Comparison of ^99mTc-pertechnetate and ¹³¹I-iodide as thyroid scan agent

Because of an appropriate gamma-energy and relatively short half-life of 6 hours, technetium-99m-pertechnetate(99mTc) has been claimed to be superior or equal to iodine-131-iodide (131I) in scanning of the thyroid gland. Thepresent communication reports the results of our clinical study on advantages of 99mTc over 131I for thyroidscanning in the subjects with normal or abnormal uptake values and with "cold" nodules. The material consisted of33 patients with various thyroid function states. We performed the 24 hour uptake study of Na131I following theoral administration of 40 Ci "atomic cocktail" Then a scan was carried out using Scintimat 2F scanner with thewindow set for 364 KeV and a 31-hole collimator. The 131I-scan was followed by 99mTc-scan 15 minutes afterintravenous injection of 2mCi of Na99mTcO4. The window was set at 140 KeV and a 396-hole collimator was used. Themean and standard deviation of Q values for the 99mTc scannin was 14.5+5.4 with the range from 8 to 27 and for the131I scanning 5.3+0.95 and from 4 to 8.5. This indicates that the scan quality was nearly 3 times superior when99mTc was used. Viewing of color scans revealed obviously improvement in the quality of the scan image in terms ofmuch more orderly color-dot distributions and sharper profile.