Automatic quantification of defect size using normal templates: a comparative clinical study of three commercially available algorithms

Infarct size assessed by myocardial single-photon emission tomography (SPET ) imaging is an important prognostic parameter after myocardial infarction (MI). We compared three commercially available automatic quantification alg orithms that make use of normal templates for the evaluation of infarct ext ent and severity in a large population of patients with remote MI. We studi ed 100 consecutive patients (80 men, mean age 63 +/- 11 years, mean LVEF 47 % +/- 15%) with a remote MI who underwent resting technetium-99m tetrofosmi n gated SPET study for infarct extent and severity quantification. The quan tification algorithms used for comparison were a short-axis algorithm (Ceda rs-Emory quantitative analysis software, CEqual), a vertical long-axis algo rithm (VLAX) and a three-dimensional fitting algorithm (Perfit). Semiquanti tative visual infarct extent and severity assessment using a 20-segment mod el with a 5-point score and the relation of infarct extent and severity wit h rest LVEF determined by quantitative gated SPET (QGS) were used as standa rds to compare the different algorithms. Mean infarct extent was similar fo r visual analysis (30% +/- 21%) and the VLAX algorithm (25% +/- 17%), but C Equal (15% +/- 11%) and Perfit (5% +/- 6%) mean infarct extents were signif icantly lower compared with visual analysis and the VLAX algorithm. Moreove r, infarct extent determined by Perfit was significantly lower than infarct extent determined by CEqual. Correlations between automatic and visual inf arct extent and severity evaluations were moderate (r = 0.47, P < 0.0001 to r = 0.62, P < 0.0001) but comparable for all three algorithms. Correlation s between LVEF and visual evaluation of infarct extent (r = -0.80, P < 0.00 01) and severity (r = -0.82: P < 0.0001) were good but correlations were si gnificantly lower for all three algorithms (r = -0.48, P < 0.0001 to r = -0 .65, P < 0.0001). Systematically lower correlations were found in non-anter ior infarctions (n = 69) and obese patients (BMI greater than or equal to 3 0 kg/m(2), n = 32) compared with anterior infarctions and non-obese patient s for all three algorithms. In this large series of post-MI patients, resul ts of infarct extent and severity determination by automatic quantification algorithms that make use of normal templates were not interchangeable and correlated only moderately with semiquantitative visual analysis and LVEF.