Automated tube voltage selection and adapted contrast media injection protocols in CT angiography of the thoracoabdominal aorta

Purpose: The aim was to assess the image quality (IQ) in computed tomography angiography (CTA) of the thoracoabdominal aorta utilizing automated tube voltage selection (ATVS) with a subsequently adapted contrast media (CM) injection protocol. Materials and methods: A total of 104 consecutive patients referred for CTA of the thoracoabdominal aorta were included. Scans were acquired on a 3rd-generation DSCT using ATVS with a quality reference tube voltage and current of 100 kV and 150 mAs. CM protocols were adapted to kV settings by modifying iodine delivery rate (IDR) whilst maintaining an identical injection time (13.3 s): 0.9 gI/s (70 kV), 1.0 gI/s (80 kV), 1.1 gI/s (90 kV) 1.2 gI/s (100 kV). Both objective (attenuation, contrast-to-noise and signal-to-noise) and subjective (4-point Likert scale: 1 = poor/2 = sufficient/3 = good/4 = excellent) IQ were assessed. Results: ATVS assigned a 70 kV (n = 88) and 90 kV (n = 16) protocol in most patients. Fewer patients were assigned to an 80 kV (n = 4) and 100 kV (n = 1) protocol, these protocols were, therefore, excluded from further analysis. Attenuation on all designated levels of the thoracoabdominal aorta was diagnostic in 99.0% of the scans; 87/88 scans (98.9%) in the 70 kV group and in 16/16 (100%) in the 90 kV group. Overall mean attenuation was 349 ± 72HU for 70 kV and 310 ± 43HU for 90 kV. Subjective IQ was diagnostic in all scans. Overall effective radiation dose for 70 kV and 90 kV was 1.8 ± 0.2 mSv and 3.4 ± 0.7 mSv, respectively. Conclusions: Adaptation of CM injection protocols (IDR) to ATVS in CTA of the aorta—scanned with 70 kV and 90 kV—is feasible and results in diagnostic image quality