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Quantitative measurement of infarct size by contrast-enhanced magnetic resonance imaging early after acute myocardial infarction

Comparison with single-photon emission tomography using Tc^99m-sestamibi

Tareq Ibrahim, MD^*, Stephan G. Nekolla, PhD, Mira Hörnke, Hubertus P. Bülow, MD, Josef Dirschinger, MD^*, Albert Schömig, MD^* and Markus Schwaiger, MD, FACC^,*

^* Deutsches Herzzentrum München and 1. Medizinische Klinik des Klinikums Rechts der Isar, Technische Universität München, Munich, Germany
Nuklearmedizinische Klinik und Poliklinik der Technischen Universität München, Munich, Germany

View larger version (91K): [in a new window]   Figure 1 Time course of contrast-enhanced magnetic resonance imaging (MRI) delayed myocardial enhancement in a representative short-axis slice of different infarct regions. (Upper row) Adjusted inversion time (TI); (lower row) constant TI of 300 ms. Using a constant TI of 300 ms for contrast-enhanced MRI showed a decrease of signal intensity and extent of enhancement on later acquisitions compared with an adjusted TI. (Right column) Corresponding single-photon emission computed tomography (SPECT) perfusion defect. (A) Transmural infarction of the inferoseptal wall eight days after infarction (creatine kinase [CK] 431 U/l); (B) subendocardial infarction of the anteroseptal wall seven days after the acute event (CK 1,150 U/l); (C) transmural infarction of the inferior, inferoseptal, and inferolateral wall six days after infarction (CK 1,765 U/l) showing an early subendocardial hypoperfusion, which disappeared on later acquisitions.

View larger version (23K): [in a new window]   Figure 2 (A) Measurement of mean signal intensity in normal and enhanced myocardium over time using different inversion times. (B) Relation of mean signal intensity in infarct regions in comparison with remote myocardium over time for different inversion times (p = 0.02). CeMRI = contrast-enhanced magnetic resonance imaging; TI = inversion time.

View larger version (24K): [in a new window]   Figure 3 (A) Measurement of mean myocardial enhancement extent by contrast-enhanced magnetic resonance imaging (CeMRI) (adjusted inversion time [TI]) over time based on different threshold analysis in comparison with remote myocardium and mean Tc99m-sestamibi single-photon emission computed tomography (SPECT) perfusion defect. (B) Mean myocardial enhancement extent by CeMRI over time based on a threshold analysis of >200% of remote myocardium. If the TI was held constant at 300 ms, the mean enhancement size significantly decreased on acquisitions after the 28th min postcontrast in comparison with CeMRI performed with an adjusted TI (p < 0.03). (C) Mean difference of CeMRI and SPECT over time. Mean difference was calculated between the size of myocardial contrast-enhancement by CeMRI based on a threshold >200% of remote myocardium and the size of SPECT perfusion defect within every patient. Using an adjusted TI CeMRI and SPECT showed a good agreement at all time points within an average difference of 3% of the left ventricular (LV) myocardium. For a constant TI of 300 ms, both modalities agreed well until 21 min after contrast injection; however, on later acquisitions the mean difference increased to about 7% of the LV myocardium at 42 min (p < 0.03).

View larger version (75K): [in a new window]   Figure 4 Comparison of contrast-enhanced magnetic resonance imaging (CeMRI) at 28 min after contrast and single-photon emission computed tomography (SPECT) perfusion defect with corresponding polar maps. Short-axis slices are orientated from apical (left) to basal (right). (A) Myocardial infarction of the inferior wall (day 6) with transmural contrast enhancement. (B) Anterior infarction (day 8) with subendocardial enhancement.

View larger version (13K): [in a new window]   Figure 5 Comparison of contrast-enhanced magnetic resonance imaging (CeMRI) at 28 min after contrast (threshold >200% of remote myocardium) and single-photon emission computed tomography (SPECT). (A) Correlation of enhancement size with SPECT perfusion defect. (B) Agreement between both modalities depicted in a Bland-Altman graph (mean value of the differences = solid line; ±2 SD = dotted line). Average value of the two measurements is plotted along the x-axis; the difference is plotted along the y-axis. LV = left ventricle.

View larger version (13K): [in a new window]   Figure 6 Myocardial contrast enhancement by contrast-enhanced magnetic resonance imaging (CeMRI) at 28 min after contrast (threshold >200% of remote myocardium) in comparison with peak creatine kinase (CK) level (A) and left ventricular (LV) ejection fraction assessed angiographically on the day of admission (B).