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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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Normal strain-time curves for healthy mice measured by 3D cine DENSE. Normal strain-time curves for healthy mice measured by 3D cine DENSE. The average Err, Ecc, and Ell values for the 7 mice studied are plotted as a function of cardiac phase. Furthermore, separate curves are shown for the subendocardial and subepicardial layers. A statistically significant difference in Ecc between the two layers was detected (B). No significant differences between layers were found for Err and Ell, although both of these strains showed consistent trends towards larger absolute values in the subendo- vs. subepicardium. Data are plotted as mean ± standard error.
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Figure 6: Normal strain-time curves for healthy mice measured by 3D cine DENSE. Normal strain-time curves for healthy mice measured by 3D cine DENSE. The average Err, Ecc, and Ell values for the 7 mice studied are plotted as a function of cardiac phase. Furthermore, separate curves are shown for the subendocardial and subepicardial layers. A statistically significant difference in Ecc between the two layers was detected (B). No significant differences between layers were found for Err and Ell, although both of these strains showed consistent trends towards larger absolute values in the subendo- vs. subepicardium. Data are plotted as mean ± standard error.

Mentions: Using 3D cine DENSE, in addition to extensive spatial coverage, myocardial mechanics are measured as a function of cardiac phase across the cardiac cycle. For example, data summarizing the time-varying normal strains at the mid-ventricular level for all seven mice are shown in Figure 6, where Err, Ecc, and Ell, are plotted. These results demonstrate the measurement of normal radial thickening, circumferential shortening, and longitudinal shortening in healthy mice. The high spatial resolution of strain provided by cine DENSE is evident in these measurements, as statistically significant transmural differences in Ecc are resolved using this technique, where the thickness of the LV wall is approximately 1 mm.


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)

Normal strain-time curves for healthy mice measured by 3D cine DENSE. Normal strain-time curves for healthy mice measured by 3D cine DENSE. The average Err, Ecc, and Ell values for the 7 mice studied are plotted as a function of cardiac phase. Furthermore, separate curves are shown for the subendocardial and subepicardial layers. A statistically significant difference in Ecc between the two layers was detected (B). No significant differences between layers were found for Err and Ell, although both of these strains showed consistent trends towards larger absolute values in the subendo- vs. subepicardium. 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 6: Normal strain-time curves for healthy mice measured by 3D cine DENSE. Normal strain-time curves for healthy mice measured by 3D cine DENSE. The average Err, Ecc, and Ell values for the 7 mice studied are plotted as a function of cardiac phase. Furthermore, separate curves are shown for the subendocardial and subepicardial layers. A statistically significant difference in Ecc between the two layers was detected (B). No significant differences between layers were found for Err and Ell, although both of these strains showed consistent trends towards larger absolute values in the subendo- vs. subepicardium. Data are plotted as mean ± standard error.
Mentions: Using 3D cine DENSE, in addition to extensive spatial coverage, myocardial mechanics are measured as a function of cardiac phase across the cardiac cycle. For example, data summarizing the time-varying normal strains at the mid-ventricular level for all seven mice are shown in Figure 6, where Err, Ecc, and Ell, are plotted. These results demonstrate the measurement of normal radial thickening, circumferential shortening, and longitudinal shortening in healthy mice. The high spatial resolution of strain provided by cine DENSE is evident in these measurements, as statistically significant transmural differences in Ecc are resolved using this technique, where the thickness of the LV wall is approximately 1 mm.

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