In vivo, thyroid and lens surface exposure with spiral and conventional computed tomography in dental implant radiography.

OBJECTIVE

To compare the surface dose exposure to the lens of the eye and the thyroid gland received by patients undergoing spiral and conventional computed tomography (CT) examinations during dental implant pretreatment evaluation in critical radiosensitive structures of the maxillofacial region.

STUDY

DESIGN

Two groups of 10 patients each had a dental implant CT examination performed, with 5 patients in each group having maxillary and 5 having mandibular examinations. One group was examined with conventional CT and the other with spiral CT. Seven examination parameters were standardized to both types of examinations. Lithium fluoride thermoluminescent dosimeters were placed over the thyroid gland, lateral orbit, and infraorbital foramen of each patient to measure the surface dose. The Wilcoxon rank sum test was used to compare doses, with statistical significance set at P <.05.

RESULTS

For the maxillary examination, there was a 57.4% reduction in the surface dose at the lateral orbit, 47% at the infraorbital foramen, and 60.8% at the thyroid when spiral CT was used instead of conventional CT with the same parameters. Similarly, for the mandibular examination, there was a 57.4% reduction at the lateral orbit, 60% reduction at the infraorbital foramen, and 70.9% at the thyroid. All the dose reductions were statistically significant at P <.05.

CONCLUSION

The use of spiral CT for preimplant evaluation reduces the surface absorbed dose in certain critical structures of the maxillofacial region compared with conventional CT.