Volume 25, Issue 7

The quality of images reconstructed by statistical iterative methods depends on an accurate model of the relationship between image space and projection space through the system matrix. The elements of the system matrix for the clinical Hi-Rez scanner were derived by processing the data measured for a point source at different positions in a portion of the field of view. These measured data included axial compression and azimuthal interleaving of adjacent projections. Measured data were corrected for crystal and geometrical efficiency. Then, a whole system matrix was derived by processing the responses in projection space. Such responses included both geometrical and detection physics components of the system matrix. The response was parameterized to correct for point source location and to smooth for projection noise. The model also accounts for axial compression (span) used on the scanner. The forward projector for iterative reconstruction was constructed using the estimated response parameters. This paper extends our previous work to fully three-dimensional. Experimental data were used to compare images reconstructed by the standard iterative reconstruction software and the one modeling the response function. The results showed that the modeling of the response function improves both spatial resolution and noise properties

统计迭代重建方法的图像质量取决于通过系统矩阵对图像空间和投影空间之间关系的精确建模。临床Hi-Rez扫描仪的系统矩阵元素是通过处理视场部分内不同位置的点源测量数据得到的。这些测量数据包括轴向压缩和相邻投影的方位角交错。测量数据针对晶体效率和几何效率进行了校正。然后，通过处理投影空间中的响应推导出整个系统矩阵。这些响应包括系统矩阵的几何和检测物理分量。对响应进行了参数化，以校正点源位置并平滑投影噪声。该模型还考虑了扫描仪使用的轴向压缩（跨度）。利用估计的响应参数构建了迭代重建的前向投影器。本文将我们之前的工作扩展到全三维。使用实验数据比较了标准迭代重建软件和模拟响应函数的重建图像。结果表明，响应函数的建模改善了空间分辨率和噪声特性。

Appropriate application of spatially variant system models can correct for degraded resolution response and mispositioning errors. This paper explores the detector blurring component of the system model for a whole body positron emission tomography (PET) system and extends this factor into a more general system response function to account for other system effects including the influence of Fourie...

恰当应用空间变异系统模型可以校正退化的分辨率响应和定位误差。本文探讨了全身正电子发射断层扫描（PET）系统模型中探测器模糊分量的作用，并将该因素扩展为更通用的系统响应函数，以解释其他系统效应，包括Fourie变换的影响...

Cupping and streak artifacts caused by the detection of scattered photons may severely degrade the quantitative accuracy of cone-beam X-ray computed tomography (CT) images. In order to overcome this problem, we propose and validate the following iterative scatter artifact reduction scheme. First, an initial image is reconstructed from the scatter-contaminated projections. Next, the scatter compone...

由散射光子探测引起的杯状和条状伪影可能严重降低锥束X射线计算机断层扫描(CT)图像的定量准确性。为了克服这一问题，我们提出并验证了以下迭代散射伪影减少方案。首先，从受散射污染的投影中重建初始图像。接下来，散射分量...

This paper presents a method to reconstruct moving objects from cone beam X-ray projections acquired during a single rotational run using a given motion vector field. The method is applicable to voxel driven cone-beam filtered back-projection reconstruction approaches. Here, a formulation based on the algorithm of Feldkamp, Davis, and Kress (FDK) is presented. The motion correction is applied duri...

本文提出了一种方法，利用给定的运动向量场，从单次旋转过程中采集的锥束X射线投影重建运动物体。该方法适用于体素驱动的锥束滤波反投影重建方法。这里提出了基于Feldkamp、Davis和Kress（FDK）算法的公式。运动校正应用于...

Cardiac interventional procedures would benefit tremendously from sophisticated three-dimensional image guidance. Such procedures are typically performed with C-arm angiography systems, and tomographic imaging is currently available only by using preprocedural computed tomography (CT) or magnetic resonance imaging (MRI) scans. Recent developments in C-arm CT (Angiographic CT) allow three-dimension...

心脏介入手术将极大地受益于复杂的三维图像引导。此类手术通常使用C臂血管造影系统进行，而断层成像目前只能通过术前计算机断层扫描（CT）或磁共振成像（MRI）扫描获得。C臂CT（血管造影CT）的最新进展使得三维...

The circular scanning trajectory is one of the most widely adopted data-acquisition configurations in computed tomography (CT). The Feldkamp, Davis, Kress (FDK) algorithm and its various modifications have been developed for reconstructing approximately three-dimensional images from circular cone-beam data. When data contain transverse truncations, however, these algorithms may reconstruct images ...

