title: Ionizing radiation in abdominal CT: unindicated multiphase scans are an important source of medically unnecessary exposure.
abstract: OBJECTIVE
  CT radiation exposure has come under increasing scrutiny because of dramatically increased utilization. Multiphase CT studies (repeated scanning before and after contrast injection) are a potentially important, overlooked source of medically unnecessary radiation because of the dose-multiplier effect of extra phases. The purpose of this study was to determine the frequency of unindicated multiphase scanning and resultant excess radiation exposure in a sample referral population.
  
  
  METHODS
  Abdominal and pelvic CT examinations (n = 500) performed at outside institutions submitted for tertiary interpretation were retrospectively reviewed for (1) the appropriateness of each phase on the basis of clinical indication and ACR Appropriateness Criteria(®) and (2) per phase and total radiation effective dose.
  
  
  RESULTS
  A total of 978 phases were performed in 500 patients; 52.8% (264 of 500) received phases that were not supported by ACR criteria. Overall, 35.8% of phases (350 of 978) were unindicated, most commonly being delayed imaging (272 of 350). The mean overall total radiation effective dose per patient was 25.8 mSv (95% confidence interval, 24.2-27.5 mSv). The mean effective dose for unindicated phases was 13.1 mSv (95% confidence interval, 12.3-14.0 mSv), resulting in a mean excess effective dose of 16.8 mSv (95% confidence interval, 15.5-18.3 mSv) per patient. Unindicated radiation constituted 33.3% of the total radiation effective dose in this population. Radiation effective doses exceeding 50 mSv were found in 21.2% of patients (106 of 500).
  
  
  CONCLUSIONS
  The results of this study suggest that a large proportion of patients undergoing abdominal and pelvic CT scanning receive unindicated additional phases that add substantial excess radiation dose with no associated clinical benefit.
authors: Department of Radiology, University of Wisconsin, Madison, Wisconsin 53792, USA.
authors: Kristie M
authors: KM
authors: Guite
authors: J Louis
authors: JL
authors: Hinshaw
authors: Frank N
authors: FN
authors: Ranallo
authors: Mary J
authors: MJ
authors: Lindstrom
authors: Fred T
authors: FT
authors: Lee
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D016001:Confidence Intervals; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D010388:Pelvis / Q000000981:diagnostic imaging; D011829:Radiation Dosage; D011830:Radiation Effects; D011839:Radiation, Ionizing; D011860:Radiography, Abdominal / Q000009:adverse effects* / Q000592:standards; D018570:Risk Assessment; D014057:Tomography, X-Ray Computed / Q000009:adverse effects* / Q000592:standards; D014481:United States; D019564:Unnecessary Procedures; D055815:Young Adult