Purpose: Application of small field of view (FOV) is effective to reduce radiation exposure indental cone-beam CT (CBCT). However, it is not easy to depict objective teeth in aFOV of 40-50mm in diameter. Therefore an automated FOV adjustment system basedon the panoramic radiography 3D mapping technique was developed. We evaluated thereproducibility of the FOV in objects with various head position.
Materials and method: A head phantom especially designed for panoramic radiography was used as an objectto be imaged. A hybrid x-ray imaging system combining digital panoramic radiographywith CBCT (QR-master H/Revo) was used. This system equiped a FOV adjustmentsystem. In the FOV adjustment system, at first a panoramic radiography was taken as ascout image. In the panoramic image, when a dentist chooses a position to be imaged, athree-dimentional position of a FOV with 50mm in diameter and 45mm in height wasdefined automatically. Panoramic radiograph and CBCT were obtained in various headposition. The reproducibility of the FOV adjustment system was evaluated in themaxillary anterior region.
Results and conclusion: The depiction of objective teeth in CBCT was stable when the position of head phantomshifted toward bilaterally. Objective teeth were protruded from FOV when the positionof phantom shifted anteroposterior direction widely. Widely vertical tilting of head alsoaffected the reproducibility of FOV. It was suggested that the FOV adjustment systemrevealed high reproducibility as far as the position of patient’s head was setappropriately.
