Accuracy in clinical electron beam dose planning using pencilbeam algorithms

The accuracy of two different pencil beam models for electron beam dose planning is shown by comparisons with measured dose distributions. The investigation is restricted to two-dimensional geometries. In one model the multiple scattering of the electrons is considered by the small angle Gaussian approximation of Fermi and Eyges. In the other, the generalized Gaussian model, the large angle single scattering events are also considered. The parallel slab approximation is used in both models. The comparisons have been made for two different anatomical phantoms. One phantom was constructed to simulate a transversal cross-section through the chest wall and lung in radiotherapy of breast cancer. The other phantom was made to simulate the head at the level of the nose. The measurements in these phantoms were made with thermoluminescence dosimetry. LiF rods. The accuracy of the oblique incidence case was investigated in a homogneous water phantom. The results show that for oblique incidence and geometries where the semi-infinite slab approximation is reasonably good, the generalized Gaussian model is more accurate. Within and behind low density civities, in the phantom, the Gaussian model often gives a better agreement to experimental data. This is shown to be due to mutually balancing erros from the semi-infinite slab approximation and the Gaussian approximation.     

倍他乐克治疗55例高血压病的疗效观察

目的探讨酒石酸美托洛尔（倍他乐克）治疗高血压患者的效果。方法将高血压患者110例随机分为治疗组和对照组,治疗组给予口服倍他乐克片治疗,对照组给予口服波依定治疗。结果治疗组治疗高血压的疗效明显优于对照组（P〈0．05）,治疗组临床症状改善优于对照组（P〈0．05）,两组不良反应发生情况差异无显著性意义。结论应用倍他乐克进行降压治疗疗效好,对患者症状改善明显,值得临床推广。     

利用深度学习提升肺癌调强质子治疗笔形束剂量计算准确性

目的 质子笔形束(PB)剂量计算可实现快速剂量计算,但在处理组织不均匀度大的区域时误差较大,而蒙特卡洛(MC)剂量计算是最精准的方法但非常耗时;深度学习技术可以通过学习PB和MC剂量分布之间的差异,将剂量计算准确度从PB水平提高到MC水平。方法 基于HD U-Net神经网络,开发了一个可将肺癌调强质子治疗患者的PB剂量转换为MC剂量的模型。该模型以患者PB剂量和CT图像作为输入来预测MC剂量。27例非小细胞肺癌患者的射束剂量和CT图像在被旋转到同一角度并作归一化后被用于模型训练与测试。模型的准确性通过比较预测剂量与MC剂量的均方误差和1mm/1%标准的γ通过率等评估。结果 模型预测剂量与MC剂量相当吻合,测试病例1mm/1%标准的平均γ通过率(剂量值超过最大MC剂量10%的体素)达到(92.8±3.4)%。模型预测所有测试病例的MC剂量所需平均时间为(6.72±2.26) s。结论 成功开发了可以快速准确地从PB剂量和CT图像预测MC剂量的深度学习模型,并可用于提高肺癌调强质子治疗PB剂量计算精度。     

Range resolution and reproducibility of a dedicated phantom for proton PBS daily quality assurance

Purpose

Wedge phantoms coupled with a CCD camera are suggested as a simple means to improve the efficiency of quality assurance for pencil beam scanning (PBS) proton therapy, in particular to verify energy/range consistency on a daily basis. The method is based on the analysis of an integral image created by a pencil beam (PB) pattern delivered through a wedge. We have investigated the reproducibility of this method and its dependence on setup and positional beam errors for a commercially available phantom (Sphinx^®, IBA Dosimetry) and CCD camera (Lynx^®, IBA Dosimetry) system.

