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Background: Radiofrequency catheter ablation is an important interventional therapy to for patient with ventricular tachycardias (VT).Scar-related VT is among the most intricate to ablate, because the myocardial scar, which is the underlying arrhythmogenic substrate, is patient-specific and often highly complex.The ablation procedures typically last more than five hours, resulting in excessive X-ray exposure both for the patients and the physicians.Late enhanced magnetic resonance imaging (LE MRI) is a noninvasive technique that can visualize the myocardial scar in vivo.The high-resolution MRI depicts heart anatomy and substrate geometry in fine scale, and if extracted and integrated into the catheterization laborotary, can largely faciliate the procedure by providing patient-specific substrate information.Purpose: To develop advanced computer methods that objectively and reliably extract scar information from LE MRI, and to evalute the revelance ofpre-acquired scar information with intraprocedural electroanatomic mapping (EAM) data.Methods: Thirteen patients (all male, mean age 60 ± 8, range 46-83 years) referred for catheter ablation, with known chronic myocardial infarction size > 25% of the left ventriulcar (LV) volume, were included.LE MR was performed preprocedurally for all patients.The myocardial scar was automatically identified from the LE MRI using combined intensity and spatial information.The estimated scar transmurality map was integrated with the EAM data by aligning the MR-dervied LV mesh and mapping points, using the left main landmark and patient pose a priori.Correlation between the scar transmurality and bipolar voltage amplitude was computed.Results: The scar transmurality in post-infarction patients demonstrated inverse correlation with the bipolar voltage amplitude.The Pearsons correlation coefficient between scar transmurality and bipolar voltage was-0.52±0.32.The average scar transmurality is 12 ± 19% in high-voltage regions (>1.5mV), and 54±34% in low-voltage regions (<0.5mV), p<0.01.Conclusions: The in vivo scar information can be derived from LE MR images and integrated into the catherazation laboratory using advanced computer methods.The results demonstrated that the preprocedural LE MRI provides highly relevant scar information, which can be used to guide the complex ablation procedure, and potentially leads to reduced procedure time and improved procedure efficacy.