五种光子放疗设备在胰腺癌立体定向放疗中剂量学比较

目的 比较射波刀、螺旋断层治疗(Tomo)、Edge加速器、Trilogy加速器和伽马刀5种设备在胰腺癌立体定向放疗中剂量学上的优劣。方法 回顾分析10例射波刀治疗的胰腺癌患者临床资料,分别由5家单位5种设备按照统一计划设计要求进行计划设计。完成后的计划统一导入MIM软件平台提取评估参数。主要参数包括计划靶区的Dmin、Dmean、Dmax、适形指数(CI和nCI)、均匀指数(HI)、梯度指数(GI)、覆盖率和胃肠Dmax及体积剂量等。结果 Trilogy获得最优CI和nCI (P<0.001);伽马刀HI最差(P<0.001);GI射波刀最优,伽马刀次之,Tomo和Edge相对最弱(P<0.001);Edge加速器和Trilogy加速器获得最大PTV Dmin值,射波刀和Tomo组获得较小PTV Dmin值(P<0.001);伽马刀组获得了最大的PTV Dmax、Dmean(P<0.001)。危及器官方面,射波刀组获得最低的空回肠Dmax及D5cm³(P<0.001)、胃Dmax(P=0.003)、十二指肠Dmax(P=0.001)、D5cm³(P<0.001)及D10cm³(P=0.005)、脊髓Dmax及D0.35cm³(P<0.001);伽马刀组空回肠Dmax最大;Edge加速器组十二指肠D5cm³最高(P<0.001);Tomo组脊髓Dmax及D0.35cm³最高(P<0.001)。结论 5种放疗设备均能很好地完成满足临床要求的胰腺癌立体定向放疗计划。射波刀和伽马刀拥有更优的剂量跌落梯度,Trilogy加速器和Edge加速器拥有更优的靶区适形性,射波刀胃肠道剂量保护相对更优。     

两种算法在宫颈癌术后调强放疗中的剂量学比较研究

目的: 比较蒙特卡罗算法与筒串卷积算法在宫颈癌术后调强放射治疗中的剂量学差异。方法: 随机选择25例宫颈癌术后行调强放疗患者,对同一治疗计划分别用两种算法进行剂量计算,通过剂量体积直方图的剂量体积参数比较两者靶区和危及器官的剂量学差异。结果: 靶区D₉₈、D₂、D₅₀、HI蒙特卡罗算法结果低于筒串卷积算法（P﹤0.05）;CI结果高于筒串卷积法（P﹤0.05）。膀胱V₃₀、V₄₀,直肠V₄₀、D₅₀,股骨头、盆骨V₃₀、V₄₀、D₅₀,脊髓D₂、D₅₀蒙特卡罗算法结果低于筒串卷积算法;靶区CI、结肠V₃₀、V₄₀、D₅₀ 蒙特卡罗算法结果高于筒串卷积算法,以上结果差异均具有统计学意义（P﹤0.05）。结论: 宫颈癌术后调强放射治疗,优先选择蒙特卡罗算法进行计划设计,同时应适当充盈膀胱,减少小肠、结肠卷入射野的体积;如果只能选用筒串卷积算法,应适当增大最小子野面积,减少子野数量。     

26例术后复发性胆管细胞癌射波刀SBRT疗效分析

目的 评价射波刀SBRT在复发性胆管细胞癌治疗中的效果及安全性。方法 回顾分析2010-2015年26例术后复发的胆管癌射波刀SBRT的患者,中位术后复发时间10个月,中位肿瘤直径为2.8 cm。中位处方剂量45 Gy,中位分割次数5次。基于增强CT或MRI评估肿瘤进展。采用Kaplan-Meier法计算OS、PFS及LC。使用CTCAE4.0版评估不良反应。结果 中位随访29.3个月,其中位OS和PFS分别为13.5个月和6.5个月,1、2年OS和PFS率分别为52%、21%和28%、15%。4例患者出现肿瘤原位进展。3例患者发生3级不良反应,包括1例胃肠道反应、1例肝功能减退、1例胆道感染;仅1例患者在晚期出现了≥4级消化道出血。结论 射波刀SBRT术后复发性胆管癌可获得较好的疗效且不良反应可耐受。     

