The isotope encephalogram in brain tumor diagnosis.

Scanning of the radioactive tracers in the calvarium represents a major advance of diagnostic techniques in the evaluation of intracranial disease. The pioneering work by Moore (18) at Mayo Clinic in 1948 utilized 1311 labeled Di-lodo-fluorescein as the tracer detected by a Geiger-Muller tube. This now primitive system demonstrated a higher concentration of the isotope tracer in the brain tumors than in normal brain, a phenomenon to which the currently more sophisticated scanning devices still owe their success. A clas sical work by Giovanni Di Chiro (6) in 1961 recorded a large series of iso tope encephalograms using 1311 labeled human serum albumin. Later Blau and Bender (2) reported a new agent for brain tumor localization, 203Hg labeled Neohydrin. In their work, a comparison of physical properties of 1311 human serum albumin and 203Hg Neohydrin showed a higher total body radiation dose from the 1311 tracer and a significant target organ (kidney) dose from 203Hg. The experienced scanning investigators using 1311human serum albumin were reporting accuracy up to 85 percent, a figure difficult to better, yet the scan images with the 203Hg tracer looked more convincing, probably due to a higher concentration or migration of the tracer through the disease altered blood brain barrier. Brain scanning became more and more popular at this time and one is hard pressed to say whether 203Hg chiormerodrin rode the wave of increasing clinical acceptance of scanning or perhaps created the wave. For all its ideal features of long shelf life, monoenergetic gamma emis sion and high affinity for brain tumors, 20311g carried an irradiation dose to the kidney which was disturbing to the point that it was listed by one observer as a contraindicated procedure in children (8). Premedication with stable Mercuhydrin reduced the dose 12-13 rads but the remaining calculated 23-27 rads (2) to kidney could not be overlooked in children or in cases requiring