螺旋断层放疗MVCT成像剂量测量及其分析

背景与目的：螺旋断层放疗中治疗前／后通常采用MVCT（megavoltage coreputed tomography,MVCT）来实行图像引导下精确定位,成像过程中势必会增加患者的辐射剂量。通过体部及头部标准模体分别模拟患者MVCT成像条件来实现其剂量学测量及研究。方法：采用螺旋断层治疗机MVCT分别对圆柱形体部模体和自制标准头模体在不同螺距比（1．0、2．0、3．0）、扫描长度（4．8、7．2、9．6、12、14．4cm）及摆位条件下进行扫描,测量模体内各点扫描平均剂量变化,并对其剂量均匀性情况进行定性分析。结果：体部模体内MVCT扫描辐射剂量在0．599～2．876cGy之间：而头部模体点平均剂量为0．913～3．231cGy。测量结果表明,模体内所受照射剂量与螺距比值、扫描长度呈密切相关性;且MVCT扫描剂量与CT螺距值基本成反比关系。不同摆位条件下辐射剂量值沿模体径向大小而相应产生出其变化趋势。结论：实验结果有助于为治疗计划设计及图像引导治疗扫描范围提供较为现实而可靠的临床依据,减小患者治疗期间可能诱发肿瘤所获取的额外剂量。     

光学投影断层成像在离体样本中的应用研究

目的利用光学投影断层成像系统对小鼠离体心脏和肝脏进行三维成像,进而通过考察三维成像效果研究光学投影断层成像的应用价值。方法对小鼠进行心脏灌注,分别取出心脏、肝脏组织,并对组织进行琼脂包埋、脱水和透明化处理,得到心脏和肝脏样本。利用光学投影断层成像系统采集心脏和肝脏的透射数据,并通过滤波反投影的方法得到心脏和肝脏的三维图像。分析得到的三维图像,研究光学投影断层成像的应用价值。结果通过上述实验方法得到心脏和肝脏样本,利用光学投影断层成像系统得到具有较高清晰度和空间分辨率的样本三维结构图像。结论利用光学投影断层成像技术可获得具有高清晰度的生物组织器官的三维结构图像,在组织分辨率水平上获得小动物器官的数据信息,为尺度在1~10 mm的生物样本提供了有力的研究手段,必将大大推动生物科学基础研究的发展。     

电阻抗断层成像硬件系统的初步研究

各种原因导致的人体重要器官的缓慢出血等是导致病人死亡或预后较差的重要原因之一,目前的医学成像技术,包括CT、MRI、PET、超声等还无法对出血的过程进行长期、连续的床旁监测和监护。电阻抗断层成像是以目标体内电阻抗的分布或变化为成像对象的一种新型成像技术,作为一种廉价的无损伤检测技术,不使用核素或射线,无毒无害,因而可以成为对病人进行长期、连续图像监护的设备。本文介绍了一个基于物理模型的电阻抗成像硬件系统(FMMU V3),包括具有32个银复合电极的物理模型、采用DDS技术的恒流激励源、高精度信号检测模块、驱动测量模式程控设置模块、数据采集模块、数字I/O模块和高精度多路电源模块。该系统基于物理模型的测量数据经100次迭加后,测量精度在小信号时为1.0%,大信号时为0.1%。采用外触发DMA方式采集一组成像数据(32 X 31个)的时间小于1秒,基本满足了基于物理模型的动态成像要求,并给出了基于物理模型的初步动态成像结果。     

螺旋断层放疗系统调强放疗验证

目的 通过螺旋断层放疗系统一系列调强放疗验证方法的研究,探讨其调强放疗的质量保证验证方法是否可行.方法 采用断层放疗计划系统进行调强放疗计划设计.为实现其剂量验证,笔者采用圆柱形固体水模体、0.056cm3 AISL电离室及EDR2胶片来实现对计划进行绝对剂量及相对剂量验证.将剂最胶片和电离室分别置于模体中,调用患者治疗计划束流数据对模体进行模拟照射;由此得出轴向截面上的等剂量分布和点绝对剂量,与计划模体的等剂量曲线及计算剂量结果进行比对.束流照射前,利用调强放疗兆伏特CT对摆位模体实行图像引导,与计划系统中模体千伏特CT图像进行配准比较,实现验证模体摆位准确性.结果 轴向测得注量分布与断层放疗计划系统计算结果相一致,测量点绝对剂量测量的结果与计划系统的计算误差均在±3%以内.测量模体的摆位误差基本可保持在1mm以内,但由于床从摆位虚拟中心到束流中心之间存在垂直下降2mm的系统误差,需要在模体或患者摆位中予以考虑.结论 3个月临床实践证明断层放疗的调强放疗所采用上述质量保证措施是切实可行的,建立了其质最保证体系.     

