• Population: From March 2023 to December 2024 50 (26M; 24F; aged 61 ± 12.4 yrs) nonconsecutive patients referred to our Institution to undergo a contrast-enhanced MDCT performed with a 128-slice Dual-Energy CT scanner (Somatom Drive, Siemens, Germany) for either a ANTA (n= 20), follow-up examinations (n= 16) or post-operative complications (n=14) were enrolled. Exclusion criteria included the presence of an impaired cardiac (pace-makers holders, EF < 50%) and/or renal function (GFR < 30 ml/min) or the absence of an adequate ante-cubital access vein.

Patients’ weight, height and serum creatinine levels were recorded and Body Mass Indices (BMI, Kg/m²) as well as Glomerular Filtration Rates (GFR, ml/min) based on the CKD-EPI formula (14) were calculated.

Based on BMI, patients were further divided into two groups (A and B) with an arbitrary threshold set at 23.9 Kg/m² (Table 1).

• CT protocol: All patients underwent a SP protocol performed using a SS (100 kVp) integrated by a delayed phase at 3-5’ performed with a DS at 80 and 140 kVp. Both SS and DS acquisitions were acquired with the following scanning parameters: detector configuration 128 x 0.6 mm; table feed: 123 mm/s; rotation time: 0.5 s; pitchX/D: 0.8/102; reconstruction thickness: 3 mm; reconstruction interval: 1.5 mm.

In all patients the SP protocol was acquired with a FID (50 s) according to the following formula:

                                                                           50+ 25 – SD

where 25 is the average of the sum of the abdominal aortic (15 s) and hepatic arrival times (35s) (15) and SD is the scan duration.  

• Iodinated contrast media: All patients received a non-ionic iodinated contrast media (370 mgI/ml, Bracco Imaging S.p.A., Milan, Italy) with an Iodine load of 0.52 gI/Kg corresponding to 1.4 ml/Kg according to vendor indications (Siemens Healthineers). In all patients, contrast injection was followed by a saline flush administered at the same rate using a dual-head automatic injector (Enpower CTA, Bracco Imaging S.p.A, Milan).

• Dosimetry: In all patients, the radiation dose delivered was reported as both volumetric CT Dose Index (CTDI_vol, mGy) and Dose-Length Product (DLP, mGy *cm).

• Image quality analysis: Quantitative analysis was performed on a dedicated workstation (OsiriX Imaging Software) on the coronal reformatted images (Figure 1). Four circular regions of interest (ROIs) ranging between 0.5 and 2 cm² were placed in the liver parenchyma, in the supra- and infra-renal abdominal aorta, the main portal vein and the psoas muscles (Figure 1a-c). The mean values in Hounsfield Units measured in each ROI were recorded and averaged to obtain the mean (m) for the liver (m_L), the abdominal aorta (m_AA), the main portal vein (m_PV) and the psoas muscle (m_M). Values of standard deviation (SD) in each ROI were also recorded and averaged to obtain the mean SD for the liver (SD_L), the abdominal aorta (SD_AA), the main portal vein (SD_PV) and the psoas muscles, this latter taken as the image noise (s). Signal- and contrast-to-noise ratios were the calculated for the liver (SNR_L, CNR_L), the abdominal aorta (SNR_AA,, CNR_AA) and the main portal vein (SNR_PV, CNR_PV) as previously reported (11).

• Statistical analysis: Dosimetric data were compared using a paired Student’s t-test whereas an unpaired t-Test was used for the image quality evaluation between patients of Group A and B, both with a significance level (p) set at < 0.05.