Brain MRI
Brain MRI was performed within 2 days after the procedure using a 1.5 Tesla (T) scanner (Achieva 1.5T Nova Dual; Philips Healthcare, Best, The Netherlands) with an 8-channel brain coil, or a 3 T scanner (Ingenia 3T; Philips) with a dS head coil, or a Vantage Titan 3T (Canon Medical Systems Corporation, Otawara, Japan) with a 16- or a 32-channel coil to defect SCEs. In each patient, axial diffusion-weighted imaging was performed using single-shot, spin-echo, echo planar imaging with twob values of 0 and 1000 sec/mm2 and three diffusion directions. Other scan parameters were as follows: repetition time/echo time 3600-5100/83-98 msec, 112-176×128-256 matrix, 288-512×288-512 reconstruction matrix, 220×220 mm field of view, slice thickness 5.0mm, slice gap 1.0 mm, and 1-4 excitations. The apparent diffusion coefficient map (ADC-map) was obtained to prevent the over-detection of T2 shine-through effects on diffusion-weighted imaging.
The definition for diagnosing SCE was based on the detection of new hyperintense lesions of the diffusion-weighted MRI with hypointense findings of the ADC-map according to a neuroimaging expert’s recommendation.11 MRI images were independently evaluated by certified radiologists in a blinded manner. A neurological examination was performed on hospital admission and after the ablation procedure by certified neurologists or certified physicians blinded to the MRI findings. The neurological dysfunction was evaluated using the National Institutes of Health Stroke Scale (NIHSS) and the modified Rankin Scale (mRS).