Comparison of Hounsfield units between two CBCT units


Akshayaa L and Jayanth Kumar Vadivel*


Cone-beam computerized tomography (CBCT) is a medical imaging acquisition system with a cone shaped X ray beam centered in a two dimensional detector. It allows the clinicians to analyse the craniofacial structures of jaw, bone and teeth in three dimensional resolution. It provides many advantages in dental treatments, planning with a lower radiation exposure.


The primary objective of our present study was to analyse and compare the hounsfield units between the two CBCT machines.

Materials And Methods

A 3 dimensional radiographic phantom made up of poly methyl methacrylate (PMMA); clear acrylic. The length of the phantom measures about 4cm and width of 2.5 cm. This radiographic phantom contains four different materials : a lead foil, GP sticks, metal ball bearing and aluminium foil. The phantom was then scanned under two CBCT units : Kodak and Sirona at two different exposure parameters. The mean value of each density of materials was compared using a one way Anova test.


In our study, we analysed and compared the mean value of densities of 4 materials in radiographic phantom which was scanned at two different exposures. A pairwise multiple comparison was done using a one way Anova test. By comparing the densities between materials in the phantom, p value for each comparison was found to be < 0.05, hence it is statistically significant. Thus there is a significant difference in the hounsfield units (density) values of each material scanned under two different CBCT units with different exposure protocols but between units the values did not differ significantly (p > 0.05).


Within the limitations of the study, it was concluded that there is a significant difference in the densities of the material obtained between two CBCT units taken under two exposures using the phantom. It was found to be statistically insignificant. So, the pseudo hounsfield units in CBCT have to be used cautiously.