The hepatic radioactivity survey.

Abstract

It is the purpose of this communication to report our experiences with the hepatic radioactivity survey for the diagnosis of cancer of the liver. The technic of the procedure and the results in a preliminary series of 65 patients have been described in a previous publication (2). The radioactivity survey has been performed on a total of 210 patients to date and has proved to be more accurate and reliable for the diagnosis of hepatic metastases than either liver-function test or needle biopsy of the liver. Iodinated human serum albumin (I*HSA) has been employed as the tracer agent, and the scintillation counter as the detector of the gamma quanta emanating from the I131. Method The I *HSA used in this study was obtained from Abbott Laboratories. I131 has a half-life of eight days and emits a gamma ray sufficiently intense to be recorded externally by the scintillation counter. Radioactive human serum albumin has been used extensively in other investigations (5), and no toxic effects have been encountered from its use in the doses required for radioactivity tracer surveys. I*HSA is a homologous serum protein and contains 5 mg. of human serum albumin per millicurie of solution (3). The wide-angle scintillation counter (1) has been modified for this application by adding 2.5 cm. of lead around the sides of the tube and 3 cm. of lead around the bottom of the tube, leaving a 3/4-inch aperture. This additional shielding minimizes background gamma radiation from parts of the body other than that under survey and is essential for the success of the procedure. It also provides collimation so that the incident angle of radiation is limited to approximately 30 degrees. The counter is mounted on a portable x-ray unit with a special adapter in order to facilitate positioning of the tube during the survey (Fig. 1). The patient is given a single sterile intravenous dose of 300 microcuries of I*HSA, in an average volume of 2 c.c. Twenty-four hours after the injection the patient is placed upon an ordinary examining table and a careful abdominal examination is done to determine the anatomic location of the costal margins, the xiphoid process, the liver edge, and any palpable masses or organs. With the aid of a perforated guide centered over the xiphoid process, co-ordinate rectolinear points are marked on the patient's skin at intervals of 5 cm., extending from the nipple line to below the umbilicus and from flank to flank. A total of 42 points are thus marked and the guide is removed. The aperture of the tube is placed flush with the patient's skin and successive counts are obtained at each point. Care is taken to maintain the counter perpendicular to the long axis of the body at all times. A sufficient number of counts are observed at each point to insure a counting error of less than 3 per cent. Approximately 5 per cent of the radioactive iodine contained in the I*HSA is present as free iodide and may be absorbed by the thyroid gland.