How does biological half-life differ from physical half-life?

Biological half-life and physical half-life are two distinct concepts in the field of radiopharmacy and pharmacokinetics. The biological half-life specifically pertains to the time it takes for the body to eliminate half of a substance, such as a drug or radiopharmaceutical, through metabolic processes and excretion. This elimination process is influenced by the organism's biology, including factors such as organ function, age, and overall health.

In contrast, the physical half-life refers to the time required for half of the radioactive substance to decay in a physical sense, which is solely determined by the properties of the radioactive material itself, independent of any biological factors.

Understanding that biological half-life focuses on how the body processes and removes a substance helps clarify why option B is the correct choice. The biological half-life is crucial for determining dosages and administration frequency in therapeutic settings, particularly for radiopharmaceuticals, where the timing of drug delivery can significantly influence therapeutic outcomes and safety.