T2*-weighted MRI technique for visualization of RF ablation lesions
© Kholmovski et al. 2016
Published: 27 January 2016
LGE-MRI is widely used to assess cardiac RF ablation lesions. However, LGE-MRI requires contrast injection and the appearance, dimensions and visibility of lesions in LGE-MRI noticeably change with time after ablation and time after contrast injection. Recently proposed non-contrast T1-weighted (T1w) technique is only applicable to visualize acute (< 3 days) RF lesions. The main goal of this study was to develop and validate a non-contrast MRI technique for assessment of sub-acute (> 3 days) RF ablations.
Non-contrast T2*-weighted (T2*w) MRI technique for RF lesion visualization has been implemented. This technique exploits the difference in T2* relaxation between normal and ablated myocardium. Reduction in T2* relaxation time of ablated myocardial tissues is caused by the transformation of hemoglobin into hemosiderin from ruptured and obstructed blood vessels as a result of RF ablation. To validate this technique, RF ablations were performed in 6 canines using ThermoCool catheter (Biosense Webster) at 30 Watts for 30 seconds. Imaging studies were performed on a 3T scanner (Verio, Siemens HealthCare) at 0, 1, 4, and 8 weeks post-ablation. Study protocol included T1w, T2*w, and LGE scans with a resolution of 1.25 × 1.25 × 2.5 mm and T1, T2 and T2* mapping.
Strong correlation (R2 = 0.908) between lesions volumes estimated from LGE and T2*w images acquired 8 weeks post-ablation was found (Fig. 2, bottom panel). Lesion volume from T2*w scans was about 27% smaller than lesion volume from LGE scans.
T2* relaxation time of cardiac RF ablation lesions significantly reduces with time after ablation. Non-contrast T2*w technique can be used to visualize sub-acute RF ablations as early as a week post-ablation. Visibility of the lesions in T2*w image considerably improves with time after ablation as T2* relaxation time of the lesions becomes shorter.
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.