调强放射治疗子野权重优化方法研究

由于子野分割带来的误差, 使得调强放疗(Intensity Modulated Radiation Therapy, 简称IMRT)计划系统所制作的计划往往不能满足临床要求。 本研究将采用基于共轭梯度法的子野权重优化方法来减小此误差, 提高制作计划的效率和效果。 采用共轭梯度法优化子野权重和微调子野形状, 最终使得子野分割前后强度误差最小。 在精确放疗系统中对常见的临床病例（鼻咽癌和周围性肺癌）进行测试, 通过对比靶区和危及器官的剂量体积直方图以及CT片上的等剂量线, 发现子野权重优化后靶区的平均剂量分别从87.0%提高到100.2%和从90.0%提高到98.4%, 更好地满足临床要求。     

基于社交网络平台自主学习核科学知识的科普化教学 研究与实践

核科学知识的普及化教育是大学物理教学之外的延伸教学, 有益于提高学生的核科学素养. 核科学技 术的理论基础较为简单, 适合于进行不受时间和地点约束的基于社交网络平台的“ 自主学习+在线讨论”的教学形 式. 本工作依托社交软件 QQ群平台, 针对我院物理类一、 二年级研究生, 开展了核科学知识的在线学习. 通过定期 分阶段发放核科学教学材料, 指导学生进行自主学习; 通过碎片式知识点的概括和讲解, 组织学生开展在线讨论, 活跃学习氛围; 及时在线解答学生的疑问, 提高学生的学习效率. 通过时间、 地点灵活的在线教学, 提高了学生的核 科学认知水平     

基于共轭梯度法的调强放疗射束强度分布优化

针对逆向调强放疗中强度分布优化涉及的参数多, 且临床上对其优化速度要求高的特点, 将医生期望的靶区剂量和周围正常组织剂量限制转化为二次函数形式的目标函数, 然后利用共轭梯度法对该目标函数进行优化。 最后采用一例C形靶区紧密包围危及器官的模拟病例和一例临床常用的前列腺实例, 在PC机（CPU E7200@2.53GHz, 2.00GB内存, Windows XP）上对强度分布优化效果进行测试, 对模拟病例10 s便找到最优解; 而对前列腺病例20 s便可以找到最优解; 且两个测试病例优化所得强度分布对应的剂量分布均满足要求。 测试结果表明, 采用共轭梯度法优化强度分布具有快速和效果好的优点, 因此可以将其应用在精确放疗系统中。 The beam intensity map optimization of Intensity Modulated Radiation Treatment(IMRT) is a large scale optimization problem because of thousands of parameters involved. A fast and efficient approach was studied in the paper according to the clinical requirement for high speed and good results. Firstly, the clinical prescribed dose of Planning Target Volume(PTV) and dose volume constraints of Normal Tissue and Organ at Risk(OAR) were transformed into a quadratic objective function. And then Conjugate Gradient(CG) was adopted to optimize the objective function. At last, a simulated case and a clinical case were used to test the approach. The results showed that the optimization process need 40 s while satisfied results could be obtained in 10 s for simulated case and the optimization process need 1 min and 20 s while optimized results could be obtained in 20 s for the clinical prostate case. So it can be found that the approach of proposed in this paper is valid and efficient, and can be used to the accurate radiation therapy system.     

Development of Accurate/Advanced Radiotherapy Treatment Planning and Quality Assurance System (ARTS)

A prototype of accurate/advanced radiotherapy treatment planning and quality assurance system (ARTS) is developed and key technical issues related to the improvement of the treatment accuracy is studied. After a brief introduction to the prototype of ARTS, the advanced development in key technical issues is presented, including image data processing and human body modeling, fast and accurate hybrid dose calculation, multi-objective optimization of inverse planning, intelligent patient positioning, and dose verification.     