射波刀肺部动态追踪精度受心脏搏动影响的不确定性分析

目的 分析心脏搏动对射波刀肺部动态追踪肿瘤位置不确定性的影响。方法 选取 48例肿瘤位置距离心脏位置较近的患者,导出其肺部动态追踪系统采集的治疗过程中的肿瘤运动位置曲线。对导出的肿瘤运动位置曲线进行滤波分析,将<1Hz的呼吸运动波形和>1Hz的心脏搏动波形进行分离。依据患者的滤波结果,按是否存在>1Hz的心脏搏动波形,将患者治疗追踪数据分为两组。依据治疗时追踪系统采集的X线影像数据,比较两组治疗分次之间的追踪误差。结果 对于准确建立心脏搏动模型的患者,身体左右、头脚和腹背方向,相关模型追踪误差分别为(1.45±0.99)、(0.46±0.21)、(0.70±0.54)mm;对于未准确建立心脏搏动模型的患者,身体左右、头脚和腹背方向的追踪误差分别为(1.52±1.17)、(0.63±0.37)、(1.07±0.62)mm。前者射波刀肺部动态追踪系统的追踪误差比后者在头脚、腹背方向分别减少28.34%、34.86%(P<0.05)。结论 准确建立心脏搏动模型,射波刀肺部动态追踪系统的追踪精度将大幅提高。     

计划靶体积概念是否适合肺癌质子调强治疗计划

目的 基于计划靶体积(PTV)和内靶体积(ITV)概念计划差异,论述PTV概念不适合于肺癌质子调强治疗(IMPT)计划,为临床提供参考。方法 基于上海质子治疗示范装置固定束模型和商业化治疗计划系统软件,对6例肺癌患者在平均CT图像上分别制作基于PTV的常规IMPT计划(PTV-IMPT)和基于ITV稳健的IMPT计划(ITV-IMPT)。所有计划均设置3个射束,采用蒙特卡罗剂量算法进行最终剂量计算。评估PTV-IMPT和ITV-IMPT计划的计划质量和稳健性能。结果 ITV-IMPT、PTV-IMPT计划的ITV适形指数分别为0.58、0.43,均匀指数分别为0.96、0.92,双肺V5Gy(RBE)分别为13.1%、13.5%,脊髓Dmax分别为8.9、9.5Gy(RBE),机器跳数分别为338、401MU。在分别轻度扰动和重度扰动场景的7种状态下, ITV-IMPT、PTV-IMPT计划的靶区覆盖稳健性指数λ范围分别为0.003~0.032、0.02~0.28,双肺500 Gy(RBE)剂量体积指标ΔV5Gy范围分别为0.06~0.11、0.07~0.13。结论 与PTV-IMPT比较,ITV-IMPT具有计划质量高、稳健性好的优势,具有重要的临床价值。因此,临床推荐使用ITV概念设计肺癌的质子调强计划。     

射波刀SBRT治疗肝门区肝癌临床疗效观察

目的 评价射波刀在肝门区肿瘤治疗中的疗效及安全性。方法 回顾分析2009—2015年间天津医科大学肿瘤医院收治的接受射波刀SBRT的 36例肝门区肝癌患者的病历资料。36例患者(37个病灶)的肿瘤直径为 15~55 mm (中位数30 mm),其中 20例患者(21个病灶)采用金标呼吸同步追踪技术,16例患者(16个病灶)采用椎体追踪技术。通过增强CT和(或) MRI评价肿瘤进展,Kaplan-Meier法计算LC、OS并Logrank检验和单因素分析。结果 中位随访时间为12.7个月。术后1、2年LC率分别为90%、76%,术后 1年OS、PFS分别为63%、39%,中位OS、PFS时间分别为15.2、10.0个月。3级不良反应为11%。结论 射波刀SBRT是肝门区肝癌的一种安全有效的治疗方式。     

