Answer to Question #11550 Submitted to "Ask the Experts"
The following question was answered by an expert in the appropriate field:
For a scan of the temporomandibular joint (TMJ) in the head and neck region, which one of these exposes a patient to more radiation: a medical computed tomography (CT) scan or a bone scintigraphy scan?
A literature search did not show any specific use of bone scintigraphy scanning for evaluation of the TMJ. Scintigraphy scanning is used for evaluation of head and neck cancers, but I doubt scintigraphy could be used for evaluation of the TMJ due to the lack of anatomical detail from scintigraphy. Nevertheless for comparison, a technicium-99m (99mTc) methyl diphosphonate (MDP) bone scan can deliver an effective dose of about 6.3 millisieverts (mSv), as listed on the third page in the Health Physics Society fact sheet on medical exams and exposures.
Regarding the use of medical CT scanning, one article (Kadesjö et al. 2015) reported the effective dose from a multislice CT scanner for a bilaterial TMJ exam to be from 0.113 to 0.124 mSv. Alternately, a cone beam CT scan, which is more commonly used in dental exams, delivers an effective dose of 0.092 to 0.184 mSv. These exposures are essentially the same and do not pose any measurable radiation risk.
John Jacobus, MS, CHP
Kadesjö N, Benchimol D, Falahat B, Näsström K, Shi XQ. Evaluation of the effective dose of cone beam CT and multislice CT for temporomandibular joint examinations at optimized exposure levels. Dentomaxillofacial Radiology 44(8); 2015.
Editor's note: The benefits of a properly performed, clinically indicated, diagnostic imaging procedure far outweigh the risks.