PET显像多层面容积重建显示技术的建立及临床应用

目的　建立可在PC机上运行的PET显像容积数据最大密度投影法 (MIP)和平均密度投影法 (AIP)多层面容积重建显示软件 ,并用于临床。方法　在PC机上 ,对1 3N NH3、1 8F 脱氧葡萄糖(FDG)PET显像原始三维容积数据 ,经归一化数据转换、三维几何和观察变换、透视变换等步骤 ,生成MIP或AIP投影图像 ,透视变换采用平行投影透视法。结果　最终的PET显像三维容积数据多层面容积重建显示程序具有灵活的交互式图形用户界面 ,可在PC机上运行 ,可生成PET显像三维容积数据多角度多方位的MIP或AIP投影图像 ;对心脏、垂体、肾脏等器官动态1 3N NH3或1 8F FDGPET显像 ,可多角度多方位投影图像 ,直观、整体显示血流灌注相靶器官及周围大血管和血池。结论　建立的PET显像三维容积数据多层面容积重建显示技术可多角度多方位直观、整体显示血流灌注相靶器官及周围大血管和血池 ,有一定的临床应用前景。     

基于表面点的高分辨率体数据三维重建

目的对高分辨率体数据实现高质量的实时三维表面浏览。方法本算法用结合阈值和形态学的分割方法提取体数据中单个器官的三维表面点集,再根据体数据中灰度梯度得到表面点的法向量。通过用表面点代替三角形面片来描述器官表面,在用户定义器官表面的颜色和透明度后,利用显卡OpenGL接口对表面点集进行三维显示。结果在微机环境下对中国数字人男性一号的CT数据集的骨骼和体表进行了三维重建,在保证图像质量的前提下重建速度超过25帧/s。结论本文提出的三维表面重建算法能对512×512×1720的高分辨率体数据进行高质量的实时三维表面浏览。     

成人中耳、内耳解剖结构螺旋CT三维重建技术

目的：探讨成人中耳，内耳解剖结构CT三维重建技术，方法：采用螺旋CT薄层扫描（层厚1mm或2mm)，小视野（FOV=5cm)，密集重建技术（间隔0.2mm或0.5mm），对75例成人中耳，内耳进行三维成像，包括多平面重组（MPR），最大密度投影（MaxIP)，表面成像（SSD）和仿真内镜成像（CTVE）。结果：中耳鼓室，听骨链，内耳及内耳道均获得满意三维图像。结论：螺旋CT三维重建技术的应用能够真实准确观察成人中耳，内耳立体结构。     

16层螺旋CT三维重建的临床应用价值

目的：探讨16层螺旋CT三维重建技术在临床的应用价值。方法：利用16层螺旋CT横断扫描，获得原始横断面图像，采用最大密度投影法（MIP）、曲面重组法（CPR）和表面阴影显示法（SSD）技术重建局部组织和器官的三维图像。结果：实现了多个观察面，立体的，接近解剖。仿真的，更形象和直观的影像学信息，充分的满足了临床诊断和治疗的需求。     

螺旋CT图像后处理技术对胸部疾病诊断的临床价值

螺旋CT图像后处理诊断技术的基本原理是利用计算机软件的功能，将扫描数据经多种技术将人体器官多平面图像、三维立体图像，空腔脏器的内表面图像重建而显示出来嘲。这些技术包括多层面重建法（MPR），含曲面重建法（CMPR）；最小密度投影法（MinIP）。     

肋骨疾病多种影像学检查价值分析

目的：对比探讨肋骨疾病多种．影像学检查价值。方法：101例患者。进行X线平片；CR图像；SCT胸部扫描并薄层重建，薄层横断及倾斜扫描，薄层图像二维多平面重建（MPR）和三维表面遮盖成像（SSD），最大密度投影（MIP）；MSCT扫描并薄层重建、MPR和三维容积（VR）及MIP成像。结果：CT扫描对肋骨疾病的诊断优于X线平片及CR图像，后者利于定位：CT可清晰显示轻微病变，但定位不准；MPR可作为横断图像的补充：三维重建可立体显示病变，利于整体观察及定位。结论：SCT、MSCT扫描及其薄层图像的二维、三维重建对肋骨病变诊断具有明显的优势。     

