Scintillation scaning of the normal human spleen utilizing sensitized radioactive erythrocytes.

Abstract

The human spleen has not been selectively demonstrable by scintillation scanning, although its partial delineation has occasionally occurred in liver scans following administration of colloidal gold 198. Recently, however, Hughes Jones et al. plotted “isocount lines” over the spleen in two patients exhibiting splenic trapping of radioactive red cells (1). The purpose of this report is to describe our preliminary experience with scintillation scanning of the normal spleen following its differential concentration of gamma-emitting red cells. The method employed in this investigation is a modification of a technic described by Jandl et al. (2) for study of the physiology of erythrocyte destruction. It has been shown by these and other workers (1, 3) that certain modifications of ABO-compatible transfused red cells lead to rapid sequestration and destruction of these cells, chiefly within the liver and spleen. Splenic trapping is quantitatively greatest when Rh0(D)-positive red cells, sensitized by coating with incomplete anti-Rh0(D) antibody, are administered to normal Rh0(D)-positive persons (2). The survival of such abnormal cells, after transfusion, has been studied by serial measurement of circulating red cell radioactivity, and the sites of sequestration found by external body surface counting, made possible by prior labeling of the red cells with chromium 51. Observations were made on 9 adults with intact, nonpalpable spleens, with Rh0(D)-positive blood and without clinical or laboratory evidence of hematologic or splenic disorder. Six milliliters of sterile sensitized Type 0, Rh0(D)-positive red blood cells were tagged with 150–200 microcuries of sodium chromate (Cr51) and injected into an antecubital vein from which a control sample of blood was first withdrawn.2 Serial samples of 5 ml. of whole blood were drawn from the opposite arm. Serial scintillation counting over the liver, spleen, and thigh was performed with two lead-shielded scintillation probes fitted with a 1-inch crystal and wide-angle collimator. The pulses from each probe were amplified and transmitted into a linear rate meter from which counts per minute were directly read. Scanning of the spleen was performed with a lead-shielded 2-inch crystal with a straight-bore cylindrical collimator with aperture of 5/8 in. diameter attached. Pulses from the crystal were amplified and transmitted into a spectrometer with its channel of 100 Kev width “focussed” on the gamma photopeak of chromium 51. Clearance of Sensitized Radioactive Erythrocytes from the Blood: In 6 cases the number of circulating sensitized radioactive red cells decreased exponentially (Fig. 1), with a half-survival time ranging from 24 to 98 minutes (mean 46.7 minutes). In Case 3, in which marked hepatic red cell sequestration occurred, the half-survival time was 11 minutes; in the other 2 it was approximately 42 minutes (Case 4) and 50 minutes (Case 8).