Somatom definition as

This retrospective study was approved by the Institutional Review Board of our hospital. Due to the retrospective nature of the current study, the requirement for written informed consent was waived. We identified 345 consecutive adult patients who underwent contrast-enhanced CT including the liver with a 128-slice multidetector-row CT (MDCT) (SOMATOM Definition AS+; Siemens Healthcare, Forchheim, Germany) by using both CARE kV and SAFIRE, between November 2012 to February 2013. The CT examinations were requested in regards to chronic liver disease or liver cirrhosis of the patients. We selected patients for evaluation (n = 67) who had been previously scanned on a 64-slice MDCT (SOMATOM Definition AS, Siemens Healthcare, Forchheim, Germany) to compare radiation dose and image quality (average time interval, 11.3 ± 7 months). The study population consisted of 48 men and 19 women, whose mean age was 62.4 ± 10.7 years (range, 27-84 years). The mean height was 163.8 ± 7.0 cm (range, 146-178 cm), the mean weight was 61.2 ± 8.6 kg (range, 44-85 kg), and the mean body mass index (BMI) was 22.8 ± 2.8 kg/m² (range, 17.3-33.2 kg/m²). There was no significant difference in the BMI of the patients between the 2 CT scans (22.9 ± 2.7 kg/m² for the initial scan and 22.8 ± 2.8 kg/m² for the follow-up scan, p = 0.48 by the Wilcoxon signed rank test).

No patient preparation was required. CT examinations were performed on either 64-slice (Somatom Definition AS+, Siemens Healthineers, Germany) or 128-slice (Somatom Definition AS+, Siemens Healthineers, Germany) CT scanners with patients in the supine position. The scanning parameters were as follows: tube voltage: 100–120 kVp; automatic tube current modulation: 100–110 mAs); pitch: 1.0–1.3 mm; matrix: 512 × 512; and slice thickness: 0.625–1 mm.
Abdominopelvic CT examinations were performed without contrast, and the arterial and venous phases were obtained after the administration of intravenous (IV) contrast material (Xenetix 300 mgI/ml, Guerbet, France, Ultravist 300 mgI/ml, Bayer, Germany; Omnipaque 300 mgI/ml, GE Healthcare, Ireland). The arterial phase was performed 30–35 seconds after an IV contrast injection, and the venous phase was performed 60–70 seconds after an IV contrast injection. Multiplanar (sagittal, coronal, and axial) images were reconstructed for the diagnosis of intussusception.

Data from the preoperative orbital imaging examinations were retrospectively analyzed. Of the 91 included patients, 73 underwent CT scans, 43 underwent MRI scans, and 25 underwent both CT and MRI scans.
The CT scans were performed using various scanners (GE Medical Systems, GE Lightspeed VCT, GE Discovery CT750 HD, GE OPTIMA CT660, Siemens Somatom Sensation 16, Siemens Somatom Definition AS, Siemens Somatom Definition Edge, Siemens Somatom Definition Flash) with multidetector capabilities ranging from 16 to 128 channels. The techniques and parameters varied depending on the system used; however, most examinations were performed using a 128-channel CT scanner (Somatom Definition Flash; Siemens Medical Solutions). The detailed CT imaging protocols are described in the Supplement.
The MRI scans were performed using various 3T MRI scanners (Magnetom Skyra, Siemens; Achieva, Philips Medical Systems; Ingenia CX, Philips Medical Systems) with a 16- or 64-channel head and neck coil. However, most examinations were performed with a 3T MRI scanner (Magnetom Skyra, Siemens) with a 64-channel head and neck coil. The MRI protocol for head and neck tumors consisted of axial and coronal T1- and T2-weighted turbo spin-echo sequences with diffusion-weighted imaging and dynamic contrast-enhanced (DCE)-MRI. The detailed MRI protocols are described in the Supplement.