an image analysis time of approximately 1 hour.

Show MeSH
Related in: MedlinePlus