MEDRADSC 2Z03 Chapter Notes - Chapter 8: Nuclear Medicine, Radionuclide, Half-Life
29 Jun 2016
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Every radioisotope has a characteristic half-life (t12) which is the time required for the radioactivity to decay to 50% of its original value. The half-lives of some of the common radioisotopes used in nuclear medicine are presented in table 2. Table 2: examples of half-lives of some of the common radioisotopes used in nuclear medicine. In one half-life, the activity a is reduced by a2. In two half-lives, the activity a is reduced by a22 (so the activity is reduced by a quarter) In three half-lives, the activity a is reduced by a23 (so the activity is reduced by an eighth) In n half-lives, the activity a is reduced by a2n. The activity of a radioisotope at any time t is given by: Figure 4, below, shows the exponential decay of radioactivity as a function of time. Figure 4: the decay of radioactivity as a function of time.
