Abstract
BackgroundMyocardial infarction (MI) can be readily assessed using late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR). Inversion recovery (IR) sequences provide the highest contrast between enhanced infarct areas and healthy myocardium. Applying such methods to small animals is challenging due to rapid respiratory and cardiac rates relative to T1 relaxation.MethodsHere we present a fast and robust protocol for assessing LGE in small animals using a multi-slice IR gradient echo sequence for efficient assessment of LGE. An additional Look-Locker sequence was used to assess the optimum inversion point on an individual basis and to determine most appropriate gating points for both rat and mouse. The technique was applied to two preclinical scenarios: i) an acute (2 hour) reperfused model of MI in rats and ii) mice 2 days following non-reperfused MI.ResultsLGE images from all animals revealed clear areas of enhancement allowing for easy volume segmentation. Typical inversion times required to null healthy myocardium in rats were between 300-450 ms equivalent to 2-3 R-waves and ~330 ms in mice, typically 3 R-waves following inversion. Data from rats was also validated against triphenyltetrazolium chloride staining and revealed close agreement for infarct size.ConclusionThe LGE protocol presented provides a reliable method for acquiring images of high contrast and quality without excessive scan times, enabling higher throughput in experimental studies requiring reliable assessment of MI.
Highlights
Myocardial infarction (MI) can be readily assessed using late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR)
In order to achieve the maximum contrast between infarcted myocardium and the normal healthy myocardium, it is necessary to use an Inversion recovery (IR) technique with the appropriate inversion time (TI)
Finding the optimum TI, in order to sufficiently null the signal from normal myocardium, can be difficult to assess at high field, as TI is typically several times longer than the R-R wave interval, even after relatively high doses of contrast agent
Summary
Myocardial infarction (MI) can be readily assessed using late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR). Inversion recovery (IR) sequences provide the highest contrast between enhanced infarct areas and healthy myocardium Applying such methods to small animals is challenging due to rapid respiratory and cardiac rates relative to T1 relaxation. Many of the CMR techniques that are used as standard in the clinical setting remain a significant challenge to implement in small animals especially at high field [6], where relatively few optimised protocols are available as standard on experimental systems One such technique, regarded as the gold standard for assessing myocardial infarction (MI) in patients [7], is late gadolinium enhancement (LGE) CMR. The extent of the LGE region is typically assessed using an inversion recovery (IR) breath-hold sequence, which can be readily applied to larger animals used in cardiovascular research [8,9]. Achieving the best contrast whilst maintaining high quality images that have optimum gating, relative to both the respiratory and cardiac cycles, is key to accurate assessment of MI using LGE CMR in small animals
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