彩色X射线成像技术新进展

X射线被发现的一个多世纪以来,在医学诊断、无损检测和安全检查等领域都发挥了不可替代的作用。随着技术的进步,X射线成像与传统摄影技术的发展过程一样,也在经历从"黑白"到"色彩"的变革。近些年具有能量响应的光子计数探测器开始用于X射线成像中,有力推动了这一变革。与传统的电荷积分式探测器不同,它可以获得不同能量区域内的光子计数,并将能谱信息融入到X射线图像中,因此可以得到"真彩色"X射线图像,使得检测更加直观准确,同时可以获得物质成分等信息。CERN等许多研究机构都在此领域开展了深入的研究,并诞生了许多新的成果。在乳腺成像、材料识别等领域,该技术已经得到了初步应用。本文介绍了彩色X射线成像和光子计数探测器的原理,光子计数探测器目前的发展,国际上彩色X射线成像技术的最新情况和其技术优势,并对该技术的未来进行了展望。     

挥发性物质体外致突变定量检测方法的研究

设计了一种新型的测试挥发性物质密闭容器装置，建立了一套简便、快速、实用的挥发性物质体外致突变定量检测方法。应用平衡原理测得挥发性物质培养基／气分配系数和致突变测试容器装置中空气浓度，通过简单公式计算，即可获得２基中受度物浓度。整个定量分析过程仅需４ｈ，挥发性物质在致突变测试容器装置内可保持特定的浓度，剂量与效应关系明确，在Ａｍｅｓ致突变测试中，对沸点低于１００℃挥发性物质质，必须用容器装置才能检测     

用于颅颌面种植外科的三维立体可视化系统

目的论文对在个人PC机上对颅颌面医学图像的可视化进行研究,开发出用于颅颌面种植外科的CT断层图像三维可视化系统。方法应用3D纹理映射的方法对颅颌面CT断层图像进行三维重建,并得到其XYZ方向上的切面图像。然后利用边缘检测的方法得到眼眶的位置,并在眼眶位置进行扇形切割,得到18幅扇形切割图像。结果该系统可以帮助医生进行手术前的骨质、骨量分析,设计种植手术的过程及模拟、预测手术的种植效果。结论建立的颅颌面种植外科三维可视化系统以其硬件配置合理、软件设计新颖、多维视角、便捷快速精确等为特色。具有较强的应用价值。     

旋转照射剂量测量仪（ArcCHECK）在螺旋断层放疗计划剂量验证中的应用

目的：研究旋转照射剂量测量仪（AreCHECK）在螺旋断层放疗（HT）计划剂量验证中的应用,寻求一种用于临床上的剂量验证方法。方法：采用AreCHECK对36例患者螺旋断层放疗（HT）计划进行剂量验证,用SNCPatients软件进行剂量分布1值分析,评估计划的剂量验证结果及实施的可行性。结果：36例患者HT计划剂量验证结果表明,采用Gamma法（3mm／3％）分析,叮≤1像素点平均通过率为99．7％±0．6％,γ通过率都大于95％。结论：ArcCHECK作为螺旋断层放疗计划的剂量验证稳定,可用于HT计划剂量分布验证。     

直线轨迹扫描断层成像中的图像重建与恢复方法

基于直线轨迹扫描的X射线断层成像方式,具有成像速度快、无物体重叠问题且造价较低等优点,在快速行李物品安检、大物体检查等领域具有较大应用潜力。不完备数据(有限角度)的图像重建及恢复是该成像方式的关键难题。本文介绍了一种适用于直线轨迹扫描断层成像的图像重建及恢复方法:在直接解析重建的基础上,利用linogram技术和总变分(Total Variation)正则化准则,实现快速稳定的外插迭代以补偿缺失数据,从而在保持图像边缘的同时,提高了图像像素值准确性,减小了图像伪影。     

