FIG. 2.

An example of exponential decay of ¹³¹I within a single patient. ¹³¹I-mIBG, as well as other radionuclides, are eliminated by two major processes within the human body: physical decay and biological decay (elimination). The amount of activity in the patient is derived from comparing the amount of activity injected to the peak dose rate given off by the patient. Due to patient movement, distance from the radiation detector changes, resulting in dose-rate fluctuations. The data is drawn on a time plot and used to estimate total dose. The black line represents the calculated amount of activity remaining in the patient at a given time based on the kinetic model. Diamond-shaped symbols represent the calculated activity in the patient based on dose rate, which is measured by the meter mounted on the ceiling above the patient.