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Original Article

Influence of CBCT settings on radiation dose and image quality

2008, Volumen 38, Número 4
Juan Martín Palomo, Pejavaridhar Rao, Jeffrey Chee-Fai Kwong, Mark Guenther Hans
Doctor en Cirugía Odontológica. Licenciado en Odontología Quirúrgica. Profesor asociado y director del Programa. Director del Centro de Imagenología Craneofacial. Departamento de Ortodoncia. Facultad de Medicina Dental. Universidad de Case Western Reserve. Cleveland, OH, EE.UU.

Cone beam computed tomography has been changing the way dental practitioners use imaging. The increase in radiation dose to the patient, how to effectively reduce the dose, and the effect of such changes in the image quality is still not completely clear to most users of this technology. The objective of this study is to quantify the change in radiation dose when using different CBCT settings, and show the effects on image quality. Methods: A CBCT machine was modified in order to allow different setting combinations. The variables consisted of 4 different mA choices (2, 5, 10, and 15), 2 kVp choices (100 and 120), 3 fields of view (6”, 9”, and 12”), and the presence or not of a copper filter. A radiation phantom, a human skull, and a fresh cadaver head were used to assess radiation dose and image quality. Results: The CBCT showed less than 5% variance in radiation dose values. An overall reduction in dose of about 0.62 times was achieved by reducing the kVp from 120 to 100. When reducing the field size the dose decreased 5 to 10%. Changing the filter setting showed significant image quality differences (p<0.006) in two pairs of the 9”. Variation in kVp showed significant differences in image quality (p < 0.006) in the 6” 5 mA images with filter. Altering mA settings showed significant image quality differences (p < 0.008) in the 6” and 12” groups. The 9” group showed significant image quality differences between 2 mA and 10/15 mA. Overall, the 6”, 9” and 12” images demonstrated diagnostic quality 56%, 99% and 99% of the time, respectively. Conclusions: There is a direct impact on image quality when using lower radiation settings, so a proper ratio needs to be established for different clinical situations.  (Rev Esp Ortod. 2008;38(4):289-308)

Key words:
Cone beam CT. Radiation dose. Image quality. ALARA.
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