Bakhshabadi Mahdi, Ghorbani Mahdi, Khosroabadi Mohsen, Knaup Courtney, Meigooni Ali S
Faculty of Medicine, North Khorasan University of Medical Sciences, Bojnurd, Iran.
Medical Physics Research Center, Mashhad University of Medical Sciences, Mashhad, Iran.
J Contemp Brachytherapy. 2016 Feb;8(1):74-81. doi: 10.5114/jcb.2016.57708. Epub 2016 Feb 5.
Low energy sources are routinely used in prostate brachytherapy. (125)I is one of the most commonly used sources. Low energy (131)Cs source was introduced recently as a brachytherapy source. The aim of this study is to compare dose distributions of (125)I, (103)Pd, and (131)Cs sources in interstitial brachytherapy of prostate.
ProstaSeed (125)I brachytherapy source was simulated using MCNPX Monte Carlo code. Additionally, two hypothetical sources of (103)Pd and (131)Cs were simulated with the same geometry as the ProstaSeed (125)I source, while having their specific emitted gamma spectra. These brachytherapy sources were simulated with distribution of forty-eight seeds in a phantom including prostate. The prostate was considered as a sphere with radius of 1.5 cm. Absolute and relative dose rates were obtained in various distances from the source along the transverse and longitudinal axes inside and outside the tumor. Furthermore, isodose curves were plotted around the sources.
Analyzing the initial dose profiles for various sources indicated that with the same time duration and air kerma strength, (131)Cs delivers higher dose to tumor. However, relative dose rate inside the tumor is higher and outside the tumor is lower for the (103)Pd source.
The higher initial absolute dose in cGy/(h.U) of (131)Cs brachytherapy source is an advantage of this source over the others. The higher relative dose inside the tumor and lower relative dose outside the tumor for the (103)Pd source are advantages of this later brachytherapy source. Based on the total dose the (125)I source has advantage over the others due to its longer half-life.
低能量源常用于前列腺近距离放射治疗。碘-125（¹²⁵I）是最常用的源之一。低能量铯-131（¹³¹Cs）源最近作为一种近距离放射治疗源被引入。本研究的目的是比较碘-125、钯-103（¹⁰³Pd）和铯-131源在前列腺间质近距离放射治疗中的剂量分布。
使用MCNPX蒙特卡罗代码模拟ProstaSeed碘-125近距离放射治疗源。此外，模拟了两个与ProstaSeed碘-125源具有相同几何形状的假设钯-103和铯-131源，同时具有它们特定的发射伽马光谱。这些近距离放射治疗源在包含前列腺的体模中以48颗籽源的分布进行模拟。前列腺被视为半径为1.5厘米的球体。在肿瘤内外沿横轴和纵轴距源的不同距离处获得绝对和相对剂量率。此外，绘制了源周围的等剂量曲线。
分析各种源的初始剂量分布表明，在相同的持续时间和空气比释动能强度下，铯-131向肿瘤传递的剂量更高。然而，钯-103源在肿瘤内的相对剂量率较高，在肿瘤外较低。
铯-131近距离放射治疗源在cGy/（h.U）方面较高的初始绝对剂量是该源相对于其他源的一个优势。钯-103源在肿瘤内较高的相对剂量和在肿瘤外较低的相对剂量是这种后一种近距离放射治疗源的优势。基于总剂量，碘-125源由于其较长的半衰期而比其他源具有优势。
