Visualization of the Spleen in Man by Radioisotope Scanning

To visualize an organ by scintillation scanning, a gamma-emitting radioisotope must reach a considerably higher concentration within the organ than in the surrounding tissues. A method for scanning the spleen has recently been reported (2). Cr51-labeled Rh0(D) positive red blood cells, “sensitized” for splenic trapping by coating with incomplete anti-Rh0(D) antibody, were administered intravenously to Rh0(D) positive persons. This method, however, could not be used in Rh negative patients and necessitated typing of each patient's blood. On the basis of the observation that heated red blood cells concentrate in the spleen (1), a simple technic which gave a good spatial image of the spleen was developed. Ten cubic centimeters of the patient's blood were withdrawn into a sterile syringe containing 2 c.c . of ACD anticoagulant. Two hundred microcuries of Cr51 sodium chromate were added. After incubation at room temperature for fifteen minutes, 50 mg. of ascorbic acid were added to reduce residual chromate to chromic ions. The tube was then incubated in a water bath at 49.5°C. ± 1° for one hour. After cooling, the blood was administered intravenously. Heating of the red blood cells increased osmotic fragility but did not cause hemolysis. By phase microscopy, the heated red cells exhibited poikilocytosis, anisocytosis, and pseudopodial bulges from the surface. In vivo counting following injection revealed maximum concentration of the altered red blood cells in the spleen between one and two hours (Fig. 1,A). Scintillation scanning was then performed with the patient supine. A 3 × 3-inch sodium iodide crystal, 12-hole focusing collimator, and scintillation spectrometer were used. The scanning image was produced by a high-contrast photorecorder on regular x-ray film. A routine abdominal radiograph was obtained on the scanning stretcher for accurate localization of the scanning image. In each of 17 subjects. the technic produced a clearly delineated image of the spleen (Fig. 2). The ratio of the counting rate in the splenic area to that of the surrounding tissues averaged five to one. Enlargements and displacements of the spleen were demonstrated. In the future, the procedure should prove valuable in the differential diagnosis of obscure abdominal masses, in the clinical assessment of splenomegaly, and in the detection of splenic infarcts, abscesses, and cysts, and of accessory spleens. The effective half-time of the radioactivity in the splenic area was approximately eight days as determined by serial in vivo counting (Fig. 1,B). Within this interval, about 25 per cent of the administered radiochromium was excreted in the urine. The total dose of radiation delivered to the spleen was calculated to be 4 rads, and the total-body irradiation less than 0.05 rads. The procedure, therefore, was within reasonable limits of radiation dosage.