The importance of delayed imaging in the study of hepatoma with a new hepatobiliary agent

Concentration of Tc-99m(Sn)-N-pyridoxyl-5-methyltryptophan (Tc-99m PMT), a biliary agent, in hepatic tumors was studied with delayed hepatobiliary imaging in 23 patients with histologically verified hepatocellular carcinomas. All 23 showed filling defects on liver images obtained with Tc-99m tin colloid. In the images taken 5 hr after Tc-99m PMT injection, ten cases showed increased uptake in the carcinoma, six nearly normal uptake, and seven decreased uptake. In those showing the increased uptake of Tc-99m PMT in the tumor, the ratio of the radioactivity in the lesion to that in the adjacent liver parenchyma (T/L ratio) increased progressively with time for 5 hr after injection. These results indicate that delayed Tc-99m PMT images, obtained 5 hr after injection, are useful in assessment of uptake of the radioactivity by hepatocellular carcinoma.