Magnetic resonance susceptibility weighted phase imaging for the assessment of reperfusion intramyocardial hemorrhage

PURPOSE: To quantitatively investigate myocardial phase in multiple-gradient-echo images to determine normal phase angle ranges as a function of echo time and anatomical position and then compare phase values from patients with myocardial infarction with those normal ranges to determine the feasibility of intramyocardial hemorrhage detection. METHODS: Fifteen normal control and 11 patients with reperfused myocardial infarction participated in this prospective study. A 1.5 T magnetic resonance system was used to perform volumetric CINE, high-pass filtered (HPF) phase, T2-weighted, T2*-weighted and late gadolinium-enhanced infarct imaging at four times points after myocardial infarction. HPF-phase analyzed using a 16-segment model was compared with late gadolinium-enhanced infarct imaging and T2* measurements. RESULTS: Myocardial HPF-phase angle in the normal control group was small (-0.008 ± 0.027 radians). There was a difference between anatomical segments, with less variation in septal segments compared with cyclic variations in non-septal segments. Abnormal phase was only shown in myocardial segments with transmural late gadolinium-enhanced and microvascular obstruction consistent with intramyocardial hemorrhage. There were six studies from three patients (seven segments at 3 days, five segments at follow-up) with HPF-phase outside of normal range indicative of intramyocardial hemorrhage. CONCLUSION: Myocardial HPF-phase angle is normally small and varies by anatomical myocardial segment. intramyocardial hemorrhage causes a phase decrease beyond normal variations.