Background and aim:   protecting   the  thyroid   gland   during panoramic radiography with shielding is not recommended. in this study ,the effect of  using  thyroid  protecting  shield  ( AKTIF EP 316 )  on thyroid dose of patients  visiting  a  private clinic in Tehran in 1392-93 was investigated

Materials and methods:  In  this  clinical  trial  study  20 men  with similar height, weight and age were  selected among patients whom prescribed panoramic radiography. The dosimeters ( TLDs) were placed on  the  front and back side of shield and radiography was performed with  similar conditions (MA=10 , KVP=72-76 , 18 s time) using a CRANEX D  machine and done for every 10 patients with similar series of dosimeters. Then the  TLDs  were read and data's were evaluated by Fischer exact test and T- test.

Results: All the  images were  assessed with the Fischer test , were acceptable and the thyroid protecting shield did not  prevent the visualization of the anterior teeth. The absorbed dose of thyroid gland when the dosimeters mounted on the front side of the shield was 0.0353 +- 0.03 mGY, while the absorbed dose was 0.0316+- 0.01 mGY when dosimeters mounted on the backside of  the shield .This shows a 10.4 % reduction which is statistically significant based on the T-test (p< 0.002).

Conclusion and recommendations:    The  use  of  the  thyroid  protecting   shield   has  a significant effect on reducing the thyroid gland absorbed dose during panoramic radiography and it’s use is strongly recommended.