Volume 17, Issue 5

Guidance systems designed for neurosurgery, hip surgery, and spine surgery, and for approaches to other anatomy that is relatively rigid can use rigid-body transformations to accomplish image registration. These systems often rely on point-based registration to determine the transformation, and many such systems use attached fiducial markers to establish accurate fiducial points for the registration, the points being established by some fiducial localization process. Accuracy is important to these systems, as is knowledge of the level of that accuracy. An advantage of marker-based systems, particularly those in which the markers are bone-implanted, is that registration error depends only on the fiducial localization error (FLE) and is thus to a large extent independent of the particular object being registered. Thus, it should be possible to predict the clinical accuracy of marker-based systems on the basis of experimental measurements made with phantoms or previous patients. This paper presents two new expressions for estimating registration accuracy of such systems and points out a danger in using a traditional measure of registration accuracy. The new expressions represent fundamental theoretical results with regard to the relationship between localization error and registration error in rigid-body, point-based registration. Rigid-body, point-based registration is achieved by finding the rigid transformation that minimizes "fiducial registration error" (FRE), which is the root mean square distance between homologous fiducials after registration. Closed form solutions have been known since 1966. The expected value (FRE/sup 2/) depends on the number N of fiducials and expected squared value of FLE, (FLE/sup 2/), but in 1979 it was shown that (FRE/sup 2/) is approximately independent of the fiducial configuration C. The importance of this surprising result seems not yet to have been appreciated by the registration community: Poor registrations caused by poor fiducial configurations may appear to be good due to a small FRE value. A more critical and direct measure of registration error is the "target registration error" (TRE), which is the distance between homologous points other than the centroids of fiducials. Efforts to characterize its behavior have been made since 1989. Published numerical simulations have shown that (TRE/sup 2/) is roughly proportional to (FLE/sup 2/)/N and, unlike (FRE/sup 2/), does depend in some way on C. Thus, FRE, which is often used as feedback to the surgeon using a point-based guidance system, is in fact an unreliable indicator of registration-accuracy. In this work the authors derive approximate expressions for (TRE/sup 2/), and for the expected squared alignment error of an individual fiducial. They validate both approximations through numerical simulations. The former expression can be used to provide reliable feedback to the surgeon during surgery and to guide the placement of markers before surgery, or at least to warn the surgeon of potentially dangerous fiducial placements; the latter expression leads to a surprising conclusion: Expected registration accuracy (TRE) is worst near the fiducials that are most closely aligned! This revelation should be of particular concern to surgeons who may at present be relying on fiducial alignment as an indicator of the accuracy of their point-based guidance systems.

设计用于神经外科、髋关节手术和脊柱手术以及其它相对刚体解剖结构的引导系统可以采用刚体变换实现图像配准。这些系统通常依赖点配准来确定变换，许多此类系统使用附着的基准标记来建立精确的配准基准点，这些点通过某种基准定位过程确定。准确性对这些系统至关重要，同样重要的是对准确性水平的了解。基于标记的系统（特别是那些标记植入骨中的系统）的一个优势是配准误差仅取决于基准定位误差（FLE），因此在很大程度上独立于被配准的特定对象。因此，应该能够根据使用模体或既往患者进行的实验测量来预测基于标记的系统的临床准确性。本文提出了两个新表达式来估计此类系统的配准准确性，并指出了使用传统配准准确性度量的危险性。新表达式代表了关于刚体点配准中定位误差与配准误差之间关系的基本理论结果。刚体点配准通过找到使“基准配准误差”（FRE）最小化的刚体变换来实现，该误差是配准后对应基准点之间的均方根距离。闭式解自1966年以来已知。期望值（FRE/sup 2/）取决于基准数量N和FLE的期望平方值（FLE/sup 2/），但在1979年发现（FRE/sup 2/）近似独立于基准配置C。这个令人惊讶的结果的重要性似乎尚未被配准学界充分认识到：由不良基准配置导致的差配准可能因为小的FRE值而显得良好。一个更关键和直接的配准误差度量是“目标配准误差”（TRE），即非基准质心的对应点之间的距离。自1989年以来一直努力描述其行为。已发表的数值模拟表明，（TRE/sup 2/）大致与（FLE/sup 2/）/N成正比，并且与（FRE/sup 2/）不同，它在某种程度上依赖于C。因此，经常用作基于点的引导系统外科医生反馈的FRE实际上是一个不可靠的配准准确性指标。在这项工作中，作者推导了（TRE/sup 2/）和单个基准的预期平方对准误差的近似表达式。他们通过数值模拟验证了这两个近似。前者表达式可用于在手术期间向外科医生提供可靠的反馈，并在术前指导标记放置，或至少警告外科医生潜在危险的基准放置；后者表达式得出一个令人惊讶的结论：预期配准准确性（TRE）在最接近对准的基准附近最差！这一发现对于目前可能依赖基准对准作为基于点的引导系统准确性指标的外科医生尤其值得关注。