Monaco计划系统控制点统计不确定度选择对鼻咽癌剂量计算影响

目的 探讨Monaco计划系统控制点统计不确定度的选择对鼻咽癌剂量分布的影响,给出蒙特卡罗计算中满足临床的单个控制点统计不确定度。方法 设置9个等机架角度间隔的10cm×10cm方野并随机抽取5例9个野调强放疗(IMRT)和5例容积调强弧形治疗(VMAT)鼻咽癌计划,以各自计划CT作为质量保证模体创建验证计划,计算时格点步长选择3mm,单个控制点的统计不确定度分别选择1%、2%、3%、4%和5%,分析选择不同统计不确定度的计算结果与选择统计不确定度为1%时的差异。结果 对于单一方野和单一调强野,当控制点统计不确定度选取为4%时中心点剂量偏差高达7%;对于9个野IMRT和单弧VMAT不同控制点统计不确定度选取时中心点剂量偏差均≤1.5%,计划靶区体积平均剂量偏差均≤0.3%;对于9个野IMRT当控制点统计不确定度≤3%和单弧VMAT当控制点统计不确定度≤4%时中心冠状平面剂量中偏差<1%的点所占比例均>99%。结论 基于蒙特卡罗计算的Monaco计划系统,控制点统计不确定度在1%~5%变化对于单一射野影响较大;在临床计算中,建议9个野IMRT的控制点统计不确定度选取应≤3%,VMAT的控制点统计不确定度选取应≤4%。     

基于图像变换的CT图像校正算法在宫颈癌放疗剂量准确性评估中的应用

目的 定量评估宫颈癌放疗计划剂量准确性。方法 提出基于图像变换的CT图像校正算法,参考CBCT图像对宫颈癌临床计划CT图像进行校正,获取更能反映实际治疗体位的校正图像;将临床计划移植至校正图像重算剂量生成测试计划,并与临床计划进行剂量学参数比较分析,评估剂量准确性。结果 对比计划靶区覆盖均能满足临床要求(>98%),均匀性指数HI无较大差别(P=0.150);测试计划剂量分布适形性较临床计划差且具有显著性差异(P<0.05)。测试计划各危及器官的Dmax较临床计划高约30 cGy并具有显著性差异(P<0.05),V50较临床计划略高,而Dmean无较大差异。结论 基于图像变换的CT图像校正算法可用于对宫颈癌放疗剂量准确性进行定量评估,为临床解决类似问题提供参考。     

基于图像变换的CT图像校正算法在宫颈癌放疗剂量准确性评估中的应用

目的 定量评估宫颈癌放疗计划剂量准确性。方法 提出基于图像变换的CT图像校正算法,参考CBCT图像对宫颈癌临床计划CT图像进行校正,获取更能反映实际治疗体位的校正图像;将临床计划移植至校正图像重算剂量生成测试计划,并与临床计划进行剂量学参数比较分析,评估剂量准确性。结果 对比计划靶区覆盖均能满足临床要求(>98%),均匀性指数HI无较大差别(P=0.150);测试计划剂量分布适形性较临床计划差且具有显著性差异(P<0.05)。测试计划各危及器官的Dmax较临床计划高约30 cGy并具有显著性差异(P<0.05),V50较临床计划略高,而Dmean无较大差异。结论 基于图像变换的CT图像校正算法可用于对宫颈癌放疗剂量准确性进行定量评估,为临床解决类似问题提供参考。     

鼻咽癌IMRT自动计划与人工计划比较

目的 将鼻咽癌调强放疗的自动计划与人工计划进行对比,探讨自动计划在鼻咽癌放疗中是否有优势。方法 回顾性纳入97例鼻咽癌患者,所有患者均在Eclipse治疗计划系统上完成调强放疗人工计划的制作。使用Pinnacle³治疗计划系统的自动计划软件包重新进行调强放疗自动计划制作。统计对比两种计划方式得到的靶区剂量95%靶区体积所对应的剂量、靶区均匀指数和靶区适形指数,正常器官剂量。结果 人工计划和自动计划PTV覆盖率和均匀性相近(P=0.30)。与人工计划相比,自动计划在正常器官保护方面更为出色,平均剂量降低了270~1870 cGy (P=0.16)。结论 自动计划在保证靶区处方剂量的同时能让正常器官的剂量进一步降低,放疗计划的质量有明显提高。     

Comparison of I-131 radioimmunotherapy tumor dosimetry: unit density sphere model versus patient-specific Monte Carlo calculations

