Evaluation of skin dose in a low dose spiral CT protocol

The authors evaluated radiation and skin doses absorbed by the eye lens, as well as the parotid and thyroid glands, during a low dose maxillary spiral computed tomography (CT).

Three spiral CTs were carried out, one after the other, changing from time to time MAS, pitch factor, Kv and consequently, CTDI/Vol, until the minimum values detectable by the equipment were reached (MAS 28, Kv 80, CTDI/Vol 2.5, Pitch 1). The quality of the images was evaluated on the grounds of being able to visualise the anatomic structures considered. The amount of radiation effectively absorbed by the soft tissue (skin doses) can be measured with the help of dosimeters placed at the level of eye lens, parotid and thyroid glands. The spiral CTs were performed with a Siemens 16 CT sensation machine, using a tissue equivalent Head-Neck RT Humanoid phantom.

From the results of this study, it appears possible to obtain high quality images, useful for diagnosing numerous skeletal pathologies in orthodontics, reducing of about 90% the radiation dose per unit of volume and, at the same time, reducing the soft tissue (skin) dose of about 85% when compared to pre-established settings.

The authors conclude their research emphasizing the possibility of applying low dose protocols, not only in orthodontics but in any dental field, whenever a spiral CT is needed for a more detailed diagnosis.