Definition edge

MRI was performed using a 1.5T or 3T MR imaging system (Siemens Magnetom Avanto/Aera/Verio, Siemens Medical Solution, Erlangen, Germany). The MRI protocol included whole brain diffusion weighted imaging (DWI) (b = 1000t, 24 slices, thickness 5 mm, TR 3200ms, TE 87ms, number of averages 2, matrix 256×256) yielding isotropic b0 and b1000. ADC maps were calculated according to the exponential relation S(b) = S(0) exp(–b • ADC), where S(b) is the signal intensity using diffusion weighting with the value b, and S(0) is the signal intensity with b = 0. Segmentation of the DWI lesion in pre-treatment imaging was performed with the OLEA Sphere Software® (OLEA Medical, La Ciotat, France) by S.B. in all patients who underwent MRI before endovascular treatment. Segmentation of the final infarct was performed with 3D slicer version 4.5.0–1 (manual slice-by-slice delineation with “draw” and “paint” tools by M.B., S.F., controlled by A.H.) in all patients with pre-treatment MRI, who received follow-up imaging by MRI (FLAIR or T2, slice thickness 5mm) or CT (slice thickness 3mm, Siemens Definition Edge, Siemens Healthcare, Erlangen, Germany) 14 days or later after stroke. Baseline and follow-up images were compared before segmentation to exclude the inclusion of infarcts from previous stroke.

Images were acquired on a Siemens Definition EDGE or a Definition Flash CT scanner (Siemens Healthcare GmbH, Erlangen, Germany), with the standard local hospital CTA protocol. Scan parameters of the University Medical Center Groningen were variable tube voltage according to the Care-kV protocol, or variable tube current according to the Care Dose 4D protocol, 0.8 mm pitch, 128 × 0.6 mm collimation, and 0.5 s rotation time. Per CTA scan, 100 mL (4 mL per second) of diluted contrast (Xenetrix 300; Guerbet, Sulzbach, Germany) was administered intravenously. Acquisition was obtained in the early arterial phase. Scan parameters of the Skåne University hospital were tube voltage 80/140 kV, 0.55 mm pitch, 128 × 0.6 mm collimation, and 0.55 s rotation time. Acquisition was obtained in the arterial phase after intravenous injection of an individual contrast volume based on body weight (Omnipaque 350 mg/mL; GE Healthcare, Oslo, Norway; maximum dose weight of 80 kg and dose of 300 mg/kg). Bolus tracking was used with the region of interest (ROI) placed at the level of the diaphragm with a threshold of 120 Hounsfield units (HUs).