To develop a Shared K-space (SharK) magnetic resonance imaging (MRI) sequence that combines angiographic and late gadolinium enhancement (LGE) acquisitions to improve atrial wall segmentation and scar identification, and to develop a novel visualization method that quantifies scar encirclement of pulmonary veins postablation treatment for atrial fibrillation.
Materials and Methods
A SharK sequence was developed and used at 3T to image the left atrium in 11 patients postcryoballoon ablation. The effects of sharing k-space between the angiographic and LGE acquisitions on the accuracy of scar were assessed. The left atrial wall was segmented and points about each pulmonary vein (PV) ostia were projected onto a bullseye to quantitatively compare PV encirclement. The parameters used to quantify encirclement were varied to perform a sensitivity analysis.
Compared to using a complete set of k-space, total atrial scar differences were significant only when sharing >75% k-space (P = 0.014), and 90% sensitivity and specificity for identifying scar was achieved when sharing 50% k-space. In patients, the right PVs showed more intersubject variance in encirclement compared to the left PVs. A 100° anteroinferior portion of the left PVs was always encircled, while the superior segments of both right PVs was ablated in only 6/11 patients.
A SharK sequence was developed to combine angiographic and LGE imaging for atrial wall segmentation and scar identification. The PV bullseye quantifies and localizes encirclement about the PVs. The left PVs showed a higher amount of scar encirclement and less variability compared to the right PVs.
Level of Evidence
Stage 1J. Magn. Reson. Imaging 2017;00:000–000.