Solberg Timothy D, DeMarco John J, Hugo Geoffrey, Wallace Robert E
Department of Radiation Oncology, UCLA School of Medicine, Los Angeles, California 98095-6951, USA.
J Appl Clin Med Phys. 2002 Spring;3(2):119-34. doi: 10.1120/jacmp.v3i2.2576.
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 125I 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 cGy h(-1) x U(-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,theta), calculated for radii from 0.5 to 7.0 cm, were similar among all source configurations. Anisotropy constants, phi(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.
为了表征新型市售近距离放射治疗源的剂量学特性，已进行了蒙特卡罗计算和热释光剂量计（TLD）测量。所有测试的源均由实心芯组成，在其上吸附了一层薄薄的125I，并封装在钛外壳内。Syncor制造的PharmaSeed BT - 125源有银芯或钯芯配置，而IsoAid的ADVANTAGE源只有银芯。根据TG - 43协议确定了剂量学特性，包括剂量率常数、径向剂量函数和各向异性特征。此外，使用蒙特卡罗精确计算了几何函数，并与点源和线源近似值进行了比较。在确定空气比释动能强度时遵循了1999年美国国家标准与技术研究院（NIST）标准。PharmaSeed BT - 125 - 1、BT - 125 - 2和ADVANTAGE源的剂量率常数分别计算为0.955±0.005、0.967±0.005和0.962±0.005 cGy h(-1) x U(-1)。TLD测量结果与蒙特卡罗计算结果非常吻合。所有源配置的径向剂量函数g(r)计算到10 cm距离，以及各向异性函数F(r,θ)计算半径从0.5到7.0 cm，结果相似。三种源的各向异性常数φ(an)分别计算为0.941、0.944和0.960。发现所有剂量学参数与先前发表的类似源配置数据非常吻合。MCNP蒙特卡罗代码似乎非常适合低能剂量学应用。
