title: Effect of automatic tube voltage selection on image quality and radiation dose in abdominal CT angiography of various body sizes: a phantom study.
abstract: OBJECTIVE
  To assess the effect of an automatic tube voltage selection technique on image quality and radiation dose in abdominal computed tomography (CT) angiography of various body sizes.
  
  
  METHODS
  An abdominal aortic phantom was filled with iodinated contrast medium and placed into three different cylindrical water containers, which simulated a small, intermediate-sized, and large patient. The phantom was scanned with a standard 120 kVp abdominal CT angiography protocol and with an optimized tube voltage protocol that was modulated by an automatic tube voltage technique. The attenuation of the aorta, background, and image noise was measured, and the contrast-to-noise ratio (CNR) was calculated. Three independent readers assessed the overall image quality.
  
  
  RESULTS
  The automatic tube voltage technique selected 70 kVp as the optimal tube voltage for the small phantom, 80 kVp for the intermediate phantom, and 100 kVp for the large phantom. Compared to the standard 120 kVp protocol, the automatic tube voltage selection yielded significantly increased CNR values in the small phantom (15.8 versus 19.4, p < 0.001), intermediate phantom (8.4 versus 8.7, p < 0.05), and large phantom (4.3 versus 4.6, p < 0.01). The automatic tube voltage selection resulted in a 55%, 49%, and 39% reduction in the volume CT dose index (CTDI(vol)) in the small, intermediate, and large phantoms, respectively. The subjective overall image quality of the three phantom sizes at different tube voltages ranged between poor and good.
  
  
  CONCLUSIONS
  Compared to a standard 120 kVp abdominal CT angiography protocol, the automatic tube voltage selection substantially reduced the radiation dose without compromising image quality in various simulated patient sizes.
authors.affiliation: Institute of Diagnostic, Interventional and Pediatric Radiology, University Hospital Berne, University of Berne, Berne, Switzerland. sschindera@aol.com
authors.forename: S T
authors.initials: ST
authors.lastname: Schindera
authors.forename: A
authors.initials: A
authors.lastname: Winklehner
authors.forename: H
authors.initials: H
authors.lastname: Alkadhi
authors.forename: R
authors.initials: R
authors.lastname: Goetti
authors.forename: M
authors.initials: M
authors.lastname: Fischer
authors.forename: R
authors.initials: R
authors.lastname: Gnannt
authors.forename: Z
authors.initials: Z
authors.lastname: Szucs-Farkas
mesh_terms: D000792:Angiography / Q000379:methods*; D001012:Aorta, Abdominal / Q000000981:diagnostic imaging*; D001331:Automation; D049628:Body Size; D006801:Humans; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011832:Radiation Injuries / Q000517:prevention & control; D011856:Radiographic Image Enhancement; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000295:instrumentation* / Q000379:methods*