T2 quantification for improved detection of myocardial edema

Abstract

BackgroundT2-Weighted (T2W) magnetic resonance imaging (MRI) pulse sequences have been used to detect edema in patients with acute myocardial infarction and differentiate acute from chronic infarction. T2W sequences have suffered from several problems including (i) signal intensity variability caused by phased array coils, (ii) high signal from slow moving ventricular chamber blood that can mimic and mask elevated T2 in sub-endocardial myocardium, (iii) motion artifacts, and (iv) the subjective nature of T2W image interpretation. In this work we demonstrate the advantages of a quantitative T2 mapping technique to accurately and reliably detect regions of edematous myocardial tissue without the limitations of qualitative T2W imaging.MethodsMethods of T2 mapping were evaluated on phantoms; the best of these protocols was then optimized for in vivo imaging. The optimized protocol was used to study the spatial, view-dependent, and inter-subject variability and motion sensitivity in healthy subjects. Using the insights gained from this, the utility of T2 mapping was demonstrated in a porcine model of acute myocardial infarction (AMI) and in three patients with AMI.ResultsT2-prepared SSFP demonstrated greater accuracy in estimating the T2 of phantoms than multi-echo turbo spin echo. The T2 of human myocardium was found to be 52.18 ± 3.4 ms (range: 48.96 ms to 55.67 ms), with variability between subjects unrelated to heart rate. Unlike T2W images, T2 maps did not show any signal variation due to the variable sensitivity of phased array coils and were insensitive to cardiac motion. In the three pigs and three patients with AMI, the T2 of the infarcted region was significantly higher than that of remote myocardium.ConclusionQuantitative T2 mapping addresses the well-known problems associated with T2W imaging of the heart and offers the potential for increased accuracy in the detection of myocardial edema.

T1, T2 Mapping and Extracellular Volume Fraction (ECV): Application, Value and Further Perspectives in Myocardial Inflammation and Cardiomyopathies

“…Furthermore, in a study by Hinojar et al, native T1 mapping enabled not only differentiation between healthy subjects and myocardial inflammation, but also of acute myocardial inflammation and convalescent disease stages [29]. In a phantom study by Giri et al, T2 mapping offered the potential for increased accuracy in the detection of myocardial edema [30] and in a study by Thavendiranathan et al T2 mapping delineated a greater extent of myocardial disease in myocarditis and takotsubo cardiomyopathy compared to other sequences [16]. A T2 cut-off value of 59 ms identified areas of involved myocardium with a sensitivity and specificity of 94 % and 97 %.…”

T‐Wave Abnormality as Electrocardiographic Signature of Myocardial Edema in Non‐ST‐Elevation Acute Coronary Syndromes

“…Myocardial T2 mapping was not available at the time CMR data were acquired in this cohort 26, 27. Further studies that incorporate CMR‐based myocardial relaxometry toward quantitation of both presence and severity of myocardial edema are warranted.…”

Coronary Thermodilution Waveforms After Acute Reperfused ST‐Segment–Elevation Myocardial Infarction: Relation to Microvascular Obstruction and Prognosis

“…The extent of myocardial edema was defined as LV myocardium with pixel values (T2) >2 standard deviations from remote myocardium 21, 22, 23, 24, 25, 26. Myocardial salvage was calculated by subtraction of percentage infarct size from percentage area at risk, as reflected by the extent of edema 23, 26, 27.…”