Ultravist 370

The imaging of tumours included MRI, DWI, CE-CT, and histological examinations. For CE-CT a positron emission tomography (PET)/CT Biograph 16 (Siemens AG, Erlangen, Germany) was used. A catheter implanted into the jugular vein was used for intravenous application of contrast material (Ultravist 370, Bayer Vital GmbH, Leverkusen, Germany) and beads. The CT protocol was: unenhanced CT scan; CE-CT after intravenous injection of 1 ml of contrast material using a small-animal injection pump (Medtron, Saarbrücken, Germany). The CT scan started 20 s after injection start. The scan specifications were 80 kV and 100 mAs; 512² pixels with a voxel resolution of 420 μm × 420 μm × 750 μm.
For MRI, a 1.5-T system and an eight-channel clinical knee coil (Magnetom Avanto, Siemens AG, Erlangen) were used. Rats were placed on a custom-made bed for gas narcosis. The following sequences were performed: T2-weighted turbo spin-echo (voxel size 0.6 mm³, time of repetition [TR] 20.12 ms, time of echo [TE] 6.04 ms, acquisition time 10 min and 53 s); three-dimensional TOF (voxel size 0.3 mm³, TR 40 ms, TE 8.01 ms, acquisition time 21 min and 46 s); DWI (voxel size 1.8 mm³, TR 6300 ms, TE 94 ms, three orthogonal diffusion gradient directions, b-values 0, 50, 100, 150, 200, 250, 300, 500, 750, and 1000 s/mm², acquisition time 17 min and 45 s).

During standard ERC in prone position under X-ray fluoroscopy, a nasobiliary probe was inserted in the common bile duct. Under sedation and analgesia, patients were transferred from a standard X-ray table to the CT table. After placing patients in the supine position, a 1 : 10 dilution of iopromid (Ultravist 370, Bayer Vital, Leverkusen, Germany) was manually injected via the catheter located in the common bile duct. The volume of contrast solution needed to obtain opacification of the whole biliary tree was estimated on the basis of the preceding ERC. After contrast administration, a CT-scan was performed with the following parameters: collimation 64 × 0.6 mm, 120 kV tube voltage, and 330 ms rotation time. Axial and coronal image data sets were reconstructed with a slice thickness of 1 and 5 mm and an increment of 0.7 mm and 3 mm, respectively. In addition, volume rendering reconstructions (VRT) and maximum intensity projections (MIP) were obtained and compared to the standard ERC projections.

The injection protocol consisted of a single-bolus contrast media injection (120 ml volume, 5 ml/s flow, 1.9 gI/s iodine flux; Ultravist® 370, Bayer Vital, Leverkusen, Germany) followed by a saline bolus (50 ml volume, 4 ml/s flow). Timing of the late arterial phase was achieved by bolus tracking in the proximal abdominal aorta with a threshold of 100-HU signal increase and 13-s post-threshold delay. The portal venous phase and delayed phase were acquired with a delay of 50 s and 180 s, respectively.

A single-source DECT examination in the same 320-row scanner (Aquilion ONE Vision Edition) with sequential volume acquisition of two different energy datasets (135 and 80 kVp) was performed before and 3 min after intravenous administration of a body-weight-adjusted dose of 80-mL ICM (1 mL/kg ULTRAVIST 370, Bayer Vital GmbH) in a patient with unclear arthritis of the hand. We used our established clinical DECT protocol for scan acquisition and image reconstruction (30 mAs at 135 kVp and 170 mAs at 80 kVp; rotation time 0.275 s; AIDR3D) and performed two-material-decomposition analysis.

All PET/CT examinations were performed on a state-of-the art clinical scanner (Biograph mCT^®, Siemens Healthineers, Erlangen, Germany). All patients fasted for at least 6 h before examination. Weight-adapted (300–350 MBq) ¹⁸F-FDG was injected intravenously 60 min prior to image acquisition. Standardized CT examination protocols included weight-adapted (90–120 mL) intravenous CT contrast agent (Ultravist 370^®, Bayer Vital GmbH, Leverkusen, Germany). Portal-venous phase acquisitions were obtained in expiration with 70 s delay time using a tube voltage of 120 kV and a reference dose of 200 mAs. Additional lung scans were performed during inspiration. PET was acquired from the skull base to the midthigh level over six to eight bed positions and was reconstructed using a 3D ordered subset expectation maximization algorithm (2 iterations, 21 subsets, Gaussian filter of 2.0 mm, matrix size of 400 × 400, and slice thickness of 2.0 mm). The PET acquisition time was two minutes per bed position.

The perfusion CT study was performed using a multi-slice scanner (SOMATOM Definition AS and Definition Flash Siemens Healthcare, Forchheim, Germany).The CT protocol consisted of a non-enhanced abdominal low-dose CT (40 mAs; 100 kV; SL, 5.0 mm; collimation, 128 0.6 mm; tube rotation time, 0.5 s; pitch, 0.6), which was obtained to localize the liver porta. Subsequently, a scan range of 6.9 cm z-axis coverage was planned over the involved liver, followed by a VPCT using an adaptive spiral scanning technique in shuttle mode. Perfusion parameters were: 80 kV; 100/ 120 mAs (for patients70 kg, respectively); collimation, 64 0.6 mm with z-flying focal spot; and 26 CT-whole coverages of the liver volume within a total scan time of 40 s. The mean radiation exposure for liver perfusion measurements was 7.5 mSv. Contrast medium was administered by using a dual-head pump injector (Stellant, Medtron, Saarbruecken, Germany). For this purpose, 50 mL Ultravist 370 (Bayer Vital, Leverkusen, Germany) were injected in all patients irrespective of patients’ weight at a flow rate of 5 mL/s in an antecubital vein followed by a saline flush of 50 mL NaCl at 5 mL/s. All images were transferred to an external workstation (Multi-Modality Workplace, Siemens, Erlangen, Germany) for analysis. An abdominal scan in portal vein phase was also obtained.