title: Dose reduction during CT fluoroscopy: phantom study of angular beam modulation.
abstract: OBJECTIVE
  To prospectively evaluate, in a phantom, the dose reductions achievable by using angular beam modulation (ABM) during computed tomographic (CT) fluoroscopy-guided thoracic interventions.
  
  
  METHODS
  To enable measurement of organ doses and effective patient dose, a female Alderson-Rando phantom was equipped with thermoluminescent dosimeters (TLDs) in 41 positions, with three TLDs in each position. Additionally, the local dose was assessed in 22 locations above the phantom to estimate the radiation exposure to the radiologist's hand and the patient's skin dose during thoracic interventions. Radiation exposure was performed with a 64-section multidetector CT scanner in the CT fluoroscopy mode, simulating a CT fluoroscopy-guided chest intervention. Effective dose, breast dose, and the dose to the radiologist's hand during the simulated chest intervention were measured with and without ABM. Image noise as an indicator for image quality was compared for both settings. Statistical significance of the measured dose reductions and the image noise was tested by using the paired-samples t test, with P < .05 indicating a significant difference.
  
  
  RESULTS
  ABM significantly reduced the effective patient dose by 35%, the skin dose by 75%, the breast dose by 47% (P < .001 for all), and the physician's hand dose by between 27% (scattered radiation, P = .007) and 72% (direct radiation, P < .001). No significant difference was found in a comparison of the image noise with and that without ABM.
  
  
  CONCLUSIONS
  ABM leads to significant dose reductions for both patients and personnel during CT fluoroscopy-guided thoracic interventions, without impairing image quality.
authors.affiliation: Department of Diagnostic Radiology, University of Technology of Aachen, Pauwelsstrasse 30, D-52057 Aachen, Germany. hohl@rad.rwth-aachen.de
authors.forename: Christian
authors.initials: C
authors.lastname: Hohl
authors.forename: Christoph
authors.initials: C
authors.lastname: Suess
authors.forename: Joachim E
authors.initials: JE
authors.lastname: Wildberger
authors.forename: Dagmar
authors.initials: D
authors.lastname: Honnef
authors.forename: Marco
authors.initials: M
authors.lastname: Das
authors.forename: Georg
authors.initials: G
authors.lastname: Mühlenbruch
authors.forename: Andreas
authors.initials: A
authors.lastname: Schaller
authors.forename: Rolf W
authors.initials: RW
authors.lastname: Günther
authors.forename: Andreas H
authors.initials: AH
authors.lastname: Mahnken
mesh_terms: D000328:Adult; D001822:Body Burden; D005260:Female; D005471:Fluoroscopy / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D015641:Radiography, Interventional / Q000295:instrumentation / Q000379:methods*; D013902:Radiography, Thoracic / Q000295:instrumentation / Q000379:methods*; D011874:Radiometry / Q000379:methods*; D012062:Relative Biological Effectiveness; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*