三维形体任意剖面轮廓线的提取方法

提出了一种快速提取由多个断层轮廓线组成的三维形体任意方向剖面轮廓线的方法。该方法首先对这些断层轮廓线进行插值、排序和旋转处理,然后用虚拟平面从任意给定方向和位置剖切由这些轮廓线构成的三维形体,根据切面与各个断层轮廓线的交点,直接提取出切面轮廓线,避免了三维重建运算和大量的求交运算,加快了处理速度,实现了三维形体中任意剖面轮廓线的快速投影显示。实验证明,该方法快速、有效。     

四种放疗计划优化方法在肺癌大分割放疗中的剂量学研究

目的 探讨物理优化与生物优化方法在肺癌大分割放疗中的剂量学差异。方法 选择10例非小细胞肺癌放疗病例,分别对每个病例使用物理函数(DV组)、生物函数-物理函数相结合(DV+EUD组、EUD+DV组)及生物函数(EUD组)优化方法重新进行VMAT计划设计;其中4个组计划约束函数不同,但约束条件与计算参数保持相同。通过计算与统计各项剂量学参数来评估4种计划优化方法在肺癌大分割放疗中的剂量学差异。结果 在靶区方面,EUD组与EUD+DV组的等效均匀剂量值相近,但这两组EUD值比另外两组分别高出2.8%~3.6%和3.2%~3.7%;EUD组与EUD+DV组的肿瘤控制率平均值也高于DV组和DV+EUD组(P<0.05)。均匀性指数值也不同(P<0.05),而适形指数值相近(P>0.05)。在危及器官方面,正常肺组织的EUD、V5、V10、V20、V30以及心脏与脊髓的剂量参数差异均相近(P>0.05),但靶区使用生物函数的两组其全肺平均剂量较另外两组的略低。结论 生物函数在提高靶区的EUD与肿瘤控制率以及保护肺组织方面都具有一定的优势,临床工作中可以此为参考选择生物函数优化方法。     

多项指标联合检测对诊断恶性肿瘤腹水价值的探讨

探讨多项指标联合检测对诊断恶性腹水的价值。方法　用生化法测定腹水中腺苷脱氨酶(ADA)及总蛋白定量(Tg),用双抗体夹心法间接ELISA检测可溶性白介素-2受体(sIL-2R),用夹心法ELISA检测白介素-8(IL-8)。结果　用本文检测方法,当腹水中sIL-2R>780u/ml、IL-8<40ng/L时,可认为是诊断恶性腹水的两项阳性结果,以上两项指标中任一项阳性时,有可能是恶性腹水,两项均阳性时可诊断为恶性腹水,两项均阴性时可排除恶性腹水。结论　多项指标联合检测可提高诊断恶性腹水的准确性。     

基于计划目标剂量的锥形线束CT图像配准方法研究

目的探究一种以剂量体积直方图参数为优化变量, 使用多目标优化算法的剂量优化配准算法, 以提高锥形线束CT(CBCT)图像验证匹配的准确性。方法回顾性分析哈尔滨医科大学附属肿瘤医院2022年收治的6例肺癌和5例宫颈癌患者的28套CBCT图像。以骨性配准的结果为剂量配准算法的初始点, 在其周围的三维空间内计算各位移点的通量加权灰度均方差, 并使用无监督k均值聚类方法筛选候选位移点。使用有限尺寸笔形束算法计算各候选位移点的三维剂量分布, 并提取直方图剂量指标作为多目标优化算法的优化变量。使用多目标遗传算法求解Pareto最优解集后, 根据预设的目标权重方案求解最优唯一解。结果采用剂量优化配准后, 肺癌病例计划靶区(PTV)的D90%、D95%、D98%、Dmean、适形度(CI)指标, 较常规配准策略分别平均提高0.23 Gy、0.49 Gy、1.05 Gy、0.15 Gy、0.03, 危及器官的剂量差异无统计学意义。宫颈癌病例PTV的D90%、D95%、D98%、Dmean、CI指标, 较常规配准策略分别平均提高0.72 Gy、1.15 Gy、2.53 Gy、0.24 Gy、0.05, 部...     

