三维图像重建的免配准图像输入

穴位解剖的计算机三维图像重建是建立在二维图像叠加的基础上的,因此二维图像的质量好坏直接关系到三维图像重建的结果.二维图像的质量包括以下两个方面:图像清晰度和图像几何位置.二维图像清晰度对三维图像重建后图像质量的影响主要体现在图像的清晰度上,而二维图像的几何位置对三维图像重建的影响则要体现在多方面上.如果我们把三维图像定义在(x,y,z)的三维空间,而二维图像则定义在(x,y)的二维空间,那么由二维图像重建为三维图像就需要建立空间坐标z的数据.为了使三维图像z方向的数据能准确地通过相邻二维图像之间的关系而获得,就必须使各层二维图像都能在几何上有统一的标准.这些标准包括:(1)要有标准的x,y方向归一化尺寸;(2)要有统一的几何中心;(3)要使每一幅二维图像的x轴和y     

红外定位系统在精确放疗中的应用

目的:介绍红外定位系统(OPS)在精确放疗的摆位和验证中的应用。方法:在患者面膜或体膜上粘贴红外自动跟踪装置专用标记球4个,通过红外线探头探测标记球的位置,在x、y、z方向上移动治疗床,将病灶中心精确定位于加速器的等中心上。比较模拟定位时荧光球与实际治疗时荧光球的位置差异,测量x、y、z方向上的摆位误差。结果:用红外定位系统测量的摆位误差结果为:摆位误差在x、y、z方向上,头颈部肿瘤误差最小,盆腔、腹部肿瘤误差为1 mm~4 mm,主要发生在x、z方向,胸部肿瘤误差为2 mm~5 mm,主要发生在y、z方向。结论:红外定位系统能准确完成摆位与验证,与EPID相比使用更加方便、效率更高、更加适应临床需要。     

三维合成胃电信号的谱分析

国内外现有的胃电信号提取方法,大多只提取空间胃电向量在一个平面内的投影信息,对信息的收集是不完全的。我们设计了收集全方位信息的正交(x.y.g)导联法。三对双极导联的放置位置:x导联:胃窦-胃体的腹部体表投影部位;y导联:通过窦-体电极安放位置连线的中点,并与之垂直,上下距中点4cm左右;y导联:腹部x、y导联的交点及对应的背部位置。     

消化道微型诊疗装置磁定位系统的软件设计

为实现对消化道微型诊疗装置在人体内的实时定位与跟踪,使用可视化工具包(VTK)在VC++.Net平台下设计了可应用于消化道微型诊疗装置的定位跟踪软件.该软件采用多线程处理技术,在实时检测电子胶囊内磁标记物的空间磁场信息基础上,利用非线性最优化算法求解出电子胶囊位置和姿态信息,最后将定位结果以二维和三维的形式实时显示并存档.实验结果表明:该程序在基于磁通传感器阵列的硬件平台下,能够稳定的实现磁传感器阵列的数据采集,对非线性最优化磁定位算法进行实时处理,以及空间定位结果的二维、三维显示和数据保存三项任务的流水线并行处理和数据回放等功能,每次传感器阵列数据采集时间小于2 s,定位算法时间小于600 ms.该软件可实时处理定位信息的采集、处理运算及结果显示,能满足消化道内微型装置实时跟踪定位的需要.     

一种新的人体腔道介入器件定位方法

为了解决介入人体腔道诊疗器件的定位问题,提出了一种利用永磁磁场解析表达式组建方程来反推位置的方法.由诊疗器件和永磁体的空间关系模型,确定了未知量的数目.在方程组个数不足时,使用平移永磁体来增加方程组个数,使得两者相等.约束方程组是一组多元非线性方程,进行了数值求解,并和预期位置进行了比较,结果发现该定位方法是切实可行的.     

