重建

3D reconstruction is one of the most challenging problems in computer vision. This project uses CAD model to increase the accuracy,robustness and speed of 3D reconstruction and five different works are conducted: 1 research on space curve 3D reconstruction method based on high curvature point nad turning point; 2 free-form curve 3D reconstruction based on B-spline and BURBS; 3 Active surface affine reconstruction based on single frame; 4 Matching and reconstruction of 3D sparse points; Data fitting method based on the iteration of nearest point.

三维重建是计算机视觉中公认的难题，本项目使用CAD模型来提高三维重建的精度、稳健性和速度的思路，围绕着空间曲线和曲面的三维重建和匹配开展了以下五个方面的研究：1）基于高曲率点和拐点分割的空间曲线三维重建方法研究；2）基于B样条和NURBS表示的空间自由曲线三维重建方法研究；3）基于单帧图像的有源曲面仿射重建；4）三维离散数据的匹配与重建；5）基于迭代最近点的数据拟合方法。

The raw data was processed by using axial, coronal and double oblique multi-planar reformation; Images obtained were graded in terms of quality with a 5-point scale(5=excellent, 4=good, 3=fair, 2=poor, and 1=nondiagnostic). In grading image quality at axial MPR, The radiologic specialists focused on the subarcuate fossa, tendon of tensor tympani, facial recess, vestibular aqueduct and pyramidal eminence, In grading image quality at coronal MPR, attention was given to the scute, crista transversa, fenestra cochleae, lateral malleal ligament and snake eyes signature of cranial nerve, In the grading of the image quality at double oblique MPR, the radiologic specialists concentrated on the malleus, incus, stirrup bone, upper bony semicircular and aquaeductus fallopii, and then to implement statistical analysis. In order to choose the minimum tube current values and the maximum pitch that can satisfy the diagnosis request, image quality of axial, coronal and double oblique reformation images was compared with different tube current groups. 15 ears of volunteers were used to test the validity with the scanning parameter. Subsequently noise, MTF and dose length product were measured by phantoms in different tube current and pitch, the parameters obtained were compared and taken into statistics analysis.

扫描模式使用临床常用的颞骨螺旋扫描方式：管电压120 kV，准直宽度20×0.6 mm，视野200 mm，重建矩阵512×512，旋转时间1 s/r，重建层厚0.6 mm，重建间隔0.3 mm，分别改变管电流(380、300、200、160、120和80 mA)和螺距(0.8、1.0和1.2)进行扫描和重建，然后对颞骨进行横断面、冠状面和双斜面多平面重组，于重组后的横断层面图像上选取弓形下窝、鼓膜张肌腱、面神经隐窝、前庭导水管和锥隆起5个解剖结构，冠状面重组图像上选取盾板、横嵴、蜗窗、面神经的蛇眼征和锤骨外侧韧带5个解剖结构，双斜面重组图像上选取锤骨、砧骨、镫骨、上骨半规管和面神经管5个解剖结构，在双盲的情况下由放射学专家分别对各管电流和螺距下扫描的重组图像进行评分，随后进行统计学处理，从中筛选出满足诊断要求的最低管电流值和最大的螺距，分别采用患者25例(15耳)用该管电流值和螺距验证其可行性；然后利用模体分别测试各管电流和螺距下的图像的空间分辨率、噪声及其剂量长度积，并对测试所得参数数值进行比较和统计学处理。

After certifying the irreality of ideal filtering function, we can get a better filter selecting a proper window function. Comparing two actual filters, we designate a good"Panama hat"filtering function. Meanwhile, an effectively linear interpolating function is introduced to raise the image reconstruction quality. Describing its realizing steps on the micro-computer briefly, we reconstructed some images from the anlogue projections of some models. The number of projection views is 180, 100 same interval parallel lines per view; the size of reconstructed images is 64×64 pixels with 64 gray levels; the reconstructing speeds are 40" on PC-386 and 12"on PC-486, respectively; each pixel is 0.31mm.

