Concentration of Technectium 99m by the Choroid Plexus

Abstract

IN AN earlier paper¹ we described the apparent visualization of the choroid plexus on brain scans utilizing sodium pertechnetate Tc^99m. Orally administered potassium perchlorate had been shown to block the active concentration of^99mTc by the thyroid gland, stomach, and salivary glands.^2-4 We found that 200 mg of potassium perchlorate administered one hour before brain scanning apparently blocked the accumulation of^99mTc by the choroid plexus (Fig 1). Since perchlorate blocked this uptake, we reasoned that the observations presented convincing, inferential evidence of an active concentration process for^99mTc by the choroid plexus. We have performed experiments on rabbits in an attempt to evaluate the hypotheses that the choroid plexus actively concentrates the pertechnetate ion above blood levels and that this accumulation can be blocked by perchlorate. Materials and Methods Eighteen rabbits weighing between 1.8 and 2.2 kg (4 and 5 lb) were