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Treasure of the Past IX: Exposure Standardization of Iodine-125 Seeds Used for Brachytherapy

View Article: PubMed Central - PubMed

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%.

No MeSH data available.


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Cross section of gold-marker and silver-wire type iodine-125 seeds.
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f1-j65lof: Cross section of gold-marker and silver-wire type iodine-125 seeds.

Mentions: Three types of iodine-125 seeds were supplied for measurement. One type incorporates a gold marker which separates two resin spheres on which the radionuclide is adsorbed. The dimensions of the seed and of the spheres are shown in figure 1. The spheres are free to move in the seed as much as 1.5 mm with the result that the distribution of radiation near the end welds can change considerably.


Treasure of the Past IX: Exposure Standardization of Iodine-125 Seeds Used for Brachytherapy
Cross section of gold-marker and silver-wire type iodine-125 seeds.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4862818&req=5

f1-j65lof: Cross section of gold-marker and silver-wire type iodine-125 seeds.
Mentions: Three types of iodine-125 seeds were supplied for measurement. One type incorporates a gold marker which separates two resin spheres on which the radionuclide is adsorbed. The dimensions of the seed and of the spheres are shown in figure 1. The spheres are free to move in the seed as much as 1.5 mm with the result that the distribution of radiation near the end welds can change considerably.

View Article: PubMed Central - PubMed

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%.

No MeSH data available.


Related in: MedlinePlus