title: Measurement of radiation dose to the thyroid using positron emission tomography.
abstract: Measurements of the functioning volume of thyroid tissue have been made in 22 patients undergoing radioiodine therapy for thyrotoxicosis, using a prototype multiwire proportional counter positron camera. Tomographic images were produced of the distribution of 124I in the thyroid. Functioning volumes were found to be in the range 21-79 cm3 with volume errors of the order of +/- 4% to +/- 14%. Radioiodine uptake varied from 28% to 98%. Using a value of 6 days for the effective half-life of radioiodine in hyperactive thyroids, radiation doses from a standard therapy administration of 75 MBq of 131I varied from 11 to 48 Gy (compared with a recommended 50-70 Gy). In five cases PET imaging showed a non-uniform distribution of radioiodine in thyroids thought to have uniform uptake from conventional pinhole scintigraphy.
mesh_terms: D006801:Humans; D007457:Iodine Radioisotopes / Q000378:metabolism; D011829:Radiation Dosage; D013961:Thyroid Gland / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000503:physiopathology; D014055:Tomography, Emission-Computed
chemical_list: D007457:Iodine Radioisotopes