C离子束放射治疗肿瘤的进展

重离子(C离子)用于肿瘤放射治疗具有物理学和生物学两方面的优势, 被誉为面向21世纪最佳放疗用射线。 综合论述了世界各国重离子束治癌的发展历史, 在日本国立放射医学综合研究所(NIRS)提供的临床试验数据基础上分析了C离子束治疗的适应症以及对正常组织的放射损伤。 此外, 通过分析潜在患者人数和治疗相关硬件与软件设备, 对C离子束治癌的运用前景做了初步评估。Heavy ions (carbon ions) were considered currently as the best radiation in radiotherapy for their two superiorities in the physical and biological properties. This paper firstly put the focus on the history of development of heavy ion radiotherapy in the world, then a comprehensive analysis of the indications and radiation damages of normal tissues in clinical trails of heavy ion therapy was made based on the published data by NIRS. Moreover, the prospect of using carbon ions in radiotherapy was estimated by analyzing the potential patients’ number, its related instruments and etc.     

弧形调强放射治疗对剂量计算方法的要求

在弧形调强放射治疗的治疗计划设计中, 由于包含有很多照射方向, 调强最优化的射束元矩阵计算需要很大的计算量和存储量, 为提高计算效率常使用简化剂量计算模型计算射束元矩阵, 因此有必要研究简化模型对治疗计划质量产生影响。 对一个模拟例子和一个临床实例, 使用没考虑散射效应的原射线剂量计算模型计算射束元矩阵, 由此进行最优化计算。 在得到最优化强度分布后, 通过比较原射线剂量计算模型和微分卷积剂量计算模型得到的剂量分布, 研究了不同射束数目条件下, 使用简化剂量计算模型计算射束元剂量矩阵对最终的剂量分布质量的影响。 结果表明, 在射线束很多的情况下(对应弧形调强照射）, 用简化的剂量计算模型, 即不考虑散射来计算射束元剂量矩阵, 会导致靶区剂量分布的质量大大低于预期的剂量分布质量, 因此, 弧形调强放射治疗的最优化计算中, 有效考虑散射的影响是必要的。 In the treatment planning for arc intensity modulated radiation therapy, because many irradiation directions are involved, the computing time and storage space needed for calculating beamlet dose matrices in optimization is quite heavy. In order to improve the computation efficiency, the simplified dose calculation is often used for the calculation of the dose matrices. Thus, it is deserved to study how this simplification could influence the quality of the treatment plan. In this paper, a simulation and a clinical case are adopted. Using the primary dose calculation model without taking into account the scattering effect to generate the dose matrices of beamlets, the optimization for beam intensity profile are firstly carried out. Then, based on the obtained intensity profile, the dose distributions are recalculated by using the primary dose calculation model and the differential convolution superposition dose calculation model which is more accurate but more time consuming. By comparing dose distributions obtained by this two models, the influence of using simplified model for dose matrix calculation on beam profile optimization is studied. The results demonstrate that when the beam number is large(corresponding to the arc modulated radiation), using the simplified model for the calculation of dose matrix of beamlets will reduce the quality of dose distribution greatly comparing with the expected dose distribution quality. Thus it is very necessary to correctly take into account the scattering effect in beam profile optimization for the arc intensity modulated radiation therapy.     

用于HIRFL重离子治癌的PET成像实验研究与蒙特卡罗模拟

为了HIRFL重离子治癌的需要,使用两个位置灵敏闪烁体探测器组成了一个简单的PET成像系统.对PET成像进行了实验研究,实验测量得到了物体成像以及γ射线能谱,对于511keV全能峰处的能量分辨率为186%,峰总比为52.4%.采用GEANT3程序对该系统进行了模拟计算,并与实验进行比较,最后对该系统进行了优化设计     

基于临床实例的影响蒙特卡罗程序MCNP计算精度和速度的若干参数模拟研究

蒙特卡罗方法是目前最精确的剂量计算方法,但其较长的模拟时间阻碍了它在临床治疗中的应用。基于蒙特卡罗程序MCNP4c,针对一临床头部病例,探讨了记数方法、电子和光子截断能、光子产生次级电子参数ENUM对计算速度和精度的影响,给出了在保证一定精度前提下的最佳计算模式,以获得计算速度的有效提升。Monte its long simulation and photons, and investigated based Carlo method is regarded as the most accurate method for dose calculation at present, whereas time hinders its clinic application. The effects of the tally method, the cut-off energy of electrons the secondary electron number parameter ENUM on precision and speed of MCNP4c have been on a clinical case to seek for a relatively optimum calculation mode.     