CBCT引导下不同体位子宫肿瘤IMRT摆位误差及其外放边界

目的:研究在千伏级CBCT引导下,不同体位子宫肿瘤患者调强放射治疗中的摆位误差及靶区的外放边界。方法:采用医科达直线加速器机载影像系统对251例子宫肿瘤患者接受调强放射治疗前行CBCT扫描,其中仰卧位117例、俯卧位134例。系统自动重建图像并与治疗计划CT图像进行配准,获得俯卧位与仰卧位患者x、y、z方向摆位误差,并分别计算患者临床靶区到计划靶区(PTV)的外放边界。结果:所有患者共行3 128次扫描,俯卧位1 679次与仰卧位1 449次。x、y、z轴的误差均小于0.3 cm为981次,占31.36%;距离治疗等中心偏差距离小于0.3 cm为415次,占13.27%。考虑摆位误差方向时,俯卧位患者的x、y、z方向上摆位误差分别为(0.109 5±0.380 7)、(-0.035 1±0.569 2)、(0.075 1±0.285 2)cm;仰卧位患者的x、y、z方向上摆位误差分别为(0.001 1±0.303 4)、(0.118 4±0.583 0)、(0.033 2±0.248 0)cm。而考虑摆位误差大小时,俯卧位患者的x、y、z方向上摆位误差分别(0.300 8±0.257 7)、(0.442 8±0.359 2)、(0.227 1±0.188 2)cm;仰卧位患者的x、y、z方向上摆位误差分别为(0.229 3±0.198 6)、(0.470 2±0.364 4)、(0.183 2±0.170 3)cm。俯卧位患者PTV在x、y、z方向分别外放0.540、0.486、0.387 cm;仰卧位患者PTV在x、y、z方向分别外放0.215、0.704、0.257 cm。结论:子宫肿瘤患者仰卧位和俯卧位这两种体位的摆位误差有一定差异,以距离治疗等中心偏差距离小于0.3 cm作为摆位误差校准较适合;俯卧位患者的靶区在x、y、z方向分别外放0.540、0.486、0.387 cm;而仰卧位患者则外放0.215、0.704、0.257 cm。     

认知控制任务下精神分裂症患者健康亲属大脑激活模式的元分析

目的:探究认知控制任务下,精神分裂症患者健康亲属的大脑激活模式。方法:首先对近年来利用认知控制任务探究精神分裂症患者激活模式的文献进行整理;而后对各项研究的激活坐标进行提取和空间转换;最后利用似然估计的方法对提取的坐标进行系统的定量分析。结果:研究发现,与正常对照组相比,精神分裂症患者的健康亲属的左侧脑岛(似然估计值ALE=0.012,峰值坐标:x=-40,y=18,z=0)和左侧扣带回(似然估计值ALE=0.011,峰值坐标:x=-2,y=10,z=38)激活水平显著降低,左侧额上回(似然估计值ALE=0.013,峰值坐标:x=0,y=8,z=50)和左侧中央前回(似然估计值ALE=0.001,峰值坐标:x=-38,y=2,z=36)激活水平显著地增高(P0.05)。结论:与认知控制有关的大脑激活模式可能可以作为精神分裂症研究的一个内观遗传表型。     

三目标最优化结合磁场信号SVD正交分解用于脑磁源的定位计算(MEG)

脑磁源的定位是脑磁图（ｍａｇｎｅｔｏｅｎｃｅｐｈａｌｏｇｒａｐｈｙ简称ＭＥＧ）研究的一个基本问题。该问题属不定问题，即根据探头测量的微小磁场所建立的方程组求得的未知脑磁源有无穷组解。因此需要通过建立合理的数学模型补充适当信息。脑磁场测量信号ＳＶＤ正交分解且进行单偶极子搜索方法（ｍｕｓｉｃ）已被广泛采用。该方法假定脑磁源是许多孤立的偶极子源，且偶极子源之间在统计上是互相独立的。若脑磁源不满足上述假定，一般讲该方法失效。三目标最优化法是最近推出的一方法，若偶极子源分布在脑空间内任意深度平行于探头表面的一层附近，该方法可给出正确的解。三目标最优化法与脑磁场测量信号的ＳＶＤ正交分解方法相结合可得一新方法，它将脑空间划分成几个子区域，每一区域在平行探头表面不同深度的一层附近。新方法仅要求每一区域内的脑磁源与其它区域内的源在统计上互相独立。而区域内的源是允许互相相关的。与前两种方法相比，新方法进一步放松了对脑磁源的要求，因此有更广泛的适用性。本文详细推导并论证该新方法并讨论它对磁场的源的独立性的要求。本文所述新方法也适用对脑电图ＥＥＧ源的定位计算。     

