title: Radiation in cardiac CT: predictors of higher dose and its reduction over time.
abstract: BACKGROUND
  Cardiac CT provides noninvasive information on cardiac anatomy, particularly in coronary artery disease. However, exposure to radiation has been identified as a limitation of this exam. The aim of this study was to evaluate variations in radiation dose over time and to identify variables associated with use of higher radiation doses.
  
  
  METHODS
  A prospective registry of 643 patients who underwent 64-slice dual source cardiac CT scan (Dual source CT--Somaton Definition, Siemens-Medical) during 2007 and 2008 was analyzed.
  
  
  RESULTS
  The sample was divided into quartiles according to the chronological order of the exams. There was a progressive reduction in median radiation dose in the quartiles analyzed (Q1: 8.9 [5.9-14.1], Q2: 6.6 [5.5-10.7], Q3: 6.4 [5.3-8.7], Q4: 6.1 [5.2-7.9] mSv), significant when the first quartile was compared with the others (p < 0.05). Along with this reduction, was a progressive increase in the use of a tube voltage of 100 kV (p < 0.001). Predictors of a higher radiation dose were higher body mass index, previous cardiac surgery, atrial fibrillation during acquisition, longer acquisition time and use of a tube voltage of 120 kV. When one or more of these variables were present (one third of the population), the radiation dose was significant higher (12.1 [9.5-14.8] vs. 5.7 [5.0-6.7] mSv, p < 0.001).
authors.affiliation: Centro Cardiovascular, Hospital da Luz, Lisboa, Portugal. p965675551@gmail.com
authors.forename: Pedro Jerónimo
authors.initials: PJ
authors.lastname: Sousa
authors.forename: Pedro Araújo
authors.initials: PA
authors.lastname: Gonçalves
authors.forename: Hugo
authors.initials: H
authors.lastname: Marques
authors.forename: Luís
authors.initials: L
authors.lastname: Raposo
authors.forename: Rita
authors.initials: R
authors.lastname: Calé
authors.forename: João
authors.initials: J
authors.lastname: Brito
authors.forename: Augusto
authors.initials: A
authors.lastname: Gaspar
authors.forename: Francisco Pereira
authors.initials: FP
authors.lastname: Machado
authors.forename: José
authors.initials: J
authors.lastname: Roquette
mesh_terms: D000368:Aged; D005260:Female; D006331:Heart Diseases / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011829:Radiation Dosage; D013997:Time Factors; D014057:Tomography, X-Ray Computed