亚硝酸盐氮的荧光光度法测定

作为食品着色剂和防腐剂的亚硝酸盐.若在食品中残存过多,则可与蛋白质的分解物仲胺类物质结合成致癌的亚硝胺,对人体产生极大的毒害作用,因此对食品中亚硝酸盐的测定是极为重要的,并已引起各国的重视.国标GB—50—77规定,肉制品中亚硝酸钠含量不超过0.03g·kg~(-1).联合国粮农卫     

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.     

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.     

P-型半导体探测器在放射治疗中的剂量特性研究

电子束半导体探测器的测量精度易受到射线的能量、剂量率、入射方向和环境温度等条件的影响。此外,电子束测量射野中半导体探测器的存在将干扰均匀射野剂量场的正常分布。通过对P-型电子束半导体探测器在不同的电子束照射条件下的实际剂量测量,定量地评估了不同照射条件下电子束半导体探测器的剂量特性,以及它对电子束均匀照射野扰动的影响。The measurement accuracy of electron beam by using semiconductor detector is easily affected by beam energy, dose rate, beam incidence direction, environment temperature etc. Furthermore, the presence of the detectors on the patient surface perturbs the distribution of the radiation field. In the paper, the dose characteristics of semiconductor detector are quantitatively discussed. The perturbation of the symmetrical radiation field is investigated based on the measured results of P-type electron beam detector under different clinical conditions.     

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.