IMPROVEMENTS in instrumentation and the utilization of radioactive mercury have made brain scanning available as a clinical diagnostic tool. The basis of differential counting and scanning procedures is a selective increase in the concentration of radioactive materials in brain lesions compared to normal brain tissue.1 Many isotopes and scanning procedures have been previously utilized; however, the development of sensitive detection devices and the use of radioactive mercury has led to increased accuracy of this technique in the localization of intracranial lesions.2-6
203Mercury has biologic and physical properties which make it suitable for photoscanning. The physical half-life is 45 days. When incorporated into a mercurial diuretic, excretion is enhanced and one half of the administered dose is excreted in eight hours.3 Approximately 10% of the labeled diuretic remains bound to the kidneys with a biologic half-life of 28 days. The usual kidney dose of 35 to 40 rads is further reduced