基于ArcCheck和电子射野影像装置脑瘤患者特异性容积调强放射治疗剂量验证过程容差限值与干预限值研究

目的:基于ArcCheck和电子射野影像装置(EPID)开展脑瘤患者特异性容积调强放射治疗(VMAT)剂量验证,明确两种不同类别验证工具对脑瘤VMAT剂量验证的适用性,探索剂量验证中γ通过率容差限值(TL)和干预限值(AL),为放射治疗质量控制提供参考。方法:采用随机数表法选取在医院实施VMAT计划的180例脑瘤患者。根据病种及部位的不同将其分为30例较大靶区胶质瘤计划(X方向≥14 cm)、30例中等靶区胶质瘤计划(X方向<14 cm)、30例较小靶区室管膜瘤计划、30例生殖细胞瘤全脑计划、30例生殖细胞瘤全脑室计划、60例生殖细胞瘤小野加量计划和30例脑膜瘤计划,分别基于ArcCheck和EPID开展剂量验证,并将其分为ArcCheck组和EPID组;γ分析均设置为3%/2 mm标准、10%剂量阈值下γ通过率≥95%;对比两组验证计划γ通过率,评价剂量验证的TL和AL。结果:(1)靶区较大胶质瘤和全脑计划中ArcCheck组γ通过率分别为98.40%和98.90%,均高于EPID组,其差异有统计学意义(Z=-4.423,Z=-4.685;P<0.05),ArcCheck组TL、AL明显高于通用限值,EPID组TL、AL较通用限值差近5%;(2)靶区中等胶质瘤和全脑室计划中ArcCheck组和EPID组γ通过率分别为96.98%、97.36%和97.11%、97.60%,两组γ通过率差异无统计学意义,两组TL和AL均≥94%和>90%;(3)小靶区的室管膜瘤计划和生殖细胞瘤小野加量计划,ArcCheck组γ通过率分别为93.45%和94.06%,均低于EPID组,其差异有统计学意义(t=-9.40%,t=-9.41;P<0.05),ArcCheck组TL较通用限值差分别为6.88%和8.47%,AL较通用限值差分别为10.40%和8.76%,EPID组TL>90%、AL接近90%;(4)靶区大小不一、形状复杂的脑膜瘤中ArcCheck组和EPID组γ通过率分别为96.75%和97.05%,差异均无统计学意义,ArcCheck组TL、AL分别为89.33%和86.86%;EPID组TL、AL分别为93.17%和89.69%,更接近通用限值。结论:在靶区较大胶质瘤和全脑VMAT计划中,推荐使用ArcCheck进行剂量验证。在靶区较小室管膜瘤、生殖细胞瘤小野和脑膜瘤VMAT计划中,推荐使用EPID进行剂量验证。

曲线压缩斜率差限值法的设计与实现

本文对传统的偏角法进行分析,并指出其不足之处,针对不足然后提出斜率差限值法,然后通过两种实验结果来说明该算法的性优越性和可靠性。

光电测距仪极坐标法测设铁路曲线闭合差限值

本文在详细分析的基础上,推导出该法测设铁路曲线的点位精度计算式,提出了该法测设时,铁路曲线控制点闭合差限值,供《铁路测量技术规则》修订时参考。

全站仪坐标导线的坐标转换法平差及应用

根据线路测量的特点 ,对全站仪坐标导线计算进行研究 ,提出了一种利用坐标转换原理直接对全站仪所测得的坐标进行平差计算的方法。通过实例证明 ,该方法具有计算简单、快速、精度高等优点。同时 ,根据该原理 ,给出了测站坐标差限值 ,从而实现了全站仪坐标导线的现场检核。

统计过程控制方法在放疗患者计划质控中的应用

目的运用统计过程控制(SPC)方法建立基于电子射野影像设备(Electronic Portal Imaging Device,EPID)在不同部位、不同放疗技术下使用3%/2mm和3%/3mm基准进行伽马分析的容差限值与干预限值。方法分别选取头颈部、胸部、腹部及其他部位的129例IMRT计划和89例VMAT计划使用EPID进行剂量验证,根据每个部位前20例患者计划的伽马通过率结果计算对应的容差限值与干预限值,绘制相应的单值控制图,实时监测各部位所有计划在不同测量基准下的伽马通过率。结果两种放疗技术在3%/3mm基准下,各部位的容差下限均大于97%,干预下限均接近于97%。3%/2mm基准下,各部位的容差下限均大于94%,干预下限均大于92%。结论SPC方法能够实时、有效的监测改进放疗患者计划质控流程,制定不同部位、不同放疗技术在不同测量基准下的个体化容差干预限值,降低失误风险,减少临床事故的发生。

