title: In vivo CT dosimetry during CT colonography.
abstract: OBJECTIVE
  The purpose of this study was to develop a method of measuring rectal radiation dose in vivo during CT colonography (CTC) and assess the accuracy of size-specific dose estimates (SSDEs) relative to that of in vivo dose measurements.
  
  
  METHODS
  Thermoluminescent dosimeter capsules were attached to a CTC rectal catheter to obtain four measurements of the CT radiation dose in 10 volunteers (five men and five women; age range, 23-87 years; mean age, 70.4 years). A fixed CT technique (supine and prone, 50 mAs and 120 kVp each) was used for CTC. SSDEs and percentile body habitus measurements were based on CT images and directly compared with in vivo dose measurements.
  
  
  RESULTS
  The mean absorbed doses delivered to the rectum ranged from 8.8 to 23.6 mGy in the 10 patients, whose mean body habitus was in the 27th percentile among American adults 18-64 years old (range, 0.5-67th percentile). The mean SSDE error was 7.2% (range, 0.6-31.4%).
  
  
  CONCLUSIONS
  This in vivo radiation dose measurement technique can be applied to patients undergoing CTC. Our measurements indicate that SSDEs are reasonable estimates of the rectal absorbed dose. The data obtained in this pilot study can be used as benchmarks for assessing dose estimates using other indirect methods (e.g., Monte Carlo simulations).
authors.affiliation: 1 Department of Imaging Physics, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd, Houston, TX 77030.
authors.forename: Jonathon W
authors.initials: JW
authors.lastname: Mueller
authors.forename: David J
authors.initials: DJ
authors.lastname: Vining
authors.forename: A Kyle
authors.initials: AK
authors.lastname: Jones
authors.forename: David
authors.initials: D
authors.lastname: Followill
authors.forename: Valen E
authors.initials: VE
authors.lastname: Johnson
authors.forename: Priya
authors.initials: P
authors.lastname: Bhosale
authors.forename: John
authors.initials: J
authors.lastname: Rong
authors.forename: Dianna D
authors.initials: DD
authors.lastname: Cody
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D023881:Colonography, Computed Tomographic; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009010:Monte Carlo Method; D010865:Pilot Projects; D011829:Radiation Dosage; D012007:Rectum / Q000528:radiation effects*; D013819:Thermoluminescent Dosimetry / Q000295:instrumentation*