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Exploring 57 Co as a new isotope for brachytherapy applications
Author(s) -
Enger Shirin A.,
Lundqvist Hans,
D'Amours Michel,
Beaulieu Luc
Publication year - 2012
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 - 10.1118/1.3700171
Subject(s) - brachytherapy , photon , monte carlo method , dosimetry , physics , radionuclide , radiation , isotope , cobalt 60 , gamma ray , nuclear medicine , materials science , radiochemistry , atomic physics , optics , chemistry , nuclear physics , irradiation , radiation therapy , mathematics , medicine , statistics
Purpose: The characteristic s of the radionuclide 57 Co make it interesting for use as a brachytherapy source. 57 Co combines a possible high specific activity with the emission of relatively low‐energy photons and a half‐life (272 days) suitable for regular source exchanges in an afterloader. 57 Co decays by electron capture to the stable 57 Fe with emission of 136 and 122 keV photons.Methods : A hypothetical 57 Co source based on the Flexisource brachytherapy encapsulation with the active core set as a pure cobalt cylinder (length 3.5 mm and diameter 0.6 mm) covered with a cylindrical stainless ‐ steel capsule (length 5 mm and thickness 0.125 mm) was simulated using Geant4 Monte Carlo (MC) code version 9.4. The radial dose function, g(r), and anisotropy function F(r,θ), for the line source approximation were calculated following the TG‐43U1 formalism. The results were compared to well‐known 192 Ir and 125 I radionuclides, representing the higher and the lower energy end of brachytherapy, respectively.Results: The mean energy of photons in water, after passing through the core and the encapsulation material was 123 keV. This hypothetical 57 Co source has an increasing g(r) due to multiple scatter of low‐energy photons, which results in a more uniform dose distribution than 192 Ir.Conclusions: 57 Co has many advantages compared to 192 Ir due to its low‐energy gamma emissions without any electron contamination. 57 Co has an increasing g(r) that results in a more uniform dose distribution than 192 Ir due to its multiple scattered photons. The anisotropy of the 57 Co source is comparable to that of 192 Ir. Furthermore, 57 Co has lower shielding requirements than 192 Ir.