Chulalongkorn Medical Journal


Background : Cone beam computed tomography (CBCT) devices with various types of field of view (FOVs) are currently available in dentistry. Thus, the selection of proper FOVs and number of scans should be considered according to the clinical applications and ALARA principle. Objective : To study the effect of the number of scans and FOVs: one scan of large FOV, one scan of medium FOV and multi-scans of small FOVs, on the radiation dose from CBCT systems using a phantom. Research design : Experimental study (in vitro). Setting : Oral and Maxillofacial Radiology Clinic, Faculty of Dentistry, Mahidol University Methods : Radiation doses from various FOVs of 3 CBCT devices were determined and recorded using a RANDO phantom. As for 3D Accuitomo170, CVOL (mGy), DLP (mGy.cm) and the effective dose (E:µSv) were determined. As for Kodak devices, DAP (mGy.cm²) was recorded. In two or three scans of small FOV, E and DAP were obtained from calculation. Results : As for 3D Accuitomo170, CVOL(mGy), DLP(mGy.cm), E(µSv) of FOV (diameter (cm) × height (cm)) 17 × 5 and 17 × 12 were 7.7, 38.5, 88.55 and 6.4, 76.8,176.64, respectively. As for Kodak devices, FOV (diameter (cm) × height (cm)) 5 × 3.7, 15 × 9, 20.6 × 18 and multismall FOVs (width (cm) × depth (cm) × height (cm)) 9.3 × 5 × 3.7, 9.3 × 7.4 × 3.7, DAP values were 131, 211, 502 and 261, 392 mGy.cm² respectively. Two and three scans of FOV 5 × 3.7 were 262 and 393 mGy.cm², respectively. Conclusion : The CBCT radiation dose is affected by the field size and number of scans taken. In one scan, the radiation dose is higher when the FOVs increase. In the same FOV, the radiation dose increases with the number of scans taken. However, one scan of medium FOV provides less radiation dose than two and three scans of small FOV. Thus, when two or three localized region are required, one scan of medium FOV is more recommended than two or three scans of small FOV. As large FOV provides highest radiation dose, it is therefore recommended to use when the maxillofacial region is required.



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