Neoplasm localization with radionuclides.

Tumor scintigraphic localization of neoplasms can be done in two ways: indirectly and directly. The first method shows alternations of the normal structure of the organ, such as "cold lesions" in liver and thyroid. Abnormalities in function as increased permeability of the blood barrier results from abnormal deposition of the radionuclide in the brain scintigram of a patient with neoplasm. Increased focal areas of uptake of bone-seeking radionuclides are very characteristic of metastases. The direct methods depend on preferential uptake of the radionuclide by the neoplastic tissue resulting from altered metabolism (e.g. Se-75). Other agents such as Gallium-67 have affinity for neoplasms. Another approach is to use antineoplastic agents and radioactive antibodies which will localize in the tumor. At this stage the most useful neoplasm seeking agents are Gallium-67 citrate and 111In-Bleomycin, even though infections can give false positives. The possibility should be considered of enhancing the uptake of radionuclides by neoplastic cells using increased O2 concentration.