Head‐to‐head comparison between delayed enhancement and percent infarct mapping for assessment of myocardial infarct size in a canine model

Abstract

Purpose: To compare a novel method, percent-infarctmapping (PIM), with conventional delayed enhancement (DE) of contrast for accurate myocardial viability assessment. Contrary to signal intensity (SI), the longitudinal relaxation-rate enhancement (⌬R1) is an intrinsic parameter linearly proportional to the concentration of contrast agent (CA). Determining ⌬R1 voxel-by-voxel, after administering an infarct-avid CA, allows determination of pervoxel percentage of infarcted tissue. The feasibility of generating PIM is demonstrated in canine reperfused infarction using an infarct-avid, persistent-CA (PCA), (Gd)(ABE-DTTA). PIM is compared to the DE method using Gd(DTPA), and both to triphenyltetrazolium chloride (TTC) staining histochemistry. Materials and Methods:In six dogs, 48 hours following closed-chest, 180-minute coronary occlusion, DE imaging was carried out. PCA was administered immediately thereafter. Pixel-by-pixel R1 maps of the entire left ventricle (LV) were generated 48 hours after PCA using inversion-recovery with multiple inversion times. R1, ⌬R1, and percentinfarct values were calculated voxel-by-voxel.Results: Significant correlations (P Ͻ 0.01, R Ն 0.8) were obtained for percent-infarct-per-slice (PIS) determined by DE or PIM vs. those from corresponding TTC-stained slices. Compared to TTC, DE overestimated PIS by 32 Ϯ 18%. PIM underestimated PIS by 2.5 Ϯ 4.9%. Infarction fraction overestimation was 29 Ϯ 6% of LV by DE, but only 1.0 Ϯ 2.3% by PIM. Errors with PIM were significantly smaller than those with DE. Infarct area determined by signal intensity was similarly overestimated whether using Gd(DTPA) or Gd(ABE-DTTA). Conclusion:The ⌬R1-based PIM method is highly reproducible and more accurate than DE for quantifying myocardial viability in vivo.

Novel MRI and CT Approaches for the Characterization of Myocardial Infarct

“…With the help of using paramagnetic relaxation rate enhancement, DR1 (the difference between inverse T1 with and without the presence of contrast agent), a continuous scale is assigned in each infarcted voxel. Based on contrast accumulation of the infarcted volume element of interest, a Percent Infarct Map (PIM) can be created [49,50]. PIM can not only assess the infarct size, or the global parameter called ''infarction fraction'', but also the density (i.e.…”

Acute infarct selective MRI contrast agent

“…This CA attains its maximum concentration in the acutely infarcted tissue around 48 h after administration, but a useful contrast is already achieved at 24 h. The contrast remains detectable in the infarct for a few days [8]. Gd(ABE-DTTA) quantifies the extent of acute MI accurately [9, 10]. …”

Percent infarct mapping for delayed contrast enhancement magnetic resonance imaging to quantify myocardial viability by Gd(DTPA)

“…(18,19) PIM quantifies infarct density in each voxel individually, and yields a percent infarct (PI) value for each voxel, based on R1-enhancement induced by the contrast agent. PIM, however, cannot be measured for the time being in a short enough time frame, since using commercially available sequences and, with the number of slices necessary to cover the left ventricle (LV), acquisition time would be on the order of 30-40 min.…”

“…Investigational contrast agent enhanced (17), R1based infarct-quantification method, percent-infarctmapping (PIM) was developed, and validated in in vivo animal studies (18,19). PIM quantifies infarct density in each voxel individually, and yields a percent infarct (PI) value for each voxel, based on R1-enhancement induced by the contrast agent.…”