Definition flash

Computed tomographic angiography (CTA) was performed prior to the intervention using a dual-energy scanner (256 slices; Siemens Definition Flash, Siemens Healthcare), using a rotation time of 280 ms at a temporal resolution of 75 ms and 0.6-mm collimation. For carotid arteries, Isovue 370 (Bracco Diagnostics; 80 mL at 5.0 mL/s) was injected through a central venous line. Images were acquired from the proximal ascending aorta to the base of the skull (dual-energy mode; 90 kVp and Sn 150 kVp). For the coronary arteries, animals were pretreated with intravenous metoprolol (5 mg every 5 minutes, for a total of 25 mg) and inhalational nitroglycerin (0.8 mg, 2 minutes before acquisition) and thereafter injected with Isovue 370 (77 mL at 5.5 mL/s). Acquisition was performed with high-pitch prospective electrocardiographic gating (FLASH) (tube voltage 70 kV). Important vascular structures (left ventricle, coronary arteries, aorta, and carotid arteries) were segmented and reconstructed in 3 dimensions from computed tomographic slices using EnSite Verismo software (Abbott Medical).

Imaging was performed using 256-row dual source CT scanners (Siemens Definition Flash®, Siemens Healthcare, Forchheim, Germany) with a gantry rotation time of 0.28 s, temporal resolution of 75 ms, 0.6-mm collimation, tube current 320 mAs for PGA. For patients with a body weight of <85 kg, a 100-kVp tube voltage was used, while 120 kVp was used for patients with a body weight of ⩾85 kg.
CTA data were acquired with a breath hold in deep inspiration. Beta-blockers were used to keep resting heart rate (HR) < 65 beats per minute (the mean HR during the scan was 67 ± 9), and all patients received sublingual nitroglycerine during the procedure. A test bolus of 15 mL of contrast agent XENETIX 350® (350 mg iodine/mL) followed by a 25-mL saline flush, both at flow rates of 6 mL/s, was administered to determine the time to peak enhancement in a region of interest in the ascending aorta. For coronary CTA, 80 mL followed by a 45-mL saline flush, both at flow rates of 6 mL/s, was administered. Image acquisition was started after the predetermined delay time plus 3 s.

All CCTA was performed using 256-slice CCTA (Siemens Definition Flash®, Siemens Healthcare, Forchheim, Germany). CCTA data were acquired while the patients held their breath during deep inspiration. We used beta-blockers before the scan to keep heart rate <65 beats/min. A test bolus technique, using 15 ml of contrast agent, was flushed with a 30ml saline, at a flow rate of 5 ml/s. Next, an injection of 80 ml contrast agent, followed by a 50ml saline flush, at a flow rate of 5 ml/s, was administered for CCTA.

Patients received NCCT, CTA, and whole brain CTP performed on 64 or 128 dual slice scanners (Siemens Definition AS+; Siemens Definition Flash, Siemens Healthcare, Forchheim, Germany; Philips Brilliance 64, Philips Medical Systems, Eindhoven, Netherlands)—CT: 120 kV, 280 to 320 mA, 5.0 mm slice reconstruction; CTA: 100 to 120 kV, 260 to 300 mA, 1.0 mm slice reconstruction, 5 mm MIP reconstruction with 1 mm increment; CTP: 80 kV, 200 to 250 mA, 5 mm slice reconstruction (maximum 10 mm), slice sampling rate 1.50 seconds (minimum 1.33 seconds), scan time 45 seconds (maximum 60 seconds), biphasic injection with 30 mL (maximum 40 mL) of highly iodinated contrast medium with 350 mg iodine/mL (maximum 400 mg/mL) injected with at least 4 mL/sec (maximum 6 mL/sec) followed by a 30 mL NaCl chaser bolus. All perfusion parameter maps were calculated on a dedicated workstation (Syngo VE52A with VPCT-Neuro, Siemens Healthcare, Forchheim, Germany) based on a deconvolution model by least mean squares fitting including cerebral blood volume (CBV), cerebral blood flow, mean transit time, and time to drain [7 (link)].