Radiation exposure during midfacial imaging using 4-and 16-slice computed tomography, cone beam computed tomography systems and conventional radiography

Objectives: Radiation doses were determined to balance risks against usefulness of the different modalities available for the imaging of the facial skeleton. Methods: An Alderson Rando Phantom, armed with lithium fluoride thermoluminescent dosemeters (TLDs) was exposed using a set of four conventional radiographs (orbital view, modified Waters view, orthopantomography, skull posterior-anterior 0degrees), two different cone beam computed tomography (CBCT) (NewTom 9000 and Siremobil Iso-C-3D), and multislice computed tomography (CT) modalities (Somatom VolumeZoom and Somatom Sensation 16). TLDs from 14 well defined anatomical sites lying within the primary beam as well as the TLD corresponding to the thyroid gland were evaluated. Results: Multislice CT showed the highest exposure values. Exposure levels of the CBCT sytems lay between CT and conventional radiography. Dose measurement for the 16-slice CT revealed nearly the same radiation exposure as the 4-slice system when adapted examination protocols were used. Conclusions: Selection of the most appropriate imaging modality should be performed in view of the delivered doses, required image quality and information and the clinical circumstances.