Late-Gadolinium enhancement MRI acquisition
All patients underwent contrast enhanced MR imaging using a 1.5-T MR system (Achiva, Philips Medical, Best, The Netherlands) equipped with a 5-channel cardiac coil one to three months before the AF ablation. This scan technique has been established, and the acquired images were used for the AF ablation procedure.8,9First, contrast enhancement–magnetic resonance angiography (CE-MRA) of the PV–LA anatomy was acquired with a breath-hold 3D fast field echo (FFE) sequence in the coronal plane during the first pass of a contrast agent (gadobutrol, Gadovist; Bayer Yakuhin, Osaka, Japan) injection at a dose of 0.1 mmol/kg. The purpose of the scanning in the coronal plane was to reduce the number of acquisition slices and shorten the breath holding time. Then the LGE-MRI of the LA with the PVs was acquired using a 3D inversion recovery, respiration navigated, electrocardiogram-gated, T1-FFE sequence in the transverse plane 15 minutes after the contrast injection, which has been previously reported. The typical parameters were as follows: repetition time /echo time = 4.7 / 1.5 ms, voxel size = 1.43 × 1.43 × 2.40 mm (reconstructed to 0.63 × 0.63 × 1.20 mm), flip angle = 15°, SENSE = 1.8, and 80 reference lines. The inversion time (TI) was set at 280 – 320 ms, using a Look-Locker scan. In case of AF, the data acquisition was performed with the shortest trigger delay of cardiac synchronization. In case of sinus rhythm, the data acquisition was performed during the mid-diastolic phase of the left ventricle. The typical scan time for the LGE-MRI study was 7 to 12 minutes depending on the patient’s heart rate and respiration pattern. The images of the CE-MRA, and LGE-MRI were transferred to customized software (MRI LADE Analysis; PixSpace Inc, Fukuoka, Japan) for a further image post processing and image analysis.