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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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Myocardial twist and torsion as a function of cardiac phase measured by 3D cine DENSE in seven mice. Myocardial twist and torsion as a function of cardiac phase measured by 3D cine DENSE in seven mice. In (A), twist angle as a function of cardiac phase is shown for basal, mid-ventricular, and apical locations. In (B), LV torsion, which is the normalized gradient of twist in the longitudinal direction, is plotted. Data are plotted as mean ± standard error.
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Figure 8: Myocardial twist and torsion as a function of cardiac phase measured by 3D cine DENSE in seven mice. Myocardial twist and torsion as a function of cardiac phase measured by 3D cine DENSE in seven mice. In (A), twist angle as a function of cardiac phase is shown for basal, mid-ventricular, and apical locations. In (B), LV torsion, which is the normalized gradient of twist in the longitudinal direction, is plotted. Data are plotted as mean ± standard error.

Mentions: Lastly, using displacements that were measured in basal, mid-ventricular, and apical slices, we calculated myocardial twist and torsion as a function of cardiac phase. These results are displayed in Figure 8. Specifically, Figure 8A shows twist as a function of cardiac phase for short-axis slices at three different levels. At the basal level, very little twisting is observed. At the mid-ventricular level, an intermediate amount of counterclockwise twisting is seen, with a peak of approximately 4° at end systole. At the apical level, a greater amount of counterclockwise twisting is seen, with a peak of approximately 8° at end systole. In all slices, untwisting is observed during diastole. From twist data measured at multiple longitudinal levels, normalized LV torsion is computed as shown in Figure 8B, with a peak end-systolic value of 5.6 ± 0.9°.


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)

Myocardial twist and torsion as a function of cardiac phase measured by 3D cine DENSE in seven mice. Myocardial twist and torsion as a function of cardiac phase measured by 3D cine DENSE in seven mice. In (A), twist angle as a function of cardiac phase is shown for basal, mid-ventricular, and apical locations. In (B), LV torsion, which is the normalized gradient of twist in the longitudinal direction, is plotted. Data are plotted as mean ± standard error.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 8: Myocardial twist and torsion as a function of cardiac phase measured by 3D cine DENSE in seven mice. Myocardial twist and torsion as a function of cardiac phase measured by 3D cine DENSE in seven mice. In (A), twist angle as a function of cardiac phase is shown for basal, mid-ventricular, and apical locations. In (B), LV torsion, which is the normalized gradient of twist in the longitudinal direction, is plotted. Data are plotted as mean ± standard error.
Mentions: Lastly, using displacements that were measured in basal, mid-ventricular, and apical slices, we calculated myocardial twist and torsion as a function of cardiac phase. These results are displayed in Figure 8. Specifically, Figure 8A shows twist as a function of cardiac phase for short-axis slices at three different levels. At the basal level, very little twisting is observed. At the mid-ventricular level, an intermediate amount of counterclockwise twisting is seen, with a peak of approximately 4° at end systole. At the apical level, a greater amount of counterclockwise twisting is seen, with a peak of approximately 8° at end systole. In all slices, untwisting is observed during diastole. From twist data measured at multiple longitudinal levels, normalized LV torsion is computed as shown in Figure 8B, with a peak end-systolic value of 5.6 ± 0.9°.

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