Assessment of myocardial reperfusion after myocardial infarction using automatic 3-dimensional quantification and template matching.
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 (201)Tl 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.


CONCLUSIONS
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.
Itti
Emmanuel
E
Nuclear Medicine, Henri Mondor Hospital, Assistance Publique-Hôpitaux de Paris, Paris XII University, Créteil, France. eitti@wanadoo.fr
Klein
Gregory
G
Rosso
Jean
J
Evangelista
Eva
E
Monin
Jean-Luc
JL
Gueret
Pascal
P
Meignan
Michel
M
Thirion
Jean-Philippe
JP
D000368:Aged; D017023:Coronary Angiography; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000000981:diagnostic imaging* / Q000601:surgery; D017202:Myocardial Ischemia / Q000000981:diagnostic imaging*; D015425:Myocardial Reperfusion / Q000009:adverse effects*; D009206:Myocardium; D017256:Technetium Tc 99m Sestamibi; D015899:Tomography, Emission-Computed, Single-Photon
D017256:Technetium Tc 99m Sestamibi