Small field of view cone beam CT temporomandibular joint imaging dosimetry

Cone beam CT (CBCT) is generally accepted as the imaging modality of choice for visualisation of the osseous structures of the temporomandibular joint (TMJ). The purpose of this study was to compare the radiation dose of a protocol for CBCT TMJ imaging using a large field of view Hitachi CB MercuRay™ unit (Hitachi Medical Systems, Tokyo, Japan) with an alternative approach that utilizes two CBCT acquisitions of the right and left TMJs using the Kodak 9000(®) 3D system (Carestream, Rochester, NY).

25 optically stimulated luminescence dosemeters were placed in various locations of an anthropomorphic RANDO(®) Man phantom (Alderson Research Laboratories, Stanford, CT). Dosimetric measurements were performed for each technique, and effective doses were calculated using the 2007 International Commission on Radiological Protection tissue weighting factor recommendations for all protocols.

The radiation effective dose for the CB MercuRay technique was 223.6 ± 1.1 μSv compared with 9.7 ± 0.1 μSv (child), 13.5 ± 0.9 μSv (adolescent/small adult) and 20.5 ± 1.3 μSv (adult) for the bilateral Kodak acquisitions.

Acquisitions of individual right and left TMJ volumes using the Kodak 9000 3D CBCT imaging system resulted in a more than ten-fold reduction in the effective dose compared with the larger single field acquisition with the Hitachi CB MercuRay. This decrease is made even more significant when lower tube potential and tube current settings are used.