High computational requirements restrict the use of Monte Carlo algorithms for dose estimation in a clinical setting, despite the fact that they are considered more accurate than traditional methods. The goal of this study was to compare mean tumor absorbed dose estimates using the unit density sphere model incorporated in OLINDA with previously reported dose estimates from Monte Carlo simulations using the dose planning method (DPMMC) particle transport algorithm. The dataset (57 tumors, 19 lymphoma patients who underwent SPECT/CT imaging during I-131 radioimmunotherapy) included tumors of varying size, shape, and contrast. OLINDA calculations were first carried out using the baseline tumor volume and residence time from SPECT/CT imaging during 6 days post-tracer and 8 days post-therapy. Next, the OLINDA calculation was split over multiple time periods and summed to get the total dose, which accounted for the changes in tumor size. Results from the second calculation were compared with results determined by coupling SPECT/CT images with DPM Monte Carlo algorithms. Results from the OLINDA calculation accounting for changes in tumor size were almost always higher (median 22%, range -1%-68%) than the results from OLINDA using the baseline tumor volume because of tumor shrinkage. There was good agreement (median -5%, range -13%-2%) between the OLINDA results and the self-dose component from Monte Carlo calculations, indicating that tumor shape effects are a minor source of error when using the sphere model. However, because the sphere model ignores cross-irradiation, the OLINDA calculation significantly underestimated (median 14%, range 2%-31%) the total tumor absorbed dose compared with Monte Carlo. These results show that when the quantity of interest is the mean tumor absorbed dose, the unit density sphere model is a practical alternative to Monte Carlo for some applications. For applications requiring higher accuracy, computer-intensive Monte Carlo calculation is needed.     

Dose distributions in SBRT of lung tumors: Comparison between two different treatment planning algorithms and Monte-Carlo simulation including breathing motions

In stereotactic body radiotherapy (SBRT) of lung tumors, dosimetric problems arise from: 1) the limited accuracy in the dose calculation algorithms in treatment planning systems, and 2) the motions with the respiration of the tumor during treatment.Longitudinal dose distributions have been calculated with Monte Carlo simulation (MC), a pencil beam algorithm (PB) and a collapsed cone algorithm (CC) for two spherical lung tumors (2 cm and 5 cm diameter) in lung tissue, in a phantom situation. Respiratory motions were included by a convolution method, which was validated. In the static situation, the PB significantly overestimates the dose, relative to MC, while the CC gives a relatively accurate estimate. Four different respiratory motion patterns were included in the dose calculation with the MC. A "narrowing" of the longitudinal dose profile of up to 20 mm (at about 90% dose level) is seen relative the static dose profile calculated with the PB.     

加速器日志文件结合胶片验证分析非均匀介质中AAA与AXB算法剂量计算的差异

目的 提取胸部模体执行模拟计划产生的加速器日志文件,解析多叶准直器(MLC)、Gap运动误差数据反馈回治疗计划系统分别进行AAA和AXB算法的剂量重建,结合胶片实测值分析2种算法的计算精度。方法 在胸部模体上模拟勾画纵隔、肺癌2种靶区和危及器官,设计调强放疗计划,分别以AAA和AXB算法进行剂量计算。利用加速器模拟治疗,同时将胶片置于模体中进行测量。通过Varian Argus软件提取日志文件,将MLC、Gap运动偏差信息导入计划系统,再次以2种算法进行剂量重建,比较模拟靶区(分析指标包括D2、D98、Dmax、V处方)和危及器官(分析指标包括双肺V5、V10、V20、Dmean;心脏V30、Dmean;脊髓Dmax)的剂量学差异。将胶片实测剂量与2种算法等中心层面剂量进行比较,采用3 mm/3%标准,以不同大小的矩阵分析高剂量区域(靶区内)和低剂量区域(靶区外上、下、左、右四个方向)的γ通过率。结果 纵隔、肺癌2种模拟靶区在AAA算法与AXB算法中存在剂量学差异,2种靶区不同算法的剂量学最大差异分别为D98(2.47%)、V处方(4.21%)。左肺受量分析最大差异指标分别为Dmean(3.58%)、V10(-2.76%),右肺受量分析最大差异指标分别为V5(-1.96%)、Dmean(0.18%),心脏受量分析最大差异指标分别为Dmean(-1.15%)、Dmean(0.18%),脊髓受量分析指标差异分别为(-3.34%、1.79%)。与胶片实测剂量相比,纵隔、肺癌模拟靶区高剂量区域2种算法不同大小分析矩阵的平均γ通过率分别为94.07%±1.32%(AAA)、93.81%±1.43%(AXB);93.73%±1.31%(AAA)、94.39%±1.32%(AXB)。对于2种靶区的低剂量区域不同方向及不同大小分析矩阵的γ通过率,AXB算法均高于AAA算法。结论 AAA和AXB算法在胸部模拟纵隔和肺部2种靶区剂量计算时存在差异。AXB算法与胶片实测值的平均γ通过率优于AAA算法,在空腔更接近于胶片实测值。     

