Abstract
Methods Acquisition Protocol: Basal, mid, and apical slices in short axis orientation were obtained in a pig (n=14) AMI model (LAD occlusion) at 3.0T (Ingenia, Philips Healthcare): a) Cine SSFP: TR/TE/a = 3/1.5 ms/45°; acquired temporal resolution: 12 ms. b) Delayed enhancement MRI (DE-MRI): 10 min after 0.2 mmol/kg of contrast, scar was visualized using a gated IR-TFE sequence with inversion delay (TI) adjusted to null normal myocardium. c) Dual-IR T2W imaging (BB): Effective TE/TR: 80 ms/2*RR interval; TSE readout. Data Analysis: Myocardial region was manually segmented from cine, DE-MRI, and BB images (Figure 1) using MATLABTM. Myocardial region was sub-divided into co-registered segments of equal mass for each animal to calculate the following quantitative parameters: 1) Normalized wall thickness (nWT) per segment = (WTES WTED)/( WTED), where ED = End-Diastole, ES-End-Systole. 2) Segmental scar burden, defined as ratio of pixels designated as scar to total number of pixels in each segment of DE-MRI. Scar pixel is one with SI > [mean + 5*Standard Deviation (SD) of normal remote myocardium]. 3) Segmental AAR, defined as regions in BB images with SI > mean + n*SD of normal remote myocardium (AAR with n = 2, 3, 4 are AAR_2SD, AAR_3SD, and AAR_4SD, respectively).
Highlights
Elevated signal intensity (SI) in T2w images is often designated as area-at-risk (AAR) following acute/subacute MI
Data Analysis: Myocardial region was manually segmented from cine, DE-MRI, and BB images (Figure 1) using MATLABTM
Myocardial region was sub-divided into co-registered segments of equal mass for each animal to calculate the following quantitative parameters: 1) Normalized wall thickness per segment = (WTES - WTED)/( WTED), where ED = End-Diastole, ES-End-Systole
Summary
Elevated signal intensity (SI) in T2w images is often designated as area-at-risk (AAR) following acute/subacute MI. Purpose In an animal model, quantify the: 1) Effect of SI threshold on estimating AAR, 2) Reduction in WT with AAR at increasing SI thresholds, and 3) Correlation between AAR and percent scar. Methods Acquisition Protocol: Basal, mid, and apical slices in short axis orientation were obtained in a pig (n=14) AMI model (LAD occlusion) at 3.0T (Ingenia, Philips Healthcare): a) Cine SSFP: TR/TE/a = 3/1.5 ms/45°; acquired temporal resolution: 12 ms.
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