基于细胞群模型的放射生物学分析

采用放射生物学方法,研究了放射性核素靶向治疗中细胞群大小对EUD和TCP的影响, 并以宏观与微观结合的方法,分析了肿瘤中心活性缺失情况下所对应的特征。 研究表明, 在活性均匀分布的情况下,EUD随细胞群(肿瘤)增大而增大。若考虑细胞间液活性的影响, EUD还会增加约47%。当肿瘤内部活性缺失时,若以TCP= 0.90作为衡量标准,周围细胞的211At α粒子的交叉效应,对于细胞核源最大可弥补边长为4层细胞的肿瘤活性中空,而其它源可弥补边长为6层细胞的肿瘤活性中空。临床治疗中,医师按照模拟结果参考给药时,应参考细胞面源的指导药量,以免由于剂量不足而造成的肿瘤控制的局部失败。TCP可以清晰地表现剂量足与不足时的差异,但是当剂量充足或过量时效果就要差些,因此它比较适合于治疗计划的制定。EUD常用于比较不同活性分布的差异,但用户在使用时一定要注意保持前后模型形状、体积的一致性。 The influence of cell cluster dimension on EUD and TCP for targeted radionuclide therapy was studied using the radiobiological method. The radiobiological features of tumor with activity lack in core were evaluated and analyzed by associating EUD,TCP and SF. The results show that EUD will increase with the increase of tumor dimension under the activity homogeneous distribution. If the extra cellular activity was taken into consideration, the EUD will increase 47%. Under the activity lack in tumor center and the requirement of TCP=0.90, the α cross fire influence of 211At could make up the maximum(48 μm)3 activity lack for Nucleus source, but (72 μm)3 for Cytoplasm, Cell Surface, Cell and Voxel sources. In clinic, the physician could prefer the suggested dose of Cell Surface source in case of the future of local tumor control for under dose. Generally TCP could well exhibit the effect difference between under dose and due dose, but not between duedose and over dose,which makes TCP more suitable for the therapy plan choice. EUD could well exhibit the difference between different models and activity distributions,which makes it more suitable for the research work. When the user uses EUD to study the influence of activity inhomogeneous distribution, he should keep the consistency of the configuration and volume of the former and the latter models.     

Varian 2300C 直线加速器6 MV X线的蒙特卡罗模拟

摘要: 利用先进的蒙特卡罗治疗头模拟程序BEAMnrc, 依据商家提供的详细设计资料, 集成多项优化模拟参数, 对医用直线加速器射线束传输部分进行了模拟, 获得与测量数据一致的模拟结果。 对复杂多叶光栏模型进行了建模, 模拟了非规则野的剂量分布, 以用于后续研究工作。 Based on the detail head structure designing provided by the manufacture, the ray transmission of VARIAN Clinic 2300C 6 MV X beam was simulated by Monte Carlo code, BEAMnrc. To accelerate the simulation efficiency, multiple optimized parameters were optimized. The simulated and the measured data were well coincident. The dose distribution of a complicated irregular field formed by MLC (Multi Leaf Collimators) was simulated, which are the base for further research work.     

模体大小对MC程序计算速度与精度的影响研究

蒙特卡罗程序的计算速度与计算模型的体积大小有一定关联。 通过改变模体的厚度， 发现除在尾部有限范围内会出现差异外， 薄模体与厚模体的结果差别很小， 然而却可以获得模拟效率的指数性提升。 通过改变模体的宽度， 发现窄模体与宽模体相比， 只要宽度比照射野半影大， 对模拟效率的影响都很小； 而当宽度与照射野半影区重合时， 效率就有一定程度的提高， 同时对剂量结果影响很小。 将此研究结果用于临床头部实例， 获得了计算速度的显著提升。     

基于注意力曲线的近代物理专题智慧课堂的设计

近代物理专题作为基础通识必修课程大学物理的延续课程,担当着帮助学生了解近代物理学的发展概貌、提高大学生的科学素养的教学目标.文章工作以固体物理基础与硅信息时代专题为例,结合注意力曲线特点,使用混合式教学方法和手段,理论与应用相结合,进行了固体物理基础和硅材料应用的智慧课堂设计.经多次教学实践,取得了良好的教学效果.     

将翻转课堂教学模式应用于大学物理教学的实践研究

针对大学物理课程教学所面临的现状和遇到的一些问题,将近年来在国内外颇受关注的翻转课堂教学模式应用于大学物理教学,构建相应的教学流程与模型并组织教学实践,通过测试、问卷调查等形式分析该教学模式对提高大学物理教学效果的作用.     

蒙特卡罗剂量分布去噪中三维高斯和Savitzky-Golay滤波器的改进与混合

对模拟粒子轨迹数较少模拟时间较短的蒙特卡罗粗糙剂量分布进行三维滤波,可以加速其收敛速度.结合蒙特卡罗剂量分布特征,改进三维高斯和Savitzky-Golay滤波器,建立三维混合滤波方法,并比较并联和级联两种基本混合方式.根据卷积性质,提出用等效卷积核简化混合滤波器结构的方法.结果表明,改进后的高斯和Savitzky-Golay滤波器的整体去噪效果得以增强,混合滤波器进一步降低滤波结果的局部误差,两种混合滤波器都能够大幅度抑制MC粗糙剂量分布中的噪声,级联混合滤波器降噪效果略优于并联混合滤波器.