Toossi Mohammad Taghi Bahreyni, Ghorbani Mahdi, Mowlavi Ali Asghar, Taheri Mojtaba, Layegh Mohsen, Makhdoumi Yasha, Meigooni Ali Soleimani
Medical Physics Department, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran.
Physics Department, School of Sciences, Sabzevar Tarbiat Moallem University, Sabzevar, Iran.
Rep Pract Oncol Radiother. 2010 Nov 9;15(6):190-4. doi: 10.1016/j.rpor.2010.10.002. eCollection 2010.
Task group number 40 (TG-40) of the American Association of Physicists in Medicine (AAPM) has recommended calibration of any brachytherapy source before its clinical use. GZP6 afterloading brachytherapy unit is a (60)Co high dose rate (HDR) system recently being used in some of the Iranian radiotherapy centers.
In this study air kerma strength (AKS) of (60)Co source number three of this unit was estimated by Monte Carlo simulation and in air measurements.
Simulation was performed by employing the MCNP-4C Monte Carlo code. Self-absorption of the source core and its capsule were taken into account when calculating air kerma strength. In-air measurements were performed according to the multiple distance method; where a specially designed jig and a 0.6 cm(3) Farmer type ionization chamber were used for the measurements. Monte Carlo simulation, in air measurement and GZP6 treatment planning results were compared for primary air kerma strength (as for November 8th 2005).
Monte Carlo calculated and in air measured air kerma strength were respectively equal to 17240.01 μGym(2) h(-1) and 16991.83 μGym(2) h(-1). The value provided by the GZP6 treatment planning system (TPS) was "15355 μGym(2) h(-1)".
The calculated and measured AKS values are in good agreement. Calculated-TPS and measured-TPS AKS values are also in agreement within the uncertainties related to our calculation, measurements and those certified by the GZP6 manufacturer. Considering the uncertainties, the TPS value for AKS is validated by our calculations and measurements, however, it is incorporated with a large uncertainty.
美国医学物理师协会（AAPM）第40任务组（TG - 40）建议在临床使用前对任何近距离放射治疗源进行校准。GZP6后装近距离放射治疗设备是一种（60）钴高剂量率（HDR）系统，最近在一些伊朗放疗中心投入使用。
本研究通过蒙特卡罗模拟和空气中测量来估算该设备3号（60）钴源的空气比释动能强度（AKS）。
采用MCNP - 4C蒙特卡罗代码进行模拟。计算空气比释动能强度时考虑了源芯及其包壳的自吸收。根据多距离法进行空气中测量；使用专门设计的夹具和一个0.6立方厘米的 Farmer 型电离室进行测量。比较了蒙特卡罗模拟、空气中测量结果以及GZP6治疗计划结果的初始空气比释动能强度（截至2005年11月8日）。
蒙特卡罗计算得到的空气比释动能强度和空气中测量值分别为17240.01微戈瑞·平方米·小时⁻¹和16991.83微戈瑞·平方米·小时⁻¹。GZP6治疗计划系统（TPS）给出的值为“15355微戈瑞·平方米·小时⁻¹”。
计算值和测量值的AKS结果吻合良好。在与我们的计算、测量以及GZP6制造商认证相关的不确定度范围内，计算 - TPS和测量 - TPS的AKS值也相符。考虑到不确定度，我们的计算和测量验证了TPS的AKS值，但该值存在较大的不确定度。
