| Abstract: | 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 visualized 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 micrometer for an imaged area 250 micrometer in diameter and a section thickness of 1-2000 nm; thus, the analytical images are element distributions representative of 3-6000 atomic layers. Distributional images can be obtained for many nuclides, whether stable or radioactive, natural or artificially administered. |
