64 slice scanners

All imaging was conducted on 64‐slice scanners (GE Healthcare, Waukesha, WI). NCCT helical scans were performed from the skull base to the vertex using the following imaging parameters: 120 kV, 340 mA, 4 × 5‐mm collimation, 1 second/rotation, and table speed of 15 mm/rotation. CTA of the cervical and intracranial vessels was performed as follows: 0.7 ml/kg contrast (maximum 90 ml), 5‐ to 10‐second delay from injection to scanning, 120 kV, 270 mA, 1 second/rotation, 1.25‐mm thick slices, and table speed 3.75 mm/rotation. CTA covered from the carotid bifurcation to vertex. CTP studies were obtained with a dynamic first‐pass bolus‐tracking methodology according to a 2‐phase imaging protocol, to avoid the truncation of time density curves, with axial shuttle mode. The 2‐phase acquisition consisted of a first phase every 2.8 seconds for 60 seconds and an additional second phase every 15 seconds for 90 seconds, which started 5 seconds after the automatic injection of 40 ml of non‐ionic contrast agent followed by a saline flush of 40 ml at the rate of 4 ml/s. Sections of 8 cm thickness were acquired at 5 mm slice thickness. The other acquisition parameters were 80 kV, 140 mAs, and 0.5 rotation time. All CTP source images were reconstructed with the standard filter and display field of view (DFOV) of 25 cm.