Introduction: Fluoroscopy is an important diagnostic technique in medicine. Among fluoroscopic procedures barium swallow (BS) and upper gastrointestinal (UGI) account for a large number of examinations. During these procedures, the thyroid of patients is normally irradiated by the primary and scatter ionizing radiation causing both the deterministic and hazardous effects on this tissue. Therefore the assessment of absorbed doses to the thyroid from these examinations becomes necessary. In addition, to perform these examinations, it is normally required that the radiologists and other radiation workers and paramedics stay in the fluoroscopic room. This puts the clinicians body and their various organs/tissues, especially their thyroid, under the secondary/scatter ionizing radiation. This research was carried out to estimate the thyroid absorbed doses of patients and radiation workers involved in fluoroscopic examinations at four different large scale general hospitals in Tehran.
Material & Methods: To assess the patient and radiation worker thyroid doses, Li-F thermoluminescent dosimeters (TLDs) were used which are known as TLD-100 and made by Harshaw Company. The TLD cubic chips were first annealed and read out using an appropriate consistent oven to make their background stored counts free. Then, they were exposed to know various amounts of radiation at Karaj Secondary Standard Dosimetry Laboratory of Iran, enabling us to determine a calibration curve for them over the range of exposure common in fluoroscopic procedures. The results of this dose assessment were also compared with those obtained in other countries and with the reference dose levels recommended by some radiation protection organizations.
Results: The results indicated an average absorbed dose to the thyroid of patients of 7.89 mGy (SE: 1.33) and 2.97 mGy (SE: 0.43) for the BS and UGI fluoroscopic examinations respectively.
Corresponding values estimated for the radiation workers were 0.70 mGy (SE: 0.01) and 0.14 mGy (SE:0.01)for the BS and UGI examinations respectively. Furthermore, estimating the annual frequencies of the above examinations from the hospitals records revealed an annual collective dose to the thyroid of the radiation workers of 9.5 and 11.6 mSv for the BS and UGI examinations respectively.
Conclusion: While our mean value of the patient thyroid absorbed dose from UGI examinations was within the range of the values reported by some researchers, it was either far less or more than some other reports. On the other hand our mean value of the patient thyroid absorbed dose from BS examinations was six folds that reported in Spain. Finally, our estimated staff dose for the thyroid was 4.1% of the dose equivalent value for this organ recommended by the US NCRP and DOE.