Self-Gated Late Gadolinium Enhancement at 7T to Image Rats with Reperfused Acute Myocardial Infarction

Objective: A failed electrocardiography (ECG)-trigger often leads to a long acquisition time (TA) and deterioration in image quality. The purpose of this study was to evaluate and optimize the technique of self-gated (SG) cardiovascular magnetic resonance (CMR) for cardiac late gadolinium enhancement (LGE) imaging of rats with myocardial infarction/reperfusion. Materials and Methods: Cardiovascular magnetic resonance images of 10 rats were obtained using SG-LGE or ECG with respiration double-gating (ECG-RESP-gating) method at 7T to compare differences in image interference and TA between the two methods. A variety of flip angles (FA: $10^{\circ}-80^{\circ}$) and the number of repetitions (NR: 40, 80, 150, and 300) were investigated to determine optimal scan parameters of SG-LGE technique based on image quality score and contrast-to-noise ratio (CNR). Results: Self-gated late gadolinium enhancement allowed successful scan in 10 (100%) rats. However, only 4 (40%) rats were successfully scanned with the ECG-RESP-gating method. TAs with SG-LGE varied depending on NR used (TA: 41, 82, 154, and 307 seconds, corresponding to NR of 40, 80, 150, and 300, respectively). For the ECG-RESP-gating method, the average TA was 220 seconds. For SG-LGE images, CNR ($42.5{\pm}5.5$, $43.5{\pm}7.5$, $54{\pm}9$, $59.5{\pm}8.5$, $56{\pm}13$, $54{\pm}8$, and $41{\pm}9$) and image quality score ($1.85{\pm}0.75$, $2.20{\pm}0.83$, $2.85{\pm}0.37$, $3.85{\pm}0.52$, $2.8{\pm}0.51$, $2.45{\pm}0.76$, and $1.95{\pm}0.60$) were achieved with different FAs ($10^{\circ}$, $15^{\circ}$, $20^{\circ}$, $25^{\circ}$, $30^{\circ}$, $35^{\circ}$, and $40^{\circ}$, respectively). Optimal FAs of $20^{\circ}-30^{\circ}$ and NR of 80 were recommended. Conclusion: Self-gated technique can improve image quality of LGE without irregular ECG or respiration gating. Therefore, SG-LGE can be used an alternative method of ECG-RESP-gating.