title: Treasure of the Past IX: Exposure Standardization of Iodine-125 Seeds Used for Brachytherapy.
abstract: A method for calibrating iodine-125 seeds in terms of exposure has been established. The standard free-air ionization chamber, used for measuring soft x rays, was chosen for the measurements. Arrays of four to six seeds were used to enhance the ionization-current-to-background-current ratio. Seeds from an array were measured individually in a re-entrant chamber. The quotient of the exposure rate for the array by the sum of the ionization currents in the re-entrant chamber is the calibration factor for the re-entrant chamber. Calibration factors were established for three types of iodine-125 seeds. The overall uncertainty for the seed exposure calibrations is less than 6%.
authors: National Bureau of Standards, Gaithersburg, MD 20899.
authors: T P
authors: TP
authors: Loftus
keywords: calibration; exposure rate; free-air chamber; iodine-125 seed; re-entrant chamber; standards