神经导航注册准确性的实验研究

目的研究神经导航注册准确性的影响因素,为临床应用提供理论指导。方法自制神经导航定位模型,分别进行CT和MRI扫描。使用不同数量、不同位置的注册坐标进行注册。结果CT组:4个坐标组的平均坐标误差(MFE)与其他3组有显著性差别,各组间预期准确性(PA)均有显著性差别。MRI组:各组间MFE均有显著性差别,除了4个坐标组的PA与6个坐标组有显著性差别外,其他各组无显著性差别。同样使用4个注册坐标,分散排列者的准确性高于平面排列者,有显著性差别。结论自制的神经导航定位模型制作简便、准确性高。随着注册坐标的增加,注册准确性和预期准确性均提高。使用CT导航,最少使用6个注册坐标;使用MRI导航,应使用10个注册坐标。注册坐标应尽量分散排列。     

Validation of CT‐MRI fusion for intraoperative assessment of stereotactic accuracy in DBS surgery

Deep brain stimulation is typically performed with intraoperative microelectrode recording and test stimulation for target confirmation. Recent studies have shown accurate, clinically efficacious results after lead placement without microelectrode recording or test stimulation, using interventional magnetic resonance imaging (MRI) or intraoperative computed tomography (CT; iCT) for verification of accuracy. The latter relies on CT–MRI fusion. To validate CT–MRI fusion in this setting, we compared stereotactic coordinates determined intraoperatively using CT–MRI fusion with those obtained on postoperative MRI. Deep brain stimulation electrodes were implanted with patients under general anesthesia. Direct targeting was performed on preoperative MRI, which was merged with preimplantation iCT images for stereotactic registration and postimplantation iCT images for accuracy confirmation. Magnetic resonance imaging was obtained 6 weeks postoperatively for comparison. Postoperative MRI was obtained for 48 patients, with 94 leads placed over a 1‐year period. Vector error of the targeted contact relative to the initial plan was 1.1 ± 0.7 mm on iCT and 1.6 ± 0.7 mm on postoperative MRI. Variance comparisons (F‐tests) showed that the discrepancy between iCT‐ and postoperative MRI‐determined errors was attributable to measurement error on postoperative MRI, as detected in inter‐rater reliability testing. In multivariate analysis, improved lead placement accuracy was associated with frame‐based stereotaxy with the head of the bed at 0° compared with frameless stereotaxy with the head of the bed at 30° (P = 0.037). Intraoperative CT can be used to determine lead placement accuracy in deep brain stimulation surgery. The discrepancy between coordinates determined intraoperatively by CT–MRI fusion and postoperatively by MRI can be accounted for by inherent measurement error. © 2014 International Parkinson and Movement Disorder Society     

导航辅助内镜下经蝶窦垂体外科的解剖学研究

目的评价导航系统在内镜下经蝶窦垂体手术中的应用。方法在20例尸头标本上模拟内镜下经蝶手术,其中采用GE-Insta Trak 3500电磁导航辅助和无导航辅助各10例。对重要解剖标志及结构变异进行测量与统计,对导航系统精确性进行评估,对导航及非导航辅助下手术的效率与安全性进行比较。结果 GE电磁导航系统误差为(0.28±0.06)mm,实际操作误差为(1.5±0.5)mm。导航系统安装启动平均时间为(11.9±2.0)min。在无解剖变异时导航与非导航辅助下手术时间无统计学差异;若存在解剖变异,前者手术用时较后者明显缩短。结论导航系统辅助内镜经蝶窦手术,在解剖变异、多次手术等解剖关系不明确的病例中,可起到迅速、精确的定位作用,使手术更加安全、高效。     

