In the acute stage, all patients underwent NCCT, CTP, and nongated head-to-heart CTA (Brilliance iCT-256, IQon Spectral CT, or Spectral CT 7500; Philips Healthcare, Best, the Netherlands) without increasing the iodine contrast agent dose used for standard stroke head-to-arch CTA. The CT parameters have been described before.12 (link) For spectral CT, extra 1-mm spectral CTA maps (monoenergetic 40 keV maps, iodine maps, and Z effective) were reconstructed.