Complementary Displacement-Encoded MRI for Contrast-Enhanced Infarct Detection and Quantification of Myocardial Function in Mice

MRI is emerging as an important modality for assessing myocardial function in transgenic and knockout mouse models of cardiovascular disease, including myocardial infarction (MI). Displacement encoding with stimulated echoes (DENSE) measures myocardial motion at high spatial resolution using phase-reconstructed images. The current DENSE technique uses inversion recovery (IR) to suppress T₁-relaxation artifacts; however, IR is ill-suited for contrast-enhanced infarct imaging in the heart, where multiple T ₁ values are observed. We have developed a modified DENSE method employing complementary acquisitions for T₁-independent artifact suppression. With this technique, displacement and strain are measured in phase-reconstructed images, and contrast-enhanced regions of infarction are depicted in perfectly coregistered magnitude-reconstructed images. The displacement measurements and T₁-weighted image contrast were validated with the use of a rotating phantom. Modified DENSE was performed in mice (N = 9) before and after MI. Circumferential (E_cc) and radial (E_rr) strain were measured, and contrast-enhanced infarcted myocardium was detected by DENSE. At baseline, E_cc was -0.16 ± 0.01 and E_rr was 0.39 ± 0.07. After MI, E _cc was 0.04 ± 0.02 and E_rr was 0.03 ± 0.04 in infarcted regions, whereas E_cc was -0.12 ± 0.02 and E _rr was 0.38 ± 0.09 in noninfarcted regions. In vivo E _cc as determined by DENSE correlated well with E_cc obtained by conventional tag analysis (R = 0.90).