SBRT of lung tumours: Monte Carlo simulation with PENELOPE of dose distributions including respiratory motion and comparison with different treatment planning systems
SBRT of lung tumours: Monte Carlo simulation with PENELOPE of dose distributions including respiratory motion and comparison with different treatment planning systems
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DOI：
10.1088/0031-9155/52/14/016
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发表时间：
2007-07-21
影响因子：
3.5
通讯作者：
Lax, Ingmar
中科院分区：
文献类型：
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作者：
Panettieri, Vanessa;Wennberg, Berit;Lax, Ingmar
本工作的目的是模拟与蒙特卡罗（MC）代码PENTAGE PE肺肿瘤的剂量分布，包括呼吸运动的立体定向体部放射治疗（SBRT）。两个模型模拟一个五边形横截面，胸壁（单位密度），肺（密度0.3 g cm（-3））和两个球形肿瘤（单位密度）的直径分别为2 cm和5 cm。计算了Varian加速器4种不同SBRT野大小（6 MV）的相空间文件（PSF），并将其用作射束源，获得了不同感兴趣体积的剂量分布和剂量-体积直方图（DVH）。模拟了5个射束照射在体模上的剂量分布。模拟进行了静态的情况下，包括呼吸运动的影响。为了再现呼吸运动的效果，进行了不同的模拟，保持射束固定，并在颅侧、尾侧和左右方向的选定位置移动体模几何形状。最后将两种运动模式与不同的位置相结合得到最终的结果。将MC结果与使用三种商业治疗计划系统（TPS）获得的结果进行比较，其中两种基于笔形射束（PB）算法，TMS-HELAX（Nucletron，Sweden）和Eclipse（Varian Medical System，Palo Alto，CA），一种基于塌陷锥算法（CC），Pinnacle（3）（Philips）。在Eclipse系统中用分析各向异性算法（AAA）进行了计算。根据临床实践，在没有模拟呼吸运动的情况下使用TPS进行所有计算。为了比较所有TPS和MC，进行了绝对剂量校准（单位：戈伊/MU）。分析表明，与MC相比，PB和CC算法计算两种肿瘤尺寸的总肿瘤体积（GTV）中心部分的剂量（戈伊/MU），准确度为2 - 3%。在GTV的外围，TPS高估剂量高达10%，而在接近GTV的肺组织中，PB算法高估剂量，CC低估剂量。当临床相关的呼吸运动包括在MC模拟中时，TPS的静态计算仍然给出了GTV中剂量的相对准确的估计。另一方面，与静态情况相比，GTV外围的剂量被高估。
The purpose of this work was to simulate with the Monte Carlo (MC) code PENELOPE the dose distribution in lung tumours including breathing motion in stereotactic body radiation therapy (SBRT). Two phantoms were modelled to simulate a pentagonal cross section with chestwall (unit density), lung (density 0.3 g cm(-3)) and two spherical tumours (unit density) of diameters respectively of 2 cm and 5 cm. The phase-space files (PSF) of four different SBRT field sizes of 6 MV from a Varian accelerator were calculated and used as beam sources to obtain both dose profiles and dose - volume histograms (DVHs) in different volumes of interest. Dose distributions were simulated for five beams impinging on the phantom. The simulations were conducted both for the static case and including the influence of respiratory motion. To reproduce the effect of breathing motion different simulations were performed keeping the beam fixed and displacing the phantom geometry in chosen positions in the cranial and caudal and left - right directions. The final resultwas obtained by combining the different position with two motion patterns. The MC results were compared with those obtained with three commercial treatment planning systems (TPSs), two based on the pencil beam (PB) algorithm, the TMS-HELAX (Nucletron, Sweden) and Eclipse (Varian Medical System, Palo Alto, CA), and one based on the collapsed cone algorithm (CC), Pinnacle(3) (Philips). Some calculations were also carried out with the analytical anisotropic algorithm (AAA) in the Eclipse system. All calculations with the TPSs were performed without simulated breathing motion, according to clinical practice. In order to compare all the TPSs and MC an absolute dose calibration in Gy/MU was performed. The analysis shows that the dose (Gy/MU) in the central part of the gross tumour volume (GTV) is calculated for both tumour sizes with an accuracy of 2 - 3% with PB and CC algorithms, compared to MC. At the periphery of the GTV the TPSs overestimate the dose up to 10%, while in the lung tissue close to the GTV PB algorithms overestimate the dose and the CC underestimates it. When clinically relevant breathing motions are included in the MC simulations, the static calculations with the TPSs still give a relatively accurate estimate of the dose in the GTV. On the other hand, the dose at the periphery of the GTV is overestimated, compared to the static case.