Tissue localization of stable and radioactive nuclides by secondary-ion microscopy

Images of the distribution of a given nuclide in a section of biological tissue can be obtained at the microscopic level by ''secondary-ion mass analysis.'' In this method, the images are formed by an ion-emission microscope wherein the specimen's atoms are progressively sputtered from the surface and the ions are selectively visualied by mass spectrometry according to their mass-to-charge ratios. Such images are obtained at the cost of the destruction of the specimen, which is progressively eroded at the rate of 1-10 atomic layers per second. The spatial resolution is better than 1 μm for an imaged area 250 μm in diameter and a section thickness of 1-2000 nm;thus, the analytical images are element distributions representaive of 3-6000 atomic layers. Distributional images can be obtained for many nuclides, whether stable or radioactive, natural or artifically administered