Fast, whole-heart, free-breathing 3D T2 mapping at 3T with application to myocardial edema imaging
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KeywordsMyocardial Edema Edema Volume Navigator Efficiency Reperfused Acute Myocardial Infarction Navigator Signal
Cardiac MRI (CMR) T2 mapping is a proven method for myocardial edema detection. However, the current approach requires multiple breath-holds and can take nearly 10-15 minutes to complete. Faster acquisitions could potentially improve patient comfort and cost-effectiveness of CMR exams. the objecttive of this study is to develop and test a free-breathing, three-dimensional, cardiac MR approach which can yield fast, accurate, T2 maps of the whole left ventricle at 3T.
We developed an ECG-triggered, free-breathing, T2-prepared, three-dimensional gradient-echo acquisitions with different echo times (0, 24, 55 ms) with near perfect navigator efficiency on a clinical 3T system. The proposed approach was tested and validated in ex-vivo porcine hearts, healthy volunteers and canines with reperfused acute myocardial infarction (rAMI). On the basis of the navigator signals, images were corrected for respiratory motion and were fit to a mono-exponential function to derive T2 maps of the whole left-ventricular myocardium.
Ex-vivo myocardial T2 values of the proposed approach (3D FB MoCo) were not different from standard 2D approaches (all p<0.05): 48.7±0.9 ms (3D FB MoCo) vs. 48.2±0.6 ms (2D spin echo) and 47.5±0.8 ms (2D T2-prepared bSSFP (T2-prep bSSFP)). In healthy volunteers, compared to 3D FB MoCo and 2D BH, myocardial T2 maps, 3D FB Non-MoCo T2 myocardial maps showed longer T2 values (p<0.05), larger coefficient-of-variations (COV) in T2 (p<0.05), and lower image quality (p<0.05). Conversely, the mean and COV in myocardial T2 and image quality of 2D BH and 3D FB MoCo T2 were not different (p=0.99, p=0.74, p=0.14, respectively). In canines with rAMI, edema volumes measured from 2D BH and 3D FB MoCo T2 maps were closely correlated (both R2 = 0.97 and p<0.05). In Bland-Altman analysis, mean T2 of edematous and remote zones and edema volumes were within the limits of agreement (bias in T2 = 0.4 ms and edema volume = 0.9%).
The proposed free-breathing, three-dimensional T2 mapping approach at 3T enabled whole-heart acquisitions within 5 minutes with an accuracy in T2 not different from that of the state-of-the-art breath-held T2 mapping approach.
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