基于AAPM-TG218报告对调强放疗计划剂量验证容差和干预限值的初步研究

目的基于AAPM-TG218号报告对河南省肿瘤医院的调强计划进行分类剂量验证,以了解剂量验证的现况,建立剂量验证的流程和确定限值。方法对河南省肿瘤医院不同肿瘤、加速器、计划系统和验证设备的组合进行验证比较,确定各项组合的容差限值和干预限值。测量要求按照报告进行,各项测量选取80例患者,测量流程按报告要求及临床经验建立的流程进行。结果本研究调强计划剂量验证临床干预限值基本能达到报告所建议范围,而容差限值稍低于报告所建议(3%/2 mm时为93.94%)。验证设备测量与敏感性有关,电子射野影像装置所测量的容差限值高于ArcCHECK,尤其在剂量/距离要求更加严格情况下(3%/2 mm时为94.12%和92.03%,P=0.074;2%/2 mm时为86.82%和74.61%,P=0.017)。结论通过AAPM-TG218号报告,建立了河南省肿瘤医院调强验证工作流程和限值范围,为以后临床剂量测量工作提供了指导。

Numerical simulation of intermediate phase growth in Ti/Al alternate foils

To investigate the diffusion reaction between Ti/Al solid diffusion couple, Ti/Al alternate foils formed by hot pressing were annealed at 525, 550, 575 and 600 °C for time ranging from 1 to 40 h. The experimental results show that TiAl3 was the only observed phase at Ti/Al interface. The interface thermodynamics favored the preferential formation of TiAl3 in Ti/Al couple. The growth of TiAl3 layer occurred mainly towards Al foil side and exhibited a parabolic law. Using the interdiffusion coefficients calculated based on the contribution of grain boundary diffusion, the growth of TiAl3 was simulated numerically with the finite difference method, and the simulated results were in good agreement with the experimental ones.

Stability of finite difference numerical simulations of acoustic logging-while-drilling with different perfectly matched layer schemes

In acoustic logging-while-drilling （ALWD） finite difference in time domain （FDTD） simulations, large drill collar occupies, most of the fluid-filled borehole and divides the borehole fluid into two thin fluid columns （radius -27 mm）. Fine grids and large computational models are required to model the thin fluid region between the tool and the formation. As a result, small time step and more iterations are needed, which increases the cumulative numerical error. Furthermore, due to high impedance contrast between the drill collar and fluid in the borehole （the difference is 〉30 times）, the stability and efficiency of the perfectly matched layer （PML） scheme is critical to simulate complicated wave modes accurately. In this paper, we compared four different PML implementations in a staggered grid finite difference in time domain （FDTD） in the ALWD simulation, including field-splitting PML （SPML）, multiaxial PML（M- PML）, non-splitting PML （NPML）, and complex frequency-shifted PML （CFS-PML）. The comparison indicated that NPML and CFS-PML can absorb the guided wave reflection from the computational boundaries more efficiently than SPML and M-PML. For large simulation time, SPML, M-PML, and NPML are numerically unstable. However, the stability of M-PML can be improved further to some extent. Based on the analysis, we proposed that the CFS-PML method is used in FDTD to eliminate the numerical instability and to improve the efficiency of absorption in the PML layers for LWD modeling. The optimal values of CFS-PML parameters in the LWD simulation were investigated based on thousands of 3D simulations. For typical LWD cases, the best maximum value of the quadratic damping profile was obtained using one do. The optimal parameter space for the maximum value of the linear frequency-shifted factor （a0） and the scaling factor （β0） depended on the thickness of the PML layer. For typical formations, if the PML thickness is 10 grid points, the global error can be reduced to 〈1% using the optimal PML parameters, and the error will decrease as the PML thickness increases.

钢筋混凝土框架结构平移参数计算

针对建筑物平移主要技术流程,总结平移各环节的现有设计方法,指出现有理论缺陷。通过力学推演并结合相关理论,提出了钢筋混凝土框架结构平移时推力计算方法,解决了此类建筑物移动过程中行程差、沉降差等重要控制指标确定问题。应用于实际工程经比较分析,吻合较好。

Seismic wavefield modeling in media with fluid-filled fractures and surface topography

We present a finite difference （FD） method for the simulation of seismic wave fields in fractured medium with an irregular （non-fiat） free surface which is beneficial for interpreting exploration data acquired in mountainous regions. Fractures are introduced through the Coates-Schoenberg approach into the FD scheme which leads to local anisotropic properties of the media where fractures are embedded. To implement surface topography, we take advantage of the boundary-conforming grid and map a rectangular grid onto a curved one. We use a stable and explicit second-order accurate finite difference scheme to discretize the elastic wave equations （in a curvilinear coordinate system） in a 2D heterogeneous transversely isotropic medium with a horizontal axis of symmetry （HTI）. Efficiency tests performed by different numerical experiments clearly illustrate the influence of an irregular free surface on seismic wave propagation in fractured media which may be significant to mountain seismic exploration. The tests also illustrate that the scattered waves induced by the tips of the fracture are re-scattered by the features of the free surface topography. The scattered waves provoked by the topography are re-scattered by the fractures, especially Rayleigh wave scattering whose amplitudes are much larger than others and making it very difficult to identify effective information from the fractures.

