Abstract
In order to verify if pixel values of bone detected by commercially available cone beam CT (CBCT) correctly reflect the quality of bone, sixteen gypsum markers were installed on the jaw bone of a dry skull and measured by medical CT and six CBCTs in air and water. The average and SD of the CT number of markers measured by MDCT in air were 1954±87 and the coefficient of variance (CV) was 0.045. The pixel value of CBCT was 2815±305 and CV was 0.108. The pixel value was different from the CT value of MDCT, and SD and CV were larger. Other CBCTs showed similar results. In water, the CT value by medical CT decreased by 8% compared with in air, while the CBCT pixel value decreased from 38 to 67%, and the CV value increased markedly. Accordingly, pixel values measured by the current CBCTs are thought to be unreliable.
