Technical considerations in scintillation scanning of the human spleen.

Abstract

The purpose of this communication is to present in detail two methods used at the School of Medicine of the University of North Carolina during the past year for area scintillation scanning of the human spleen. The feasibility of one of these methods has been outlined in a preliminary report (1); the result of investigation of the normal and diseased spleen, using both methods, has been presented elsewhere (2). These methods, derived from experimental technics of Jandl et al. (3) and Harris et al. (4) for studying red cell destruction, are in essence means of modifying red blood cells so as to promote their rapid selective sequestration from the circulation, primarily within the functioning spleen. Method 1. Preparation of Red Cells: In preparation for scintillation scanning, red cells may be altered in two ways. In the D-positive subject, isologous red cells may be “sensitized” in vitro by coating with incomplete anti-D antibody. In subjects of all blood group genotypes, red cells may be modified by controlled heating to produce changes in morphology and in osmotic and mechanical fragility similar to those seen in the erythrocytes of patients with hereditary spherocytosis. a. “Sensitized” Red Cells: From a D-positive subject a quantity of venous blood sufficient to contain 6 ml. of red cells is withdrawn; this is placed in a heparinized tube. Sterile technic is used throughout the entire procedure. The red cells are washed five or six times, or until washings are clear, each with 2 volumes of sterile isotonic saline to remove plasma proteins. The cells are then resuspended in 1 to 2 ml. of sterile isotonic saline. To the red cell suspension is added 0.5 ml. of a 1∶128 saline dilution of sterile pyrogen-free human anti-D serum.3 The mixture is incubated at 37 °C. for fifteen minutes. Thereafter red cell testing with a standard Coombs' serum is performed to insure that full sensitization has occurred. Alternatively, homologous D-positive red cells may be utilized in an identical manner, after compatibility with the recipient is demonstrated by cross-matching. Such cells can be obtained from outdated (one day overage) banked blood. b. Heated Red Cells: Isologous or compatible homologous red cells are prepared as follows: A quantity of venous blood containing 6.0 to 8.0 ml. of red cells is obtained as described above. The whole blood is placed in a sterile rubber-sealed bottle and heated in a water bath at 49.6 to 49.8 °. for fifteen minutes. It is then cooled immediately in a second water bath at room temperature for fifteen minutes. c. Chromium-51 Labeling of Red Cells: One hundred to two hundred microcuries hexavalent chromium 51, as sodium chromate,4 added to the suspension of the sensitized red cells, which is then periodically agitated gently for one hour while remaining at room temperature. The labeling process is then terminated by the addition of 100 mg. of ascorbic acid.