Dose distribution for dental cone beam CT and its implication for defining a dose index

R. Pauwels, C. Theodorakou, A. Walker, H. Bosmans, R. Jacobs, K. Horner, R. Bogaerts

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Objectives: To characterize the dose distribution for a range of cone beam CT (CBCT) units, investigating different field of view sizes, central and off-axis geometries, full or partial rotations of the X-ray tube and different clinically applied beam qualities. The implications of the dose distributions on the definition and practicality of a CBCT dose index were assessed. Methods: Dose measurements on CBCT devices were performed by scanning cylindrical head-size water and polymethyl methacrylate phantoms, using thermoluminescent dosemeters, a small-volume ion chamber and radiochromic films. Results: It was found that the dose distribution can be asymmetrical for dental CBCT exposures throughout a homogeneous phantom, owing to an asymmetrical positioning of the isocentre and/ or partial rotation of the X-ray source. Furthermore, the scatter tail along the z-axis was found to have a distinct shape, generally resulting in a strong drop (90%) in absorbed dose outside the primary beam. Conclusions: There is no optimal dose index available owing to the complicated exposure geometry of CBCT and the practical aspects of quality control measurements. Practical validation of different possible dose indices is needed, as well as the definition of conversion factors to patient dose. © 2012 The British Institute of Radiology.
    Original languageEnglish
    Pages (from-to)583-593
    Number of pages10
    JournalDentomaxillofacial Radiology
    Volume41
    Issue number7
    DOIs
    Publication statusPublished - 1 Oct 2012

    Keywords

    • Cone beam computed tomography
    • Quality control
    • Radiation dosimetry
    • Thermoluminescent dosimetry

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