SCTA在微小脑动脉瘤诊断中的应用

目的 探讨螺旋CT血管造影（SCTA）在直径小于10mm的脑动脉瘤诊断中的临床应用和价值。方法 选择12例直径小于10mm的脑动脉瘤患，进行SCTA，DSA或MRA检查，SCTA成像技术为表面遮盖法（SSD）和最大密度投影法（MIP）。结果 12例微小脑动脉瘤患术前均准确定性，定位，全部经神经外科手术证实。结论 SCTA是一种无创伤性血管成像方法，在诊断脑动脉瘤方面，具有分辨率高，快速，准确，经济等优点，可为临床诊断与治疗提供更多的信息。     

多层螺旋CT脑血管造影对颅脑动脉血管显示的临床意义

目的：探讨颅脑多层螺旋CT血管造影（MSCTA）对颅脑血管的显示及其临床应用价值。方法：对10例临床怀疑脑血管疾病的病人进行MSCTA检查,将所得薄层图像传至AW 4.1工作站上,分别用最大密度投影（MIP）、容积再现（VR）、曲面重建技术进行血管后期重建。结果：MSCTA能清晰显示颅脑1～4级血管。其中4例动脉瘤,3例动静脉畸形,3例未发现异常血管。结论：MSCTA是一种安全、微创的检查方法,可作为脑血管疾病的首选筛检方法。     

肩胛骨骨折的螺旋CT多平面和三维重建诊断

目的 探讨螺旋CT多平面重建（MPR）、表面遮盖显示法（SSD）及最大密度投影法（MIP）在肩胛骨骨折诊断中的价值。方法 回顾性分析40例肩胛骨骨折患者的MPR、SSD及MIP图像；所有病例均用Mareoni Ultra Z型螺旋CT机扫描，并在图像工作站上用MPR、SSD及MIP技术获得多平面和三维图像。结果 MPR、SSD及MIP重建图像清晰显示了40例共45处肩胛骨骨折及7例肩关节脱位；MPR、SSD及MIP能多方位、立体、全面地显示肩胛骨骨折部位和程度。MPR在显示微小骨折方面较好，而MIP、SSD在显示骨折的位置、形态、范围及移位方面较好。结论 MPR、SSD及MIP是诊断肩胛骨骨折的有效方法，对肩胛骨骨折分类、手术入路及内固定器选择等方案的制定有帮助。     

64层螺旋CT肝血管三维重建研究及其意义

目的：探讨64层螺旋CT应用于正常人体肝脏血管研究的可行性，观察三维重建肝血管一般形态及分布规律。方法：3例正常受试者经肘正中静脉注射对比剂后，使用64层螺旋CT进行上腹部扫描，图像采集后经容积再现（Volume rendering，VR）、最大密度投影（Maximum intenstiy projection，MIP）、反向MIP（Reverse direction maximum intenstiy projection），重建肝动脉、门静脉和肝静脉。结果：重建图像清晰，可显示出6～8级血管及与周围组织间的关系。结论：64层螺旋CT可以作为研究肝血管形态的有效手段，三维重建能直观立体显示肝血管全程及血管间的关系，对于活体肝脏血管的研究、临床应用、教学具有重要意义。     

螺旋CT三维重建成人髋关节周围血管的初步研究

目的：探讨螺旋CT应用于正常人体髋关节周围血管研究的可行性，观察重建髋关节周围血管一般形态及分布规律。方法：16例正常受试者经肘正中静脉注射造影剂后，使用16排多层螺旋CT进行盆腔扫描，图像采集后经表面显示法（shaded surface display，SSD）、容积法（volume rendering，VR）和最大密度投影（maximum intensity projection，MIP）技术重建髋关节周围动、静脉，鉴别显影血管及各血管分（属）支。结果：16例均可显示出3-4级血管，平均30s可以清晰的显示动脉系统，90～130s之间为动、静共同显示，并且在130s时静脉系统显影最为清晰，而230S后由于组织强化作用显著增强，静脉边缘显示不够清晰。结论：多排螺旋CT可以作为正常人体髋关节周围血管解剖学研究的手段，随着软件的升级可以更加清晰、准确地分离动静脉，对于今后临床髋关节疾病的研究及教学具有重要意义。     

