Pranav Bhagirath

116 Chapter 6 Table 2. Ablation stages and utilized CMR sequences. Procedural stage Type sequence Availability References Pre-procedural Substrate identification T1-weighted PSIR turbo-GRE Roadmap MRA (3D respiratory navigated and ECG-gated GRE) Commercial 24 3D self-navigation strategies Experimental 41 Catheter guidance Catheter navigation Real-time balanced SSFP (8 fps) Commercial 31 Catheter tip at ablation site T1-weighted FLASH (5-6 fps) Experimental 21, 23 Real-time balanced SSFP (8 fps) Commercial 31 Ablation lesion Edema T2-weighted HASTE Commercial 23 T2-weighted TSE Commercial 31 High-resolution quantitative 2D and 3D T 2 -mapping strategies Experimental 42, 43 Necrosis 3D respiratory-navigated IR-GRE Experimental 24 T1-weighted PSIR turbo-GRE Commercial 31 Catheter navigation and tip localization It has been observed that a frame-rate of approximately 5 frames per second (fps) is acceptable for catheter guidance in EP procedures 11 . Currently, commercially available, real-time SSFP sequences provide frame rates ranging between 5-8 fps 31 . The easy availability of these sequences facilitates passive tracking in every center with a diagnostic CMR scanner. This encourages clinical translation without a demand for major device modifications. However, due to its inherent advantages and despite the current pre-clinical state of development, active tracking features are considered to be the method of choice for clinical EP and ablation in the near future. Lesion evaluation A unique strength of CMR, compared to other imaging modalities, is the ability to performtissue characterization. This can be used to identify and distinguish between the two cellular reactions that occur during an ablation; 1) Acute (Edema) and 2) Permanent (Necrosis). Both edema and necrosis can be evaluated using commercially available sequences 6, 31 . T2-weighted Ultrafast Spin Echo sequences 6, 23, 31 and quantitative high-