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266 Radiochemistry and Nuclear Chemistry

9.5. Applications to life sciences

The largest field of application of radionuclides is in the life sciences. A survey is
presented in Table 9.3.
In the reactions leading to the desired product (column A) many factors must be
considered. They are of such importance that we devote several separate chapters to this:
Ch. 12 on nuclear reactions, Ch. 13 on particle accelerators and Ch. 15 on production of
radionuclides. The incorporation of the radionuclide in a chemical compound (labelling,
w provides it with unique properties, such as specific biological affinity (w
When such labelled compounds are taken up by organisms (A4b ~ B1) they move to
specific sites in the organs, signalling normal or abnormal behavior. When used in medicine
(primarily C1 and C3) these compounds are referred to as radiopharmaceuticals (A4b).
The use of labelled compounds in life sciences is extensive, in fact, the largest single user
of radionuclides is medical science. It has been said that radioactive tracers have been of
equal importance to medicine as the discovery of the microscope. Presently one out of ten
hospitalized patients in the United States is admitted to some nuclear medical procedure.
If the intended use of the radionuclide is as an external radiation source (A4a ~ B2
C2.1 or C3) its chemical matrix is of minor importance. Such sources are used for radiation
treatment of cancer (C3b), radiation sterilization of food (C3c), etc. The radiation effects
on biological systems are discussed separately in Ch. 18. In this chapter we focus our
interest on radionuclides with specific chemical properties, in the order of column C, Table
9.3.

TABLE 9.3. Survey of radionuclide use in life sciences

A Radionuclide production C Technique/application [detection]
1 Target chemistry, 1 Biochemical analysis
2 irradiation, (a) autoradiography [photographic]
3 isolation (b) immunoassay [counting]
4 and processing, yields (c) DNA-analysis [photographic]
(a) pure radionuclide, or (d) direct tracing [counting]
(b) labelled compound 2 Medical imaging
(radiopharmaceuticals) 2.1 Transmission Tomography (TCT)
[photographic, or by
B Source, position/administration counting---computer-~isplay]
1 Internally (a, fl or 7) 2.2 Emission Computed Tomography (ECT)
(a) injection, [counting---computer-~isplay]
(b) inhalation, or (a) Single Photon Emission Computed
(c) oral intake. Tomography (SPECT)
2 Externally as 7-source (b) Positron Emission Tomography
(PET)
3 Irradiation uses
(a) by internal sources (therapeutically)
(b) by external sources (therapeutically)
(c) by external sources (sterilization etc)