- Workshop presentation
- Open Access
Non-contrast T1 and T2 relaxometry characterizes reperfusion injury of acute MI in swine
© Ding et al; licensee BioMed Central Ltd. 2015
- Published: 3 February 2015
- Myocardial Infarction
- Acute Myocardial Infarction
- Reperfusion Injury
- Balloon Occlusion
- Microvascular Obstruction
Reperfusion injury in acute myocardial infarction (MI) results in edema, necrosis, microvascular obstruction (MVO), and intramyocardial hemorrhage (IMH), the latter presents an interesting clinical target.  Cardiovascular MRI has been shown capable of characterizing all of these tissue components. Other than MVO, which is currently detected by flow-deficient regions in contrast enhanced imaging, all other tissue components can be identified by T1 and T2 (T2*). Theoretically, the byproducts of blood breakdown observed with IMH lead to decreased T1 and T2 (T2*).  Conversely, free water accumulation (edema) and necrosis lead to increased T1 and T2.  Hence, direct and quantitative measurement of relaxation rates is promising in myocardial tissue characterization, avoiding ambiguity typical of weighted images (i.e. T2-weighted spin-echo), undesired signal loss from T2* (weighted) images or the uncertainty introduced by contrast agent kinetics. Hypothesis: Combined T1 and T2 mapping can characterize reperfused MI without contrast agents.
MI was induced in swine by 1 (N=3) or 2 (N=3) hr balloon occlusion of the LAD after the first diagonal, with MRI 7-9 days post MI (Achieva TX, Philips). Relaxometry: 3D respiratory navigator-gated T2-mapping ; 2D Breath-hold T1-mapping (MOLLI) . Clinical standard: breath-hold black-blood T2W TSE (BB-T2-STIR) ; early (3 min post) gadolinium-enhanced images (EGE) using PSIR and 0.2 mmol/kg Magnevist. . IMH was identified in T2W images/T1/T2 maps as areas of hypointensity surrounded by hyperintense signal/T1/T2 representing edema. MVO was defined in EGE images as hypointense areas surrounded by enhanced MI. The co-localization of tissue types among techniques was examined.
Though either T1 or T2 can be used to separate tissues, combined T1 and T2 mapping may allow for more accurate detection of IMH in reperfusion injury, without variability from contrast kinetics, or BB-T2-STIR artifacts.  Based on a small number of animals, T2 was superior in edema detection, while T1 performed better in IMH detection. Combined relaxometry may identify tissues with better specificity than individual and may help clarify the link between MVO and IMH. High-resolution relaxometry may be necessary to avoid partial volume.
Funded in part by the American Heart Association - 11SDG5280025.
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.