Advanced kernel methods vs. Monte Carlo-based dose calculation for high energy photon beams

Purpose

The aim of this study was to compare the dose calculation accuracy of advanced kernel-based methods and Monte Carlo algorithms in commercially available treatment planning systems.

Materials and methods

Following dose calculation algorithms and treatment planning (TPS) systems were compared: the collapsed cone (CC) convolution algorithm available in Oncentra Masterplan, the XVMC Monte Carlo algorithm implemented in iPlan and Monaco, and the analytical anisotropic algorithm (AAA) implemented in Eclipse. Measurements were performed with a calibrated ionization chamber and radiochromic EBT type films in a homogenous polystyrene phantom and in heterogeneous lung phantoms. Single beam tests, conformal treatment plans and IMRT plans were validated. Dosimetric evaluations included absolute dose measurements, 1D γ-evaluation of depth-dose curves and profiles using 2 mm and 2% dose difference criteria for single beam tests, and γ-evaluation of axial planes for composite treatment plans applying 3 mm and 3% dose difference criteria.

Results

Absolute dosimetry revealed no large differences between MC and advanced kernel dose calculations. 1D γ-evaluation showed significant discrepancies between depth-dose curves in different phantom geometries. For the CC algorithm γ_mean values were 0.90 ± 0.74 vs. 0.43 ± 0.41 in heterogeneous vs. homogeneous conditions and for the AAA γ_mean values were 1.13 ± 0.91 vs. 0.41 ± 0.28, respectively. In general, 1D γ results obtained with both MC TPS were similar in both phantoms and on average equal to 0.5 both for profiles and depth-dose curves. The results obtained with the CC algorithm in heterogeneous phantoms were slightly better in comparison to the AAA algorithm. The 2D γ-evaluation results of IMRT plans and four-field plans showed smaller mean γ-values for MC dose calculations compared to the advanced kernel algorithms (γ_mean for four-field plan and IMRT obtained with Monaco MC were 0.28 and 0.5, respectively, vs. 0.40 and 0.54 for the AAA).

Conclusion

All TPS investigated in this study demonstrated accurate dose calculation in homogenous and heterogeneous phantoms. Commercially available TPS with Monte Carlo option performed best in heterogeneous phantoms. However, the difference between the CC and the MC algorithms was found to be small.     

Four-dimensional stereotactic radiotherapy for early stage non-small cell lung cancer: a comparative planning study

In this study we sought to assess the potential of the respiratory tumor tracking system of the CyberKnife to administer 3 fractions of 15 Gy in the treatment of early stage non-small cell lung cancer (NSCLC). The CyberKnife plans were compared to those developed for 3-D conformal radiotherapy (3-D CRT) administering 20 fractions of 3 Gy based on a slow CT. Ten patients with stage I NSCLC, who were previously treated with 3-D CRT, were re-planned with the CyberKnife treatment planning system. In the 3-D CRT plan, the planning target volume (PTV) included the gross tumor volume (GTV)(slow) and a 15-mm margin, whereas in the CyberKnife plan the margin was 8 mm. The physical doses from both treatment plans were converted to normalized total doses (NTD) using the linear quadratic model with an alpha/beta(tumor) of 10 Gy and alpha/beta(organs at risk (OAR)) of 3 Gy. The average minimal and mean doses administered to the PTV with the CyberKnife and 3-D CRT were 93 and 115.8 Gy and 61 and 66 Gy, respectively (p<0.0001). The mean V(20) of the CyberKnife and 3-D CRT plans were 8.2% and 6.8%, respectively (p=0.124). Both plans complied with the OAR constraints. In conclusion, 4-dimensional stereotactic radiotherapy can increase the minimal and mean biological dose with 51% and 75%, in comparison with 3-D CRT without significantly increasing the V(20), respectively.     

