All scans were performed using a dual-layer spectral CT scanner (Philips IQon Spectral CT and Spectral CT7500, Philips Healthcare, Eindhoven, Netherlands). All patients underwent a standard CT protocol of the institute, which included pre-contrast (true non-contrast, TNC) and post-contrast phases. Patients were placed in a supine position. All scans were performed with a 120 kVp tube voltage, 1.4:1 helical pitch, and 0.4-second rotation time with a reconstructed FOV of 512 mm2. Automated mAS and beam collimation were applied and varied according to patient thickness. The detector configurations were 64 × 0.625 mm and 128 × 0.625 mm for Philips IQon Spectral CT and Spectral CT7500, respectively.
After an anteroposterior scout, TNC phase was scanned from skull base to aortic arch in the cranio-caudal direction. Subsequently, a weight adapted amount (1.5 mL/kg) of non-ionic iodinated contrast agent (Ultravist 300 MCT, Bayer Vital GmbH, Leverkusen, Germany) followed by a 30-mL saline chaser was injected intravenously with a rate of 2.5 mL/sec using a dual syringe injection system (Stellant, MEDRAD, Indianola, Pennsylvania). The post-contrast phase was acquired at 70 seconds after contrast administration in the same field of view and scan direction as performed on TNC. All datasets were reconstructed in the axial images by using a section thickness and an interval of 3.5 mm.
After an anteroposterior scout, TNC phase was scanned from skull base to aortic arch in the cranio-caudal direction. Subsequently, a weight adapted amount (1.5 mL/kg) of non-ionic iodinated contrast agent (Ultravist 300 MCT, Bayer Vital GmbH, Leverkusen, Germany) followed by a 30-mL saline chaser was injected intravenously with a rate of 2.5 mL/sec using a dual syringe injection system (Stellant, MEDRAD, Indianola, Pennsylvania). The post-contrast phase was acquired at 70 seconds after contrast administration in the same field of view and scan direction as performed on TNC. All datasets were reconstructed in the axial images by using a section thickness and an interval of 3.5 mm.