All image-guided neurosurgical systems that the authors are aware of assume that the head and its contents behave as a rigid body. It is important to measure intraoperative brain deformation (brain shift) to provide some indication of the application accuracy of image-guided surgical systems, and also to provide data to develop and validate nonrigid registration algorithms to correct for such defo...

所有作者所知的图像引导神经外科系统都假设头部及其内容物表现为刚性体。测量术中脑变形（脑移位）对于提供图像引导手术系统的应用准确性指示以及提供数据以开发和验证用于校正此类变形的非刚性配准算法非常重要。

A preoperative planning system for oral implant surgery was developed which takes as input computed tomographies (CT's) of the jaws. Two-dimensional (2-D) reslices of these axial CT slices orthogonal to a curve following the jaw arch are computed and shown together with three-dimensional (3-D) surface rendered models of the bone and computer-aided design (CAD)-like implant models. A technique is d...

开发了一种用于口腔种植手术的术前规划系统，该系统以颌骨的计算机断层扫描（CT）作为输入。计算这些轴向CT切片中垂直于跟随牙弓曲线的二维（2-D）重切片，并与骨的三维（3-D）表面渲染模型和类似计算机辅助设计（CAD）的种植体模型一起显示。提出了一种技术...

This paper describes augmented reality visualization for the guidance of breast-conservative cancer surgery using ultrasonic images acquired in the operating room just before surgical resection. By combining an optical three-dimensional (3-D) position sensor, the position and orientation of each ultrasonic cross section are precisely measured to reconstruct geometrically accurate 3-D tumor models ...

本文描述了使用在手术切除前于手术室采集的超声图像进行乳腺癌保乳手术引导的增强现实可视化。通过结合光学三维（3-D）位置传感器，精确测量每个超声截面的位置和方向，以重建几何精确的3-D肿瘤模型...

Most previously reported registration techniques that align three-dimensional image volumes by matching geometrical features such as points or surfaces use a single type of feature. The authors recently reported a hybrid registration technique that uses a weighted combination of multiple geometrical feature shapes. In this study they use the weighted geometrical feature (WGF) algorithm to register...

大多数先前报道的通过匹配点或表面等几何特征来对齐三维图像体积的配准技术使用单一类型的特征。作者最近报道了一种混合配准技术，该技术使用多种几何特征形状的加权组合。在本研究中，他们使用加权几何特征（WGF）算法进行配准...

Describes new methods for rigid registration of a preoperative computed tomography (CT)-scan image to a set of intraoperative X-ray fluoroscopic images, for guiding a surgical robot to its trajectory planned from CT. Our goal is to perform the registration, i.e., compute a rotation and translation of one data set with respect to the other to within a prescribed accuracy, based upon bony anatomy on...

描述了新的方法，用于将术前计算机断层扫描（CT）图像与一组术中X射线荧光透视图像进行刚性配准，以引导手术机器人沿CT规划的轨迹运动。我们的目标是基于骨性解剖，在规定的精度内进行配准，即计算一个数据集相对于另一个数据集的旋转和平移。

The purpose of this paper was to assess to what extent an optical tracking system (OTS) used for position determination in computer-aided surgery (CAS) can be enhanced by combining it with a direct current (DC) driven electromagnetic tracking system (EMTS). The main advantage of the EMTS is the fact that it is not dependent on a free line-of-sight. Unfortunately, the accuracy of the EMTS is highly...

本文旨在评估在计算机辅助手术（CAS）中用于定位的光学追踪系统（OTS）与直流（DC）驱动电磁追踪系统（EMTS）结合后，其性能提升的程度。EMTS的主要优势在于它不依赖于无障碍视线。不幸的是，EMTS的准确性高度...