多项指标联合检测对诊断恶性肿瘤腹价值的探讨

目的 探讨多项指标联合检测对诊断恶性腹水的价值。方法 用生化法测定腹水中腺苷脱氨酶（ＡＤＡ）及总蛋定量，用双抗体夹心法间接ＥＬＩＳＡ检测可溶性白介素－２受体，用夹心法ＥＬＩＳＡ检测白介素－８。结果 用本文检测方法，当腹水中ｓＩＬ－２Ｒ〉７８０ｕ／ｍｌ，ＩＬ－８〈４０ｎｇ／Ｌ时，可认为是诊断腹水的两项阳性结果，以上两项指标中任一项阳性时，有可能是恶性腹水，两项均阳性时可诊断为恶性腹水，两项均阴性时可     

基于视差梯度的图像拼接算法研究

图像拼接的关键技术在于特征点的匹配。Lowe等提出的基于SIFT特征算子的匹配算法具有尺度、旋转、视角、光照不变性,能够有效地用于目标的三维重建以及复杂目标识别。该算子使用128维向量来表示每个特征点,使处理的数据量较大,难以满足实时性的要求。本文通过改变特征点描述子的结构实现了特征向量的简化,并且提出基于视差梯度约束的特征点匹配算法,在匹配过程中使用最小中值估计算法去除伪匹配点对。实验说明,当图像存在较大的变形、畸变和噪声影响时的情况下,在保证算法的鲁棒性同时,能够降低图像匹配的计算量,从而保证算法的实时性。     

一种基于立体像对稠密匹配的三维重建方法

为了提高三维重建的性能,提出了一种新的基于立体像对稠密匹配的三维重建方法。该方法首先采用SIFT算法提取立体像对的特征点,并通过特征点的相似性判定进行特征匹配,然后从中选取种子点,并对种子点进行区域传播稠密匹配,再用对称对极点距离法消除误匹配得到精确匹配点对,然后利用摄像机矩阵计算出对应点的空间三维坐标,最后通过三角剖分和纹理渲染重建出三维模型。真实图像实验结果表明,这种重建方法显著优化了现有的基于稠密匹配算法的三维重建,且其效率和精度远远优于传统的基于稀疏匹配的重建方法。     

基于等效均匀剂量的目标函数在调强放疗计划优化中的应用

目的 介绍基于等效均匀剂量（EUD）的目标函数在调强放疗计划中的应用。方法 分别用基于EUD和基于剂量的目标函数优化6例肺癌病例治疗计划。选择遗传算法，种群规模101，迭代次数100，交叉概率0．8，变异概率0．008。对其中1例病例，在保持照射条件不变情况下，改变基于EUD目标函数中的参数，通过试验结果来分析参数对目标函数的影响。算法由C#语言编程实现，采用了基于三维光子笔射束的剂量计算模型。结果 与基于剂量的目标函数相比，采用基于EUD的目标函数，肿瘤区域剂量分布的适形效果更好、肿瘤剂量分布均匀且危险器官受照射剂量明显减少。结论 基于EUD的目标函数表达式简单，提供了广阔的解空间，具有良好微分性和凸性，可更好模拟生物效应。     

基于小波变换的材料断口SEM图像体视匹配

本文将近年来兴起的小波理论应用于双目立体视觉技术，提出了一种新立体匹配算法，并将其应用于金属材料断口ＳＥＭ图像体视匹配，获得了较好的效果。该算法以二进小波变换局部模极大值边缘点作为匹配基元，重要的是可以从变换系数中推出水平和垂直方向分量的幅度变化信息，合称为边缘分量幅度变化相似约束，他们直接反映了图像结构的变化，对于复杂景物的匹配尤其重要。算法综合利用边缘点的特征属性和一系列约束条件，从边缘点局部相似和全局匹配相容两个方面解决模糊匹配问题。实验结果表明，该算法稳定可靠，具有较强的处理复杂景物的能力     

一种基于高斯混合模型与Markov建模的灰度图像分割方法

当灰度图像中存在区域间灰度变化不明显或者含有噪声时,图像分割效果会受到比较严重的影响,本文针对此类问题,基于高斯混合模型,提出了一种改进的灰度图像分割算法。首先,基于马尔可夫随机场建模,将梯度因素引入邻域约束,推导图像的能量函数。然后,采用改进的期望最大（EM）算法对能量函数进行求解,E步通过图割法求解各像素点的分类,M步通过改进的期望最大（EM）算法求解高斯混合模型中的各参数。实验结果表明,本文的方法相对于直接用图割法能够求得更低的能量值,获得较好的分割结果。     

