Brain Tumor Localization Utilizing Mercury 203

Abstract

The localization of brain tumors by scintillation scanning has been studied for many years, but has ailed to gain widespread use as a diagnostic tool. In 1960, Bender and Blau (1,4) reported that mercury 203 was localized in some brain tumors and that it was readily eliminated as the compound Neohydrin (mercurated allylurea). In this study we have used Hg203 chlormerodrin (Neohydrin) with a physical half-life of forty-seven days and a single gamma-energy emission of 280 kev (Fig. 1). The material was supplied with an activity of 0.09 millicuries per milligram at a concentration of 5.3 milligrams per milliliter. The low gamma photopeak minimizes the scattering problem and the low energy of the beta particles (210 kev) from mercury 203 reduces the radiation dosage to the patient. Technic: In all patients studied brain tumors were suspected clinically. In all instances, the patients had diagnostic studies such as cerebral arteriograms, ventriculograms and/or skull roentgenograms. Twenty-four hours prior to the administration of the radioisotope, 1 c.c. of stable Neohydrin was administered intramuscularly to block renal concentration of the material. A dosage of 10 microcuries of Hg203 Neohydrin per kilogram of body weight was administered intravenously, the maximum dose being limited to 700 microcuries. Scintillation scanning was performed with a Picker Magnascanner utilizing a 3 × 2-inch thallium-activated sodium iodide crystal with a 19-hold focusing collimator shielded with 2.5 cm of lead. A 50 kev spectrometric window centered on the 280 kev photopeak of Hg203 was used. Scanning was performed in both the anteroposterior and lateral projections at two and a half, five, twenty-four, and forty-eight hours. Twenty-four- and forty-eight hour urinary excretion determinations of Hg203 were made, and blood level radioactivity was also measured. There was no evidence of toxicity or untoward effects from the radioisotope and no significant difficulty was experienced in the scanning. Seventeen patients have been studied, 1 on two occasions, with this technic (Table I). Five areas of brain tumor (primary or metastatic carcinoma) were identified and proved. In 1 patient, the brain scan showed no areas of localization, but an ependymoma was found at operation (Case VII). This is probably related to the fact that ependymomas are midline in location, are in an area difficult to scan accurately, and are relatively avascular. In Case VI, the arteriogram showed a left cerebral vascular tumor but the scan was negative. No adequate explanation can be offered for this. There were no false positives. In 9 patients the absence of tumor was confirmed by the Hg203 brain scan. The urinary excretion of Hg203-labeled Neohydrin was determined at twenty-four and forty-eight hours. At the end of twenty-four hours, an average of 20 per cent of the administered dose had been excreted in the urine.