THE JOURNAL OF THE TOKYO DENTAL COLLEGE SOCIETY

Vol. 108 No. 2      April 2008

ISSN: 0037-3710      UBIC: 342-J

ABSTRACT

The CB Throne is a cone beam computed tomography unit for dental use, and the smaller version of the CB MercuRay developed by Hitachi Medico Co. We investigated which exposure conditions were suitable in the clinical use. Suitable exposure conditions were determined by simple subjective comparisons. The right temporomandibular joint of the head phantom was scanned at all possible combinations of lube voltage (60. 80, 100, l20kV)and tube current(10, l5mA). Oblique-sagittal images of the same position were obtained using multiplanar reconstruction (MPR) function. Images obtained at 120kV and l5mA. which are the highest exposure conditions and certain to produce images of the best quality, were used to establish the standard. Eight oral radiologists observed each image and standard image on a LCD monitor. They compared subjectively spatial resolution and noise between each image and standard image using a 10cm scale. Evaluation points were obtained from the cheek positions on the scales. The Steel method was used to determine significant differences. The images at 60kV/l0mA and 80kV/t5mA showed significantly lower evaluation points un spatial resolution. The images at 60kV/l0mA, 60kV/l5mA and 80kV/l0mA showed significantly lower evaluation points on noise. In conclusion, even if exposure conditions are reduced to l00kV/l0mA, l00kV/l5mA or 120kV/l0 mA, the CB Throne will produce images of the best quality. (The Shikwa Gakuho. 108 : 104-109, 2008) Key words: cone beam CT, exposure condition, spatial resolution, noise.

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