大分割碳离子放射治疗中相对生物学效应与剂量依赖关系的研究

应用碳离子束进行大分割放射治疗从而缩短治疗周期是碳离子束治疗的优势之一。为研究大分割放疗增加单次照射剂量后,碳离子束相对生物学效应（RBE）的变化,应用细胞存活线性平方（LQ）模型推导出RBE与剂量的依赖关系。基于此关系研究了具有不同辐射敏感性的肿瘤细胞和正常组织细胞RBE随剂量的变化。结果表明,在0~20 Gy范围内,不论肿瘤细胞与正常组织细胞具有怎样的辐射敏感性,肿瘤细胞的RBE值始终大于正常组织细胞。此外,基于理论推导和对相关实验数据的分析,证实了RBE随剂量增加而递增现象的存在。这些结果对应用碳离子束进行大分割放射治疗具有重要的指导作用。Short treatment course due to the suitability of hypofractionated regimen for carbon ion beam is one of the advantages of carbon ion radiotherapy. To study the dependence of relative biological effectiveness (RBE) on dose, the relationship between RBE and dose was deduced through the linear-quadratic (LQ) model. Based on the relationship, the change of RBE of tumor cells and normal tissue cells with different radiosensitivities with dose was studied. The results showed that the RBE value of tumor cells was always greater than that of normal tissue cells in the dose range of 0~20 Gy, regardless of the radiosensitivity of tumor and normal tissue cells. In addition, based on theoretical deduction and analysis of the relevant experimental data, the existence of RBE increase with increasing dose was verified. These results are of great significance for conducting hypofractionated radiotherapy with carbon ion beam.     

基于蒙特卡罗方法的6 MV Truebeam剂量计算

使用蒙特卡罗方法快速准确地模拟6 MV Varian Truebeam医用电子直线加速器射野剂量特性,探究厂家提供相位空间源的可用性及模拟方法的准确性。以Varian公司提供的出束窗口位置处相位空间文件作为Beamnrc/EGSnrc输入源,模拟射野形成结构并计算10 cm10 cm射野下的均匀水体模中的剂量分布,将计算结果与相同条件下的实验测量数据进行比较。同一计算机模拟时,传统完整机头模拟方法需4~5 h,文中所述方法模拟时间可缩减至48 min,剂量计算结果与相同条件下所得实际测量数据可较好地吻合,两者的百分深度剂量差异低于3%,且建成区吻合良好;不同深度处80%等剂量线所包含的射野区域内百分离轴剂量比差异均低于3%,且半影区效果好。使用厂家提供相位空间文件作为EGSnrc入射源,能快速模拟治疗头,得到剂量计算结果与实际测量值的差异满足剂量计算精度要求。     

均匀磁场下碳离子笔形束的剂量变化分析及位置修正方法

分析外加均匀磁场对于碳离子笔形束剂量分布的影响,并考虑修正这种影响,为磁共振成像引导碳离子放射治疗的临床应用提供指导。本文利用蒙特卡罗方法模拟计算了不同能量碳离子笔形束在不同强度磁场下的剂量分布情况,发现垂直于碳离子束入射方向的均匀磁场对于碳离子笔形束射程缩短的影响很小,磁场对碳离子束的主要影响是引起束流横向偏转,特别是碳离子束布拉格峰位置的横向侧移。横向侧移程度与碳离子束的能量和磁场强度相关,根据模拟结果,得到了一个计算碳离子束布拉格峰在磁场中相对横向偏转的方程,并提出一种校正外加磁场引起的碳离子束布拉格峰横移的角度修正方法。这些结果可用于指导磁共振图像引导碳离子放射治疗计划系统的研发。     

120~430 MeV/u 碳离子的微剂量学特性研究(英文)