This paper describes research work motivated by an innovative medical application: computer-assisted transbronchial biopsy. This project involves the registration, with no external localization device, of a preoperative three-dimensional (3-D) computed tomography (CT) scan of the thoracic cavity (showing a tumor that requires a needle biopsy), and an intraoperative endoscopic two-dimensional (2-D)...

本文描述了由一项创新医学应用（计算机辅助经支气管活检）所驱动的研究工作。该项目涉及在无外部定位设备的情况下，将术前三维胸部CT扫描（显示需要针吸活检的肿瘤）与术中二维内镜图像进行配准...

Many critical functionally distinct subcortical structures are not distinguishable on anatomical magnetic resonance imaging (MRI) scans. In order to provide the neurosurgeon with this missing information, a deformable volumetric atlas of the basal ganglia and thalamus has been created from the Schaltenbrand and Wahren atlas of cryogenic slices. The volumetric atlas can be automatically deformed to...

许多关键的功能性皮质下结构在解剖磁共振成像（MRI）扫描中无法区分。为了向神经外科医生提供这些缺失信息，我们根据Schaltenbrand和Wahren的冷冻切片图谱创建了一个可变形的丘脑和基底节体积图谱。该体积图谱可自动变形至…

This paper presents a method designed to register preoperative computed tomography (CT) images to vertebral surface points acquired intraoperatively from ultrasound (US) images or via a tracked probe. It also presents a comparison of the registration accuracy achievable with surface points acquired from the entire posterior surface of the vertebra to the accuracy achievable with points acquired on...

本文提出了一种方法，旨在将术前计算机断层扫描（CT）图像与术中从超声（US）图像或通过跟踪探针获取的椎体表面点进行配准。本文还比较了从整个椎体后表面获取的表面点所能达到的配准精度与从...获取的点所能达到的精度。

This paper addresses one of the major problems in interventional magnetic resonance imaging (MRI): the visualization of interventional devices. For visualization locally induced magnetic fields are used, which disturb the homogeneity of the main magnetic field of the MR scanner. This results in signal loss in the vicinity of the device due to intravoxel dephasing, and leads to a disturbance of the...

本文讨论了介入性磁共振成像（MRI）中的一个主要问题：介入设备的可视化。可视化利用局部感应磁场，该磁场会干扰MR扫描器主磁场的均匀性。这导致由于体素内去相位而在设备附近出现信号丢失，并引起……

New biopsy techniques, increased life expectancy, and prostate-specific antigen (PSA) screening have contributed to an increase in the reported incidence of prostate cancer. Among several treatment options available to the patients, transperineal prostate brachytherapy has emerged as a medically successful, cost-effective outpatient procedure for treating localized prostate cancer. Transperineal p...

新的活检技术、预期寿命的增加以及前列腺特异性抗原（PSA）筛查使得报道的前列腺癌发病率有所上升。在可用的多种治疗方案中，经会阴前列腺近距离治疗已成为治疗局限性前列腺癌的一种医学上成功、成本效益高的门诊手术。经会阴前列腺...

Magnetic resonance imaging (MRI) offers potential advantages over conventional X-ray techniques for guiding and evaluating vascular interventions. Image guidance of such interventions via passive catheter tracking requires real-time image processing. Commercially available MR scanners currently do not provide this functionality. This paper describes an image processing environment that allows near...

磁共振成像（MRI）在引导和评估血管介入方面比传统X射线技术具有潜在优势。通过被动导管追踪进行此类介入的图像引导需要实时图像处理。商用MR扫描仪目前不提供此功能。本文描述了一种能够实现近实时图像处理的图像处理环境。

Application of ionizing radiation to prevent restenosis in atherosclerotic vessels treated by balloon angioplasty is a new treatment under investigation in interventional cardiology and radiology. There is variability in dose prescription, and both /spl gamma/- and /spl beta/-emitters are used, leading to a wide range of dose distribution over the arterial vessel wall. The authors present a new mo...

应用电离辐射预防球囊血管成形术治疗的动脉粥样硬化血管再狭窄是一个新治疗方法，正在介入心脏病学和放射学中研究。剂量处方的变异性以及使用γ和β放射源导致动脉血管壁上的剂量分布范围广泛。作者提出了一种新的方法...

