Dependence of contrast to noise ratio between ablation scar and other tissues on patient heart rate and flip angle for late gadolinium enhancement imaging of the left atrium

Abstract

Background Radiofrequency (RF) ablation of the left atrium (LA) and pulmonary vein ostia has become a clinically acceptable therapy for atrial fibrillation (AF). High-resolution 3D Late Gadolinium Enhancement (LGE) imaging can detect pre-ablation re-modeling of the LA wall and also visualize post-ablation scar in AF patients treated using RF ablation. The 3D Inversion Recovery prepared Gradient Recalled Echo (IR-GRE) LGE sequence typically used, is dependent on parameters like the flip angle and inversion time. However the effect of patient heart rate (HR) on the CNR between scar and fat, myocardium and blood has not been studied before. Here, we simulate the IR-GRE sequence acquisition at different HRs with the aim of improving the performance of this approach to assess post ablation scars. Methods In 3D LGE of the LA, the inversion pulse is applied every heartbeat (RR interval) after which data are acquired. Realistic T1 values at 3T for post-ablation scar, myocardium, fat and blood were estimated from analyzing TI-scout images of 50 patient studies to be 120, 420, 254 and 312 ms respectively. Simulations were performed with these values of T1 and different HRs, TR=3.1 ms, TE=1.4 ms, and multiple flip angles, using MATLAB (Mathworks Inc. Natick, MA). Retrospective analysis of 58 patients’ data acquired on a 3T Verio scanner (Siemens Healthcare, Germany) was performed. High resolution LGE images were acquired