在证明了理想滤波器的不可实现性之后，得知通过选择适当的窗函数可获得很好的滤波函数，经过两个实际滤波器的效果对比，我们选取了较好的"巴拿马帽"形滤波函数，同时也介绍了一个有效的提高重建质量的线性内插函数，概要地叙述了平行射束图象重建的计算机具体实现步骤后，对几个物体的模拟投影数据进行了重建：投影角为180°，每视角下有100个平行投影数据点，在386微机上重建尺寸为64×64，时间约为40秒；在486/33MHz微机上只用了12秒，图象的象点精度是0.31mm。

An iterative factorization method based on linear subspace for projective reconstruction is presented in the paper. It relies on the facts that the rows in the matrix including all the image points span the same linear subspace as the rows in the matrix including space points and the fact that any basis of the subspace can be regarded as projective reconstruction. The projective reconstruction and the depth factors are obtained based on linear iteration.

摘要该文提出了一种基于子空间线性迭代的射影重建方法，该方法利用所有的图像序列构成的行向量生成的线性子空间之和与射影重建结构点构成的行向量生成的子空间是同一线性子空间及在该子空间中任何一个基底都可以作为射影重建的特性，线性迭代地求取射影重建及图像深度因子。

The reconstruction problem is ill-posed, so two optimal criterions, the least module and the smoothness criterion base on Tikhonov regularization technique, are introduced into reconstruction algorithm. Many regularization parameters choice strategies are investigated, and the TPA(Two—Parameter Algorithm) strategy which is based on the Morozov discrepancy principles, is implemented in two regularization reconstruction algorithms.Numerical experiment results show that the nonnegative and smoothness constraint condition can overcome the difficulty of iteration semiconvergent, preconditioned technique can improve convergence rate and reconstruction accuracy, smoothness regularization criterion can meliorate ill-posed problem of reconstruction and enhance iteration stability, and the TPA is an effective strategy of regularization parameters choice.

数值试验表明：在共轭梯度法中引入非负约束和光滑约束改善了迭代的"半收敛"性，非负约束保证了解的非负性，光滑约束抑制了重建解的振荡现象，约束算法的重建精度与无约束算法相比大幅度提高；在约束共轭梯度重建算法中引入预优技术，可以加快算法的收敛速度，提高迭代的稳定性和重建精度；引入光滑准则的正则化技术可以有效改善图像重建问题的不适定性，加快迭代的收敛速度，提高迭代的稳定性和图像重建质量，计算正则参数的TPA算法在闪光照相图像重建中是有效的。

The advantages of this new method are:(1) The field conductivity distribution function is fitter the actual condition than tradition methods:(2) On the condition of triangle elements cut of field, making the calculation speed increase in large degree than tradition methods.

与单元电导率重建算法相比，节点电导率重建算法的优点有：(1)使场域电导率分布函数更符合实际情况，克服了传统算法中对电导率作离散化处理的缺陷；(2)当场域采用三角形单元剖分方式时，在场域的剖分密度保持不变的情况下，可以大大提高重建计算的速度；(3)在场域采用三角形单元剖分方式时，场域的剖分密度可以比以前加大一倍，在不降低重建计算速度的前提下，可以改善重建计算的精度；(4)由于重建的是所有节点的电导率，避免了先前单元电导率重建图像中"阶梯"状边缘和"锯齿"状边缘的出现，明显地改善了图像的视觉效果。

It shows that the lensless Fourier transform digital hologram can be reconstructed at any distance by Fresnel transform algorithm. For convolution algorithm,the whole reconstructed image with high resolution can be acquired in an optimal reconstruction range or a small area around it.

