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The exposure rate constant for a silver wire 125 I seed
Author(s) -
Hashemi Alex M.,
Mills Michael D.,
Hogstrom Kenneth R.,
Almond Peter R.
Publication year - 1988
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.596275
Subject(s) - spectrometer , fluence , scintillation , optics , analytical chemistry (journal) , photon , semiconductor detector , anisotropy , materials science , scintillation counter , detector , physics , chemistry , laser , chromatography
The physical characteristics of the newer silver wire 125 I seed were measured with a scintillation spectrometer to compare them with those of the original gold sphere 125 I seed. The exposure rate constant was determined by converting the count rate from a scintillation spectrometer into the photon‐fluence rate incident upon the detector, then calculating the exposure rate from the photon‐fluence rate. The exposure rate constant measured perpendicular to the long axis of the seed is 1.361 R cm 2 /mCi h (1.192 cGy cm 2 /mCi h)±3.7%, a value that compares favorably with the theoretical exposure rate constant of 1.354 R cm 2 /mCi h (1.186 cGy cm 2 /mCi h) calculated from the 125 I emissions data. A value of 1.309 R cm 2 /mCi h was previously reported for the gold sphere 125 I seed using the same technique. The angular intensity distribution and anisotropy factor of the silver wire 125 I seed are shown to be very similar to those of the gold sphere 125 I seed, leading to the conclusion that the clinical application of the two types of 125 I seeds need not change.