螺旋断层放射治疗在头颈部肿瘤中的应用

头颈部肿瘤是常见的恶性肿瘤之一,放射治疗不仅治疗效果理想,还可保留患者的容貌及功能,故在头颈部肿瘤的治疗中发挥了重要的作用。螺旋断层放射治疗（helical tomotherapy, HT）是近十年发展起来的一种新的调强适形放疗技术,目前已初步用于鼻咽癌、口咽癌等多种头颈部肿瘤的治疗。与常规加速器调强放疗相比,螺旋断层放疗在放疗靶区的剂量覆盖及危及器官的保护等方面具有一定优势。     

Validation of Segmented Brain Tumor from MRI Images Using 3D Printingthe

Background: Early diagnosis of a brain tumor is important for improving the treatment possibilities. Manually segmenting the tumor from the volumetric data is time-consuming, and the visualization of the tumor is rather challenging. Methods: This paper proposes a user-guided brain tumour segmentation from MRI (Magnetic Resonance Imaging) images developed using Medical Imaging Interaction Toolkit (MITK) and printing the segmented object using the 3D printer for tumour quantification. The proposed method includes segmenting the tumour interactively using connected threshold method, then printing the physical object from the segmented volume of interest. Then the distance between two voxels was measured using electronic callipers on the 3D volume in a specific direction. And next, the same distance was measured in the same direction on the 3D printed object. Results: The technique was tested with n=5 samples (20 readings) of brain MRI images from RIDER Neuro MRI dataset of National Cancer Institute. MITK provides various tools that enable image visualization, registration, and contouring. We were able to achieve the same measurements using both the approaches and this has been tested statistically with paired t-test method. Through this and the observer’s opinion, the accuracy of the segmentation was proved. Conclusion: When the difference in measurement of tumor volume through the electronic calipers and with 3D printed object equates to zero, proves that the segmentation technique is accurate. This helps to delineate the tumor more accurately during radio therapy.     

基于工业CT断层图像的三维可视化

工业CT图像三维可视化能够对工业构件提供真实、直观的反映。体绘制技术可以显示工业CT三维数据的整体特征和内部细节信息。根据光线投射算法的特点，采用对原始数据场进行最大熵原则的预处理的方法，加快了绘制速度，在一定程度上改进了光线投射算法，取得了较好的显示效果。     

Cone-beam CT localization of internal target volumes for stereotactic body radiotherapy of lung lesions

PURPOSE: In this study, we investigate a technique of matching internal target volumes (ITVs) in four-dimensional (4D) simulation computed tomography (CT) to the composite target volume in free-breathing on-board cone-beam (CB) CT. The technique is illustrated by using both phantom and patient cases. METHODS AND MATERIALS: A dynamic phantom with a target ball simulating respiratory motion with various amplitude and cycle times was used to verify localization accuracy. The dynamic phantom was scanned using simulation CT with a phase-based retrospective sorting technique. The ITV was then determined based on 10 sets of sorted images. The size and epicenter of the ITV identified from 4D simulation CT images and the composite target volume identified from on-board CBCT images were compared to assess localization accuracy. Similarly, for two clinical cases of patients with lung cancer, ITVs defined from 4D simulation CT images and CBCT images were compared. RESULTS: For the phantom, localization accuracy between the ITV in 4D simulation CT and the composite target volume in CBCT was within 1 mm, and ITV was within 8.7%. For patient cases, ITVs on simulation CT and CBCT were within 8.0%. CONCLUSION: This study shows that CBCT is a useful tool to localize ITV for targets affected by respiratory motion. Verification of the ITV from 4D simulation CT using on-board free-breathing CBCT is feasible for the target localization of lung tumors.     

Four-dimensional image-based treatment planning: Target volume segmentation and dose calculation in the presence of respiratory motion

PURPOSE: To describe approaches to four-dimensional (4D) treatment planning, including acquisition of 4D-CT scans, target delineation of spatio-temporal image data sets, 4D dose calculations, and their analysis. METHODS AND MATERIALS: The study included patients with thoracic and hepatocellular tumors. Specialized tools were developed to facilitate visualization, segmentation, and analysis of 4D-CT data: maximum intensity volume to define the extent of lung tumor motion, a 4D browser to examine and dynamically assess the 4D data sets, dose calculations, including respiratory motion, and deformable registration to combine the dose distributions at different points. RESULTS: Four-dimensional CT was used to visualize and quantitatively assess respiratory target motion. The gross target volume contours derived from light breathing scans showed significant differences compared with those extracted from 4D-CT. Evaluation of deformable registration using difference images of original and deformed anatomic maps suggested the algorithm is functionally useful. Thus, calculation of effective dose distributions, including respiratory motion, was implemented. CONCLUSION: Tools and methods to use 4D-CT data for treatment planning in the presence of respiratory motion have been developed and applied to several case studies. The process of 4D-CT-based treatment planning has been implemented, and technical barriers for its routine use have been identified.     

