[Nuclear medicine for evaluation of liver functions]

The clinical usefulness of colloid liver scintigraphy to detect space occupying lesions in the liver has been reduced by X-ray CT and ultrasonography. However, scintigraphic examinations have potentials for characteristic diagnosis of liver tumors, such as 99mTc RBC SPECT for hepatic hemangioma, 99mTc PMT for positive imaging of hepatocellular carcinoma and its extrahepatic metastasis, and radioimmunoscintigraphy for metastatic tumors. Moreover, prediction of the prognosis and monitoring therapeutic effect to liver cancer can be made by the use of nuclear medicine techniques. Recently, 99mTc galactosyl serum albumin (GSA), a newly developed radiotracer to evaluate hepatocyte function, has become commercially available. Quantitative parameters of liver functions can be obtained by analysis of time-activity curve in blood and liver after 99mTc-GSA administration. In several cases, 99mTc-GSA study showed intrahepatic unevenness of function, which could not be depicted by other imaging examinations. Positron emission tomography (PET) with 18F-fluoro-2-deoxy glucose (FDG) is useful to detect malignant tumors in the liver. Since PET can provide absolutely quantitative data in better resolution, it is expected that regional true metabolic functions in the liver may be able to be quantitatively evaluated with PET in near future.