Assessment of Myocardial Injury Using Magnetic Resonance Imaging
Left ventricular dysfunction may be the result of reversible or irreversible myocardial injury. Because there is significant difference in prognosis and clinical management for patients with damaged but viable myocardium and for those with nonviable myocardium, distinguishing the status of the myocardium has significant clinical relevance. One avenue that has been explored is magnetic resonance (MR) imaging in conjunction with MR contrast agents. However, there are conflicting reports on the accuracy of the common MR techniques, T1- and T2★-weighted imaging, as indicators of myocardial viability. To improve the reliability, we have developed a new MR imaging method, interleaved T1-T2★ imaging. This new approach monitors both T1 and T2★ signal intensities simultaneously during the first pass of an MR contrast agent. The interleaved T1-T2★ imaging separates viable from nonviable myocardium based on the contrast-induced changes in T1 and T2★ signals, which is related to the integrity of the cell membrane. Using isolated pig hearts we have found that the signal-time courses of the interleaved-T1-T2★ images obtained from normal myocardium are significantly different from those obtained from infarct rim and infarct core. The results of this study suggest that the integrity of cell membrane can be reliably assessed using the interleaved T1-T2★ imaging in conjunction with an MR contrast agent. Moreover, use of the new MR approach differentiates viable from nonviable myocardial viability.
Key wordsMyocardial infarction magnetic resonance imaging contrast reagent pig heart
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