CT angiography of the aorta using 80 kVp in combination with sinogram‐affirmed iterative reconstruction and automated tube current modulation: Effects on image quality and radiation dose

The objective of this study was to evaluate image quality and radiation dose of a CT angiography ( CTA ) protocol using 80  kVp in combination with iterative reconstruction and automated tube current modulation. Methods Ninety‐five aortic CTA examinations were included in this study. A novel 80  kVp aortic CTA ‐protocol with iterative reconstruction was introduced in our department in March 2012 for patients with a body mass index ( BMI ) below 32 kg/m 2 . The first 72 consecutive examinations were retrospectively assigned to group A (56 patients, 42 men, 14 women, mean age 69.6 ± 10.7years, BMI range 19.7–31.1 kg/m 2 ). For comparison, the last 23 consecutive examinations performed with the old protocol (100  kVp ) were assigned to group B (21 patients, 13 men, 8 women, mean age 67.4 ± 11.1years, BMI range 19.7–31.9 kg/m 2 ). Thoracic and abdominal contrast‐to‐noise ratio ( CNR ), signal‐to‐noise ratio ( SNR ) and aortic attenuation were assessed. Subjective image quality was rated on a 5‐point scale (1 =  non diagnostic ; 5 =  excellent ). Furthermore, dose length product ( DLP ) and volumetric computed tomography dose index ( CTDI vol ) were analysed. Results All examinations achieved diagnostic image quality. Attenuation of the aorta was significantly higher in group A compared with B (thoracic: 443.5 ± 90.5 H ounsfield units ( HU ) vs. 296.0 ± 61.0  HU ; abdominal: 426.3 ± 94.2  HU vs. 283.6 ± 60.5  HU ; P  < 0.05, respectively). CNR , SNR and subjective image quality were comparable between both groups ( CNR : 12.8 ± 3.7 vs. 13.0 ± 7.4; SNR 14.4 ± 3.9 vs. 14.9 ± 8.2; subjective image quality: 4.3 ± 0.6 vs. 4.5 ± 0.6; P  > 0.05, respectively). CTDI vol and DLP were significantly lower in group A (1.9 ± 0.5  mGy ; 139.2 ± 41.1  mGy × cm ) as compared with group B (4.2 ± 1.4  mGy ; 292.1 ± 91.5  mGy × cm ; P  < 0.001, respectively). Conclusion Low‐dose CTA of the aorta using 80  kVp with iterative reconstruction enables a significant dose reduction of up to 50% compared with a 100  kVp protocol in patients with a BMI below 32 kg/m 2 while diagnostic image quality is maintained.