Factors affecting the trapping performance of xenon holdup—filters in nuclear medicine applications

Abstract

Activated charcoal traps are used in nuclear medicine departments to capture exhaled radioactive Xe gas. The trapping performance of charcoal was investigated for different qualities in experimental and clinical situations. Various factors affecting the trapping capacity were identified, such as the charcoal mass, moisture and CO2 concentrations in the sweep gas, gas-flow rate through the trap and temperature. Improper drying of the exhaled air prior to passage through the charcoal bed was a critical factor, leading to a much earlier breakthrough of Xe. Commercial Xe traps intended for ambient temperature operation were useful only for a limited number of patients due to an early breakthrough point. By refrigerating the trap, a larger capacity was achieved. If correctly managed, Xe traps constitute a useful alternative for isolated 133Xe wastes in clinical and experimental applications.