基于位平面编码的超光谱图像压缩方法

针对超光谱图像的特点和硬件实现的实际需要,提出了一种基于小波变换的前向预测帧间去相关超光谱图像压缩算法。通过图像匹配和帧间去相关,消除超光谱图像帧间的冗余,对残差图像的压缩采用基于小波变换的快速位平面结合自适应算术编码的压缩算法,按照率失真准则控制输出码流,实现了对超光谱图像的高保真压缩。通过实验证明了该方案的有效性, 基于小波变换的快速位平面结合自适应算术编码的压缩算法速度优于SPIHT,而且易于硬件实现。     

一种基于X射线图像和特征曲线的危险品检测方法

目前,车站行李安检系统检测危险品主要依靠人眼观察安检仪监视器识别危险品,容易出现漏检、错检以及视觉疲劳等问题。为此,提出一种基于X射线图像和特征曲线的危险品检测方法,该方法依据x射线安检仪获得的平均有效原子序数将物体分为两大类：当物体的平均有效原子序数大于等于10时,对x射线图像采用小波将其分解为近似、水平、垂直和对角线方向的4个子图像,并分别采用不同的边缘检测算子进行边缘提取,然后进行小波重构和形态学后处理以提取完整目标轮廓,通过目标与标准危险品图像进行轮廓曲率角点匹配,实现危险品的形状检测;当平均有效原予序数小于10时,获取被检物体的高低能灰度值进行曲线拟合,并与标准危险品的特征曲线进行比较以判别是否存在危险品。实验结果表明,利用图像形状和高低能灰度特征曲线相结合的方式对旅客携带物品进行检测,可以较全面地检测出危险品。     

Methods for extracting dose response curves from radiation therapy data,I: A unified approach

This paper discusses an approach to fitting models to radiation therapy data in order to extract dose response curves for tumor local control and normal tissue damage. The approach is based on the method of maximum likelihood and is illustrated by several examples. A general linear logistic equation which leads to the Ellis nominal standard dose (NSD) equation is discussed; the fit of this equation to experimental data for mouse foot skin reactions produced by fractionated irradiation is described. A logistic equation based on the concept that normal tissue reactions are associated with the surviving fraction of cells is also discussed, and the fit of this equation to the same set of mouse foot skin reaction data is also described. These two examples illustrate the importance of choosing a model based on underlying mechanisms when one seeks to attach biological significance to a model's parameters.     

多通道投影立体拼接显示墙的关键技术研究

就多投影立体拼接显示墙关键技术进行了研究和探讨,提出了影响立体感的两个指标最大视差和正负视差配比,给出了立体视差调节的指导性原则。首次提出了以实时曲线拟合生成边缘融合函数的方法,并基于平行双目投影模型,结合几何校正技术对多通道立体显示拼接墙进行了实现。实验证明,最大视差和正负视差配比对虚拟现实系统的立体感有着重要影响,并且基于曲线拟合的边缘融合方法能够快速实现多通道投影的无缝拼接。     

Dose-wall histograms and normalized dose-surface histograms for the rectum: a new method to analyze the dose distribution over the rectum in conformal radiotherapy

PURPOSE: To develop an accurate method to generate a dose-volume histogram (DVH) of the rectum wall, solely based on the outer contours of the rectum wall. METHODS AND MATERIALS: A mathematical model for the rectum wall is developed, incorporating the stretching of the rectum wall due to variable rectal filling and neighboring structures. The model is based on the assumption that the amount of intersected rectum wall tissue normal to the central axis of the rectum is constant. The main objective of the model is to determine the thickness of the rectum wall in each wall element. Two approaches are described, each yielding a DVH of the rectum wall, based only on the delineated outer contours of the rectum. In the first approach, the model is used to create a set of inner contours out of the axial outer contours. Both sets of contours are used to derive a dose-wall histogram (DWH) of the rectum. In the second approach, the model is used to generate a normalized 2D sampling space, which is subsequently binned into a normalized dose-surface histogram (NDSH). The model is verified using 20 sets of CT data (5 patients x 4 scans) in which both outer and inner contours of the rectum are carefully delineated. The DWHs and NDSHs are compared with DVHs of the rectum wall, which require contouring of the outer and inner surfaces of the rectum wall, and with DVHs of the total rectum (including rectal filling). The variation between DWHs, NDSHs, and DVHs is investigated using normal tissue complication probability (NTCP) calculations. RESULTS: The local wall thickness of the rectum as outlined on CT data was in conformity with the described rectum model. The amount of rectum wall tissue per unit length rectum varied considerably between patients (27%, 1 SD). In all analyzed patients, the DWHs and NDSHs corresponded well to the DVHs of the rectum wall. Much more discrepancies were observed between the DVHs of the total rectum and the DVHs of the rectum wall. CONCLUSION: The applied methods yield accurate dose distributions of the rectum wall, without delineating the inner surface of the rectum. This reduces both the workload and variations due to inaccurate delineation of the rectum wall. The DWH and NDSH are effective tools to evaluate 3D dose distributions of the rectum wall and to estimate the complication probability of the rectum in high-dose conformal radiotherapy.     

