Types and arrangement of thyroid shields to reduce exposure of surgeons to ionizing radiation during intraoperative use of C-arm fluoroscopy.

STUDY DESIGN

Measurement of radiation dose from C-arm fluoroscopy during a simulated intraoperative use in spine surgery.

OBJECTIVE

To assess how the radiation dose is affected by changes in the types of thyroid shields used and by the arrangements or ways in which they are worn during the intraoperative use of C-arm fluoroscopy.

SUMMARY OF BACKGROUND DATA

Although the danger to the thyroid from exposure to radiation is well known, there are no guidelines for the proper use of thyroid shields.

METHODS

Two photoluminescence dosimeters were used to measure the dose of scattered radiation arriving at the location of the thyroid in a whole-body phantom in the position of the surgeon. On an operating table beside this setup was an anthropomorphic chest phantom representing a patient for which treatment with C-arm fluoroscopy was simulated. Radiation doses were measured using 3 different arrangements of the thyroid shield: worn tightly, worn loosely, and worn loosely with a bismuth masking reagent. The same tests were performed using 2 kinds of thyroid shield: lead and lead-equivalent.

RESULTS

For the lead-shield group, radiation doses were measured in 3 arrangements; worn tightly, worn loosely, and worn loosely with a bismuth masking reagent, for which the results were 1.91 ± 0.13, 2.35 ± 0.22, and 1.86 ± 0.13 μSv/min, respectively. Wearing the shield tight against the throat and wearing it loose with a bismuth masking reagent led to lower radiation exposure levels than by simply wearing the shield loosely (P ≤ 0.001). For the lead-equivalent shield group, doses were measured for the same 3 arrangements, for which the results were 1.79 ± 0.12, 1.82 ± 0.11, and 1.74 ± 0.12 μSv/min. Lower scattered radiation doses were delivered to the thyroid in the lead-equivalent thyroid shield group compared with the lead thyroid shield group (P ≤ 0.001). The unshielded thyroid group received a radiation dose of 16.32 ± 0.48 μSv/min.

CONCLUSION

The use of some form of thyroid shield is essential during the use of C-arm fluoroscopy. It was found that the best way to reduce scattered radiation exposure to the thyroid was wearing the thyroid shield tightly or wearing it loosely in combination with a bismuth masking reagent.

LEVEL OF EVIDENCE