Chandola Rakesh M, Tiwari Samit, Painuly Nirmal K, Choudhary Vivek, Azad Surendra K, Beck Manjula
Department of Radiotherapy, Pt JNM Medical College and Dr BRAM Hospital, Raipur, Chhattisgarh, India.
J Cancer Res Ther. 2011 Jan-Mar;7(1):29-34. doi: 10.4103/0973-1482.80453.
The conventional treatment planning system (TPS) gives analytical calculations with approximately ± 15-20% dose uncertainty, which may lead to over exposure of critical organs or under dose of target as well as the presence of inhomogeneities, and the position of source affects the exact dose calculation like in breast and intraluminal brachytherapy.
To obtain dose distribution parameters of GammaMed Plus high dose rate (HDR) 192 Ir source using Monte Carlo (MC) EGSnrc and GEANT4 codes as well as to find the effect on dose distribution due to source position, and due to presence of air and cortical bone by using MC GEANT4 code, and to find the similarity of both studies with any past study of any HDR brachytherapy source for either as input to TPS or verification of TPS calculations.
It is done using different software of the computer, e.g., excel, MS word, etc.
The source, source position for different studies, water phantom, water characteristics, points of measurements, air and cortical bone inhomogeneities, and position of inhomogeneities were simulated.
For uncertainties calculation, mean and probability are used.
The calculated dose rate constant, radial dose function, and 2D anisotropy function of the source show similarity with published data. Calculated dose distribution differences due to presence of air and cortical bone, and position of source in water phantom also show similarity with published data.
These results can either be implemented in TPS or can be used for verification of TPS calculations.
传统治疗计划系统（TPS）进行的分析计算存在约±15 - 20%的剂量不确定性，这可能导致关键器官过度照射或靶区剂量不足，以及存在不均匀性，并且源的位置会影响精确的剂量计算，如在乳腺和腔内近距离放射治疗中。
使用蒙特卡罗（MC）EGSnrc和GEANT4代码获取伽马Med Plus高剂量率（HDR）192铱源的剂量分布参数，通过使用MC GEANT4代码找出源位置、空气和皮质骨的存在对剂量分布的影响，并找出这两项研究与以往任何HDR近距离放射治疗源研究的相似性，以便作为TPS的输入或验证TPS计算。
使用计算机的不同软件完成，如Excel、MS Word等。
对源、不同研究的源位置、水体模、水的特性、测量点、空气和皮质骨不均匀性以及不均匀性的位置进行了模拟。
用于不确定性计算的是均值和概率。
计算得到的源的剂量率常数、径向剂量函数和二维各向异性函数与已发表数据相似。由于空气和皮质骨的存在以及源在水体模中的位置导致的计算剂量分布差异也与已发表数据相似。
这些结果既可以应用于TPS，也可以用于验证TPS计算。
