Morphological and dynamic studies of the accumulation of 123I and 99Tc sup (m) in the thyroid

This investigation was undertaken to compare the use of 131I, 123I and 99Tc sup (m) for scintigraphic studies of the thyroid. 123I has the most ideal physical and biological characteristics for this purpose. The detectability of 123I with scintillation camera was found to be more than 200 times better than of 131I in consideration of the absorbed dose to the patient. We have found that an activity of about 200μCi 123I is enough for thyroid scintigraphy. This activity will give about the same count rate with the scintillation camera as when 2 mCi 99Tc sup (m)-pertechnetate is used. Oblique scintillation camera views, which have been found to be of value especially when cold areas were present in the thyroid, can be performed with both 123I and sup 99Tc sup (m). But when sup 99Tc sup (m) is used, a greater fraction of circulating activity is registered. After i.v. administration of 123I or 99Tc sup (m) -pertechnetate sequential scintigrams were registered over the thyroid and the aortic region with a scintillation camera. The activity time curves were analyzed and uptake parameters were evaluated with a computer. The initial trapping curve could thus be studied in patients with different thyroid disorders. (author)