Internal or in-scan validation: a method to assess CBCT and MSCT gray scales using a human cadaver.

Objective: This study aimed to explore whether cone beam computed tomography (CBCT) and multislice computed tomography (MSCT) can be used to quantify tissue density and to determine if the Hounsfield unit scale is applicable.

Study Design: A clinical MSCT scanner and effective energy adjusted photon beam attenuation references were used to compare the gray scale of CBCT images of the mandible region. A phantom was scanned using axial cadaver slices and 4 different homogeneous reference objects. The consistency of the references' gray values and 12 linear profile lines from both scanner data sets were compared.

Results: The gray values of the 2 scans showed strong correlation with quantified position-dependent differences as an outcome of the validation process.

Conclusions: The introduced internal, in-scan validation is able to estimate and has a potential to compensate for the differences between MSCT and CBCT protocols. This validation serves as a guide in situations where the users can expect deviations.