en Medical Physics Medical Physics تحقيق بديع Original Research <div style="text-align: justify;">Background: Salivary flow rate (SFR), to estimate salivary gland dysfunction and radioactivity in different body fluids, to evaluate its intensity, were determined in thyroid patients after 131-I therapy. Material and Methods: For determination of SFR an innovative sponge test was adopted and the radioactivity in saliva, blood and serum of thyroid patients was determined by NaI (TI) Scintillation Radiation Detector. Results: There was a significant reduction in SFR at 2 weeks after RAIT. At 3 hours after administration of 555&minus;1073 MBq to the benign thyroid patients, the radioactivity in 1 g of saliva, 2.5 mL of blood and 0.6 mL of serum was 17.24, 0.74 and 0.25 MBq respectively. In the same patients, at 2 weeks after RAIT, the radioactivity was decreased and was found to be 0.22, 0.13 and 0.09 MBq in saliva, blood and serum respectively. In malignant thyroid patients treated with 3700&minus;9250 MBq, the radioactivity at 3 hours after RAIT in the studied samples of saliva, blood and serum was 200.72, 9.14 and 3.07 MBq and at 2 weeks after RAIT, radioactivity in samples was decreased up to 0.15, 0.05 and 0.03 MBq respectively. Conclusions: An indigenously designed sponge test was simple, safe and quick method to determine the SFR. The sudden increase of radioactivity was found in all studied samples within 3 hours after RAIT and reduced significantly at 2 weeks after RAIT. The raised radioactivity at 3 hours after RAIT was sufficient to impart its harmful effects even to all interactive persons.</div> Radioiodine therapy, Radioactivity in saliva, Radioactivity in blood, Radioactivity in serum. 197 203 http://ijrr.com/browse.php?a_code=A-10-2055-102&slc_lang=en&sid=1 A. Rakha drarmalik45@gmail.com 7900319475328460020028 7900319475328460020028 Yes Department of Biochemistry, Punjab Medical College, Faisalabad, Pakistan. K. Rehman 7900319475328460020029 7900319475328460020029 No Department of Biochemistry, University of Agriculture, Faisalabad, Pakistan. M. Shahid 7900319475328460020030 7900319475328460020030 No Department of Biochemistry, University of Agriculture, Faisalabad, Pakistan. N. Jahan 7900319475328460020031 7900319475328460020031 No Department of Chemistry, University of Agriculture, Faisalabad, Pakistan. M. Babar Imran 7900319475328460020032 7900319475328460020032 No Pakistan Institute of Nuclear Medicine (PINUM), Faisalabad, Pakistan.