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Stunned, Infarcted, and Normal Myocardium in Dogs: Simultaneous Differentiation by Using Gadolinium-enhanced Cine MR Imaging with Magnetization Transfer Contrast¹

¹ From the Laboratory of Cardiac Energetics, National Heart, Lung, and Blood Institute, National Institutes of Health, Department of Health and Human Services, 10 Center Dr, Bldg 10, Rm B1D416, MSC 1061, Bethesda, MD 20892-1061. Received February 11, 2002; revision requested March 11; revision received May 20; accepted July 24. Address correspondence to A.E.A. (e-mail: araia@nih.gov).

View larger version (23K): [in a new window]   Figure 1. Illustration of MTET pulse sequence. EPI = echo-planar imaging, GP = phase-axis gradient, GR = read-axis gradient, GS = section-axis gradient, RF = radio frequency, TR = repetition time. (Detailed parameters are outlined in the Materials and Methods section.)

View larger version (38K): [in a new window]   Figure 2. Percentages of regional left ventricular (LV) systolic wall thickening compared in infarcted (seven dogs), stunned (five dogs), and remote (12 dogs) regions of the myocardium, as measured by using the MTET sequence, on day 1 and day 8. The infarcted myocardium showed no significant improvement by day 8, but wall thickening of the stunned myocardium increased to 40% on day 8 (P < .02). On day 1, regional left ventricular wall thickening was used to differentiate normal from either stunned or infarcted myocardium, but it could not help differentiate stunned from infarcted myocardium. NS = not significant.

View larger version (138K): [in a new window]   Figure 3. Comparison of infarction findings in a dog on postcontrast MTET (top left; 28/1.8, 20° flip angle, 800° MT flip angle) and fast gradient-echo (top right; 11.6/6.5, 15° flip angle) MR images obtained on day 8, an ex vivo inversion-recovery spin-echo MR image (bottom left; 10/2, inversion time, 500 msec), and a TTC-stained tissue sample (bottom right). Visualization of the infarction (arrows) on the MTET image compares well with that on the ex vivo inversion-recovery MR image and the TTC-stained tissue.

View larger version (50K): [in a new window]   Figure 4. Quantitative comparisons of left ventricular (LV) infarction: A, In vivo infarct volume measured with MTET MR imaging versus ex vivo infarct size measured with inversion-recovery MR imaging (R = 0.92); B, In vivo infarct volume measured with MTET MR imaging versus ex vivo infarct size measured with TTC staining (R = 0.98); C, Difference in infarct size between MTET and inversion-recovery MR imaging measurements versus average infarct size with MTET and inversion-recovery MR imaging. D, Difference in infarct size between MTET MR imaging and TTC staining measurements versus average infarct size with MTET MR imaging and TTC staining. There was a close correlation between the infarct size measured with in vivo MTET MR imaging and that measured with either ex vivo inversion-recovery MR imaging or pathologic TTC staining analysis. Corresponding Bland-Altman plots are included below each correlation.

View larger version (44K): [in a new window]   Figure 5. Signal intensity analysis of the blood pool, infarcted myocardium (MI), and normal myocardium (ie, region remote from the infarction), as depicted on a bar graph (left) and MTET image (28/1.8, 20° flip angle, 800° MT flip angle) (right). Left: Data are means ± standard errors of the mean. Right: There was no significant difference between the signal intensities measured in any of the three regions on day 1 and those measured on day 8.

View larger version (45K): [in a new window]   Figure 6. Contrast-to-noise ratios between infarcted and normal myocardium are compared with MT on and with MT off, before (Pre-Gd) and after (Post-Gd) gadolinium-based contrast material administration on day 8. Data are means ± standard errors of the mean. With contrast material administration, MT facilitated an increase in contrast-to-noise ratio. NS = not significant.