Dosimetric parameters of three new solid core I‐125 brachytherapy sources

Abstract

Monte Carlo calculations and TLD measurements have been performed for the purpose of characterizing dosimetric properties of new commercially available brachytherapy sources. All sources tested consisted of a solid core, upon which a thin layer of normalI125 has been adsorbed, encased within a titanium housing. The PharmaSeed BT‐125 source manufactured by Syncor is available in silver or palladium core configurations while the ADVANTAGE source from IsoAid has silver only. Dosimetric properties, including the dose rate constant, radial dose function, and anisotropy characteristics were determined according to the TG‐43 protocol. Additionally, the geometry function was calculated exactly using Monte Carlo and compared with both the point and line source approximations. The 1999 NIST standard was followed in determining air kerma strength. Dose rate constants were calculated to be 0.955±0.005,0.967±0.005, and 0.962±0.005 cGynormalh−1normalU−1 for the PharmaSeed BT‐125‐1, BT‐125‐2, and ADVANTAGE sources, respectively. TLD measurements were in excellent agreement with Monte Carlo calculations. Radial dose function, g(r), calculated to a distance of 10 cm, and anisotropy function F(r, θ), calculated for radii from 0.5 to 7.0 cm, were similar among all source configurations. Anisotropy constants, trueϕ¯an, were calculated to be 0.941, 0.944, and 0.960 for the three sources, respectively. All dosimetric parameters were found to be in close agreement with previously published data for similar source configurations. The MCNP Monte Carlo code appears to be ideally suited to low energy dosimetry applications.PACS number(s): 87.53.–j

Episcleral eye plaque dosimetry comparison for the Eye Physics EP917 using Plaque Simulator and Monte Carlo simulation

“…However, Λ from this study agrees with MC and TLD results reported by Solberg et al (25) within 0.4 and 0.2% respectively and to within 0.1% of recent work by Taylor and Rogers, (17) using point voxel scoring cells. When compared with Λ, calculated using WAFAC voxel scoring cells, Λ from this study is 3.6% higher (17) .…”

“…When compared with more recent work by Taylor and Rogers (17) and Aryal et al, (26) the agreement is much better ranging from $-0.1\%$ to 1.9% and $-0.2\%$ to 4.8%, respectively. The difference between the consensus gL(r) values and recent work, including this study, is primarily due to the different cross‐section libraries and photon energy spectra used, as described by Aryal et al (26) The outdated photoelectric cross sections used by Solberg et al (25) were the XCOM tabulation of Berger and Hubbell (30) and the ${\hspace{0.17em}}^{125}\mathrm{I}$ decay spectrum was taken from that of Attix (31) . This study used the MCNP default 04p cross‐section library, based upon ENDF/B‐VI Release 8 Photoatomic Data, (32) and the NNDC decay spectrum (18) …”

“…The scoring cells used in this study for dose to water at 1 cm and air kerma strength in vacuo at 5 cm were 0.02 cm high, 0.02 cm deep rings, this is smaller than the point voxel scoring cells used by Taylor and Rogers ($0.1\times 0.1\times 0.05\hspace{0.17em}\text{cm}$ for air‐kerma strength in vacuo and $0.01\times 0.01\times 0.01\hspace{0.17em}\text{cm}$ for dose to water). Solberg et al (25) calculated Λ based upon air‐kerma strength calculated in a small voxel 50 cm from the source 25. As expected, Λ from this study is comparable to the point voxel‐based Λ.…”

“…The model IAI‐125 seed design parameters used in this study are the same as those used by Taylor and Rogers (17) and Meigooni et al (16) with a maximum capsule end weld thickness of 0.1 mm and a $1\hspace{0.17em}\mu \mathrm{m}$ thick AgI source coating. The end weld thickness and source AgI coating thickness used by Solberg et al (25) were 0.24 mm and $0.5\hspace{0.17em}\mu \mathrm{m}$, respectively. When compared to recent work by Aryal et al, (26) there is good agreement at all radial distances for $\theta \ge {30}^{\circ }$, but for $\theta <{30}^{\circ }$, the difference increases reaching a maximum of $-31.5\%$ at a radial distance of$0.5\hspace{0.17em}\text{cm at}\hspace{0.17em}\theta =0^{\circ }$.…”

Dosimetric characterization of GMS BT‐125‐1 125I radioactive seed with Monte Carlo simulations and experimental measurement

“…The uncertainty of the experimental method became larger when the measured distance from the seed was small owing to the high gradient dose distribution near the radioactive seed. The Monte Carlo results of g ( r ) for the GMS BT‐125‐1 125 I seed were found in agreement (within 3.3%) with corresponding results for the PharmaSeed BT‐125‐2 125 I seed 29. However, it is different from PharmaSeed BT‐125‐1 125 I seed and Model 6711 125 I seed due to the different structures and materials of the seeds used in the Monte Carlo simulation.…”