单粒子微剂量谱在放射治疗中是一个极其重要的参数,它可以用来评估辐射场的生物学效应。利用蒙特卡洛程序FLUKA模拟计算了由碳离子产生的混合辐射场能量沉积的微观模式。从已公开发表的文献中选取了实验测量300 MeV/u 碳离子的线能能谱,并与相同物理条件下模拟计算得到的线能能谱相比较,结果吻合得很好。此外,还计算了120~430 MeV/u 的碳离子的剂量平均线能能谱、频率平均线能和剂量平均线能。所得到的频率平均线能值为185~ 28.3 keV/m而剂量平均线能值则为272~ 64.1 keV/m。本文的结果对于制定碳离子放射治疗的治疗计划有着重要的意义.Microdosimetric single event spectrum is a significant parameter in radiotherapy, which can be used to evaluate the radiation biological effect. In this paper, microscopic patterns of energy deposition are simulated with Monte Carlo code FLUKA at mixed radiation fields during carbon ions therapy. The results are compared with experimental measured results at 300 MeV/u carbon ion and good agreement has been found. Meanwhile, dose-weighted lineal energy spectra, frequency averaged lineal energy values and dose averaged lineal energy values of carbon ion with energy from 120 to 430 MeV/u were calculated,too. The frequency averaged lineal energy values are from 185 to 28.3 keV/m while the dose averaged lineal energy values are from 272 to 64.1 keV/m. These studies are useful for treatment plan in carbon ion radiotherapy.     

重离子加速器示范装置被动式束流配送系统次级中子特征的蒙特卡罗研究

在碳离子放射治疗中,碳离子束在剂量配送过程中会与束流输运线相互作用,形成以中子辐射为主的外辐射场.由于中子是高LET射线,具有较高的相对生物学效应,减少碳离子放疗中产生的次级中子有助于降低放疗后正常组织并发症几率及二次肿瘤风险.利用蒙特卡罗方法对保守情况(能量为400 MeV/u,多叶光栅完全闭合)下碳离子治疗被动式束...     

碳离子在不同材料叶片的多叶光栅上产生的次级粒子研究

在碳离子放射治疗中,碳离子束与治疗头设备和患者身体相互作用产生的次级粒子可以到达患者体内的许多区域,在产生的次级粒子中以中子和$\gamma $射线的产额为最大。在不影响束流配送功能的情况下,减少碳离子放疗中产生的次级中子和$\gamma $射线对于降低放疗后出现的正常组织并发症及二次肿瘤风险有着非常重要的意义。本文利用蒙特卡罗(Monte Carlo)方法模拟计算了被动式束流配送系统下,400 MeV/u碳离子束照射到由不同材料叶片构成的多叶光栅(MLC)形成典型的10 cm×10 cm方形射野时,在水模体中产生的次级中子和$\gamma $射线所沉积的剂量及空间分布等。模拟结果显示:碳离子束通过MLC形成射野后在水模体中产生的次级中子主要分布在水模体的入射端,次级$\gamma $射线较为均匀的分布在整个水模体内,且较多分布在具有展宽Bragg峰(SOBP)射野在水模体中贯穿时的坪区。对于MLC叶片材料的选择,则需根据实际情况对叶片厚度以及次级粒子当量剂量的要求来确定。本文通过模拟研究不同MLC叶片材料产生次级粒子的情况,为被动式束流配送系统中MLC叶片及其他元件的材料选择提供了科学依据。     

Simulation of 12C+12C elastic scattering at high energy by using the Monte Carlo method

The Monte Carlo method is used to simulate the ¹²C+¹²C reaction process. Taking into account the size of the incident ¹²C beam spot and the thickness of the ¹²C target, the distributions of scattered ¹²C on the MWPC and the CsI detectors at a detective distance have been simulated. In order to separate elastic scattering from the inelastic scattering with 4.4 MeV excited energy, we set several variables: the kinetic energy of incident ¹²C, the thickness of the ¹²C target, the ratio of the excited state, the wire spacing of the MWPC, the energy resolution of the CsI detector and the time resolution of the plastic scintillator. From the simulation results, the preliminary establishment of the experiment system can be determined to be that the beam size of the incident ¹²C is φ 5 mm, the incident kinetic energy is 200-400 A MeV, the target thickness is 2 mm, the ratio of the excited state is 20%, the ight distance of scattered ¹²C is 3 m, the energy resolution of the CsI detectors is 1%, the time resolution of the plastic scintillator is 0.5%, and the size of the CsI detectors is 7 cm×7 cm, and we need at least 16 CsI detectors to cover a 0° to 5° angular distribution.     

