Quantitative myocardial infarction on delayed enhancement MRI. Part I: Animal validation of an automated feature analysis and combined thresholding infarct sizing algorithm

Abstract

Purpose: To develop a computer algorithm to measure myocardial infarct size in gadolinium-enhanced magnetic resonance (MR) imaging and to validate this method using a canine histopathological reference. Materials and Methods:Delayed enhancement MR was performed in 11 dogs with myocardial infarction (MI) determined by triphenyltetrazolium chloride (TTC). Infarct size on in vivo and ex vivo images was measured by a computer algorithm based on automated feature analysis and combined thresholding (FACT). For comparison, infarct size by human manual contouring and simple intensity thresholding (based on two standard deviation [2SD] and full width at half maximum [FWHM]) were studied.Results: Both in vivo and ex vivo MR infarct size measured by the FACT algorithm correlated well with TTC (R ϭ 0.95-0.97) and showed no significant bias on Bland Altman analysis (P ϭ not significant). Despite similar correlations (R ϭ 0.91-0.97), human manual contouring overestimated in vivo MR infarct size by 5.4% of the left ventricular (LV) area (equivalent to 55.1% of the MI area) vs. TTC (P Ͻ 0.001). Infarct size measured by simple intensity thresholdings was less accurate than the proposed algorithm (P Ͻ 0.001 and P ϭ 0.007). Conclusion:The FACT algorithm accurately measured MI size on delayed enhancement MR imaging in vivo and ex vivo. The FACT algorithm was also more accurate than human manual contouring and simple intensity thresholding approaches.

Infarct Tissue Heterogeneity by Magnetic Resonance Imaging Identifies Enhanced Cardiac Arrhythmia Susceptibility in Patients With Left Ventricular Dysfunction

“…First, it could result merely from the volume-averaging effects of an area of uniformly fibrotic tissue (dense infarct scar) with an adjacent area of completely preserved, viable myocardium, particularly in situations in which spatial resolution is limited. 7,28,30 In this case, anatomically, there would be a single border between fibrotic scar and viable myocardium, and the limited spatial resolution would render an apparent intermediate SI in that border region. Certainly, partial volume effects because of this averaging effect of normal and necrotic tissue have been demonstrated by ceMRI in experimental animal studies 7,28,30 and are contributory.…”

“…7,28,30 In this case, anatomically, there would be a single border between fibrotic scar and viable myocardium, and the limited spatial resolution would render an apparent intermediate SI in that border region. Certainly, partial volume effects because of this averaging effect of normal and necrotic tissue have been demonstrated by ceMRI in experimental animal studies 7,28,30 and are contributory. However, a second possibility is that intermediate SI arises from the intermingling of discrete areas of preserved myocardium with bundles of fibrotic, infarcted scar within the same voxel.…”

Relationship Between Infarct Tissue Characteristics and Left Ventricular Remodeling in Patients With Versus Without Early Revascularization for Acute Myocardial Infarction as Assessed With Contrast-Enhanced Cardiovascular Magnetic Resonance Imaging

“…As it was shown that pathological assessment of infarct size can be better approximated by the use of the full width at half maximum criteria than simple intensity thresholding based on the standard deviation of normal myocardial signal intensities, we used this semiautomatic thresholding technique to measure infarct size. 25) After outlining the myocardial segment containing the region with high signal intensity, the maximum signal intensity region was determined. Scar was divided into an infarct core zone and a heterogeneous zone (ie, peri-infarct zone).…”

Motion corrected free‐breathing delayed‐enhancement imaging of myocardial infarction using nonrigid registration

“…Infarct size was compared between single-shot, inversion-recovery (IR) true-FISP with motion-corrected averaging (eight averages) and conventional segmented IR turbo-FLASH using a previously validated semiautomatic computerized method (20,21) of objective measurement. Infarct size was measured on surface coil intensity-corrected PSIR images.…”