目标函数设置对放疗逆向计划多目标优化过程的影响

目前放疗逆向计划中常用的目标函数有两种:基于剂量分布的目标函数和基于剂量．体积直方图（DVH）的目标函数。实际系统都基于单目标优化算法进行,不考虑逆向计划的多目标性。在Pareto多目标优化理论的基础上,研究逆向计划的目标函数设置问题,比较基于剂量分布的目标函数和基于DVH的目标函数对多目标优化过程的影响,包括优化时间、收敛性和存在的问题等,为逆向计划过程中多目标优化目标函数的设置提供依据。There are two kinds of objective functions in radiotherapy inverse planning: dose distribution-based and Dose-Volume Histogram （DVH）-based functions. The treatment planning in our days is still a trial and error process because the multi-objective problem is solved by transforming it into a single objective problem using a specific set of weights for each object. This work investigates the problem of objective function setting based on Pareto multi-optimization theory, and compares the effect on multi-objective inverse planning of those two kinds of objective functions including calculation time, converge speed, etc. The basis of objective function setting on inverse planning is discussed.     

浅谈CT

 CT(ComputedTomography)是计算机断层摄影技术的简称,它是自X射线在医学领域应用以来一个划时代的成就,是近代飞速发展的计算机技术和X射线成像检查技术相结合的产物。CT的发展历程CT图像是通过数学重建技术完成的。早在1917年,奥地利数学家J.Radon就从数学理论上证明了二维或三维物体可以通过其无限多个投影的集合唯一地重建图像。1938年德国的CabrielFrank首先在X线诊断中用光子方法进行图像重建。     

Strong Exciton-Plasmon Coupling and Hybridization of Organic-Inorganic Exciton-Polaritons in Plasmonic Nanocavity

We investigate strong exciton-plasmon coupling and plasmon-mediated hybridization between the Frenkel(F)and Wannier-Mott(WM)excitons of an organic-inorganic hybrid system consisting of a silver ring separated from a monolayer WS_2 by J-aggregates.The extinction spectra of the hybrid system calculated by employing the coupled oscillator model are consistent with the results simulated by the finite-difference time-domain method.The calculation results show that strong couplings among F excitons,WM excitons,and localized surface plasmon resonances(LSPRs) lead to the appearance of three plexciton branches in the extinction spectra.The weighting efficiencies of the F exciton,WM exciton and LSPR modes in three plexciton branches are used to analyze the exciton-polaritons in the system.Furthermore,the strong coupling between two different excitons and LSPRs is manipulated by tuning F or WM exciton resonances.     

不同TS-1分子筛含量条状催化剂的丙烯环氧化性能

环氧丙烷(PO)是重要的有机化工原料，主要用于生产聚醚多元醇、丙二醇及其它化工产品。现在工业上主要采用氯醇法和Halcon法生产环氧丙烷，但分别存在污染和联产物量大等问题，人们在改进原有工艺的同时，致力于寻找流程短、副产少、无污染的新工艺。TS-1分子筛的成功合成^[1]及其在以     

Controlling optical properties of periodic gold nanoparticle arrays by changing the substrate, topologic shapes of nanoparticles, and polarization direction of incident light

The effects of various parameters including thickness and dielectric constants of substrates,shapes of nanoparticles,and polarization direction of incident light,on the extinction spectra of periodic gold nanoparticle arrays are investigated by the full-vectorial three-dimensional (3D) finite difference time domain (FDTD) method.The calculated results show that the substrate affects the extinction spectra by coupling the fields co-excited by the substrate and gold nanoparticles.Extinction spectra are influenced by the shapes of the nanoparticles,but there are no obvious changes in extinction spectra for similar shapes.The polarization direction of incident light has a great influence on the extinction spectra.The implications of these results are discussed.     

基于混合Batho修正的RBM剂量计算方法在仿真头模实验中的剂量学验证

基于混合Batho修正的规则束模型剂量计算方法可以根据放射治疗过程中加速器相关物理参数和从病人的医学影像数据中获取的人体组织非均匀信息计算出人体内的剂量场数据。在简要介绍该方法的基础上,通过将其计算结果与仿真头模的实测结果进行对比,初步证明了该方法可以作为一种较为可靠的快速剂量计算方法供临床治疗计划系统使用。The dose distribution can be calculated by the Regular Beam Model （RBM） dose engine based on the accelerator parameters and the inhomogeneity data of the patient for the radiotherapy planning. In this paper, the newly-developed mixed Batho correction based RBM is introduced, and then the calculation results are compared with the measured ones using the head phantom. The results demonstrate that the RBM dose engine can be used as a kind of reliable fast dose calculation tool in the clinical treatment planning system.