Medich David C, Munro John J
Radiation Laboratory, University of Massachusetts Lowell, 1 University Avenue, Lowell, Massachusetts 01854, USA.
Med Phys. 2003 Sep;30(9):2503-8. doi: 10.1118/1.1601914.
The SeedLink brachytherapy system is comprised from an assembly of I-Plant 3500 interstitial brachytherapy seeds and bioresorbable spacers joined together by a 6-mm-long titanium sleeve centered over each seed. This device is designed to maintain specified spacing between seeds during treatment thereby decreasing implant preparation time and reducing radionuclide migration within the prostate and periprostatic region. Reliable clinical treatment and planning applications necessitate accurate dosimetric data for source evaluation, therefore the authors report the results of a Monte Carlo study designed to calculate the AAPM Task Group Report No. 43 dosimetric parameters for the SeedLink brachytherapy source and compare these values against previously published Monte Carlo study results of the I-Plant 3500 brachytherapy seed. For this investigation, a total of 1 x 10(9) source photon histories were processed for each set of in-water and in-air calculations using the MCNP4C2 Monte Carlo radiation transport code (RSICC). Statistically, the radial dose function, g(r), and the dose-rate constant, lambda, were identical to the values calculated previously for the Model 3500 with the dose-rate constant evaluated to be lambda = 1.000+/-0.026 cGyh(-1) U(-1). The titanium sleeve used in SeedLink to bind together Model 3500 seeds and spacers resulted in slightly greater dosimetric anisotropy as exhibited in the anisotropy function, F(r, theta), the anisotropy factor, phi(an) (r), and the anisotropy constant, phi(an), which was calculated to be phi(an) = 0.91 +/- 0.01, or roughly 2% lower than the value calculated previously for the Model 3500. These results indicate that the radiological characteristics of the SeedLink dosimetry system are comparable to those obtained for previously characterized single seeds such as the Implant Sciences Model 3500 I-Plant seed.
SeedLink近距离放射治疗系统由I-Plant 3500组织间近距离放射治疗籽源和生物可吸收间隔物组件组成，这些组件通过一个位于每个籽源中心的6毫米长钛套管连接在一起。该装置旨在在治疗期间保持籽源之间的特定间距，从而减少植入准备时间，并减少放射性核素在前列腺和前列腺周围区域内的迁移。可靠的临床治疗和计划应用需要准确的剂量学数据用于源评估，因此作者报告了一项蒙特卡罗研究的结果，该研究旨在计算SeedLink近距离放射治疗源的美国医学物理学家协会任务组第43号报告剂量学参数，并将这些值与先前发表的I-Plant 3500近距离放射治疗籽源的蒙特卡罗研究结果进行比较。对于本次研究，使用MCNP4C2蒙特卡罗辐射传输代码（RSICC）对每组水中和空气中的计算处理了总共1×10⁹个源光子历史。从统计学上讲，径向剂量函数g(r)和剂量率常数λ与先前为3500型计算的值相同，剂量率常数评估为λ = 1.000±0.026 cGy h⁻¹ U⁻¹。SeedLink中用于将3500型籽源和间隔物结合在一起的钛套管导致剂量学各向异性略有增加，如在各向异性函数F(r,θ)、各向异性因子φ(an)(r)和各向异性常数φ(an)中所示，计算得出φ(an) = 0.91±0.01，比先前为3500型计算的值低约2%。这些结果表明，SeedLink剂量学系统的放射学特征与先前表征的单个籽源（如植入科学公司3500型I-Plant籽源）所获得的特征相当。
