Comparison of CT numbers between cone-beam CT and multi-detector CT

Kim, Dong Soo; Han, Won Jeong; Kim, Eun Kyung

Abstract

PURPOSE
To compare the CT numbers on 3 cone-beam CT (CBCT) images with those on multi-detector CT (MDCT) image using CT phantom and to develop linear regressive equations using CT numbers to material density for all the CT scanner each.
MATERIALS AND METHODS
Mini CT phantom comprised of five 1 inch thick cylindrical models with 1.125 inches diameter of materials with different densities (polyethylene, polystyrene, plastic water, nylon and acrylic) was used. It was scanned in 3 CBCTs (i-CAT, Alphard VEGA, Implagraphy SC) and 1 MDCT (Somatom Emotion). The images were saved as DICOM format and CT numbers were measured using OnDemand 3D. CT numbers obtained from CBCTs and MDCT images were compared and linear regression analysis was performed for the density, rho (g/cm3), as the dependent variable in terms of the CT numbers obtained from CBCTs and MDCT images.
RESULTS
CT numbers on i-CAT and Implagraphy CBCT images were smaller than those on Somatom Emotion MDCT image (p<0.05). Linear relationship on a range of materials used for this study were rho=0.001H+1.07 with R2 value of 0.999 for Somatom Emotion, rho=0.002H+1.09 with R2 value of 0.991 for Alphard VEGA, rho=0.001H+1.43 with R2 value of 0.980 for i-CAT and rho=0.001H+1.30 with R2 value of 0.975 for Implagraphy.
CONCLUSION
CT numbers on i-CAT and Implagraphy CBCT images were not same as those on Somatom Emotion MDCT image. The linear regressive equations to determine the density from the CT numbers with very high correlation coefficient were obtained on three CBCT and MDCT scan.