title: Radiation dosimetry for electron beam CT.
abstract: OBJECTIVE
  To measure the radiation dose profile, multiple-scan average dose (MSAD), and computed tomography dose index (CTDI) for electron beam CT and to determine the accuracy of ionization-chamber and manufacturer estimates of patient dose.
  
  
  METHODS
  High-resolution dose profiles along the longitudinal axis were acquired at several positions within the scan plane with use of radiographic film. The full-width-at-half-maximum values, peak radiation dose, CTDI, and MSAD were calculated from the digitized film profiles. CTDI was also measured with an ionization chamber.
  
  
  RESULTS
  The full-width-half-maximum value of the radiation profiles were significantly wider than the nominal scan width for the 6-mm single-section and 8-mm multisection modes. In the single-section mode, the CTDI underestimated the MSAD by 15%-30%. The multisection radiation profile was nonuniform and asymmetric.
  
  
  CONCLUSIONS
  Patient doses in electron beam CT are approximately 125% of the ionization-chamber CTDI measurements in the single-section mode. For the multisection mode, the average patient dose over the scan volume is approximately 70%-85% of the ionization-chamber CTDI measurements.
authors.affiliation: Department of Diagnostic Radiology, Mayo Clinic, Rochester, MN 55905.
authors.forename: C H
authors.initials: CH
authors.lastname: McCollough
authors.forename: F E
authors.initials: FE
authors.lastname: Zink
authors.forename: R L
authors.initials: RL
authors.lastname: Morin
mesh_terms: D006801:Humans; D011829:Radiation Dosage; D014057:Tomography, X-Ray Computed