title: γ-H2AX foci as in vivo effect biomarker in children emphasize the importance to minimize x-ray doses in paediatric CT imaging.
abstract: OBJECTIVE
  Investigation of DNA damage induced by CT x-rays in paediatric patients versus patient dose in a multicentre setting.
  
  
  METHODS
  From 51 paediatric patients (median age, 3.8 years) who underwent an abdomen or chest CT examination in one of the five participating radiology departments, blood samples were taken before and shortly after the examination. DNA damage was estimated by scoring γ-H2AX foci in peripheral blood T lymphocytes. Patient-specific organ and tissue doses were calculated with a validated Monte Carlo program. Individual lifetime attributable risks (LAR) for cancer incidence and mortality were estimated according to the BEIR VII risk models.
  
  
  RESULTS
  Despite the low CT doses, a median increase of 0.13 γ-H2AX foci/cell was observed. Plotting the induced γ-H2AX foci versus blood dose indicated a low-dose hypersensitivity, supported also by an in vitro dose-response study. Differences in dose levels between radiology centres were reflected in differences in DNA damage. LAR of cancer mortality for the paediatric chest CT and abdomen CT cohort was 0.08 and 0.13 ‰ respectively.
  
  
  CONCLUSIONS
  CT x-rays induce DNA damage in paediatric patients even at low doses and the level of DNA damage is reduced by application of more effective CT dose reduction techniques and paediatric protocols. .
authors.affiliation: Department of Basic Medical Sciences, Ghent University, Proeftuinstraat 86, 9000, Gent, Belgium, charlot.vandevoorde@ugent.be.
authors.forename: C
authors.initials: C
authors.lastname: Vandevoorde
authors.forename: C
authors.initials: C
authors.lastname: Franck
authors.forename: K
authors.initials: K
authors.lastname: Bacher
authors.forename: L
authors.initials: L
authors.lastname: Breysem
authors.forename: M H
authors.initials: MH
authors.lastname: Smet
authors.forename: C
authors.initials: C
authors.lastname: Ernst
authors.forename: A
authors.initials: A
authors.lastname: De Backer
authors.forename: K
authors.initials: K
authors.lastname: Van De Moortele
authors.forename: P
authors.initials: P
authors.lastname: Smeets
authors.forename: H
authors.initials: H
authors.lastname: Thierens
mesh_terms: D015415:Biomarkers / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D004249:DNA Damage / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006657:Histones / Q000378:metabolism*; D006801:Humans; D007223:Infant; D008297:Male; D009010:Monte Carlo Method; D009381:Neoplasms, Radiation-Induced / Q000517:prevention & control*; D011446:Prospective Studies; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods; D014057:Tomography, X-Ray Computed / Q000009:adverse effects*
chemical_list: D015415:Biomarkers; C468783:H2AX protein, human; D006657:Histones