质子碳离子笔形束扫描技术治疗Ⅰ期非小细胞肺癌的初步结果

目的 在国内首次报道采用质子碳离子射线治疗Ⅰ期非小细胞肺癌（NSCLC）的近期疗效和不良反应。方法 2014年8月至2015年12月,共收治10例病理证实的Ⅰ期NSCLC患者。使用IONTRIS设备笔形束扫描技术,通过可以调节能量的点扫描、实现对靶区更加适形的目的,2~4个射野给予质子和碳离子放疗。根据肿瘤部位给予不同分割方式照射,4例周围型接受 50~70 GyE/10次放疗,3例中间型60~64 GyE/15~16次,3例中央型66~72 GyE/22~24次。结果 中位随访时间为18.1（11.9~28.1）个月,最后一次随访时患者均存活。10例患者局部控制率100%,其中6例患者完全缓解,3例部分缓解,1例疾病稳定;2例放疗后随访中出现远处转移。放疗开始3个月内,无3级及以上放疗相关急性不良反应发生。随访期内未观察到2级及以上的晚期不良反应。放疗后1和3~5个月肺功能（最大通气量、第1秒通气量及CO弥散量）与放疗前相比略有上升,差异无统计学意义（P>0.05）。结论 对Ⅰ期非小细胞肺癌患者,质子碳离子笔形束扫描技术治疗短期随访结果安全、有效。     

Experimental validation of a 4D dose calculation routine for pencil beam scanning proton therapy

Respiratory induced organ motion poses a major challenge for high-precision radiotherapy such as pencil beam scanning proton therapy (PBS). In order to employ PBS for target regions affected by respiratory motion, the implementation of dedicated motion mitigation techniques should be considered and residual uncertainties need to be assessed. For the latter purpose, a routine simulating the delivery of a scanned proton beam to a moving target was developed and implemented in the commercial treatment planning system RayStation. The time structure of the beam delivery was extracted from electronic irradiation protocols of the delivery system. Alternatively to electronic irradiation protocols, an empirical time model of the beam delivery was created to allow for prospective estimations of interplay effects between target motion and pencil beam scanning. The experimental validation of the routine was performed using a two-dimensional ionization chamber array and a dynamic phantom. A 4D CT data set, including 10 respiratory phases, provided the spatial temporal information about the phantom motion. The dosimetric comparison of the measured and the calculated dose distribution yielded gamma pass rates above 96% using a 3% dose difference and a 3 mm distance to agreement criterion. Thus, a tool for the evaluation of interplay effects is available in a clinical software environment and patient-specific quality assurance can be extended to dynamic treatment scenarios.     

呼吸运动对质子调强放疗的影响及研究进展

相比于光子调强放疗,质子调强放疗有明显的剂量优势。质子的布拉格峰比较陡峭,容易受射程偏差、摆位偏差、器官形变等因素的影响。呼吸运动造成的计划剂量和实际照射剂量之间的差异阻碍了质子调强放疗在胸部肿瘤中的广泛应用。本文综述了呼吸运动对质子调强放疗的影响及减小这种影响的研究进展,为临床和研究提供参考。     

蒙特卡罗系统验证PBC和CCC算法精确度的临床研究

目的 运用蒙特卡罗系统验证PBC、CCC算法在肺癌放疗计划时的精确度。方法 使用Oncentra Masterplan TPS对本院2012—2013年间收治的24例肺癌患者分别进行PBC、CCC计算。设计2个IMRT计划和2个3DCRT计划,将计划的DICOM-RT文件导入蒙特卡罗系统进行剂量重建。配对t检验差异。结果 4个计划中无论是IMRT还是3DCRT计划CCC、PBC计算的靶区平均剂量与蒙特卡罗计算值的差别均随靶体积减小而增大(P=0.00、0.00、0.00、0.00),且IMRT计划比3DCRT的大(P=0.00、0.01)。IMRT计划中CCC计算的D_98%、D_95%、D_90%、D_50%、D_2%与蒙特卡罗计算值差别逐渐减小(P=0.00、0.00、0.00、0.00、0.00),上述现象同样出现在PBC算法中,但CCC计算的3DCRT计划中的不显著(P=0.18、0.08、0.62、0.08,0.97)。IMRT和3DCRT计划中,CCC算法高估了整个患侧肺剂量;PBC算法高估了患侧肺V₂₀(P=0.00、0.00),低估了患侧肺V₅(P=0.00、0.00),但3DCRT计划中V₁₀值相近(P=0.47)。结论 建议在肺癌放疗计划计算时使用精确度更高的算法而不使用PBC算法。蒙特卡罗比其他算法精度更高。