肝癌肝内血管系统三维重建及整合的X线解剖学研究及临床意义

目的：探讨三维动态增强多层螺旋CT血管造影（three dimensional dynamic contrast enhance muhislice spiral compute tomography angiography，3D DCE MSCTA），以及肝内血管系统重建并与肝癌病灶进行整合技术在临床治疗中的指导作用。方法：对16例肝癌患者采用上腹部3D DCE MSCTA扫描技术采集影像资料，经最大密度投影（maximum intensity projection，MIP）、容积再现（volume rendering，VR）和表面遮盖（surface shaded display，SSD）法重建肝内血管及肝癌病灶，并与三维数字减影血管造影（three dimensional distal subtraction angiography，3D DSA）对照。结果：肝内血管与肿块关系：肝内血管系统主分支未见异常5例，由肝动脉发出供血动脉11例，肝内血管主干受压移位10例，其中门静脉或下腔静脉癌栓3例。MIP法在显示重建血管级数方面高于SSD法，VR法显示图像的立体感优于MIP法和SSD法，3D DSA显示肝动脉及门静脉优于VR、MIP和SSD。结论：肝脏血管系统和肝癌病灶三维重建与整合技术可以较好的显示血管和病灶的立体解剖关系，有助于临床医生确定能否手术及手术的方式、范围。     

CT血管成像后处理技术在肠系膜血管栓塞诊断中的应用

目的 探讨CT血管成像(CT Angiography,CTA)后处理技术在肠系膜血管栓塞诊断中的应用价值.方法 50例肠系膜血管栓塞患者,均行螺旋CT增强扫描,原始数据采用多平面重组(MPR)、容积成像(VR)和最大密度投影(MIP)方法进行后处理,观察其对明确诊断所起的作用.结果 MPR、VR和MIP方法均能显示病变,以MPR显示率最高,结合3种方法可以获得明确诊断.结论 CTA能够明确肠系膜血管栓塞的诊断,MPR进行图像后处理的价值最大.     

螺旋CT血管造影对肺动脉栓塞的诊断价值

目的 评价螺旋CT血管造影（SCTA）对肺动脉栓塞（PE）的诊断价值。方法 对临床疑诊PE的20例患者进行螺旋CT血管造影成像（SCTA）．结果 20例患者中确诊PE7例。7例PESCTA直接征象：肺动脉主干或分支内混合性、附壁性、中心性充盈缺损。间接征象：局限性肺纹理稀疏，肺动脉高压，右心室增大，胸腔积液等。结论 螺旋CT血管造影具有准确、快速、无创性的优点，对肺动脉栓塞的诊断具有广泛应用价值。     

CT最大密度投影重建在颅底骨折中的应用

目的通过与螺旋CT多平面重建(MPR)和表面掩盖法重建(SSD)比较,探讨螺旋CT最大密度投影(MIP)在颅底骨折中的临床应用价值.方法对30例外伤颅底骨折患者进行螺旋CT轴位容积扫描,常规层厚1～2mm,重建间隔1mm,螺距为1～1.5,原始轴位图像传输至工作站进行MPR、SSD、MIP等方法重建,分析比较各种技术、图像在骨折显示能力、骨折线连续性、碎骨片移位、塌陷程度和空间关系方面的优势.结果 30例颅底骨折患者中,SSD显示14例,11例显示不全, 5例未能显示;MIP显示22例,8例显示不全;MPR结合轴位图像全部显示.SSD在显示碎骨片明显移位的空间关系较MIP、MPR好,而MIP在显示微小骨折、结构细节和骨折连续性方面有优势.结论 MIP重建图像显示颅底骨折效果良好,尤其在中颅窝显示微小骨折和有关孔、裂结构是否受累完整方面明显优于轴位CT和 MPR、SSD重建,对估计所在神经和血管是否受累有重要帮助.     

肩胛骨骨折的螺旋CT多平面和三维重建诊断

目的探讨螺旋CT多平面重建(MPR)、表面遮盖显示法(SSD)及最大密度投影法(MIP)在肩胛骨骨折诊断中的价值.方法回顾性分析40例肩胛骨骨折患者的MPR、SSD及MIP图像;所有病例均用Marconi Ultra Z型螺旋CT机扫描,并在图像工作站上用MPR、SSD 及MIP技术获得多平面和三维图像.结果 MPR、SSD及MIP重建图像清晰显示了40例共45处肩胛骨骨折及7例肩关节脱位;MPR、SSD及MIP能多方位、立体、全面地显示肩胛骨骨折部位和程度.MPR在显示微小骨折方面较好,而MIP、SSD在显示骨折的位置、形态、范围及移位方面较好.结论 MPR、SSD及MIP是诊断肩胛骨骨折的有效方法,对肩胛骨骨折分类、手术入路及内固定器选择等方案的制定有帮助.     