大脑前动脉和中动脉水平段的立体定位及其临床意义

在100套正常成人脑血管造影正、侧位 X 线片上,测量了颈内动脉分杈点和大脑前、中动脉由水平位转向上的转角点在立体坐标中的位置。该坐标的原点位于外耳门前上缘,向前至眶下缘最低点的连线为 x 轴;向上的垂线为 y 轴:伸向内侧垂线为 z 轴。在 xoy 平面上可确定大脑前、中动脉在颅侧面投影位置,在 z 轴上的数值可确定它们在颅侧面的深度。     

肠道沙门菌双相亚利桑那亚种的一个新血清型17∶z_(52)∶e,n,x,z_(15)在我国发现

沙门菌是人和动物的重要病原菌,沙门菌历来受到世界各国重视。1999年夏天从南昌市农贸市场活杀眼镜蛇肠内容物分离到 1 株沙门菌,编号为 S9948。标准菌株 50059 S kirkee (17∶b∶1, 2),50174 SⅡ tulear (6,8∶a∶z52 ), 50016 Sabortusequi (4,12∶-∶e, n, x, z16, z19 ),50715 S chester (4, 5, 12∶e, h∶e, n, x,z17, z19 ), 50768 SⅡ daressalaam (1, 9,12∶lw∶e, n, x, z16, z18), 50009 S sandiego(4, 5, 12∶e, h∶e, n, z15, z17, z19 ),50064 S urbana (30∶b∶e, n, x, z16)来自中国药品生物制品检定所。…     

A system for intravascular,radially orientation-independent electromagnetic flow- and diameter-sensing

Summary The difficulty of optimally orienting an intravascular loop probe of an extracorporeal field electromagnetic flow meter is circumvented by uniting 2 mutually perpendicular loop sensors into a single flow-diameter probe. When one of the loops is unfavorably oriented in the magnetic field, the orientations of the other loop is more favorable. The most unfavorable case is a 45° angle between the magnetic field and the planes of the loops, when the signal drops to 70.7% of the optimal value. By taking the square root of the sum of the squares of the 2 loop transducer signals, one obtains an output for flow and diameter measurements which is independent of the probe orientation. This operation can be accomplished electronically.     

Volumetric characterization of the Aurora magnetic tracker system for image-guided transorbital endoscopic procedures

In some medical procedures, it is difficult or impossible to maintain a line of sight for a guidance system. For such applications, people have begun to use electromagnetic trackers. Before a localizer can be effectively used for an image-guided procedure, a characterization of the localizer is required. The purpose of this work is to perform a volumetric characterization of the fiducial localization error (FLE) in the working volume of the Aurora magnetic tracker by sampling the magnetic field using a tomographic grid. Since the Aurora magnetic tracker will be used for image-guided transorbital procedures we chose a working volume that was close to the average size of the human head. A Plexiglass grid phantom was constructed and used for the characterization of the Aurora magnetic tracker. A volumetric map of the magnetic space was performed by moving the flat Plexiglass phantom up in increments of 38.4 mm from 9.6 mm to 201.6 mm. The relative spatial and the random FLE were then calculated. Since the target of our endoscopic guidance is the orbital space behind the optic nerve, the maximum distance between the field generator and the sensor was calculated depending on the placement of the field generator from the skull. For the different field generator placements we found the average random FLE to be less than 0.06 mm for the 6D probe and 0.2 mm for the 5D probe. We also observed an average relative spatial FLE of less than 0.7 mm for the 6D probe and 1.3 mm for the 5D probe. We observed that the error increased as the distance between the field generator and the sensor increased. We also observed a minimum error occurring between 48 mm and 86 mm from the base of the tracker.     

