title: Automated attenuation-based tube potential selection for thoracoabdominal computed tomography angiography:  improved dose effectiveness.
abstract: OBJECTIVE
  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).
  
  
  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%.
  
  
  CONCLUSIONS
  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.
authors: Department of Radiology, University Hospital Zurich, Zurich, Switzerland.
authors: Anna
authors: A
authors: Winklehner
authors: Robert
authors: R
authors: Goetti
authors: Stephan
authors: S
authors: Baumueller
authors: Christoph
authors: C
authors: Karlo
authors: Bernhard
authors: B
authors: Schmidt
authors: Rainer
authors: R
authors: Raupach
authors: Thomas
authors: T
authors: Flohr
authors: Thomas
authors: T
authors: Frauenfelder
authors: Hatem
authors: H
authors: Alkadhi
mesh_terms: D000368:Aged; D000465:Algorithms; D017023:Coronary Angiography / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D011829:Radiation Dosage; D059629:Signal-To-Noise Ratio; D014057:Tomography, X-Ray Computed / Q000379:methods*