容积重建法CT脑血管造影的临床应用

目的：探讨CT三维容积重建（volume rendering,VR)脑血管造影的成像方法，评价其临床价值。方法：分析62例CT三维容积重建法脑血管造影的图像，三维观察正常血管及血管病变显示情况，同时与表面遮盖法（surface shade display,SSD)，最大强度投影法（maximum intensity project,MIP)图像比较，并对照DSA和（或）手术结果。结果：VR法脑血管造影显示及脑血管分支清楚，走行自然，能透过骨结构显示血管管腔，血管之间，血管与周围器官的相互关系，显示脑血管病变50例，显示率80．6％，与DSA或手术结果对照，48例诊断正确，2例假阳性，诊断正确率为96．0％，VR图像脑血管的显示与SSD，MIP比较差异无显著性意义（P＞0．25）。结论：VR法脑血管造影是最新的快速而有效的无创伤性三维血管成像术，能部分替代并弥补DSA，VR 旬具有显示血管管腔，重叠血管及避免去骨处理等优点。     

螺旋CT三维和多平面重建在腰椎峡部裂中的应用

目的：探讨螺旋CT（SCT）三维和多平面重建在腰椎峡部裂中的临床价值。资料与方法：分析15例腰椎峡部裂的轴位、多平面重组CT及三维CT表现。结果：最大密度投影（MIP）图像对峡部裂显示良好，15例33处均显示清晰；表面重建（SSD）图像在显示峡部裂方面不及MIP和多平面重组（MPR）图像，仅显示6例9处峡部裂，但在显示椎体滑脱方面效果良好；MPR矢状面和反角度（平行椎弓）轴位重建对15例33处椎弓峡部裂均显示良好，轴位重组对裂隙骨赘、骨痂、纤维组织增生、椎间盘病变等征象显示清晰，正中矢状面重建对椎体滑脱、椎体撕裂或骨赘后突显示良好。结论：SCT三维重建（MIP、SSD）和MPR对腰椎椎弓峡部裂衣其所引起的相关改变具有良好的显示效果，有利于临床制定手术方案。     

MSCT在胆道成像技术中的应用

目的：探讨多层螺旋CT在胆道成像技术的临床应用。方法：选取27例经13超检查疑有胆道疾病的患者，静脉滴注10％胆影葡胺100ml．行MSCT扫描。扫描数据传送到工作站行二维或三维重建，包括多平面重建（MPR）、遮蔽表面显示法（SSD）和最大强度投影法（MIP）。结果：27例胆道成像均获得成功．发现胆结石10例，胆总管癌1例，胰头癌2例，壶腹癌1例。二维或三维重建图像能清晰显示胆管解剖结构．梗阻部位或病变形态。结论：MSCT胆道成像是一种安全、便捷、非创的检查方法，可使多幅轴位图像的主要信息在一幅二维或三维图像上显示出来，有直观、整体和更全面显示病变的优点．因此，它具有较高的临床应用价值。     

内耳结构及病变的MRI技术应用研究

目的：探讨内耳膜迷路、面神经及位听神经的MRI技术方法及其临床应用价值。方法：对35例可疑内耳病变的急者采用平衡式三维梯度回波(B—TFE)尽三维快速自旋回波T2W序列(T2／3D／TSE)、轴位及斜失状位扫描，最大信号强度投影(MIP)、多平面投影(MPR)法图像重建。结果：所有内耳膜迷路、面神经及位听神经结构均得到了良好显示。其中26例正常，9例异常。结论：MRIB—TFE和T2／3D／TSE扫描序列及MIP、MPR重建技术，可很好地显示内耳结构及其微小病变，对内耳病变的诊断具有较高的临床应用价值。     

Investigation of BPF algorithm in cone-beam CT with 2D general trajectories

A mathematical derivation was conducted to illustrate that exact 3D image reconstruction could be achieved for z-homogeneous phantoms from data acquired with 2D general trajectories using the back projection filtration (BPF) algorithm. The conclusion was verified by computer simulation and experimental result with a circular scanning trajectory. Furthermore, the effect of the non-uniform degree along z-axis of the phantoms on the accuracy of the 3D reconstruction by BPF algorithm was investigated by numerical simulation with a gradual-phantom and a disk-phantom. The preliminary result showed that the performance of BPF algorithm improved with the z-axis homogeneity of the scanned object.     

Accelerated 3D-OSEM image reconstruction using a Beowulf PC cluster for pinhole SPECT

