75Se-selenomethionine in hepatic focal lesions

Abstract

The focal lesion of the liver is usually characterized by the absence of the liver's uptake of radioactive scanning agents. In the focal lesion, the incorporation of 75Se-selenomethionine is related to its vascularity and capacity to metabolize methionine. Modification of the rectilinear scanner permits it to function in a dual-channel subtraction mode, to subtract 198Au from 75Se in the liver, and to present the display of the liver in one color and the selenium in the pancreas and the focal lesion in another. The avascular lesions, including cysts, abscesses, scars, pseudotumors, and extrinsic pressure defects, show little or no 75Se activity. Metastatic lesions may have varying levels of selenium concentration. The hepatocellular carcinoma concentrates selenium in amounts equal to the normal hepatic parenchyma and can only be visualized in the 75Se-selenomethionine scan by the subtraction technique. The correlation between vascularity and 75Se concentration is high but not necessarily directly proportional, and in specific instances may be poorly correlated. Knowledge of the selenomethionine content in a focal defect is considered to enhance the diagnostic value of liver scanning.