圆形扫描轨迹是计算机断层扫描（CT）中最广泛采用的数据采集配置之一。Feldkamp、Davis、Kress（FDK）算法及其各种改进方法已被开发用于从圆形锥束数据中近似重建三维图像。然而，当数据包含横向截断时，这些算法可能会重建图像…

Due to the extended imaging times employed in single photon emission computed tomography (SPECT) and positron emission tomography (PET), patient motion during imaging is a common clinical occurrence. The fast and accurate correction of the three-dimensional (3-D) translational and rotational patient motion in iterative reconstruction is thus necessary to address this important cause of artifacts. ...

由于单光子发射计算机断层扫描（SPECT）和正电子发射断层扫描（PET）中成像时间较长，成像过程中的患者运动是常见的临床问题。因此，在迭代重建中快速准确地校正患者的三维（3-D）平移和旋转运动对于处理这一重要的伪影原因至关重要。...

Fourier-based approaches for three-dimensional (3-D) reconstruction are based on the relationship between the 3-D Fourier transform (FT) of the volume and the two-dimensional (2-D) FT of a parallel-ray projection of the volume. The critical step in the Fourier-based methods is the estimation of the samples of the 3-D transform of the image from the samples of the 2-D transforms of the projections ...

基于傅里叶的三维（3-D）重建方法基于体积的三维傅里叶变换（FT）与体积的平行射线投影的二维（2-D）傅里叶变换之间的关系。基于傅里叶方法的关键步骤是从投影的二维变换的样本中估计图像三维变换的样本……

We derive formulations of the four exact helical Katsevich algorithms in the native cylindrical detector geometry, which allow efficient implementation in modern computed tomography scanners with wide cone beam aperture. Also, we discuss some aspects of numerical implementation

我们推导了四种精确螺旋Katsevich算法在本机圆柱探测器几何中的表述，这些表述允许在现代具有宽锥束孔径的计算机断层扫描仪中高效实现。此外，我们还讨论了数值实现的某些方面。

The purpose of this paper is to derive a technique for accelerating the computation of cone-beam forward and backward projections that are the basic steps of tomographic reconstruction. The cone-beam geometry of C-arm systems is commonly described with projection matrices. Such matrices provide a continuous framework for analyzing the flow of operations needed to compute backprojection for analyti...

本文旨在推导一种加速计算锥形束正向和反向投影的技术，这些是断层重建的基本步骤。C臂系统的锥形束几何通常用投影矩阵来描述。这样的矩阵提供了一个连续的框架来分析计算反投影所需操作流程...

The mathematical analysis of exact filtered back-projection algorithms is strictly related to Radon inversion. We show how filter-lines can be defined for the helical trajectory, which serve for the extraction of contributions of particular kinds of Radon-planes. Due to the Fourier-slice theorem, Radon-planes with few intersections with the helix are associated with low-frequency contributions to ...

精确滤波反投影算法的数学分析严格与氡变换相关。我们展示了如何为螺旋轨迹定义滤波线，这些滤波线用于提取特定类型氡平面的贡献。根据傅里叶切片定理，与螺旋线交点较少的氡平面对应于低频贡献……

In medical helical cone-beam CT, it is common that the region-of-interest (ROI) is contained inside the helix cylinder, while the complete object is long and extends outside the top and the bottom of the cylinder. This is the Long Object Problem. Analytical reconstruction methods for helical cone-beam CT have been designed to handle this problem. It has been shown that a moderate amount of over-sc...

在医学螺旋锥束CT中，感兴趣区域（ROI）通常位于螺旋圆柱体内，而完整物体较长，延伸到圆柱体的顶部和底部之外。这就是长物体问题。已经设计了螺旋锥束CT的解析重建方法来处理这个问题。已经证明，适度的过扫描...

In order to reconstruct attenuation maps with improved spatial resolution and quantitative accuracy, we developed an approximate method of incorporating system resolution compensation (RC) in the ordered-subset transmission (OSTR) algorithm for transmission reconstruction. Our method approximately models the blur caused by the finite intrinsic detector resolution, the nonideal source collimation a...

为了重建具有更高空间分辨率和定量准确性的衰减图，我们开发了一种近似方法，将系统分辨率补偿（RC）纳入有序子集透射（OSTR）算法进行透射重建。我们的方法近似模拟了由有限的固有探测器分辨率、非理想源准直引起的模糊。

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展示本期期刊的目录。