Visualization of Suppressed Thyroid Tissue by Technetium-99m-Tertiary Butyl Isonitrile: An Alternative to Post-TSH Stimulation Scanning

: The autonomously functioning thyroid nodule (AFTN) is a discrete, nodular structure which operates independently of pituitary control and without relation to the remaining thyroid tissue. Presently, for the visualization of a suppressed thyroid lobe, a patient has to undergo the thyrotropin (TSH) stimulation test, which has several disadvantages. In this study we have used tertiary butyl isonitrile (99mTc-TBI), well known as a myocardial imaging agent, for visualization of the suppressed lobe. Thirteen of fourteen patients studied demonstrated a contralateral lobe on a 99mTc-TBI scan which was not visualized with a 99mTc0(4) or 131I scan. Although it is not possible to demonstrate the autonomous nature of the hyperfunctioning thyroid nodule using 99mTc-TBI, we conclude that it is feasible to use this agent to visualize the lobe without the TSH test.