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Quantitative first-pass perfusion MRI of the mouse heart

Introduction

First-pass contrast-enhanced MRI is well established for quantifying myocardial perfusion in humans and large animals. This method would be valuable for genetically-engineered mice to study the roles of individual genes in myocardial perfusion. However, the small size and rapid heart rate of mice present technical challenges.

Purpose

To develop first-pass MRI of the mouse heart and evaluate these methods in a myocardial infarction (MI) model.

Methods

Imaging was performed on a 7 T scanner using a gradient system with a full strength of 650 mT/m and a slew rate of 6666 mT/m/ms, using a 30 mm diameter birdcage RF coil. A saturation-recovery spiral sequence was implemented, with TE = 0.36 msec, TR = 3.9 msec, interleaves = 10, FOV = 25.6 × 25.6 mm, matrix = 128 × 128, saturation delay = 40 msec, alpha = 20°, and slice thickness = 1 mm. Data acquisition was placed near the end of the cardiac cycle and its duration was 39 msec/image, approximately 1/3 of the R-R interval. Wild-type mice were imaged at baseline (n = 4) and 1 day after MI (n = 3). MI was induced by a 1 hour coronary artery occlusion. Mice were anesthetized with 1.2% isoflurane and maintained at 37°C during MRI. The dual-bolus technique was used, acquiring the arterial input and tissue functions (AIF and TF) separately. Perfusion was quantified using Fermi function deconvolution. Perfusion images were acquired for one mid-ventricular short-axis slice, and late gadolinium-enhanced (LGE) images were acquired covering the left ventricle (LV).

Results

First-pass images demonstrated uniform perfusion at baseline and reduced perfusion in the infarct zone (as defined by LGE) after MI. Example [Gd] vs. time curves for the AIF, remote zone, and infarct zone are shown in Figure 1A. Figure 1B quantifies perfusion at baseline and 1 day after MI for the infarct and remote zones. Example images are shown in Figure 1C before (i), 2 seconds after (ii), and 4 seconds after (iii) Gd injection. The perfusion defect can be observed in the anterior wall. Baseline perfusion was 4.7 ± 0.4 ml/g/min. One day after MI, infarct zone perfusion of 1.4 ± 0.4 ml/g/min was significantly lower than baseline perfusion (p < .01), while remote zone perfusion of 3.7 ± 1.6 ml/g/min was not significantly different than baseline.

figure1

Figure 1

Conclusion

To the best of our knowledge, this is the first report of first-pass cardiac MRI in mice. This technique demonstrated homogenous perfusion in normal hearts and the expected regional heterogeneity of perfusion on day 1 post-MI.

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Correspondence to Patrick F Antkowiak.

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Open Access This article is published under license to BioMed Central Ltd. This is an Open Access article is distributed under the terms of the Creative Commons Attribution 2.0 International License (https://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Antkowiak, P.F., Janiczek, R.L., Gibberman, L.B. et al. Quantitative first-pass perfusion MRI of the mouse heart. J Cardiovasc Magn Reson 12, M10 (2010). https://doi.org/10.1186/1532-429X-12-S1-M10

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Keywords

  • Myocardial Perfusion
  • Infarct Zone
  • Remote Zone
  • Rapid Heart Rate
  • Baseline Perfusion