A novel method for real-time magnetic marker monitoring in the gastrointestinal tract

In internal medicine, a simple method for the functional examination of the gastrointestinal tract without the risk of radiation exposure is required. We describe a novel principle based on the monitoring of magnetic markers which meets these demands. Our method employs a special permanent magnet which is repeatedly aligned by a vertically oriented pulsed magnetic field. Due to this alignment, the marker position can be derived from the stray field components measured by commercial field sensors. Our method was evaluated by means of a 3D intestinal phantom. The monitoring procedure yielded the time course of the marker position as a 3D plot either in real-time or as a time-lapse movie. The spatial resolution, expressed by the mean square deviation, was better than 10 mm and is thus sufficiently high to distinguish between adjacent loops of the gut. The temporal resolution, i.e. the minimum time between two successive measurements, was about 1 s. The presented method has very moderate technical demands and allows us to monitor magnetic markers in real-time. The technique may be useful with respect to functional examination of the gastrointestinal tract. In pharmaceutical research, our method offers the opportunity for remote drug release at any position of the gut.     

Comparison of linear accelerations from three measurement systems during "reach & grasp"

Given the increased use of accelerometers in movement analysis, validation of such inertial sensors against conventional 3D camera systems and performance comparisons of different sensors have become important topics in biomechanics. This paper evaluates and compares linear acceleration trajectories obtained from two different 3D accelerometers and derived from Vicon position data for an upper limb "reach & grasp" task. Overall, good correspondence between the three measurement systems was obtained. Sources of error are discussed.     

Ambulatory human motion tracking by fusion of inertial and magnetic sensing with adaptive actuation

Over the last years, inertial sensing has proven to be a suitable ambulatory alternative to traditional human motion tracking based on optical position measurement systems, which are generally restricted to a laboratory environment. Besides many advantages, a major drawback is the inherent drift caused by integration of acceleration and angular velocity to obtain position and orientation. In addition, inertial sensing cannot be used to estimate relative positions and orientations of sensors with respect to each other. In order to overcome these drawbacks, this study presents an Extended Kalman Filter for fusion of inertial and magnetic sensing that is used to estimate relative positions and orientations. In between magnetic updates, change of position and orientation are estimated using inertial sensors. The system decides to perform a magnetic update only if the estimated uncertainty associated with the relative position and orientation exceeds a predefined threshold. The filter is able to provide a stable and accurate estimation of relative position and orientation for several types of movements, as indicated by the average rms error being 0.033 m for the position and 3.6 degrees for the orientation.     

An augmented reality simulator for ultrasound guided needle placement training

Details are presented of a low cost augmented-reality system for the simulation of ultrasound guided needle insertion procedures (tissue biopsy, abscess drainage, nephrostomy etc.) for interventional radiology education and training. The system comprises physical elements; a mannequin, a mock ultrasound probe and a needle, and software elements; generating virtual ultrasound anatomy and allowing data collection. These two elements are linked by a pair of magnetic 3D position sensors. Virtual anatomic images are generated based on anatomic data derived from full body CT scans of live humans. Details of the novel aspects of this system are presented including; image generation, registration and calibration.     

Cardiac anatomy revisited

In tomorrow's world of clinical medicine, students will increasingly be confronted by anatomic displays reconstructed from tomographically derived images. These images all display the structure of the various organs in anatomical orientation, this being determined in time-honoured fashion by describing the individual in the 'anatomical position', standing upright and facing the observer. It follows from this approach that all adjectives used to describe the organs should be related to the three orthogonal planes of the body. Unfortunately, at present this convention is not followed for the heart, even though most students are taught that the so-called 'right chambers' are, in reality, in front of their 'left' counterparts. Rigorous analysis of the tomographic images already available, along with comparison with dissected hearts displayed in attitudinally correct orientation, calls into question this continuing tendency to describe the heart in terms of its own orthogonal axes, but with the organ positioned on its apex, so that the chambers can artefactually be visualized with the right atrium and right ventricle in right-sided position. Although adequate for describing functional aspects, such as 'right-to-left' shunting across intracardiac communications, this convention falls short when used to describe the position of the artery that supplies the diaphragmatic surface of the heart. Currently known as the 'posterior descending artery', in reality it is positioned inferiorly, and its blockage produces inferior myocardial infarction. In this review, we extend the concept of describing cardiac structure in attitudinally correct orientation, showing also how access to tomographic images clarifies many aspects of cardiac structure previously considered mysterious and arcane. We use images prepared using new techniques such as magnetic resonance imaging and computerized tomography, and compare them with dissection of the heart made in time-honoured fashion, along with cartoons to illustrate contentious topics. We argue that there is much to gain by describing the components of the heart as seen in the anatomical position, along with all other organs and structures in the body. We recognize, nonetheless, that such changes will take many years to be put into practice, if at all.     

