Stability of pixel density in cone-beam computed tomographic images

• Published in: Journal of Osaka Dental University Vol. 48; no. 2; pp. 97 - 102
• Main Authors: Nakashima, Yukako, Yotsui, Yoritaka, Shimizutani, Kimishige
• Format: Journal Article
• Language: English
• Published: Osaka Odontological Society 2014
• Subjects: CT number; Density; Dental cone-beam CT
• ISSN: 0475-2058; 2189-6488
• DOI: 10.18905/jodu.48.2_97

Cone-beam computed tomography (CBCT) is not well equipped to provide readouts in CT number (CTN). We examined the correlation between the pixel density of CBCT images from two machines and CTN of multi-detector row computed tomography (MDCT) from one machine. A quality assurance phantom was used to evaluate the stability of the images. The contrast medium lopamidol (lopamiron 300®; Bayer Health, Osaka, Japan) at 6 different concentrations (0,1, 2.5, 5, 10 and 20%) were placed in 5 mL syringes. Test objects were positioned in several patterns and both CBCT and MDCT images were obtained. The pixel density was measured and analyzed with an image workstation. We found that the CBCT image became less dense closer to the edge of the imaging area, while the density of the MDCT image was stable throughout. A strong correlation was observed between the pixel density of CBCT and the CTN of MDCT in the same materials. Placing materials around the object resulted in smaller values. We concluded that the density near the center of the field of view (FOV) is accurate in CBCT images. A high correlation and linear relationship between the CTN and pixel density were observed for each parameter.