Medrad

Each dual-energy CT scan was conducted using a third-generation dual-source CT system (SOMATOM Force, Siemens Healthineers, Erlangen, Germany). Imaging was performed in the portal venous phase, initiated 80 s after the administration of a body weight-adjusted contrast medium (0.5 mL/kg, Imeron 400, Bracco, Milan, Italy), delivered at a rate of 2.0 ± 0.5 mL/s using a dual-syringe injection system (Medrad, Bayer, Leverkusen, Germany) and followed by a 40 mL saline flush. Image acquisition utilized dynamic tube current modulation technology (CareDose4D, Siemens Healthineers, Erlangen, Germany) to optimize the dose during the scans. The dual-energy CT protocol included settings of 100 kV for tube A and tin-filtered 150 kV (Sn150 kV) for tube B, which were calibrated to reference tube current–time products of 190 mAs for tube A and 95 mAs for tube B. The system featured a collimation of 0.6 × 192 mm, a helical pitch of 0.6 and a gantry rotation duration of half a second. Reconstructions of the dual-energy series were generated on a specialized DECT workstation (syngo.via VB10B, Siemens Healthineers) in both the axial and coronal planes with thin 1.5 mm slices.

Dual‐bolus perfusion scans were acquired using a validated hardware phantom with a synthetic multicapillary myocardium.²⁵, ²⁶ The phantom was scanned on a 3‐T system (Biograph mMR; Siemens Healthcare, Erlangen, Germany) equipped with a 12‐channel anterior/posterior phased‐array coil system. One slice was acquired over the synthetic myocardium for a fixed reference MBF of 3 mL/g/min. Scanning was repeated three times for each of three different input HR simulated with retrospective ECG triggering (60 bpm, 90 bpm, and 120 bpm). A saturation recovery spoiled gradient echo sequence with fixed parameters was used: TR = 2.1 msec, TE = 1.1 msec, saturation recovery time = 100 msec, flip angle = 10°, pixel bandwidth = 1002 Hz, field of view = 280 × 210 mm², acquired/reconstructed resolution = 1.5 × 1.5 mm², slice thickness = 8 mm, and parallel acceleration factor = 2. Matching the clinical dual‐bolus MR perfusion protocol used in our institution, a dilute and a neat CA bolus with concentrations 0.0075 mmol/kg and 0.075 mmol/kg, respectively (Gadobutrol, Gadovist®, Bayer AG, Leverkusen, Germany) were injected in the vena cava of the phantom at 4 mL/sec using an injector pump (Spectris Solaris, Medrad®, Bayer AG). Each bolus was followed by a 25‐mL saline flush.