Autoradiography is an imaging technique that is used to detect radioactive materials. Autoradiography is one of the most important modern cytochemical methods to study the synthesis of molecules and trace the metabolic events in the cells.
This is done by the use of substances labeled with radioisotopes. The most widely used isotopes are tritium (3H), carbon (14C), and phosphorus (32P).
- Tritium, a carbon labeled thymidine is used for studying the synthesis of DNA
- Tritium or carbon-labeled uridine is used for the synthesis of RNA
- Tritiated or carbon-labeled amino acids are used for tracing protein synthesis
Types
Indicative of the type of specimen containing the radioactivity, the kind of emulsion necessary for image formation, and the method of examining the results.
- Microautoradiography
- Macroautoradiography
Microautoradiography and macroautoradiography are techniques used to study the distribution of radiolabeled molecules in a sample. In microautoradiography, a thin slice of a sample is exposed to a sheet of X-ray film, which is then developed to show the distribution of the radiolabeled molecules.
In macroautoradiography, a larger sample is exposed to a sheet of X-ray film and then developed, usually with the aid of a microscope. Both techniques are used to help track the movement of radiolabeled molecules in a sample, and can also be used to study the metabolism or degradation of radioactive molecules.
This autoradiographic technique contrasts with the techniques such as positron emission tomography (PET) and single-photon emission computerized tomography (SPECT) where the exact 3-dimensional localization of the radiation source is provided by the use of coincidence counting, gamma counters, and other devices.