Atrial fibrillation cardiac radioablation target visibility on magnetic resonance imaging

Magnetic resonance imaging (MRI) guided cardiac radioablation (CR) for atrial fibrillation (AF) is a promising treatment concept. However, the visibility of AF CR targets on MRI acquisitions requires further exploration and MRI sequence and parameter optimization has not yet been performed for this application. This pilot study explores the feasibility of MRI-guided tracking of AF CR targets by evaluating AF CR target visualization on human participants using a selection of 3D and 2D MRI sequences.MRI datasets were acquired in healthy and AF participants using a range of MRI sequences and parameters. MRI acquisition categories included 3D free-breathing acquisitions (3D_acq), 2D breath-hold ECG-gated acquisitions (2D_ECG-gated), stacks of 2D breath-hold ECG-gated acquisitions which were retrospectively interpolated to 3D datasets (3D_interp), and 2D breath-hold ungated acquisitions (2D_real-time). The ease of target delineation and the presence of artifacts were qualitatively analyzed. Image quality was quantitatively analyzed using signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and non-uniformity. Confident 3D target delineation was achievable on all 3D_interp datasets but was not possible on any of the 3D_acq datasets. Fewer artifacts and significantly better SNR, CNR and non-uniformity metrics were observed with 3D_interp compared to 3D_acq. 2D_real-time datasets had slightly lower SNR and CNR than 2D_ECG-gated and 3D_{interp n} datasets. AF CR target visualization on MRI was qualitatively and quantitatively evaluated. The study findings indicate that AF CR target visualization is achievable despite the imaging challenges associated with these targets, warranting further investigation into MRI-guided AF CR treatments.