MATERIALS AND METHODS

Technetium-99m as sodium pertechnetate, which is widely used for brain scintigraphy, rapidly accu mulates in the choroid plexus and salivary glands after intravenous injection (1). The presence of substantial amounts of 99mTc in these organs de grades the quality of brain scintigrams. Hence, in many laboratories patients routinely receive perchlo rate (KC1O4 or NaClO4) prior to brain scintigraphy in order to inhibit salivary gland and choroid plexus accumulation of pertechnetate (1). Perchlorate is generally administered by mouth. Although this route is suitable for most patients, it cannot be used conveniently when patients are un conscious or uncooperative (unless a nasogastric tube is in place) or when oral intake is restricted. Intravenous injection of sterile pyrogen-free solu tions of perchlorate has been advocated (2,3), but this mode of administration may be painful (3). Furthermore, preparations of perchlorate suitable for intravenous injection are not commercially avail able (4). Pertechnetate and iodide rapidly appear in the blood after rectal administration in dogs (5), as does pertechnetate introduced through a colostomy in a human (1). The similar biologic behaviors of perchlorate, iodide, and pertechnetate suggested that rectal administration of perchlorate might be an ef fective way of blocking salivary gland and choroid plexus trapping of O9mTcO4—in unconscious patients who are sent for brain scintigraphy without naso gastric tubes in place. The following experiment was performed to test this hypothesis