Comparison of image validity between cone beam computed tomography for dental use and multidetector row helical computed tomography

Objectives: To evaluate and compare the image validity of a cone beam CT machine for dental use (3DX) and the latest medical CT system, multidetector row helical CT (MDCT). Methods: A dried right maxilla of an Asian adult was used as a phantom. It was cut from the zygomatic process towards the midline, parallel to the midline plane, into eight slices of 2 mm thickness. This phantom was imaged with the 3DX and MDCT machines. Images were evaluated by comparing them with one selected bone slice from the phantom. In this comparison, two types of MDCT images were used: one with the window level (WL) and window width (WW) suitable for observing teeth (MDCT tooth image), and the other appropriate for observing bone (MDCT bone image). Three dentists and one radiographer then used our reported subjective five-level scale to evaluate and compare images generated by the two systems in terms of validity. Cancellous bone as well as enamel, dentin, pulp cavity, periodontal ligament space, lamina dura and overall impression were evaluated. Results: Statistically significant differences (P < 0.05) were found for almost all observation items. Our subjective evaluation clarified that 3DX was superior to MDCT in terms of image validity. Few significant intra- or interevaluator errors were found. Conclusions: Our subjective evaluation of image validity clarified 3DX as being superior to MDCT. Taken together with the low skin dose we previously reported for 3DX, the results demonstrate 3DX to be beneficial for imaging diagnosis of hard tissues in the maxillofacial region.