Evaluating the extent of acute radiofrequency ablation lesions in the heart using an inversion recovery SSFP sequence
© Celik et al; licensee BioMed Central Ltd. 2013
Published: 30 January 2013
Current MRI methods for radiofrequency ablation (RFA) visualization have problems in accurately delineating the extent of lesions at an early phase. The aim of this study is to evaluate a non-gadolinium enhanced (NGE) multi-contrast inversion recovery steady state free precession (IR-SSFP) imaging method  to visualize acute ablation lesions.
15 lesions were created in the endocardium of 13 pigs using approved animal protocols. NGE IR-SSFP and T2-w black-blood (double IR-FSE) images were acquired in <60min after ablation. Then, Gd-DTPA (Magnevist, 0.2 mmol/kg) was injected and LGE images were acquired repeatedly over one hour. Gross pathology was used as the reference for lesion size measurements. Two regions were measured in this reference: the pale "inner" lesion core and the "outer" lesion border including the dark rim on pathology (see Results).
The lesion sizes measured in LGE images were always larger than those in IR-SSFP images. While the lesion sizes in IR-SSFP images were better correlated with the size of the inner lesion core on gross pathology (Fig 1g), the lesion sizes in LGE images were highly correlated with size of the "outer" lesion border (Fig 1j). Yet to be determined is whether either of these borders corresponds to permanent lesion extent in chronic studies. However, it is clear that double IR-FSE images do not provide reliable data for size measurements.
IR-SSFP images without Gd enhancement demonstrated good contrast between the ablation lesions and normal myocardium. The lesion size from IR-SSFP images also correlated well with lesion size in gross pathology. Among the imaging methods used in this study, IR-SSFP provided the most reliable and consistent data for RFA lesion characterization.
We gratefully acknowledge support from GE Healthcare, the Ontario Research Fund, and Canadian Institutes of Health Research.
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