Читать книгу Essentials of Nuclear Medicine Physics, Instrumentation, and Radiation Biology - Rachel A. Powsner - Страница 63

Transient equilibrium is illustrated in Figure 3.2. In this example, the half‐life of the parent nuclide is approximately 10 times that of the daughter. Following an elution that removes all of the available daughter, the amount of the daughter nuclide rapidly increases until the daughter activity slightly exceeds that of the parent at about four to five half‐lives. Thereafter the daughter activity declines at the same rate as the parent.

The preceding example of transient equilibrium is based on a decay scheme in which 100% of the parent nuclide decays to the daughter nuclide. However, in the commonly used ⁹⁹Mo–^99mTc generator, only 86% of the parent molybendum‐99 decays to the daughter technetium‐99m; the remainder decays directly to Technetium‐99 (Figure 3.3). As a result, the activity of ^99mTc is always less than the activity of ⁹⁹Mo (see Figure 3.3).