A patient is to be given an injection of iodine-131 in investigation of her blood volume.Sample A is injected into the patient while sample B is set on one side.
Each sample has an initial activity of 1000 Bq and iodine-131 has half-life of 8 days.
After 24days, total activity of iodine-131 remaining in the patient body is estimated to be 400 Bq. Calculate the biological half-life of iodine-131 in the body of the patient.
Answer:
Let N0 = 1000
N(t) = 400
so exp(-λt) = 400/1000 = 2/5
-λt = ln (2/5) = -0.9163, where t = 24 days
so λ = 0.038179, where λ = ln 2 / half-life
Thus, ln 2 / half-life = 0.038179
half-life = 18 days
