title: Ureteral calculi detection using low dose computerized tomography protocols is compromised in overweight and underweight patients.
abstract: OBJECTIVE
  Low dose computerized tomography protocols have demonstrated a reduction in radiation exposure while maintaining excellent sensitivity and specificity in the detection of stones in patients of average size. Low dose computerized tomography protocols have not yet been evaluated in subjects in the extremes of weight. We evaluated the effect of body weight when using low dose protocols to detect ureteral calculi.
  
  
  METHODS
  Three cadavers of increasing weight (55, 85 and 115 kg) were prepared by inserting 721 calcium oxalate stones (range 3 to 7 mm) in 33 random configurations into urinary tracts. Cadavers were then scanned using a GE LightSpeed® at 7 radiation settings. An independent, blinded review by a radiologist was conducted to generate ROC curves, with areas under the curve compared using a 1-way ANOVA (α = 0.05).
  
  
  RESULTS
  Sensitivity and specificity were significantly lower in the low and high weight cadavers compared to the medium weight cadaver at 5 mAs (p <0.001) and 7.5 mAs (p = 0.048). Differences in sensitivity and specificity at radiation settings of 15 mAs or greater were not significant.
  
  
  CONCLUSIONS
  The sensitivity and specificity for the detection of ureteral calculi on computerized tomography were decreased for underweight and overweight subjects when using extremely low dose radiation settings (less than 1 mSv). Low dose protocols of 15 mAs (2 mSv) can still be used for these subjects without jeopardizing the ability to identify ureteral stones.
authors.affiliation: Department ofUrology and Radiology, Loma Linda University Medical Center, Loma Linda, California 92354, USA.
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Heldt
authors.forename: Jason C
authors.initials: JC
authors.lastname: Smith
authors.forename: Kirk M
authors.initials: KM
authors.lastname: Anderson
authors.forename: Gideon D
authors.initials: GD
authors.lastname: Richards
authors.forename: Gautum
authors.initials: G
authors.lastname: Agarwal
authors.forename: Damien L
authors.initials: DL
authors.lastname: Smith
authors.forename: Amy
authors.initials: A
authors.lastname: Schlaifer
authors.forename: Nicholas T
authors.initials: NT
authors.lastname: Pittenger
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Han
authors.forename: Brenton D
authors.initials: BD
authors.lastname: Baldwin
authors.forename: Gabriel T
authors.initials: GT
authors.lastname: Schroeder
authors.forename: D Duane
authors.initials: DD
authors.lastname: Baldwin
mesh_terms: D001835:Body Weight; D002102:Cadaver; D006801:Humans; D050177:Overweight / Q000150:complications*; D012372:ROC Curve; D011829:Radiation Dosage; D015203:Reproducibility of Results; D013851:Thinness / Q000150:complications*; D014057:Tomography, X-Ray Computed; D014514:Ureteral Calculi / Q000150:complications / Q000000981:diagnostic imaging*