Clinical impact of dose overestimation by effective path length calculation in stereotactic ablative radiation therapy of lung tumors

PurposeTo determine the clinical impact of calculated dose differences between effective path length (EPL) and Monte Carlo (MC) algorithms in stereotactic ablative radiation therapy (SABR) of lung tumors.Methods and MaterialsWe retrospectively analyzed the treatment plans and clinical outcomes of 77 consecutive patients treated with SABR for 82 lung tumors between 2003 and 2009 at our institution. Sixty treatments were originally planned using EPL, and 22 using MC. All plans were recalculated for the same beam specifications using MC and EPL, respectively. The doses covering 95%, 50%, and 5% (D95, D50, D5, respectively) of the target volumes were compared between EPL and MC (assumed to be the actual delivered dose), both as physical dose and biologically effective dose. Time to local recurrence was correlated with dose by Cox regression analysis. The relationship between tumor control probability (TCP) and biologically effective dose was determined via logistic regression and used to estimate the TCP decrements due to prescribing by EPL calculations.ResultsEPL overestimated dose compared with MC in all tumor dose-volume histogram parameters in all plans. The difference was >10% of the MC D95 to the planning target volume and gross tumor volume in 60 of 82 (73%) and 52 of 82 plans (63%), respectively. Local recurrence occurred in 13 of 82 tumors. Controlling for gross tumor volume, higher physical and biologically effective planning target volume D95 correlated significantly with local control (P = .007 and P = .045, respectively). Compared with MC, prescribing based on EPL translated to a median TCP decrement of 4.3% (range, 1.2%-37%) and a > 5% decrement in 46% of tumors.ConclusionsClinical follow-up for local lung tumor control in a sizable cohort of patients treated with SABR demonstrates that EPL overestimates dose by amounts that substantially decrease TCP in a large proportion. EPL algorithms should be avoided for lung tumor SABR.     

PET/CT下非小细胞肺癌三维适形放疗中肿瘤退缩及对治疗计划参数的影响

目的:观察PET/CT下非小细胞肺癌(NSCLC)三维适形放疗(3D-CRT)中肿瘤退缩对靶区周围危及器官治疗计划参数的影响.方法:分析在PET/CT定位下行根治性3D-CRT的NSCLC患者55例,根据PET/CT融合图像勾画初始肿瘤放疗靶区,给予根治剂量处方量60~66 Gy/30~33 f 制定3D-CRT计划;放疗20次40 Gy时根据肿瘤退缩情况重新CT定位勾画靶区,修改照射野后重新制定放疗计划完成治疗.比较两次定位影像上GTV的体积VGTV(cm3)、PTV的体积VPTV(cm3) 差异;并对初始放疗计划和实际完成的计划靶区周围危及器官的剂量分布进行比较.结果:55例NSCLC患者中,除1例GTV体积增大(1.77cm3,4%)外,其余54例GTV体积均有不同程度缩小(6%~67%),差异有统计学意义(t=6.635,P=0.000).相应的,除1例PTV体积增大(17.13cm3,8%)外,其余54例PTV体积均有不同程度缩小(3%~59%),差异有统计学意义(t=8.045,P=0.000).两种计划参数VGTV、VPTV、VL20、VR20、SCM、MSD、MLD、MRD、MHD、ESM差异有统计学意义(P=0.000、0.000、0.000、0.000、0.001、0.000、0.000、0.000、0.002、0.031).结论:在NSCLC放疗过程中,肿瘤体积发生明显变化,而根据肿瘤退缩情况适时缩野、重新制定放疗计划,可显著降低肺及脊髓的受照射剂量,为提高靶区剂量、优化放疗计划提供了可能.