Assessment of myocardial infarction in mice by Late Gadolinium Enhancement MR imaging using an inversion recovery pulse sequence at 9.4T

MRI was performed at 9.4T in mice, two days after induction of myocardial infarction (n = 4). For cardiovascular MR imaging, a segmented magnetization-prepared fast low angle shot (MP-FLASH) sequence was used with varied TIs ranging from 40 to 420 ms following administration of gadolinium-DTPA at 0.6 mmol/kg. Contrast-to-noise (CNR) and signal-to-noise ratio (SNR) were measured and compared for each myocardial region of interest (ROI).The optimal TI, which corresponded to a minimum SNR in the normal myocardium, was 268 ms ± 27.3. The SNR in the viable myocardium was significantly different from that found in the infarcted myocardium (17.2 ± 2.4 vs 82.1 ± 10.8; p = 0.006) leading to a maximal relative SI (Signal Intensity) between those two areas (344.9 ± 60.4).Despite the rapid heart rate in mice, our study demonstrates that LGE MRI can be performed at 9.4T using a protocol similar to the one used for clinical MR diagnosis of myocardial infarction.Late Gadolinium Enhancement (LGE) cardiovascular magnetic resonance (CMR) imaging using a T1-weighted sequence with an inversion recovery (IR) pre-pulse is commonly used for the clinical diagnosis of myocardial infarction in humans [1,2], and experimentally in large animals [3]. The time to inversion (TI) is selected to null the signal intensity (SI) in the non-infarcted (viable) myocardium, following administration of chelated gadolinium, in order to increase contrast between the viable and hyper-enhanced infarcted myocardium [1]. Late gadolinium enhancement MR imaging with inversion recovery techniques has been shown to correlate well as an early marker of irreversible injury and eventual fibrosis [3].More recently, the mouse model has been used increasingly for investigating the mechanisms of myocardial diseases. Hence, its essential to assess myocardial infarction in pre-clinical models in a manner similar to that used for clinical diagnosis. At present the assessment of infarct size in small animals at high magnetic f