Finite-sized high-performance planar magnetic field gradient coils in today's open configuration magnetic resonance imaging (MRI) systems have always been desirable for ever demanding imaging applications. The authors present a Lagrange multiplier technique for designing a minimum-energy gradient coil under a finite-size planar geometry constraint in addition to a set of magnetic field constraints...

在当今开放式配置的磁共振成像系统中，有限尺寸的高性能平面磁场梯度线圈一直备受追求，以满足日益苛刻的成像应用需求。作者提出了一种拉格朗日乘子技术，用于在有限尺寸平面几何约束以及一组磁场约束条件下设计最小能量梯度线圈。

X-ray computed tomography fluoroscopy (CTF) enables image guidance of interventions, synchronization of scanning with contrast bolus arrival, and motion analysis. However, filtered backprojection (FB), the current method for CTF image reconstruction, is subject to motion and metal artifacts from implants, needles, or other surgical instruments. Reduced target lesion conspicuity may result from inc...

X射线计算机断层透视（CTF）可实现介入操作的影像引导、扫描与对比剂团注到达的同步以及运动分析。然而，当前用于CTF图像重建的滤波反投影（FB）方法易受运动以及来自植入物、针头或其他手术器械的金属伪影影响。目标病变的可见度降低可能由于不完整......

Spatial fidelity is a paramount issue in image guided neurosurgery. Until recently, three-dimensional computed tomography (3D CT) has been the primary modality because it provides fast volume capture with pixel level (1 mm) accuracy. While three-dimensional magnetic resonance (3D MR) images provide superior anatomic information, published image capture protocols are time consuming and result in sc...

空间保真度是图像引导神经外科中的一个首要问题。直到最近，三维计算机断层扫描（3D CT）一直是主要模态，因为它能够提供像素级（1毫米）精度的快速体积采集。虽然三维磁共振（3D MR）图像提供了优越的解剖信息，但已发表的图像采集协议耗时且导致...

This work describes a newly developed magnetic resonance imaging (MRI) data-acquisition strategy which replaces the standard Fourier phase-encoding with the spatially localized coefficients of wavelet-encoding and offers a new technique for image guidance when combined with a dynamic tracking algorithm. By using this new technique, only a specific fraction of the entire raw data set needs to be up...

本研究描述了一种新开发的磁共振成像（MRI）数据采集策略，该策略用空间局部化的小波编码系数替代标准的傅里叶相位编码，并与动态追踪算法相结合，为图像引导提供了一种新技术。利用这种新技术，只需更新整个原始数据集中的特定部分...

Coil embolization is a safe treatment for cerebral aneurysms only if the width of the neck in relation to the fundus of the aneurysm is small. Therefore, accurate visualization of the aneurysmal neck is required both in the diagnostic process and during the intervention. Conventional digital subtraction angiography (DSA) is still the preferred modality for the examination of cerebrovascular abnorm...

线圈栓塞术是治疗脑动脉瘤的安全方法，仅当动脉瘤颈相对于动脉瘤底部的宽度较小时。因此，在诊断过程中和介入过程中都需要准确显示动脉瘤颈。传统的数字减影血管造影（DSA）仍然是检查脑血管异常的首选方式...

Interventional magnetic resonance imaging (MRI) can be defined as the use of MR images for guiding and monitoring interventional procedures (e.g., biopsy, drainage) or minimally invasive therapy (e.g., thermal ablation). This work describes the development of a prototype graphical user interface and the appropriate software methods to accurately overlay a representation of a rigid interventional d...

介入性磁共振成像（MRI）可以定义为使用MR图像来指导和监测介入手术（例如活检、引流）或微创治疗（例如热消融）。本工作描述了一个原型图形用户界面的开发以及适当的软件方法，以准确叠加刚性介入...

A new template technique has been developed for implanting hyperthermia catheters in the treatment of brain tumors. The technique utilizes an imaging template and a drill template which can be rigidly secured to the head with three skull screws. The anatomic and vascular information needed for hyperthermia treatment planning may be assessed with three-dimensional magnetic resonance (MR) imaging an...

开发了一种新的模板技术，用于在脑肿瘤治疗中植入热疗导管。该技术利用成像模板和钻孔模板，可通过三颗颅骨螺钉牢固固定在头部。热疗治疗规划所需的解剖和血管信息可通过三维磁共振成像获取……