Objective A conventional pinhole single-photon emission computed tomography (SPECT) with a single circular orbit has limitations associated with non-uniform spatial resolution or axial blurring. Recently, we demonstrated that three-dimensional (3D) images with uniform spatial resolution and no blurring can be obtained by complete data acquired using two-circular orbit, combined with the 3D ordered subsets expectation maximization (OSEM) reconstruction method. However, a long computation time is required to obtain the reconstruction image, because of the fact that 3D-OSEM is an iterative method and two-orbit acquisition doubles the size of the projection data. To reduce the long reconstruction time, we parallelized the two-orbit pinhole 3D-OSEM reconstruction process by using a Beowulf personal computer (PC) cluster. Methods The Beowulf PC cluster consists of seven PCs connected to Gbit Ethernet switches. Message passing interface protocol was utilized for parallelizing the reconstruction process. The projection data in a subset are distributed to each PC. The partial image forward- and back-projected in each PC is transferred to all PCs. The current image estimate on each PC is updated after summing the partial images. The performance of parallelization on the PC cluster was evaluated using two independent projection data sets acquired by a pinhole SPECT system with two different circular orbits. Results Parallelization using the PC cluster improved the reconstruction time with increasing number of PCs. The reconstruction time of 54 min by the single PC was decreased to 10 min when six or seven PCs were used. The speed-up factor was 5.4. The reconstruction image by the PC cluster was virtually identical with that by the single PC. Conclusions Parallelization of 3D-OSEM reconstruction for pinhole SPECT using the PC cluster can significantly reduce the computation time, whereas its implementation is simple and inexpensive.     

用于荧光断层成像的边缘反投影三维表面轮廓提取算法

目的为非接触式荧光分子断层成像提供一种快速、准确、简单易行的三维表面轮廓提取方法。方法在获得了成像物体的多角度白光图像后,首先用水平集方法提取边界,然后用基于边缘的反投影方法获得断层图像,最后通过提取每一断层图像的轮廓而最终获得成像物体的三维表面轮廓数据。结果仿体实验和小动物实验表明该方法与以往所采用的基于滤波反投影的表面轮廓提取方法具有相当的精度,提取速度则加快了1～25倍。结论该方法简单易行,能够适用于荧光分子断层成像系统,并能快速、准确地为后续断层重建提供所需的三维表面轮廓。     

Development of a cone angle weighted three-dimensional image reconstruction algorithm to reduce cone-beam artefacts

OBJECTIVES: Image reconstruction from cone-beam projections collected along a single circular source trajectory is commonly done using the Feldkamp algorithm, which performs well only with a small cone angle. In this report, we propose an algorithm to reduce cone-beam artefacts by increasing the cone angle by several fold to achieve satisfactory image quality at the same radiation dose. METHODS: To examine the factors involved in the occurrence of cone-beam artefacts, a microspheres-phantom was arranged longitudinally at different positions and a computer simulation was performed. Due to differences in projection angle, data projected onto the detector surface were projected along trajectories shown as different periodic functions depending on the distance and position from the mid-plane position. Therefore, projection along several detector channels based on different projection data resulting from different periodic functions is considered responsible for the increase in cone-beam artefacts associated with an increase in the distance of reconstruction planes from the mid-plane position. Our recommended algorithm to reduce such artefacts features a change in weighting with respect to projection data obtained at different projection angles, three-dimensional back-projection of corrected projection data. RESULTS: Numerical phantom simulation and real human head origin study (a prototype cone-beam CT) showed that the effect of the reduction in cone-beam artefacts of an object located at the edges was markedly enhanced at reconstruction planes at positions further from the mid-plane position. CONCLUSION: We propose a projection angle weight-based algorithm to increase the cone angle by several fold to achieve satisfactory image quality at the same radiation dose. These findings confirmed that this algorithm reduces cone-beam artefacts and generates high-quality reconstruction images.     

A proposed algorithm for adaptive computer tomography

We propose a quite simple, recursive algorithm of image reconstruction in computer tomography (CT) based only on Bayes' theorem. Object image estimation is carried out with detection or coincidence event-base for emission type CT, and projection event-base for transmission type CT. This event-base method implies, in principle, real-time image reconstruction in CT, and provides a new paradigm called structure adaptive CT, such as parameter adjustable and regions-of-interest CTs.     

Three-dimensional volume rendering of spiral CT data: theory and method.

Three-dimensional (3D) medical images of computed tomographic (CT) data sets can be generated with a variety of computer algorithms. The three most commonly used techniques are shaded surface display, maximum intensity projection, and, more recently, 3D volume rendering. Implementation of 3D volume rendering involves volume data management, which relates to operations including acquisition, resampling, and editing of the data set; rendering parameters including window width and level, opacity, brightness, and percentage classification; and image display, which comprises techniques such as "fly-through" and "fly-around," multiple-view display, obscured structure and shading depth cues, and kinetic and stereo depth cues. An understanding of both the theory and method of 3D volume rendering is essential for accurate evaluation of the resulting images. Three-dimensional volume rendering is useful in a wide variety of applications but is just now being incorporated into commercially available software packages for medical imaging. Although further research is needed to determine the efficacy of 3D volume rendering in clinical applications, with wider availability and improved cost-to-performance ratios in computing, 3D volume rendering is likely to enjoy widespread acceptance in the medical community.     