结果表明：利用菲涅耳变换算法对离轴无透镜傅里叶变换数字全息进行重建时，无重建距离的限制；采用卷积重建法只能在最佳再现距离附近一个非常小的范围内才能获得高分辨率再现像；而采用角谱重建法在略小于最佳再现距离及大于最佳再现距离较大范围内重建，均能获得高分辨率的再现像。

Two construction methods for fewer views from limited range—ART and SART are studied, and simulated a physical fields views whose variation of deflection is equal to double-Gauss function, and then reconstructed it, and still analyzed the accuracy of the reconstruction methods.After study and analysis on the theory of ART and SART, and after analysis the properties resulted from their theory root cause, A modified simultaneous algebraic reconstruction method is presented, which is based on ART, this method takes into account both the pixel itself and the pixels close by it which are crossed by the same ray.

论文研究了两种有限投影方向的非轴对称场的CT重建算法——代数重建法和联合代数重建法，并用VC++程序模拟实现了折射率分布为双高斯函数的场的正向投影及重建过程，并对所用算法的重建精度进行了分析。

The reconstruction problem is ill-posed, so two optimal criterions, the least module and the smoothness criterion base on Tikhonov regularization technique, are introduced into reconstruction algorithm. Many regularization parameters choice strategies are investigated, and the TPA(Two—Parameter Algorithm) strategy which is based on the Morozov discrepancy principles, is implemented in two regularization reconstruction algorithms.Numerical experiment results show that the nonnegative and smoothness constraint condition can overcome the difficulty of iteration semiconvergent, preconditioned technique can improve convergence rate and reconstruction accuracy, smoothness regularization criterion can meliorate ill-posed problem of reconstruction and enhance iteration stability, and the TPA is an effective strategy of regularization parameters choice.

数值试验表明：在共轭梯度法中引入非负约束和光滑约束改善了迭代的&半收敛&性，非负约束保证了解的非负性，光滑约束抑制了重建解的振荡现象，约束算法的重建精度与无约束算法相比大幅度提高；在约束共轭梯度重建算法中引入预优技术，可以加快算法的收敛速度，提高迭代的稳定性和重建精度；引入光滑准则的正则化技术可以有效改善图像重建问题的不适定性，加快迭代的收敛速度，提高迭代的稳定性和图像重建质量，计算正则参数的TPA算法在闪光照相图像重建中是有效的。

On the basement of conventional direct fan-beam reconstruction, this paper gives a newly improved algorithm-"fast filtering-backprojection". This method utilizes the symmetrical circle geometry to sample projection data, and reconstructs image on the Polarcoordinate firstly, then translates this reconstructed image onto the cartesian coordinate system with two interpolating operations so that the computer can show the result image on the VGA screen. This algorithm rebates the calculating backprojection greatly, and shortens a few times of reconstructing time than same kinds of means. With the size of image enlarging, the reconstructing time abates with 2 exponent times. In addition, according to the idea of parallel-beam, we rearrange the fan-beams and reconstruct image using parallel-beam method fastly. The rearranging constraint condition is given here.

本文首先在传统的扇束直接重建方法的基础上，提出了一个改进的快速滤波反投影重建算法，它利用旋转采集投影数据的圆周对称的几何关系，先在极坐标系统内进行图象的重建，然后通过两次内插运算再将图象转换到计算机显示方式下的笛卡尔坐标系中去，该方法将以往的直接重建方法中的反投影时所需的运算大大降低，并将重建时间比同类方法缩短了几倍，而且随着重建图象的尺寸的增大，重建时间以2的指数次方倍相对缩短，并获得了较好质量的重建图象；另外，又根据平行束投影重建图象的思想，对扇形射束进行了重排，然后利用平行束重建图象的方法进行扇束的重建，并推导了&扇束重排重建图象&方法的约束条件。

Neither the killing of Mr Zarqawi nor any breakthrough on the political front will stop the insurgency and the fratricidal murders in their tracks.

在对危险的南部地区访问时，他斥责什叶派民兵领导人对中央集权的挑衅行为。

In fact,I've got him on the satellite mobile right now.

实际上 我们已接通卫星可视电话了