Definition flash

The imaging protocol at admission included a standard non-contrast CT, CTA, and spatio-temporal (4D) CTP, which were always acquired in this order on 64 or 128 dual slice CT scanners (Siemens Definition AS+; Siemens Definition Flash; Philips Brilliance 64). A follow-up standard non-contrast CT was acquired between 48 hours and 7 days after admission.
The imaging parameters used were as follows: CT: 120 kV, 280–320 mA, with 5.0 mm slice reconstruction. CTP: 80 kV, 200–250 mA, with 5 mm slice reconstruction (max. 10 mm), slice sampling rate of 1.50 s (min. 1.33 s), scan time 45 s (max. 60 s), biphasic injection with 30 ml (max. 40 ml) of highly iodinated contrast medium with 350 mg iodine/ml (max. 400 mg/ml) injected with at least 4 ml/s (max. 6 ml/s) followed by 30 ml saline solution bolus. CT and CTP images were interpolated to an in-slice resolution of 0.37 mm with 5.0 mm slice thickness. CTA: 100–120 kV, 260–300 mA, with 1.0 mm slice reconstruction, 5 mm maximum intensity projection (MIP) reconstruction with 1 mm increment.

Imaging was performed using Definition Flash dual-source CT or a Philips 64 spiral CT with tube voltage of 120 kV, tube current of 200 mA, slice thickness and spacing of 5 mm, and the pitch value was 0.6. Patients fasted for 6–10 h before the CT scan. Between 10 min before the scan, patients drank 800–1000 ml of warm water to fill the gastrointestinal tract. Throughout the scanning procedure, patients were in the supine position, and they were instructed to hold their breath before scans were initiated, which included a whole-abdomen plain CT scan and an enhanced three-phase scan. For the enhanced scan, first sweep imaging was performed. Next, a bolus of 80–100 ml iodixanol was delivered intravenously at a speed of 2.5 ml/s through the median cubital vein to allow dynamic contrast-enhanced scans, which were performed during the arterial phase, venous phase, and delayed phase at 30 s, 60 s, and 180 s, respectively, after the infusion was started.