Quantification of myocardial hemorrhage using T2* cardiovascular magnetic resonance at 1.5T with ex-vivo validation

Figures

• 

  Fig. 1. Representative Findings in Patients—Subject-Specific T2* (ssT2*) vs. 20-ms Absolute T2* (aT2* < 20 ms) Cut-off for Hemorrhage Characterization. Representative 2D short-axis T2*-weighted and T2* image sets, along with late-gadolinium-enhanced (LGE) CMR, acquired at 1.5T in patients with hemorrhagic myocardial infarction (MI) in the left anterior descending coronary artery (LAD), left circumflex coronary artery (LCX) and right coronary artery (RCA) territories in the acute (A) and chronic (B) myocardial infarction (MI) phases are shown. Both raw and processed image sets [using ssT2* (second column of panels A and B) and aT2* < 20 ms (third column of panels A and B)] are shown side-by-side for comparison. Magnified representation of T2* maps for the LAD infarction in panels A, B are shown in panel C. Note that although the location of intramyocardial hemorrhage (IMH) is the same with both ssT2* and aT2* < 20 ms, the extent of IMH identified using aT2* < 20 ms approach are visually smaller (see red arrows) compared to that determined using ssT2*

• 

  Fig. 2. Representative Findings in Canines—Subject-Specific T2* vs. 20-ms Absolute T2* Cut-off for Hemorrhage Characterization. Representative T2* maps and corresponding LGE acquired at 1.5T in a canine with hemorrhagic MI in the LAD territory in the acute and chronic phases A. Ex-vivo T2* maps, along with histological validation of IMH are shown in panel B. Perl’s stain showed the presence of the iron deposition in the infarcted myocardium (arrow) which is not evident in the remote territory. In panels A, B both raw and processed image sets [using ssT2* (second column) and aT2* < 20 ms (third column)] are shown side-by-side for comparison. Panel C shows magnified representation of T2 maps from panels A, B. Note that similar to patients, although the location of IMH is the same with both ssT2* and aT2* < 20 ms, the extent of IMH identified using aT2* < 20 ms approach are visually smaller (see red arrows) compared to that determined using ssT2*

• 

  Fig. 3. Linear Regression Analysis and Bland–Altman Plot for T2* of IMH Determined Using ssT2* and aT2* < 20 ms. A Linear regression analysis in patients (left—acute; right—chronic) were strongly correlated but the absolute T2* values deviated significantly (slopes < 1.0, both p < 0.001), which was also shown by Bland–Altman plot (B). C Linear regression analysis in animals at acute (left—acute; middle—chronic; and right—ex-vivo) show similar strong regressions and highly discordance T2* values as evidenced by the lines of best fit having slopes < 1.0 (all p ≤ 0.001). D shows Bland–Altman plot. The black solid lines denote the 95% confidence bands, and for reference the dotted line denoting the line of identify is shown

• 

  Fig. 4. Linear Regression Analysis and Bland–Altman Plot for IMH Volume Determined Using ssT2* and aT2* < 20 ms. A Linear regression analysis in patients (left—acute; right—chronic MI) were strongly correlated but the IMH volumes deviated significantly (slopes < 1.0, both p < 0.001), which was also shown by Bland–Altman plot (B). C Linear regression analysis in animals at acute MI (left—acute; middle—chronic; and right—ex-vivo) show similar strong regressions and highly discordance IMH volumes as evidenced by the lines of best fit having slopes < 1.0 (all p < 0.05). D shows Bland–Altman plot. The black solid lines denote the 95% confidence bands, and for reference the dotted line denoting the line of identify is shown

• 

  Fig. 5. Relation between T2* and Iron Concentration Determined Using ssT2* and Absolute T2* with Various Cut-offs. A T2* and iron concentration ([Fe]Hemo) determined with ssT2* at cut-offs of mean-2SD, mean-3SD and mean-4SD. B T2* and iron concentration determined with absolute T2* at cut-offs of 15 ms, 20 ms and 25 ms. Note that both ssT2* and absolute T2* approaches yield a high correlation between log (T2*) and -log ([Fe]Hemo). However, note that the slope of the absolute T2* approach is markedly lower compared to ssT2* approach, regardless of the threshold, which supports the notion that the absolute T2* has a lower sensitivity compared to ssT2* approach for detecting changes in iron concentration. The regression lines are shown in blue and 95% confidence are shown in black

• 

  Fig. 6. Optimization of Absolute T2* Cut-offs for Detecting IMH and Quantifying IMH volume. ROC curves for IMH detection based on segmental analysis of T2* images obtained in the acute and chronic phases using absolute T2* cut-offs in patients are shown in A left panel. A right panel shows optimized T2* cut-off with corresponding area under the cure (AUC), sensitivity, specificity and accuracy. B left panel shows the IMH volume detected at the whole-heart level at the various absolute T2* thresholds of 5–30 ms (in increments of 5 ms) and ssT2*. B right panel shows IMH volume detected at the whole-heart level in the acute and chronic phases based on optimized absolute T2* cut-off identified in A relative to ssT2*. ROC curves for IMH detection based on segmental analysis of T2* images obtained in the acute and chronic phases using absolute T2* cut-offs in animals are shown in C left panel. C right panel shows optimized T2* cut-off with corresponding area under the cure (AUC), sensitivity, specificity and accuracy. D left panel shows the IMH volume detected at the whole-heart level at the various absolute T2* thresholds of 5–30 ms (in increments of 5 ms) and ssT2*. D right panel shows IMH…