Chulalongkorn Medical Journal


Background : Cone beam computed tomography (CBCT) devices with varioustypes of field of view (FOVs) are currently available in dentistry. Thus,the selection of proper FOVs and number of scans should beconsidered according to the clinical applications and ALARA principle.Objective : To study the effect of the number of scans and FOVs: one scan oflarge 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, MahidolUniversityMethods : Radiation doses from various FOVs of 3 CBCT devices weredetermined and recorded using a RANDO phantom. As for 3DAccuitomo170, CVOL (mGy), DLP (mGy.cm) and the effective dose(E:µSv) were determined. As for Kodak devices, DAP (mGy.cm²) wasrecorded. In two or three scans of small FOV, E and DAP wereobtained 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 multismallFOVs (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.cm²respectively. Two and three scans of FOV 5 × 3.7 were 262 and 393mGy.cm², respectively.Conclusion : The CBCT radiation dose is affected by the field size and number ofscans taken. In one scan, the radiation dose is higher when the FOVsincrease. In the same FOV, the radiation dose increases withthe number of scans taken. However, one scan of medium FOVprovides less radiation dose than two and three scans of small FOV.Thus, when two or three localized region are required, one scan ofmedium FOV is more recommended than two or three scans of smallFOV. As large FOV provides highest radiation dose, it is thereforerecommended to use when the maxillofacial region is required.


Faculty of Medicine, Chulalongkorn University

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