锥形束CT图像与计划CT图像配准方法分析

目的:通过我院开展图像引导放射治疗(IGRT)技术以来,治疗的头颈部、胸部及腹部等不同位的肿瘤的配准结果比较分析影响图像配准的各种因素及图像配准时应注意的问题,并对患者体模的制作及技术员的摆位提出改进意见。方法:病人采用平卧位,塞块式体板或颈肩板加热塑膜固定,行KVCBCT扫描,在VARIAN4DITC工作站上采用自动和手动图像配准,对于同一病例由不同人员来进行配准。结果:头颈部图像配准结果好于胸腹部配准结果,不同人员配准结果不同。结论:头颈部配准中采用自动配准一般就可达到要求,胸腹部配准采用自动和手动两种配准方法;采用人工配准方法时人员是影响配准结果的重要因素之一,图像配准最好由临床医生来确定;患者位置重复性是决定配准结果的另一重要因素,要求定位、摆位时保证患者体位姿势尽量保持一致;图像配准中最好以骨性标识或变化不大的器官作为配准点。     

精确锥形束CT和扇形束CT三维变形配准

自适应放疗可根据患者解剖和/或生理的变化对放疗计划进行修正。与加速器集成的锥形束CT成像装置是最普遍的在线影像获取设备。但是,由于锥形束CT固有的电子散射,重建影像的电子密度不准确,使得通常采用的基于密度的配准算法配准计划扇形束CT和在线获取的锥形束CT影像时,会产生较大的配准误差。我们通过建模图像变形配准问题为一个求解梯度距离能量泛函的极值问题,然后通过变分法和Gauss-Seidel方法获得一种新型的基于梯度信息的变形配准算法的迭代公式。该方法在迭代过程中同时考虑梯度信息的吻合和变形场的连续性,产生准确光滑的变形场。此算法迭代公式的局部特性,使其便于并行实施。通过OpenCL编程将此算法在图形处理器(GPU)上并行实施,大大缩短了配准时间。利用配准结果结合flood filling和cubic matching算法,可以快速地完成在线器官映射。算法临床数据配准结果表明,本文提出的基于梯度场的配准算法与基于密度的算法相比可以更准确地配准临床锥形束CT和扇形束CT影像。由于配准可以在很短的时间内完成,配准结果可用于在线器官映射和在线重新计划优化。     

带有预处理的计划CT和在线CT的形变配准方法

CT扫描中,水溶性碘造影的存在使得计划CT和在线CT图像中血管内的HU值出现非常大的偏差,从而导致计划CT和在线CT图像错配。针对该问题,本研究提出了一种基于预处理的计划CT和在线CT形变配准方法。首先,根据CT图像组织和结构的信息,利用阈值分割方法分割出血管,并将所有分割中最大的联通区域作为初始分割的强化血管;其次,利用分割得到的强化血管区域外扩5 mm,作为外扩的强化血管,并将血管用固定的HU值进行填充;最后,对完成填充后的图像利用Demons算法进行形变配准。实验结果显示本文提出的带有预处理的形变配准方法,可以较好地解决水溶性碘造影剂引起的CT错配问题。     

基于Contourlet变换的CT和锥形束CT图像配准算法

目的提出一种基于Contourlet变换,用于放射治疗定位的CT与锥形束CT（cone beam CT,CBCT）图像配准的方法。方法利用Contourlet变换多尺度多方向的分辨特性,将待配准图像进行Contourlet变换分解,分解后的高频方向子带合成梯度图像,采用归一化互信息作为相似性测度,把梯度图像与低频方向子带以加权函数结合,进行临床医学图像的刚性配准,有效弥补了互信息配准中缺少空间信息的不足。结果通过已知空间变换参数图像的配准结果验证了算法的准确性。配准后lO幅图像变换参数的误差极小,且均方根误差接近于0。结论该图像配准算法精确度高,并具有很好的鲁棒性,有助于提高图像引导放射治疗（image guid edradiation therapy,IGRT）中解剖组织结构和靶区的定位精度。     

Image registration algorithm in CT and cone beam CT based on Contourlet transform

目的提出一种基于Contourlet变换,用于放射治疗定位的CT与锥形束CT(cone beam CT,CBCT)图像配准的方法.方法 利用Contourlet变换多尺度多方向的分辨特性,将待配准图像进行Contourlet变换分解,分解后的高频方向子带合成梯度图像,采用归一化互信息作为相似性测度,把梯度图像与低频方向子带以加权函数结合,进行临床医学图像的刚性配准,有效弥补了互信息配准中缺少空间信息的不足.结果 通过已知空间变换参数图像的配准结果验证了算法的准确性.配准后10幅图像变换参数的误差极小,且均方根误差接近于0.结论 该图像配准算法精确度高,并具有很好的鲁棒性,有助于提高图像引导放射治疗(image guided radiation therapy,IGRT)中解剖组织结构和靶区的定位精度.     