Systematics of back angle 12C scattering — the 12C + 20Ne and 12C + 24Mg systems

The back angle scattering of ²⁰Ne and ²⁴Mg ions from ¹²C display structured excitation functions and oscillatory angular distributions. These measurements bridge the gap between the previously studied ¹²C + ¹⁶O and ¹²C + ²⁸Si systems.     

Microscopic investigation of the 12C + 12C interaction

The ¹²C + ¹²C system is studied in the framework of the generator coordinate method. Each ¹²C nucleus is described by a closed $\text{p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ subshell. Phase shifts and resonances are determined for several effective two-body interactions involving a spin-orbit term. The existence and properties of simple local equivalent potentials for the ¹²C + ¹²C collision are discussed. The ¹²C + ¹²C system is too light to be well described by potentials independent of the angular momentum or weakly dependent on it.     

Intermediate resonance of inelastic 12C + 12C scattering

The intermediate resonances observed in the inelastic ¹²C + ¹²C cross sections to the single and mutual 2₁⁺(4.43 MeV) excitations and the single 3₁^? (9.64 MeV) excitation are studied by the coupled-channel method with the use of the coupling interaction derived by the folding procedure between ¹²C and ¹²C. It is shown that the model is successful in reproducing the gross structures of the inelastic cross sections and especially the correlated resonance energies of the inelastic channels. The inelastic resonances are shown to be due to the molecular resonances in an adiabatic potential between two ¹²C, which reproduces correctly the coupled channel resonances.     

Statistical fluctuations and compound elastic scattering for 12C(12C, 12C)12C and 16O(16O, 16O)16O

The difference between the observed fluctuations in the elastic excitation functions for carbon-carbon and oxygen-oxygen scattering, just above the Coulomb barrier, is interpreted in terms of the compound nucleus model.     

Alignment and resonances in 12C+12C inelastic scattering

Using the out-of-plane γ-ray particle coincidence method we have measured the spin alignment P_zz of excited ¹²C(2⁺) nuclei from ¹²C+¹²C inelastic scattering in the energy range 16 MeV ? E_cm ? 33 MeV.P_zz varies strongly as a function of energy and angle. The correlation of resonant structures in the cross section with maxima of the alignment is particularly clear in mutual inelastic scattering and in θ_cm = 90° single inelastic scattering.     

Spins of resonances in the 12C + 12C system

By measuring angular distributions we have assigned J^π = 6⁺ to a resonance at E_c.m. = 7.50 ±0.05 MeV in the ¹²C + ¹²C system.     

194Pt(12C, 12C′) reaction and the triaxial-rotor model

Elastic and inelastic scattering differential cross sections for the ¹⁹⁴Pt(¹²C, ¹²C′) reaction at a bombarding energy of 78 MeV have been measured. Data have been obtained for 0⁺, 2⁺, 4⁺, and 2^+′, states in ¹⁹⁴Pt. The data have been analyzed using a rigid asymmetric-rotor model in coupled-channels reaction calculations. It is found that satisfactory fits to all data can be obtained but only if the hexadecapole deformation is included in the asymmetric-rotor model.     

Nuclear charge radii of the carbon isotopes 12C, 13C and 14C

Muonic X-ray energies of the K-series of the carbon isotopes ¹³C and ¹⁴C have been determined relative to ¹²C. For the first time, muonic atom measurements using radioactive ¹⁴C have been performed. Model-independent equivalent nuclear charge radii R_k,α and their differences have been deduced. The R_k,α radii increase by 10(14) and 32(11) am respectively with the filling of the $\text{1}\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ neutron Subshell. The results are compared with recent elastic electron scattering data. The former natural carbon data have been reanalysed using a new value for the nuclear polarization. In terms of the rms charge radius, we then obtain $\text{〈r}{}^2\text{〉}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 2.472(16)}\text{fm}$ for the ¹²C isotope.     

Low energy fusion of 12C + 12C and 16O + 16O systems

The adiabatic time-dependent Hartree-Fock method (ATDHF) is applied to the calculation of low energy fusion of ¹²C + ¹²C and ¹⁶O + ¹⁶O systems. The energy dependence of the results is in good agreement with experiment, while the order of magnitude is not correct. It is shown that the dynamical effects included in ATDHF are very important and cannot be neglected at the energies of astrophysical interest.