Imeron

Imaging was performed on a 192-detector-row dual-source-CT scanner (Somatom Force; Siemens Healthineers, Erlangen, Germany) according to the vendor’s recommendations. The following optimized scan parameters were applied for CTP in each patient: whole brain coverage with a scan length of 294 mm, applying a tube voltage of 70 kV, a fixed tube current of 250 mAs and a rotation time of 0.25 s and acquiring 32 scans with a time interval of 1.5 s between two scans. The contrast agent was administered in the antecubital vein as a bolus of 40 mL, with 300 mg iodine per mL (Imeron; Bracco Imaging Deutschland, Konstanz, Germany) at a flow rate of 6 mL per second, followed by a saline bolus of 50 mL. The scan phase began 8 s after the start of the contrast agent injection. For the CT angiography of the carotid arteries, the contrast agent was administered as a bolus of 40 mL at a flow of 5 mL per second, and the first bolus tracking scan began 7 s after injection. The tracking scans were performed at the level of the ascending aorta, with a frequency of 1 per second. The scanning period of the CT angiography began as the intraluminal enhancement of the aorta reached the threshold CT attenuation value of 100 HU.

Contrast-enhanced 4D CT was performed within seven days prior to AVS using a 320-row detector scanner (Aquilion One; Canon Medical Systems). Scanning parameters were as follows: 11 phases with the volume scan mode; 100 kVp with Real EC, 150 mA tube current, and 0.5 s per rotation; 0.5 mm × 320 collimation and CTDI_vol of 54.7 mGy. All settings were as consistent as possible among patients. A non-ionic contrast bolus (Imeron, Bracco Imaging Deutschland GmbH, Konstanz, Germany) was injected into the antecubital vein with 600 mg of iodine per kilogram of body weight. The injection time was fixed at 25 s, achieving a varied injection rate in accordance with patient’s weight. Images were continuously obtained in 11 series at 3-s intervals, beginning from 25 s after the onset of the contrast injection during the same breath hold in the shallow expiratory phase. A few patients failed to hold their breath at the last one or two phases, but the optimal visibility of venous vessels was still obtained. According to the range confirmed by pre-contrast abdominal scan, the imaging area was 160 mm centered on the right adrenal gland^{8 (link)}. The reconstruction parameters were as follows: FC 13 kernel, 0.5 mm slice thickness with intervals of 0.25 mm. As for the exposure, we made 4D CT scanning within the radiation dose of 3D CT protocol.

CT images were acquired on a 128-slice CT (Somatom Definition AS+, Siemens Healthcare AG, Forchheim, Germany). CT angiography was performed using bolus tracking after intravenous injection of 50 ml iodinated contrast agent (Imeron®, 400 mg iodine/ml, Bracco Imaging, Konstanz, Germany) followed by a 60-ml saline chaser at a flow rate of 4 ml/s. For the CTA the following scanning parameters were used: automatic tube current modulation (CARE Dose 4D, Siemens Healthcare AG, Forchheim, Germany) with a reference mAs setting of 120, Care kV with a reference setting of 120 kV, 0.75 mm collimation, 0.3 s rotation time, 0.55 spiral pitch factor. Axial MPRs were reconstructed from the raw data with a FOV of 240 mm, matrix size 512 × 512 and a slice thickness of 1.5 mm using the reconstruction kernel I26f in conjunction with advanced modeled iterative reconstruction (ADMIRE) software (Siemens Healthcare AG) strength 2.