Human tooth pulp anatomy visualization by 3D magnetic resonance microscopy

Background

Precise assessment of dental pulp anatomy is of an extreme importance for a successful endodontic treatment. As standard radiographs of teeth provide very limited information on dental pulp anatomy, more capable methods are highly appreciated. One of these is 3D magnetic resonance (MR) microscopy of which diagnostic capabilities in terms of a better dental pulp anatomy assessment were evaluated in the study.

Materials and methods

Twenty extracted human teeth were scanned on a 2.35 T MRI system for MR microscopy using the 3D spin-echo method that enabled image acquisition with isotropic resolution of 100 μm. The 3D images were then post processed by ImageJ program (NIH) to obtain advanced volume rendered views of dental pulps.

Results

MR microscopy at 2.35 T provided accurate data on dental pulp anatomy in vitro. The data were presented as a sequence of thin 2D slices through the pulp in various orientations or as volume rendered 3D images reconstructed form arbitrary view-points. Sequential 2D images enabled only an approximate assessment of the pulp, while volume rendered 3D images were more precise in visualization of pulp anatomy and clearly showed pulp diverticles, number of pulp canals and root canal anastomosis.

Conclusions

This in vitro study demonstrated that MR microscopy could provide very accurate 3D visualization of dental pulp anatomy. A possible future application of the method in vivo may be of a great importance for the endodontic treatment.     

四维与三维CT模拟定位确定食管癌原发肿瘤靶区位移和体积的比较研究

目的 比较四维CT(four-dimensional computed tomography,4D-CT)和三维CT(three-dimensional CT,3D-CT)模拟定位技术确定食管癌原发肿瘤的位移和体积.方法 前瞻性入组22例经病理证实的拟行调强放疗的食管癌患者序贯完成3D-CT和4D-CT模式下胸部模拟定位增强扫描.比较3种不同方法获得的食管肿瘤内在大体肿瘤靶区体积(internal gross tumor target volume,IGTV):4D-CT的10个呼吸时相的GTV得到IGTV4D;4D-CT的吸气末和呼气末时相GTV融合得到IGTV4D';基于3D-CT的GTV再依据4D-CT测得的靶区运动范围外扩得到IGTV3D.比较IGTV4D、IGTV4D、和IGTV3D三维方向的位移差异.计算不同段食管癌原发肿瘤靶区IGTV4D与IGTV3D和IGTV4D'的相似度指数(dice similarity coefficient,DSC)和交叉指数(overlap index,OI).结果 胸中段和胸中下段原发肿瘤10个时相上的靶区中心在左右、前后和头足方向的位移比较差异均具有统计学意义(均P＜0.01).食管癌原发肿瘤体积IGTV3D＞ IGTV4D＞ IGTV4D'(P＜0.05).设定IGTV4D为食管肿瘤的金标准,IGV3D有9.1％ ～24.1％周围正常组织可能受到不必要的照射;IGTV4D'有10.5％ ～ 34.5％肿瘤靶区可能被漏照.结论 在食管癌调强放疗模拟定位中,4D-CT模拟定位技术优于3 D-CT模拟定位技术.     

A new, accurate and conventional five-point method for quantitative evaluation of ascites using plain computed tomography in cancer patients

