Assessment of myocardial infarction in mice by late gadolinium enhancement MR imaging using an inversion recovery pulse sequence at 9.4T.

Catherine Chapon,Amy H Herlihy,Kishore K Bhakoo

doi:10.1186/1532-429x-10-6

Abstract

PurposeTo demonstrate the feasibility of using an inversion recovery pulse sequence and to define the optimal inversion time (TI) to assess myocardial infarction in mice by late gadolinium enhancement (LGE) MRI at 9.4T, and to obtain the maximal contrast between the infarcted and the viable myocardium.MethodsMRI 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).ResultsThe 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).ConclusionDespite 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.

Highlights

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]
Transmural myocardial infarction was confirmed in all mice using TTC staining (Figure 2)
The signal-to-noise ratio (SNR) in the viable myocardium was at its minimum (17.2 ± 2.4, ranging from 12.8 to 23.1) for a mean TI of 268 msec ± 27.3 corresponding to the optimal TI

Summary

Introduction

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]. At present the assessment of infarct size in small animals at high magnetic fields is performed using a 'cine gradient echo pulse sequence' with a high dose of gadolinium chelates [4]. This type of MR protocol is limited in its ability to accurately delineate the infarcted tissue from the normal non-infarcted myocardium [1,5]. This approach has not been extensively described in the literature for cardiac MR studies in small animals at high magnetic field (such as 9.4T), due to the rapid heart rate (500–600 bpm in mice and 300–400 bpm in rats) [4]

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