THE PRACTICALITY of utilizing technetium (99mTc) pertechnetate as an agent for routine scanning was established by Harper in 1964.1 It has a short physical half-life (six hours) and is obtained by pouring sterile saline through a generator containing the longer half-life (67 hours) molybdenum-99 "parent." The short half-life of the99mTc makes possible the administration of large millicurie doses of the radionuclide but, at the same time, causes only minimal radiation dose to the patient. The high count rates associated with large doses make rapid scanning possible. Further, its 140-kev gamma emission is easily collimated for good resolution.
Sodium pertechnetate (99mTc) is handled by the body in the same fashion as the iodide ion. As with iodide, pertechnetate is actively accumulated by the thyroid gland, stomach, and salivary glands.2 Both Lugol's solution and potassium perchlorate have been used to block this active concentration and thus
Witcofski RL, Janeway R, Maynard CD, Bearden EK, Schultz JL. Visualization of the Choroid Plexus on the Technetium 99m Brain Scan: Clinical Significance and Blocking by Potassium Perchlorate. Arch Neurol. 1967;16(3):286–289. doi:10.1001/archneur.1967.00470210062007
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