Safire strength level 3

All patients underwent CTA on a second-generation, dual-source, multidetector CT scanner (Somatom Definition Flash, Siemens Medical Systems, Erlangen, Germany). A programmable power injector with a dedicated injection protocol (OptiBolus, Covidien, Austria) was used to administer 90 ml of a low osmolar, non-ionic iodinated contrast agent (ioversol, Optiray 350, Covidien, Austria). In this protocol, a monophasic contrast agent injection with an exponentially decreasing flow rate (3.5–2.6 ml/s) over 35 s was followed by a 35-ml saline flush at a flow rate of 2.6 ml/s [24 (link)]. Starting 10 s after the contrast injection, the reference scan was repeated each second in the aorta at the origin of the renal arteries until the enhancement reached 150 Hounsfield units (HU). The final scan was initiated after another 4-s delay, covering a volume from the renal arteries to the mid-foot. Whereas the tube voltage was set to 80 kV in all patients, the reference for tube current modulation was set to 120 and 150 mAs for patients with a BMI smaller than or equal to 25 or a BMI larger than 25, respectively [25 (link)]. Iterative image reconstruction (SAFIRE strength level 3, Siemens Medical Systems, Erlangen, Germany) was applied during the reconstruction of 1.5-mm-thick axial slices.

CTA studies were conducted on a 3rd generation dual source CT system (SOMATOM Force; Siemens Healthineers, Forchheim, Germany) according to standard of care at our institution. Image acquisition was performed using prospective electrocardiographic (ECG) triggering at 70% of the R–R interval if the heart rate was < 70 bpm or 40% if the heart rate was > 70 bpm. Automated tube current modulation (CareDose, Siemens Healthineers) was utilized, with a reference tube current time product of 256 mAs per rotation, gantry rotation time 280 ms, and collimation 64 × 2 × 0.6 mm. Iodinated contrast material (Iohexol; 350 mg of organic iodine/ml, Omnipaque 350, GE Healthcare, Waukesha, Wisconsin, USA) was intravenously administered. CTA raw data were reconstructed using a standard medium-sharp (I26f) reconstruction algorithm and sinogram affirmed iterative reconstruction (Safire, strength level 3, Siemens). Images were reconstructed with 0.75 mm slice thickness at 0.3 mm increments.