title: Lowering kilovoltage to reduce radiation dose in contrast-enhanced abdominal CT: initial assessment of a prototype automated kilovoltage selection tool.
abstract: OBJECTIVE
  The purpose of this study was to determine whether the use of an automated CT kilovoltage (kV) selection tool (Auto kV) can result in lower radiation dose without sacrificing image quality in contrast-enhanced abdominopelvic CT.
  
  
  METHODS
  Tube potential, radiation dose, and iodine contrast-to-noise ratio (CNR) were retrospectively evaluated in 36 patients who underwent abdominopelvic CT with Auto kV, and compared with results from size-matched control patients using identical protocols. Two radiologists evaluated image quality (sharpness, noise, and diagnostic confidence) blinded to kV. Volume CT dose index (CTDI(vol)) was also compared with what each patient would have received from scanning at 120 kV.
  
  
  RESULTS
  Mean (SD) CTDI(vol) was 16.0 (4.4) mGy after Auto kV versus 19.5 (4.0) mGy using standard 120-kV prescription and was 19.3 (6.0) mGy in control subjects (yielding dose reductions of 18.0% and 17.2%, respectively; p < 0.001 for both). Thirty of 36 patients were scanned at 100 kV (median dose reduction, 25%). Auto kV images were rated as very sharp in 33 (92%) and 36 (100%) cases versus 36 (100%) and 35 (97%) of the control cases, with all cases scored as having optimal noise. Readers had full diagnostic confidence in 34 (94%) and 36 (100%) of Auto kV cases; one reader scored "probably confident" in two cases (6%). Iodine CNRs for the aorta, liver, and portal vein were similar between Auto kV cases and control cases (p > 0.50, all comparisons).
  
  
  CONCLUSIONS
  The use of an automated kV selection tool results in significant dose savings while maintaining diagnostic image quality and iodine CNR.
authors.affiliation: Department of Radiology, Mayo Clinic, 200 First St SW, Rochester, MN 55905, USA.
authors.forename: David M
authors.initials: DM
authors.lastname: Hough
authors.forename: Joel G
authors.initials: JG
authors.lastname: Fletcher
authors.forename: Katharine L
authors.initials: KL
authors.lastname: Grant
authors.forename: Jeff L
authors.initials: JL
authors.lastname: Fidler
authors.forename: Lifeng
authors.initials: L
authors.lastname: Yu
authors.forename: Jennifer R
authors.initials: JR
authors.lastname: Geske
authors.forename: Rickey E
authors.initials: RE
authors.lastname: Carter
authors.forename: Rainer
authors.initials: R
authors.lastname: Raupach
authors.forename: Bernhard
authors.initials: B
authors.lastname: Schmidt
authors.forename: Thomas
authors.initials: T
authors.lastname: Flohr
authors.forename: Cynthia H
authors.initials: CH
authors.lastname: McCollough
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D003287:Contrast Media; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D011835:Radiation Protection / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted; D011860:Radiography, Abdominal / Q000379:methods*; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media