A comparison of record linkage yield for health research using different variable sets

As part of a study on childbearing and survival, we linked records of young women with invasive breast cancer identified through three population-based cancer registries, to state birth certificate records. In Michigan prior to 1989, only maternal social security number (SSN) was available for matching; other data became available in 1989 including name, birth date, address, and infants surname. To examine the quality of the linkage using SSN as the sole matching criterion, we conducted two procedures using data for 1989–1994 to compare linkages identified by SSN, to linkages identified using other available variables. Linkage was conducted using a deterministic approach based on seven variables and 14 steps. In each step a string of relevant variables was created and in successive phases selected variables were substituted or removed with decreasingly stringent requirements. A manual review was done to check for accuracy. Utilizing all available variables, the linkage process yielded 793 matches (live births) among 4496 patients, 780 [98%] of which would have been identified using SSN alone. Five of seven matches identified by SSN were not confirmed by manual review. SSN appears to be fairly accurate for linkage and can be valuable for linking cancer registries to other data sources.     

Development of a semi-automatic alignment tool for accelerated localization of the prostate

PURPOSE: Delivering high dose to prostate with external beam radiation has been shown to improve local tumor control. However, it has to be carefully performed to avoid partial target miss and delivering excessive dose to surrounding normal tissues. One way to achieve safe dose escalation is to precisely localize prostate immediately before daily treatment. Therefore, the radiation can be accurately delivered to the target. Once the prostate position is determined with high confidence, planning target volume (PTV) safety margin might be reduced for further reduction of rectal toxicity. A rapid computed tomography (CT)-based online prostate localization method is presented for this purpose. METHODS AND MATERIALS: Immediately before each treatment session, the patient is immobilized and undergoes a CT scan in the treatment position using a CT scanner situated in the treatment room. At the CT console, posterior, anterior, left, and right extents of the prostate are manually identified on each axial slice. The translational prostate displacements relative to the planned position are estimated by simultaneously fitting these identified extents from this CT scan to a template created from the finely sliced planning CT scan. A total of 106 serial CT scans from 8 prostate cancer patients were performed immediately before treatments and used to retrospectively evaluate the precision of this daily prostate targeting method. The three-dimensional displacement of the prostate with respect to its planned position was estimated. RESULTS: Five axial slices from each treatment CT scan were sufficient to produce a reliable correction when compared with prostate center of gravity (CoG) displacements calculated from physician-drawn contours. The differences (mean +/- SD) between these two correction schemes in the right-left (R/L), posterior-anterior (P/A), and superior-inferior (S/I) directions are 0.0 +/- 0.4 mm, 0.0 +/- 0.7 mm, and -0.4 +/- 1.9 mm, respectively. With daily CT extent-fitting correction, 97% of the scans showed that the entire posterior prostate gland was covered by PTV given a margin of 6 mm at the rectum-prostate interface and 10 mm elsewhere. In comparison, only 74% and 65% could be achieved by the corrections based on daily and weekly bony matching on portal images, respectively. CONCLUSIONS: Results show that daily CT extent fitting provides a precise correction of prostate position in terms of CoG. Identifying prostate extents on five axial CT slices at the CT console is less time-consuming compared with daily contouring of the prostate on many slices. Taking advantage of the prostate curvature in the longitudinal direction, this method also eliminates the necessity of identifying prostate base and apex. Therefore, it is clinically feasible and should provide an accelerated localization of the prostate immediately before daily treatment.