Objective: Evaluation of cone beam CT (CBCT) examination with a low-dose scanning protocol for assessment of the temporomandibular joint (TMJ). Methods: 34 adult patients referred for CBCT imaging of the TMJ underwent two examinations with two scanning protocols, a manufacturer-recommended protocol (default) and a low-dose protocol where the tube current was reduced to 20% of the default protocol. Three image stacks were reconstructed: default protocol, low-dose protocol, and processed (using a noise reduction algorithm) low-dose protocol. Four radiologists evaluated the images. The Sign test was used to evaluate visibility of TMJ anatomic structures and image quality. Receiver operating characteristic analyzes were performed to assess the diagnostic accuracy. κ values were used to evaluate intraobserver agreement. Results: With the low-dose and processed protocols, visibility of the TMJ anatomical structures and overall image quality were comparable to the default protocol. No significant differences in radiographic findings were found for the two low-dose protocols compared to the default protocol. The area under the curves (Az) averaged for the low-dose and processed protocols, according to all observers, were 0.931 and 0.941, respectively. Intraobserver agreement was good to very good. Conclusion: For the CBCT unit used in this study, the low-dose CBCT protocol for TMJ examination was diagnostically comparable to the manufacturer-recommended protocol, but delivered a five times lower radiation dose. There is an urgent need to evaluate protocols for CBCT examinations of TMJ in order to optimize them for a radiation dose as low as diagnostically acceptable (the as low as diagnostically acceptable principle recommended by NCRP).

Objectives. The aim of this study was to map and compare the distributions of absorbed doses with Gafchromic film for panoramic radiography and cone beam computed tomography (CBCT) examinations of the temporomandibular joint (TMJ) by using adult and child phantoms. Study Design. Gafchromic films were placed at 5 selected levels of anthropomorphic head phantoms of an adult and a child. Clinical protocols for panoramic and CBCT imaging of the TMJ were used for three 2-dimensional or 3-dimensional dental x-ray units. Mean absorbed doses in a set of radiosensitive tissues within the oral and maxillofacial regions were estimated. Results. The absorbed doses varied considerably among and within radiosensitive tissues. The bone surface and the salivary glands received the highest absorbed doses compared with other tissues, in both panoramic and CBCT examinations of the TMJ. The radiation burden to the adult phantom was generally higher than that to the child phantom. Small right and left fields of view were associated with lower amounts of radiation, in contrast to a single larger field of view. Conclusions. The absorbed dose within all radiosensitive tissues varied considerably in relation to examination type, x-ray unit, clinical settings, and patient age. The mean doses were smaller when using 2 (bilateral) 4 £ 4 cm volumes than with use of one 14 £ 5 cm volume.

The present educational programme could be a helpful material on recognising possible osseous changes of TMJ and it can be used as a part of a training programme for GDP and for specialist candidates.