2.2 MRI acquisition
All patients underwent contrast-enhanced MRI using a 1.5-T MR system
(Achieva; Philips Medical, Best, The Netherlands) equipped with a
5-channel cardiac coil before the AF ablation. This scan technique has
been previously reported.5 First, contrast-enhancement
magnetic resonance angiography (CE-MRA) of the pulmonary vein (PV) -
left atrium (LA) anatomy was acquired with a breath-hold
three-dimensional (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.6
The purpose of the scanning in the coronal plane was to reduce the
number of acquisition slices and shorten the breath-hold 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.7 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
factor = 1.8, and 80 reference lines. The inversion time was set at 280
to 320 ms, using a Look-Locker scan. 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.