Accuracy and precision of chronic myocardial infarct characterization with native T1 mapping at 3T
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KeywordsInfarct Size Standard Deviation Late Gadolinium Enhancement Late Gadolinium Enhancement Image Remote Myocardium
Native T1-maping at 3T has been shown to reliably characterize chronic myocardial infarctions (MIs). In this study, we evaluated the accuracy and precision of different thresholding techniques and visual delineation for characterizing chronic MIs on native T1 maps at 3T.
Canines (n=23) underwent CMR at 4 months following MI. Native T1 maps (MOLLI; 8 TIs with 2 inversion blocks of 3+5 images; minimum TI=110ms; ΔTI=80ms; TR/TE=2.2/1.1ms) and Late Gadolinium Enhancement images (LGE; IR-prepared FLASH; TI optimized to null remote myocardium; TR/TE=3.5/1.75ms) were acquired at 3T. Infarct size and transmurality measured using Mean + 2 standard deviations (SD), Mean+3SD, Mean+4SD, Mean+5SD, Mean+6SD, Otsu's, and visual delineation methods were compared against the Mean+5SD LGE measurements, and their relative diagnostic performance was evaluated.
Relative to LGE images, mean infarct size and transmurality measured from native T1 maps were significantly over-estimated by Mean+2SD, Mean+3SD, and Mean+4SD techniques (p<0.001, for all cases). Mean+6SD criterion and visual delineation significantly underestimated infarct size (p<0.001 for both cases) and transmurality (p=0.01 for Mean+6SD; p<0.001 for visual) on native T1 maps. Otsu's technique showed no difference for measuring infarct size on native T1 maps compared to LGE images (p=0.27), but it over-estimated the infarct transmurality (p<0.001). Mean+5SD criterion showed no difference for measuring either infarct size (p=0.61) or transmurality (p=0.81) on T1 maps relative to LGE images. Mean CNR of LGE images was nearly 4-fold higher than that of native T1 maps (p<0.001). Mean+5SD criterion for detecting chronic MIs on native T1 maps at 3T showed the strongest diagnostic performance (area-under-curve=0.99, p<0.001), while visual delineation showed the weakest diagnostic performance (area-under-curve=0.84, p<0.001).
Threshold-based analysis using Mean+5SD criterion can accurately and precisely estimate the size, location and transmurality of chronic MIs on native T1 maps as reliably as LGE at 3T.
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