Dosimetry parameters of BARC OcuProsta I-125 seed source

A new model of 125I seed source, named OcuProsta seed, was designed and fabricated by Radiopharmaceuticals Division of Bhabha Atomic Research Centre for ophthalmic and interstitial applications. AAPM TG 43 recommended dosimetry parameters for this seed source were determined experimentally using TLD as well as by Monte Carlo (MC) simulation. Measured and MC calculated values of the dose rate constant (DRC) are 0.95 +/- 0.065 cGyh(-1)U(-1) and 0.972 +/- 0.005 cGyh(-1)U(-1), respectively. The mean of measured and calculated DRC (lambda = 0.96 cGyh(-1)U(-1)) was recommended for the clinical dosimetry of OcuProsta seed. Measured and MC calculated radial dose function, g(r), anisotropy function, F(r,theta), anisotropy factor and anisotropy constants are also found to be in good agreement to each other. Dosimetry parameters of OcuProsta seed were compared with the published values of similar in-design 125I seed sources. The DRC of BARC OcuProsta seed is very close to Amersham 6711 seed and is also comparable to the DRC of Best model 2301, Syncor PharmaSeed and Isotron selectSeed within the uncertainty of measurement/calculation. The g(r) of OcuProsta seed shows a difference of up to 10% in comparison to the g(r) values of the similar in-design seed sources. The values of anisotropy function of OcuProsta are 7-13% different from the anisotropy function of Amersham 6711 and Syncor PharmaSeed. The anisotropy constant of OcuProsta is close to Amersham 6711 seed while it is about 9% smaller than the anisotropy constant of Best model 2301 and Synchor PharmaSeed.