title: Does the amount of tagged stool and fluid significantly affect the radiation exposure in low-dose CT colonography performed with an automatic exposure control?
abstract: OBJECTIVE
  To determine whether the amount of tagged stool and fluid significantly affects the radiation exposure in low-dose screening CT colonography performed with an automatic tube-current modulation technique.
  
  
  METHODS
  The study included 311 patients. The tagging agent was barium (n = 271) or iodine (n = 40). Correlation was measured between mean volume CT dose index (CTDI (vol)) and the estimated x-ray attenuation of the tagged stool and fluid (ATT). Multiple linear regression analyses were performed to determine the effect of ATT on CTDI (vol ) and the effect of ATT on image noise while adjusting for other variables including abdominal circumference.
  
  
  RESULTS
  CTDI (vol) varied from 0.88 to 2.54 mGy. There was no significant correlation between CTDI (vol) and ATT (p = 0.61). ATT did not significantly affect CTDI (vol) (p = 0.93), while abdominal circumference was the only factor significantly affecting CTDI (vol) (p < 0.001). Image noise ranged from 59.5 to 64.1 HU. The p value for the regression model explaining the noise was 0.38.
  
  
  CONCLUSIONS
  The amount of stool and fluid tagging does not significantly affect radiation exposure.
authors.affiliation: Department of Radiology, Seoul National University Bundang Hospital, Bundang-gu, Seongnam-si, Gyeonggi-do, 463-707, Korea.
authors.forename: Hyun Kyong
authors.initials: HK
authors.lastname: Lim
authors.forename: Kyoung Ho
authors.initials: KH
authors.lastname: Lee
authors.forename: So Yeon
authors.initials: SY
authors.lastname: Kim
authors.forename: Kil Joong
authors.initials: KJ
authors.lastname: Kim
authors.forename: Bohyoung
authors.initials: B
authors.lastname: Kim
authors.forename: Hyunna
authors.initials: H
authors.lastname: Lee
authors.forename: Seong Ho
authors.initials: SH
authors.lastname: Park
authors.forename: Jeffrey H
authors.initials: JH
authors.lastname: Yanof
authors.forename: Seung-Sik
authors.initials: SS
authors.lastname: Hwang
authors.forename: Young Hoon
authors.initials: YH
authors.lastname: Kim
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001464:Barium; D001822:Body Burden; D001826:Body Fluids / Q000737:chemistry; D023881:Colonography, Computed Tomographic / Q000706:statistics & numerical data*; D004733:Enema; D005243:Feces / Q000737:chemistry; D005260:Female; D006801:Humans; D017613:Iodine Compounds; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D011835:Radiation Protection; D011874:Radiometry / Q000706:statistics & numerical data*; D056910:Republic of Korea / Q000453:epidemiology; D018570:Risk Assessment; D012307:Risk Factors
chemical_list: D017613:Iodine Compounds; D001464:Barium