Measurement of electric fields induced in a human subject due to natural movements in static magnetic fields or exposure to alternating magnetic field gradients

A dual dipole electric field probe has been used to measure surface electric fields in vivo on a human subject over a frequency range of 0.1-800 Hz. The low-frequency electric fields were induced by natural body movements such as walking and turning in the fringe magnetic fields of a 3 T magnetic resonance whole-body scanner. The rate-of-change of magnetic field (dB/dt) was also recorded simultaneously by using three orthogonal search coils positioned near to the location of the electric field probe. Rates-of-change of magnetic field for natural body rotations were found to exceed 1 T s(-1) near the end of the magnet bore. Typical electric fields measured on the upper abdomen, head and across the tongue for 1 T s(-1) rate of change of magnetic field were 0.15+/-0.02, 0.077+/-0.003 and 0.015+/-0.002 V m(-1) respectively. Electric fields on the abdomen and chest were measured during an echo-planar sequence with the subject positioned within the scanner. With the scanner rate-of-change of gradient set to 10 T m(-1) s(-1) the measured rate-of-change of magnetic field was 2.2+/-0.1 T s(-1) and the peak electric field was 0.30+/-0.01 V m(-1) on the chest. The values of induced electric field can be related to dB/dt by a 'geometry factor' for a given subject and sensor position. Typical values of this factor for the abdomen or chest (for measured surface electric fields) lie in the range of 0.10-0.18 m. The measured values of electric field are consistent with currently available numerical modelling results for movement in static magnetic fields and exposure to switched magnetic field gradients.     

Three-dimensional orientation tuning in macaque area V4

Tuning for the orientation of elongated, linear image elements (edges, bars, gratings), first discovered by Hubel and Wiesel, is considered a key feature of visual processing in the brain. It has been studied extensively in two dimensions (2D) using frontoparallel stimuli, but in real life most lines, edges and contours are slanted with respect to the viewer. Here we report that neurons in macaque area V4, an intermediate stage in the ventral (object-related) pathway of visual cortex, were tuned for 3D orientation--that is,for specific slants as well as for 2D orientation. The tuning for 3D orientation was consistent across depth position (binocular disparity) and position within the 2D classical receptive field. The existence of 3D orientation signals in the ventral pathway suggests that the brain may use such information to interpret 3D shape.     

Noncommutative control in the rotational vestibuloocular reflex

To investigate the role of noncommutative computations in the oculomotor system, three-dimensional (3D) eye movements were measured in seven healthy subjects using a memory-contingent vestibulooculomotor paradigm. Subjects had to fixate a luminous point target that appeared briefly at an eccentricity of 20 degrees in one of four diagonal directions in otherwise complete darkness. After a fixation period of approximately 1 s, the subject was moved through a sequence of two rotations about mutually orthogonal axes in one of two orders (30 degrees yaw followed by 30 degrees pitch and vice versa in upright and 30 degrees yaw followed by 20 degrees roll and vice versa in both upright and supine orientations). We found that the change in ocular torsion induced by consecutive rotations about the yaw and the pitch axis depended on the order of rotations as predicted by 3D rotation kinematics. Similarly, after rotations about the yaw and roll axis, torsion depended on the order of rotations but now due to the change in final head orientation relative to gravity. Quantitative analyses of these ocular responses revealed that the rotational vestibuloocular reflexes (VORs) in far vision closely matched the predictions of 3D rotation kinematics. We conclude that the brain uses an optimal VOR strategy with the restriction of a reduced torsional position gain. This restriction implies a limited oculomotor range in torsion and systematic tilts of the angular eye velocity as a function of gaze direction.