title: Severe obesity is associated with 3-fold higher radiation dose rate during ureteroscopy.
abstract: OBJECTIVE
  To investigate and characterize the association between fluoroscopy radiation dose rate and various patient size metrics during ureteroscopy.
  
  
  METHODS
  Fluoroscopy data were collected from 100 patients undergoing ureteroscopy for stone disease. Radiation dose rates were determined from fluoroscopy dose and time. Estimated entrance skin dose was calculated from air kerma (AK) by applying correction factors. Effective dose (ED) was estimated with Monte Carlo-based simulation software. Patient size metrics included body mass index (BMI), anterior-posterior (AP) midline distance, AP transrenal thickness, and region of interest (ROI) pixel value magnitude on computed tomography scout. Univariate and multivariate regression analyses were performed to determine the association between AK dose rate and patient size metrics, adjusting for laterality and stone location.
  
  
  RESULTS
  Obese patients (>30 kg/m(2)) comprised 46% of the cohort. Mean fluoroscopy time, displayed AK, entrance skin dose, and ED were 4.2 ± 6.0 second, 1.2 ± 2.1 mGy, 1.2 ± 2.2 mGy, and 0.08 ± 0.15 mSv, respectively. Mean AK dose rate and ED dose rates were 0.30 ± 0.23 mGy/second and 0.021 ± 0.016 mSv/second, respectively. Compared with the nonobese category, the highest BMI category (≥35 kg/m(2)) had over a 3-fold higher mean AK rate (0.50 vs 0.16 mGy/second). On univariate and multivariate analysis, BMI, AP midline distance, AP transrenal thickness, and computed tomography scout region of interest pixel value magnitude were each significantly associated with dose rate.
  
  
  CONCLUSIONS
  Larger patients experience higher radiation dose rates under fluoroscopy. Severely obese patients receive 3-fold higher dose rates compared with nonobese patients. Given the higher incidence of stone disease in obese patients, all attempts should be made to minimize radiation exposure during ureteroscopy.
authors: Department of Urology, University of Washington School of Medicine, Seattle, WA.
authors: Ryan S
authors: RS
authors: Hsi
authors: David A
authors: DA
authors: Zamora
authors: Kalpana M
authors: KM
authors: Kanal
authors: Jonathan D
authors: JD
authors: Harper
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D005260:Female; D005471:Fluoroscopy; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity; D011446:Prospective Studies; D011829:Radiation Dosage; D012720:Severity of Illness Index; D014057:Tomography, X-Ray Computed / Q000706:statistics & numerical data*; D018666:Ureteroscopy / Q000379:methods; D055815:Young Adult
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