Application of the double absorbing boundary condition in seismic modeling

We apply the newly proposed double absorbing boundary condition（DABC）（Hagstrom et al., 2014） to solve the boundary reflection problem in seismic finite-difference（FD） modeling. In the DABC scheme, the local high-order absorbing boundary condition is used on two parallel artificial boundaries, and thus double absorption is achieved. Using the general 2D acoustic wave propagation equations as an example, we use the DABC in seismic FD modeling, and discuss the derivation and implementation steps in detail. Compared with the perfectly matched layer（PML）, the complexity decreases, and the stability and fl exibility improve. A homogeneous model and the SEG salt model are selected for numerical experiments. The results show that absorption using the DABC is considerably improved relative to the Clayton–Engquist boundary condition and nearly the same as that in the PML.

True-amplitude wavefield separation using staggered-grid interpolation in the wavenumber domain

Wavefield separation of multicomponent seismic data to image subsurface structures can be realized in either the space domain or the wavenumber domain. However, as the particle velocity components used in the wavenumber-domain wavefield separation are not defined at the same grid point with the staggered-grid finite-difference method for elastic wavefield simulation, we propose the wavenumber-domain interpolation method to estimate the required values at the common grid points prior to the wavenumber-domain true-amplitude wavefield separation. Moreover, numerical experiments show that the wavenumber-domain interpolation method has high interpolation accuracy and the trueamplitude wavefield separation method shows good amplitude preservation. The application of the proposed methodology to elastic reverse-time migration can obtain good amplitudepreserved images even in the case of some velocity error.

3-D acoustic wave equation forward modeling with topography

In order to model the seismic wave field with surface topography, we present a method of transforming curved grids into rectangular grids in two different coordinate systems. Then the 3D wave equation in the transformed coordinate system is derived. The wave field is modeled using the finite-difference method in the transformed coordinate system. The model calculation shows that this method is able to model the seismic wave field with fluctuating surface topography and achieve good results. Finally, the energy curves of the direct and reflected waves are analyzed to show that surface topography has a great influence on the seismic wave＇s dynamic properties.

Rough interfaces and ultrasonic imaging logging behind casing

Ultrasonic leaky Lamb waves are sensitive to defects and debonding in multilayer media. In this study, we use the finite-difference method to simulate the response of flexural waves in the presence of defects owing to casing corrosion and rough fluctuations at the cement-formation interface. The ultrasonic obliquely incidence could effectively stimulate the flexural waves. The defects owing to casing corrosion change the amplitude of the early- arrival flexural wave, which gradually decrease with increasing defect thickness on the exterior walls and is the lowest when the defect length and wavelength were comparable. The scattering at the defects decreases the energy of flexural waves in the casing that leaks directly to fluids. For rough cement-formation interface, the early-arrival flexural waves do not change, whereas the late-arrival flexural waves have reduced amplitude owing to the scattering at rough interface.

Three-dimensional numerical modeling of fullspace transient electromagnetic responses of water in goaf

The full-space transient electromagnetic response of water-filled goaves in coal mines were numerically modeled. Traditional numerical modeling methods cannot be used to simulate the underground full-space transient electromagnetic field. We used multiple transmitting loops instead of the traditional single transmitting loop to load the transmitting loop into Cartesian grids. We improved the method for calculating the z-component of the magnetic field based on the characteristics of full space. Then, we established the full- space 3D geoelectrical model using geological data for coalmines. In addition, the transient electromagnetic responses of water-filled goaves of variable shape at different locations were simulated by using the finite-difference time-domain （FDTD） method. Moreover, we evaluated the apparent resistivity results. The numerical modeling results suggested that the resistivity differences between the coal seam and its roof and floor greatly affect the distribution of apparent resistivity, resulting in nearly circular contours with the roadway head at the center. The actual distribution of apparent resistivity for different geoelectrical models of water in goaves was consistent with the models. However, when the goal water was located in one side, a false low-resistivity anomaly would appear on the other side owing to the full-space effect but the response was much weaker. Finally, the modeling results were subsequently confirmed by drilling, suggesting that the proposed method was effective.

