Effects of CT based Voxel Phantoms on Dose Distribution Calculated with Monte Carlo Method

A few CT-based voxel phantoms were produced to investigate the sensitivity of Monte Carlo simulations of X-ray beam and electron beam to the proportions of elements and the mass densities of the materials used to express the patient‘s anatomical structure. The human body can be well outlined by air, lung, adipose, muscle, soft bone and hard bone to calculate the dose distribution with Monte Carlo method. The effects of the calibration curves established by using various CT scanners are not clinically significant based on our investigation. The deviation from the values of cumulative dose volume histogram derived from CT-based voxel phantoms is less than 1% for the given target.     

Investigation of phantom circuit benefits for next generation xDSL systems

This paper is focused on measurements and analysis of phantom mode benefits in G.fast and next generation xDSL systems. The investigation is based on real measurements performed for a multi‐quad metallic cable together with theoretical evaluations of phantom circuit potentials. Because the presence of phantom circuits leads into increasing the summary crosstalk level in a metallic cable, the application of a phantom mode is questionable in practice. That is why the investigation was performed, and conclusions provided in this paper can be helpful to decide potential benefits of this method for future applications. The elimination of a crosstalk can be performed by using advanced modulation techniques such as vectored discrete multi‐tone modulation (VDMT); however, its application in practice is limited because of its complexity and computational demands. That is why several scenarios are currently being discussed with either no VDMT application or with only partial crosstalk compensation. Because of that, this paper is focused on comparing the results for a first scenario without using any far‐end crosstalk (FEXT) elimination technique, whereas a second scenario is based on partial FEXT suppression by VDMT application, to decide the effectiveness of using phantom modes in practice. Copyright © 2014 John Wiley & Sons, Ltd.     

IEC62209-2中的SAR评估方法

介绍了靠近身体使用的无线通信设备SAR评估方法适用范围、测量系统规格;详细解读SAR评估规程,包括人体组织模拟液和系统准备、待测设备准备、电池一次充电进行多次SAR测量的方法、待测设备相对于模型的位置布置、测试频率、要执行的测量、测试步骤、多频段同时发射的待测设备的测量以及后处理。     

适应网络变结构的最小断点集更新算法

提出一种在网络变结构情况下利用虚拟断点集快速更新最小断点集的新方法。该方法首先根据静态网络拓扑形成包含保护关联矩阵、最小断点集、保护相对顺序表以及断点相关元素集的网络初始信息库。当网络结构发生变化后,首先判断变结构类型,再根据网络初始信息库确定虚拟断点集,在此基础上,重构保护关联矩阵,利用其部分元素计算新增或可删除断点...     

两种QCT体模的分析比较及相互换算的研究

研究在QCT骨密度测量中使用的羟磷灰石(Ca5OH(PO4)3)固体体模和磷酸氢二钾(K2HPO4)液体体模的相互换算。根据这两种体模的X线辐射特性,利用CT值的定义及辐射计量常用数据,推导了这两种体模骨密度测量值的相互换算的公式,给出了在CT机上常用的60～100keV X线能量范围内的相互换算数据,为两种体模在骨密度测量中进行相互比较提供了方便。     

基于放射疗法剂量给药对比的X射线直线加速器输出特性评估

剂量对比研究对确保临床试验的统一辐射剂量给药具有相当重要的意义。本文研究了拉合尔国际剂量学调查团以及核医学与肿瘤学协会（INMOL）所做的x射线高功率直线加速器的性能对比分析。实验采用基于国际原子能机构（IAEA）关于吸收剂量-水剂量标准TRS-398协议的柱形电离室进行测量,偏差百分比为0．5％-1％。研究发现拉合尔1NMOL关于直线加速器输出特性的实验结果与IAEA剂量调查团的研究结果一致。     

微波等效体模电磁特性的实验研究

分别测量不同配方微波等效体模的复介电常数，研究在不同频率下微波等效体模所表现出的电磁特性，这种测试方法对于生物组织复介电常数的研究以及微波等效体模的配制，都具有十分重要的意义。     

基于micro-CT图像的骨复合体素模型建模研究

已建立的人体体素模型中,骨松质均采用均匀模型代替,使骨剂量的计算精度受到影响。目前国际上利用白种人骨松质的NMR、micro-CT图片开展了骨微观模型的建模及剂量学研究,但我国尚未开展这方面的研究。本文利用micro-CT成像,建立了基于中国人骨松质的骨微观模型,同时与已建立的中国成年男性参考体素模型中的宏观骨模型相结合,建立了骨复合体素模型。利用该模型初步计算了骨盆骨小梁体源、骨小梁面源和红骨髓源对骨内膜的电子吸收分数。计算结果显示,基于中国人骨松质的骨微观模型计算的吸收分数曲线变化趋势与白种人的计算结果一致,最大差异分别为5.7%、1.4%和2%。     

A Large Area Thin Nal(Tl) Detector for External Counting of Low-Energy Emitters in Lung

A new type lung monitor was designed for the detection of ²³⁹Pu and ²³⁵U in the lungs, and a preliminary calibration undertaken thereon. The detector consists of a 9.5 in. dia. by 0.5 in. thick NaI(Tl)-crystal and seven photo-tubes. Besides its use as an ordinary lung monitor, the instrument can be employed as an image detector giving a rough indication of the distribution of the activities in the lungs. This paper describes the structural arrangement of the detector, the preliminary calibration performed thereon and the limits of detection derived as function of the subject's effective tissue thickness.