Robust multimodality registration for brain mapping

We present a robust intrasubject registration method for the synergistic use of multiple neuroimaging modalities, with applications to magnetic resonance imaging (MRI), functional MRI, perfusion MRI, MR spectroscopy, and single-photon emission computed tomography (SPECT). This method allows user-friendly processing of difficult examinations (low spatial resolution, advanced pathology, motion during acquisition, and large areas of focal activation). Registration of three-dimensional (3D) brain scans is initially estimated by first-order moment matching, followed by iterative anisotrophic chamfer matching of brain surfaces. Automatic brain surface extraction is performed in all imaging modalities. A new generalized distance definition and new specific methodologies allow registration of scans that cover only a limited range of brain surface. A new semiautomated supervision scheme allows fast and intuitive corrections of possible false automatic registration results. The accuracy of the MRI/SPECT anatomical-functional correspondence obtained was evaluated using simulations and two difficult clinical populations (tumors and degenerative brain disorders). The average discrimination capability of SPECT (12.4 mm in-plane resolution, 20 mm slice thickness) was found to be better than 5 mm after registration with MRI (5 mm slice thickness). Registration accuracy was always better than imaging resolution. Complete 3D MRI and SPECT registration time ranged between 6–11 min, in which surface matching represented 2–3 min. No registration failure occurred. In conclusion, the application of several new image processing techniques allowed efficient and robust registration. Hum. Brain Mapping 5:3–17, 1997. © 1997 Wiley-Liss, Inc.     

三维虚拟图像导航技术在脊柱椎弓根螺钉固定中的应用☆

背景：近年来经椎弓根螺钉固定技术显著提高了脊柱固定强度和融合效率,但是椎弓根螺钉置入位置不佳可能损害脊髓和神经引起严重并发症。 目的：评估置入前CT扫描三维虚拟图像导航技术在脊柱椎弓根螺钉固定中的应用价值。 设计、时间及地点：前瞻性、随机对照观察,于2006-01/2008-12在中国医学科学院北京协和医院骨科完成。 对象：纳入因脊柱疾病行椎弓根螺钉固定的患者95例,导航组45例,常规组50例。 方法：将95例患者按随机数字表法分为2组,导航组术中在计算机导航技术辅助下置入椎弓根螺钉,常规组采用传统的解剖标志法结合术中透视定位置入椎弓根螺钉。 主要观察指标：比较2组间螺钉钉道准备时间、螺钉位置优良率及螺钉置入后并发症的发生率。 结果：导航组中36例患者共置入椎弓根螺钉206枚,优良率96.1%;有9例患者因故未能行导航。常规组50例患者共置入椎弓根螺钉285枚,优良率100.0%,无位置差的螺钉。2组患者的螺钉位置优良率差异无显著性意义(P > 0.05)。导航组的钉道准备时间显著长于常规组[(360±22),(56±8) s,P < 0.01]。2组患者螺钉置入后均无并发症发生。 结论：与传统解剖标志定位法相比,应用置入前CT扫描三维虚拟图像导航技术置入椎弓根螺钉的精度无明显差异,且延长了手术时间,其在脊柱椎弓根螺钉固定中的应用价值有限。     

Computer-assisted stereotactic neurosurgery with framework neurosurgery navigation

OBJECTIVE: To evaluate mechanical registration in a stereotactic system with framework neurosurgery navigation, setting scalp markers as the mutual frame of reference. MATERIALS AND METHODS: The system can automatically convert the coordinates of the stereotactic device and CT or MRI images, and realize computer-assisted neurosurgery by the stereotactic system (framework neurosurgery navigation). We set targets in the skull; seven patients were operated on by open-skull stereotactic neurosurgery for clinical trials. Three cases were operated on by this method; the other four cases were treated by this method and the ASA620S operation plan system at the same time as a comparison. RESULTS: The targets were accurately located in seven patients. Four patients underwent the two different localization methods; the probe directed equally accurately (vector error: 3.96+/-1.90 vs. 3.26+/-1.22, P=0.06>0.05, paired t-test). All surgical procedures were successful. CONCLUSIONS: Framework neurosurgery navigation has equal localization accuracy compared with the traditional stereotactic device. Framework neurosurgery navigation does not require installation of a stereotactic framework before imaging or narcotic intubation; this differs from the traditional stereotactic technique. It can alleviate patient suffering, shorten preparation time, benefit anesthesia, and aid patient positioning during surgery.     

Accuracy of stereotaxic localisation using MRI and CT.

The accuracy of stereotaxic coordinates determined using the Leksell apparatus with CT and MRI was investigated using an Agar filled head phantom. Both imaging techniques were found to produce an accuracy of better than 2 mm with the exception of the Z coordinate as measured by CT (2.3 mm). This latter error is greater because of the 3 mm slice width used. Direct coronal views were used to determine Z more accurately using MRI. The measurement procedures are described and it is shown that the Leksell system of using orthogonal coordinates enables the scaling of images, which is particularly necessary with MRI, to be done easily.     