高速铁路控制网测量三个技术指标的探讨和分析

高速铁路控制网测量有3个非常重要的技术指标:GNSS二次复测与第一次复测较差判别指标、隧道洞外GNSS坐标反算与全站仪实测角度较差的限差判别指标、GNSS坐标反算与全站仪实测并经过投影改正后的距离较差的限差判别指标,但这3个技术指标在《高速铁路工程测量规范》(TB10601-2009)中并未作明确规定。大量实测数据表明,GNSS二次复测与第一测复测坐标较差在5mm内是可被接受的。根据GNSS和全站仪两种不同测量方式的先验中误差,并按照误差传播定律进行公式推导,提出GNSS坐标反算的角度、距离值与全站仪实测结果较差限差的计算公式。通过较差限差公式,可以较为直观地判别GNSS和全站仪两种不同测量方式的结果是否互相吻合。

GIS-based Numerical Modelling of Debris Flow Motion across Three-dimensional Terrain

The objective of this study is to incorporate a numerical model with GIS to simulate the movement, erosion and deposition of debris flow across the three dimensional complex terrain. In light of the importance of erosion and deposition processes during debris flow movement, no entrainment assumption is unreasonable. The numerical model considering these processes is used for simulating debris flow. Raster grid networks of a digital elevation model in GIS provide a uniform grid system to describe complex topography. As the raster grid can be used as the finite difference mesh, the numerical model is solved numerically using the Leap-frog finite difference method. Finally, the simulation results can be displayed by GIS easily and used to debris flow evaluation. To illustrate this approach, the proposed methodology is applied to the Yohutagawa debris flow that occurred on 2oth October 2010, in Amami- Oshima area, Japan. The simulation results that reproduced the movement, erosion and deposition are in good agreement with the field investigation. The effectiveness of the dam in this real-ease is also verified by this approach. Comparison with the results were simulated by other models, shows that the present coupled model is more rational and effective.

Reduction of mode Q-factor due to coupling between fundamental and first order whispering-gallery modes in coupled microdisks

The mode characteristics for twin coupled microdisks are investigated by finite-difference time-domain technique. In the coupled microdisks,the same order whispering-gallery(WG) modes can form coupled modes with split mode wavelengths. We find that the coupled fundamental and first order WG modes can have anticrossing mode coupling as their wavelengths approach the same value in some case,which prevents the cross of the coupled mode wavelengths. The anticrossing mode coupling greatly reduces the coupled mode Q-factor,because the coupled mode field distribution transfers between the fundamental and the first order WG modes.

One-dimensional consolidation of double-layered soil with non-Darcian flow described by exponent and threshold gradient

Based on non-Darcian flow law described by exponent and threshold gradient within a double-layered soil, the classic theory of one-dimensional consolidation of double-layered soil was modified to consider the change of vertical total stress with depth and time together. Because of the complexity of governing equations, the numerical solutions were obtained in detail by finite difference method. Then, the numerical solutions were compared with the analytical solutions in condition that non-Darcian flow law was degenerated to Dary's law, and the comparison results show that numerical solutions are reliable. Finally, consolidation behavior of double-layered soil with different parameters was analyzed, and the results show that the consolidation rate of double-layered soil decreases with increasing the value of exponent and threshold of non-Darcian flow, and the exponent and threshold gradient of the first soil layer greatly influence the consolidation rate of double-layered soil. The larger the ratio of the equivalent water head of external load to the total thickness of double-layered soil, the larger the rate of the consolidation, and the similitude relationship in classical consolidation theory of double-layered soil is not satisfied. The other consolidation behavior of double-layered soil with non-Darcian flow is the same as that with Darcy's law.

MATLAB fitting for overcurrent relay and a new digital algorithm study

The overcurrent (OC) protection limit is set usually accorging to a OC protection setting table on digital integrated protection equipment in mine explode isolation high voltage (HV) vacuum switch. For digital integrated protection equipment, OC protection setting table must be converted to be a microcomputer algorithm. This paper first intro-duced a method of the fitting OC protection setting table to be OC relay inverse time characteristics equations using MATLAB least square fitting. On the basis of analyzing these fitting equations, a notion, “integral limit rate” was put forward initially and a OC in-verse time digital algorithm was developed. MATLAB simulation results and a digital signal processor (DSP) based digital integrated protection equipment running test indicate that this algorithm has less calculation amount, less taking up memory, high control accuracy, implements the no-grade setting of OC delay values, suits for all kinds of low-middle mi-crocomputer system implementation.