BACKGROUND: To assess the exact response of the malignant ascites to the treatment, the objective measurement of the volume of ascites is essential. We have developed a simple method to measure the volume of ascites by using standard abdomino-pelvic computed tomography (CT). The aim of the study is to validate the accuracy of the measurements by comparing them with the standard volume calculation by using 3D-CT. METHODS: Twelve consecutive patients with cancer who had measurable ascites underwent 15 helical CT examinations. On conventional CT images, the thickness of ascites in centimeters was measured in three planes such as the bilateral subphrenic space (A and B), the bilateral paracolic space (C and D) and the pre-bladder space (E), and the average thickness: (A + B + C + D + E)/5 was then multiplied by the area of standard abdominal cavity in the anterior projection, that was assumed to be 1000 cm(2), to yield the volume of ascites: (A + B + C + D + E) x 200 (ml). The volume of ascites was compared with the exact volume, that was obtained from 3D-CT with the volume rendering method. RESULTS: The volume of ascites measured by the present method and the volume rendering method ranged from 140 to 4040 ml and from 86 to 4279 ml, respectively. The correlation was statistically significant with a correlation coefficient of 0.956 (P < 0.01) using the Spearman's rank correlation. In 13 examinations with the exact volume > or =300 ml, the average ratio of the absolute difference in the volume was 12.9 +/- 13.9% as compared with 62.8 and 162.0% in two examinations with the exact volume < 300 ml. CONCLUSION: The preliminary study indicated that the present five-point method using a conventional CT was accurate in patients with the volume of ascites > or =300 ml. Because this procedure is simple and easy to perform, it should be feasible in many hospitals for the follow-up of ascites after treatment.     

PET/CT模拟定位系统在放射治疗中的初步应用

目的:评价PET/CT模拟定位系统在放射治疗中的作用。方法:将PET/CT、三维激光定位系统和Focus3.2.1三维计划系统通过网络连接,形成放疗科专用的三维PET/CT模拟定位计划系统,分别对62例肿瘤患者进行PET/CT模拟定位和治疗计划。结果:通过改造组成的PET/CT模拟定位系统,比CT模拟定位提供更丰富和准确的图像信息,指导靶区GTV的勾画和放疗效果的评价。结论:PET/CT模拟定位系统明显提高放疗的定位精度,是未来放疗治疗定位的发展趋势。     

由CT三维数据重建物体曲面剖面技术研究

用X-CT设备对被检测物体扫描后获得了一系列的二维图像,然后通过计算机图形图像学中的可视化技术从这些二维图像中重建出物体内部的三维结构。这正成为无损检测中一项重要的技术。而重建被检测物体的任意剖面的技术正是三维可视化技术的重要组成部分。本文在总结以前绘制物体任意剖面的众多方法基础上,对其中主要两种任意剖面方法进行深入探讨和比较研究,针对绘制曲面剖面的重采样困难,并结合基于体元的剖面直接生成方法的内在特点,在不影响剖面图像质量的前提下,提出了绘制曲面剖面的近似方法,而且使用数据预处理技术对其算法进行改进,大大提高了运算速度,达到实时绘制的要求。这改进的方法不仅能够绘制任意平面剖面,而且能够绘制包括球面等曲面剖面,因而它具有良好的扩展性和广阔的应用前景。     

Volumetric visualization of head and neck CT data for treatment planning.

PURPOSE: To demonstrate the utility of volume rendering, an alternative visualization technique to surface rendering, in the practice of CT based radiotherapy planning for the head and neck. METHODS AND MATERIALS: Rendo-avs, a volume visualization tool developed at the University of Chicago, was used to volume render head and neck CT scans from two cases. Rendo-avs is a volume rendering tool operating within the graphical user interface environment of AVS (Application Visualization System). Users adjust the opacity of various tissues by defining the opacity transfer function (OTF), a function which preclassifies voxels by opacity prior to rendering. By defining the opacity map (OTF), the user selectively enhances and suppresses structures of various intensity. Additional graphics tools are available within the AVS network, allowing for the manipulation of perspective, field of view, data orientation. Users may draw directly on volume rendered images, create a partial surface, and thereby correlate objects in the 3D scene to points on original axial slices. Information in volume rendered images is mapped into the original CT slices via a Z buffer, which contains the depth information (Z coordinate) for each pixel in the rendered view. Locally developed software was used to project conventionally designed GTV contours onto volume rendered images. RESULTS: The lymph nodes, salivary glands, vessels, and airway are visualized in detail without prior manual segmentation. Volume rendering can be used to explore the finer anatomic structures that appear on consecutive axial slices as "points." Rendo-avs allowed for acceptable interactivity, with a processing time of approximately 5 seconds per 256 x 256 pixel output image. CONCLUSIONS: Volume rendering is a useful alternative to surface rendering, offering high-quality visualization, 3D anatomic delineation, and time savings to the user, due to the elimination of manual segmentation as a preprocessing step. Volume rendered images can be merged with conventional treatment planning images to add anatomic information to the treatment planning process.