Ultra-low dose CT attenuation correction for PET/CT

A challenge for positron emission tomography/computed tomography (PET/CT) quantitation is patient respiratory motion, which can cause an underestimation of lesion activity uptake and an overestimation of lesion volume. Several respiratory motion correction methods benefit from longer duration CT scans that are phase matched with PET scans. However, even with the currently available, lowest dose CT techniques, extended duration cine CT scans impart a substantially high radiation dose. This study evaluates methods designed to reduce CT radiation dose in PET/CT scanning. We investigated selected combinations of dose reduced acquisition and noise suppression methods that take advantage of the reduced requirement of CT for PET attenuation correction (AC). These include reducing CT tube current, optimizing CT tube voltage, adding filtration, CT sinogram smoothing and clipping. We explored the impact of these methods on PET quantitation via simulations on different digital phantoms. CT tube current can be reduced much lower for AC than that in low dose CT protocols. Spectra that are higher energy and narrower are generally more dose efficient with respect to PET image quality. Sinogram smoothing could be used to compensate for the increased noise and artifacts at radiation dose reduced CT images, which allows for a further reduction of CT dose with no penalty for PET image quantitation. When CT is not used for diagnostic and anatomical localization purposes, we showed that ultra-low dose CT for PET/CT is feasible. The significant dose reduction strategies proposed here could enable respiratory motion compensation methods that require extended duration CT scans and reduce radiation exposure in general for all PET/CT imaging.     

Immuno-SPET/CT and immuno-PET/CT: a step ahead to translational imaging

Malignant tumours have the remarkable property to express cell surface antigens. Pressman was first reporting that radiolabeled antibodies were capable of organ localization. It was a promising challenge but the expected success and the development of this imaging method was limited by a poor imaging resolution despite a rather good specificity of the antibodies used. Identification of key cell surface markers is opening a new era as potential molecular imaging biomarkers in oncologic applications. Antibodies production has been promoted by the development of engineered fragments with preserved immunological properties and pharmacokinetics optimized for molecular imaging. A good compromise has to be obtained between the biological properties of the antibody and the physical half-life of the radionuclide. Several positron emission tomography (PET) radionuclides such as iodine-124, copper-64, yttrium-86 or zirconium-89 have been the focus of recent immuno-PET studies with interesting informative images in preclinical and clinical studies. Thanks to the development of more sensitive new detectors and specific software, molecular imaging methods, particularly PET imaging, allow nowadays the detection of lesions smaller than 5 mm in human. Immuno-PET can potentially be used for tumour detection and identification at diagnosis, staging and restaging, for treatment selection and monitoring, and during follow-up. Moreover the availability of matched imaging or therapeutic radionuclide pairs, such as ¹²⁴I/¹³¹I, ⁶⁴Cu/⁶⁷Cu and ⁸⁶Y/⁹⁰Y, make easier the quantification of tissue uptake and dosimetry calculation for radioimmunotherapy.     

Simulation of four-dimensional CT images from deformable registration between inhale and exhale breath-hold CT scans

PURPOSE: We propose to simulate an artificial four-dimensional (4-D) CT image of the thorax during breathing. It is performed by deformable registration of two CT scans acquired at inhale and exhale breath-hold. MATERIALS AND METHODS: Breath-hold images were acquired with the ABC (Active Breathing Coordinator) system. Dense deformable registrations were performed. The method was a minimization of the sum of squared differences (SSD) using an approximated second-order gradient. Gaussian and linear-elastic vector field regularizations were compared. A new preprocessing step, called a priori lung density modification (APLDM), was proposed to take into account lung density changes due to inspiration. It consisted of modulating the lung densities in one image according to the densities in the other, in order to make them comparable. Simulated 4-D images were then built by vector field interpolation and image resampling of the two initial CT images. A variation in the lung density was taken into account to generate intermediate artificial CT images. The Jacobian of the deformation was used to compute voxel values in Hounsfield units. The accuracy of the deformable registration was assessed by the spatial correspondence of anatomic landmarks located by experts. RESULTS: APLDM produced statistically significantly better results than the reference method (registration without APLDM preprocessing). The mean (and standard deviation) of distances between automatically found landmark positions and landmarks set by experts were 2.7(1.1) mm with APLDM, and 6.3(3.8) mm without. Interexpert variability was 2.3(1.2) mm. The differences between Gaussian and linear elastic regularizations were not statistically significant. In the second experiment using 4-D images, the mean difference between automatic and manual landmark positions for intermediate CT images was 2.6(2.0) mm. CONCLUSION: The generation of 4-D CT images by deformable registration of inhale and exhale CT images is feasible. This can lower the dose needed for 4-D CT acquisitions or can help to correct 4-D acquisition artifacts. The 4-D CT model can be used to propagate contours, to compute a 4-D dose map, or to simulate CT acquisitions with an irregular breathing signal. It could serve as a basis for 4-D radiation therapy planning. Further work is needed to make the simulation more realistic by taking into account hysteresis and more complex voxel trajectories.