Purpose: To introduce a novel algorithm of automated attenuation-based tube potential selection and to assess its impact on image quality and radiation dose of body computed tomography angiography (CTA).
Materials and methods: In all, 40 patients (mean age 71±11.8 years, body mass index (BMI) 25.7±3.8 kg/m², range 18.8-33.8 kg/m²) underwent 64-slice thoracoabdominal CTA (contrast material: 80 mL, 5 mL/s) using an automated tube potential selection algorithm (CAREkV), which optimizes tube-potential (70-140 kV) and tube-current (138.8±18.6 effective mAs, range 106-177 mAs) based on the attenuation profile of the topogram and on the diagnostic task. Image quality was semiquantitatively assessed by 2 blinded and independent readers (scores 1: excellent to 5: nondiagnostic). Attenuation and noise were measured by another 2 blinded and independent readers. Contrast-to-noise ratio was calculated. The CT dose index (CTDIvol) was recorded and compared with the estimated CTDIvol of a standard 120 kV protocol without using the algorithm in each patient. Selected tube potentials were correlated with BMI and attenuation of the topogram.
Results: Diagnostic image quality was obtained in all patients (excellent: 14; good: 21; moderate: 5; interreader agreement: κ=0.78). Mean attenuation, noise, and contrast-to-noise ratio were 260.8±63.5 Hounsfield units, 15.5±3.3 Hounsfield units, and 14±4.2, respectively, with good to excellent agreement between readers (r=0.50-0.99, P<0.01 each). Automated attenuation-based tube potential selection resulted in a kV-reduction from 120 to 100 kV in 23 patients and to 80 kV in 1 patient, whereas tube potential increased to 140 kV in 1 patient. Automatically selected tube potential showed a significant correlation with both BMI (r=0.427, P<0.05) and attenuation of the topogram (r=0.831, P<0.001). CTDIvol (7.95±2.6 mGy) was significantly lower when using the algorithm compared with the standard 120 kV protocol (10.59±1.8 mGy, P<0.001), corresponding to an overall dose reduction of 25.1%.
Conclusion: Automated attenuation-based tube potential selection based on the attenuation profile of the topogram is feasible, provides a diagnostic image quality of body CTA, and reduces overall radiation dose by 25% as compared with a standard protocol with 120 kV.