A new three-dimensional reconstruction method using algebraic reconstruction techniques

Three-dimensional image reconstruction plays a very important role in noninvasive diagnosis of biological systems and nondestructive evaluation of manufactured work-pieces. A new direct three-dimensional reconstruction algorithm, called TART (Three-dimensional ART), is presented in this paper. Oblique projection data are used and an ART-based algorithm is introduced to compensate for the limiting constraints of incomplete projection and/or limited angular coverage. The fact that oblique projection gives useful information to the reconstruction algorithm is shown mathematically. The algorithm can be used to solve the reconstruction problem under the conditions of both complete data and incomplete data. The algorithm first maps geometric information and projection data from an oblique plane into a horizontal plane, then calculates the weighting factors for the voxels based on this horizontal plane, and finally performs a 3-D ART reconstruction. Two experimental results illustrate the superiority of the algorithm over the previous reconstruction methods.     

Segmentation and three-dimension reconstruction of Chinese digitized human cerebrum.

OBJECTIVE: A 3D digitized visible model of human cerebrum was built to provide anatomical structure for making plans of cerebral surgical operation and realizing accurate simulation of cerebrum on computer. METHODS: Transverse sectional anatomy data of the cerebrum were chosen from the first Chinese visible human (one male and one female). Semi-automated segmentation and Photoshop software were selected to segment cerebral cortex, white matter, basal nuclei, lateral ventricle, hippocampus, etc. On personal computer, the segmented structures were reconstructed in 3D with volume rendering reconstruction and surface rendering reconstruction. RESULTS: Two accurately segmented images of the main structures of cerebrum were completed. The reconstructed structures can be displayed singly, in small groups or as a whole and can be continuously rotated in 3D space at different velocities. CONCLUSION: Combining volume-rendering reconstruction with surface rendering reconstruction overcomes the defects of surface rendering reconstruction that lack of internal anatomical information, which provides a new method for 3D reconstruction. The reconstructed cerebrum and the main internal structures are realistic, which demonstrates the natural shape and exact position of the structures. It provides an accurate model for the automated segmentation algorithmic study and provides a digitized anatomical mode of cerebrum.     

Karl 3D 迭代重建技术对胸部低剂量 CT 图像质量的影响

目的：探讨 Karl 3D 迭代重建技术在胸部低剂量 CT 检查中应用的可行性。方法将本院做健康体检,体质量指数(BMI)为中等的120例胸部平扫人员随机平均分成2组。A 组60例为对照组,采用传统120 kV,150 mAs 的常规剂量扫描和滤波反投影算法(FBP)重建图像;B 组60例为研究组,使用120 kV,80 mAs 低剂量扫描,分别采用 FBP 和 Karl 3D 5级迭代重建算法重建图像。由2名主治医师采用5分制双盲阅片的方式对图像质量做出主观评价,并用 Kappa 检验评价观察者间的一致性;各组图像主支气管分叉平面,胸降主动脉区域画感兴趣区(ROI),测量其 CT 值及标准差(SD),以 SD 对图像的噪声做出客观评价;并且比较2组研究对象的 CT 剂量指数(CTDIvol)、剂量长度乘积(DLP),并估算有效剂量(ED),通过统计软件分析其结果。结果2名医师对图像质量评分的一致性较好(Kappa =0.890)。B 组低剂量 Karl 3D 5级迭代重建算法重建的图像与 A 组常规剂量图像质量相当,两者差异无统计学意义(P =0.09);并且辐射剂量明显下降(达47.47%),差异有统计学意义(P <0.01)。B 组使用 Karl 3D 5级迭代重建的图像较 FBP 重建的图像噪声明显下降,图像质量明显提高,两者差别有统计学意义(P <0.01)。结论Karl 3D 迭代重建技术完全可以运用在胸部低剂量 CT 检查中。     

Conditional entropy maximization for PET image reconstruction using adaptive mesh model.

Iterative image reconstruction algorithms have been widely used in the field of positron emission tomography (PET). However, such algorithms are sensitive to noise artifacts so that the reconstruction begins to degrade when the number of iterations is high. In this paper, we propose a new algorithm to reconstruct an image from the PET emission projection data by using the conditional entropy maximization and the adaptive mesh model. In a traditional tomography reconstruction method, the reconstructed image is directly computed in the pixel domain. Unlike this kind of methods, the proposed approach is performed by estimating the nodal values from the observed projection data in a mesh domain. In our method, the initial Delaunay triangulation mesh is generated from a set of randomly selected pixel points, and it is then modified according to the pixel intensity value of the estimated image at each iteration step in which the conditional entropy maximization is used. The advantage of using the adaptive mesh model for image reconstruction is that it provides a natural spatially adaptive smoothness mechanism. In experiments using the synthetic and clinical data, it is found that the proposed algorithm is more robust to noise compared to the common pixel-based MLEM algorithm and mesh-based MLEM with a fixed mesh structure.