ABSTRACT
The basis for radiobioassay procedures is the introduction of a radioactive substrate to a sample. The radioactive substrate is chemically identical to the native substrate of the sample, but physically different in that it emits radiation, particles, and photons. Subsequently, the emitted particles and/or photons are detected and quantitated. Radiobioassay instrumentation, therefore, depends on the interaction of radiation with matter, i.e., the detector material. Radiation detection depends upon the fact that electromagnetic and particle radiation interact with matter to produce ion pairs. In a sense, then, detection of radiation is an indirect process. There are three basic types of radiation detectors: gas filled ionization chambers, scintillation detectors, and solid state detectors. Radiobioassay procedures utilize scintillation detectors of both types, solid and liquid. Certain radiobioassay procedures require labeling with tritium or Carbon-14, both of which are ß- emitters. Such low-energy beta particles are absorbed by even a thin window between source and detector.
