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Assessment of Myocardial Reperfusion After Myocardial Infarction Using Automatic 3-Dimensional Quantification and Template Matching

¹ Nuclear Medicine, Henri Mondor Hospital, Assistance Publique-Hôpitaux de Paris/Paris XII University, Créteil, France
² Research and Development, Quantificare S.A., Sophia-Antipolis, France
³ Cardiology, Henri Mondor Hospital, Assistance Publique-Hôpitaux de Paris/Paris XII University, Créteil, France

Assessment of perfusion defect extent is essential for determining prognosis after a myocardial infarction (MI), but quantification methods usually rely on segmental analysis, which may lack accuracy. We present an automated voxel-based and template-based approach for precise quantification of perfusion defect extent and reperfusion evolution. Methods: Coronary angiography and stress/reinjection ²⁰¹Tl tomography were performed prospectively on 49 patients with recent MI (45 men; mean age ± SD, 54 ± 10 y), before and 3 mo after revascularization (40 angioplasties and 9 bypasses). Perfusion defect extent was quantified using expert 16-segment visual scoring of the slices and a 3-dimensional (3D) method with spatial normalization between times 1 and 2. Briefly, the latter automatically extracted myocardial edges, matched them to a reference template, and compared the perfusion intensity in each voxel with the intensity of the corresponding voxel in a control population of 100 healthy subjects. Results: Reocclusion occurred in 12 patients within 3 mo of surgery (all had undergone angioplasty). The perfusion gain between times 1 and 2, assessed by visual analysis, was significantly higher in permeable patients than in reoccluded patients: 12.4% ± 13.3% and 2.3% ± 8.2% of the initial stress defect, respectively (P = 0.02). Proportional gains, measured with the quantitative 3D method, were 4.5% ± 3.6% and 1.9% ± 2.7%, respectively (P = 0.02). Furthermore, the 3D method allowed measurement within the initial ischemic defect (reversible part of the stress defect at time 1), the extent of myocardium whose perfusion improved at time 2 (reperfusion), and the extent of myocardium whose perfusion remained unchanged (residual ischemia). A voxel-by-voxel analysis of these regions revealed that the proportion of reperfusion was significantly higher in permeable patients than in reoccluded patients: 60.0% ± 21.3% versus 40.0% ± 22.5%, respectively (P = 0.008). This was cumbersome to quantify using visual analysis and did not reach statistical significance, likely because of segmental division (partial-volume effect) and absence of spatial normalization. Conclusion: The 3D voxel-based quantification allows satisfying assessment of reperfusion 3 mo after MI. Moreover, the automated analysis using spatial normalization should facilitate a reproducible assessment of large populations over time.

Key Words: quantification • coregistration • myocardial perfusion • myocardial infarction

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