Abstract Introduction: The goal of health physics is to prevent the occurrence of deterministic effects and to reduce the likelihood of stochastic effects by minimizing the exposure of patients and radiation workers during radiographic examination. Regarding to panoramic radiography is the most common radiograph in the head and neck region and thyroid gland is the most sensitive area and also the extensive variety in panoramic machines, this comparative study was designed. Objective: Comparison of skin absorbed dose in thyroid gland area of planmeca and cranex tome panoramic machines. Materials and Methods: In this in vitro study a dry skull and a Pocket ion-chamber dosimeter were used. At first, panoramic examination was done in different exposure conditions for small, medium, large and child patients in planmeca machine. After every exposure, the charge of dosimeter was read and recorded. These stages were repeated for Cranex Tome Machine. Then statistical analysis was performed by sample paired test with %95 confidence. Results: In both panoramic machines, the highest mean thyroid skin dose was detected in large size patient and in the highest level of exposure factors. The mean values of doses were recorded 0.11 mSV in planmeca machine and 0.14 mSV in Cranex Tome machine. There was the least mean absorbed dose in child programs and 0.03 mSV in planmeca machine and 0.02 mSV in Cranex Tome machine. There was no significant statistical difference between mean absorbed doses in patients with different size in two panoramic machines Conclusion: There was no difference between two panoramic machines for thyroid skin dose .Child program reduced thyroid skin dose definitely in both systems.

Keywords: Radiography- Panoramic, Radiometry, Thyroid gland

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