First case report using optical topographic-guided navigation in revision spinal fusion for calcified thoracic disk

Computer assisted navigation systems are frequently used in spine surgery to improve the accuracy of pedicle screw placement. The 7D Surgical System utilizes optical topographic imaging (OTI) with a camera positioned directly above the surgical field to perform rapid registration from a pre-operative CT scan onto anatomical landmarks with zero intra-operative radiation exposure. This current technology requires an open approach with well-exposed bony anatomy, raising concerns about using the 7D Surgical System in revision surgery, where typical anatomical landmarks may be altered, missing, or obscured by prior hardware. To overcome this, the 7D Surgical System is capable of registering off prior hardware. Here, we present the first published report of 7D Surgical System’s registration off prior hardware in a revision spinal fusion. The registration was accurate, and the workflow was easy and efficient with one registration required for 3 levels of instrumentation and discectomy/corpectomy. This demonstrates that the 7D Surgical System can be used in revision cases with altered, missing, or obscured anatomy.     

影像导航下经鼻内镜视神经减压术(附12例临床分析)

目的 探讨影像导航技术在经鼻内镜的视神经减压术中应用的有关问题.方法 回顾性分析本科自2005～2006年收治的视神经损伤性病变12例,均在影像导航下经鼻内镜行视神经减压手术.结果 影像导航术前准备时间(包括配准、头架定位、常规器械注册等)5～10min,平均7min.手术区域影像标志与实体解剖标志间的误差≤1.5m.4例术前无光感者术后2例有效,其余8例有残存光感者术后5例有效(视力提高1个级别以上).结论 影像导航系统与鼻内镜相结合下的视神经减压术,可以帮助术者在影像导航下准确定位视神经管,颈内动脉等重要标志,并可清晰显示其毗邻关系,可提高手术的精确性和安全性.尤其体现在局部解剖结构因外伤导致的毗邻关系改变的情况下行手术.     

An augmented reality system characterization of placement accuracy in neurosurgery

Computer assisted navigation (CAN) is a technology which has been available for commercial use in operating rooms for quite some time now. CAN relies on the information presented in patient imaging (usually CT or MRI images) and the surgical site. The method for registration between these two sets of data is crucial for safe image guided navigation during surgery. Although the existing technologies are extremely accurate, they still pose problems in the operating. Motivation for this study is to explore the possibility of using augmented reality (AR) to improve ease of use for surgical navigation and provide a system which complements the existing operating room workflow. As with all commercially available surgical navigation systems, registration accuracy is of utmost important to maintain patient safety. In this paper, we propose a novel method to quantify registration accuracy for augmented reality (AR) devices in neurosurgery.     

Electromagnetic Navigation Technology for More Precise Electrode Placement in the Foramen Ovale: A Technical Report

Introduction. Interventional pain management techniques require precise positioning of needles or electrodes, therefore fluoroscopic control is mandatory. This imaging technique does however not visualize soft tissues such as blood vessels. Moreover, patient and physician are exposed to a considerable dose of radiation. Computed tomography (CT)‐scans give a better view of soft tissues, but there use requires presence of a radiologist and has proven to be laborious and time consuming. Objectives. This study is to develop a technique using electromagnetic (EM) navigation as a guidance technique for interventional pain management, using CT and/or magnetic resonance (MRI) images uploaded on the navigation station. Methods. One of the best documented interventional procedures for the management of trigeminal neuralgia is percutaneous radiofrequency treatment of the Gasserian ganglion. EM navigation software for intracranial applications already exists. We developed a technique using a stylet with two magnetic coils suitable for EM navigation. The procedure is followed in real time on a computer screen where the patient's multislice CT‐scan images and three‐dimensional reconstruction of his face are uploaded. Virtual landmarks on the screen are matched with those on the patient's face, calculating the precision of the needle placement. Discussion. The experience with EM navigation acquired with the radiofrequency technique can be transferred to other interventional pain management techniques, for instance, for the placement of a neuromodulation electrode close to the Gasserian ganglion. Currently, research is ongoing to extend the software of the navigation station for spinal application, and to adapt neurostimulation hardware to the EM navigation technology. This technology will allow neuromodulation techniques to be performed without x‐ray exposure for the patient and the physician, and this with the precision of CT/MR imaging guidance.     

基于互信息的医学图像快速准确配准策略**★

对CT和MRI图像进行配准，利用主轴法配准速度快、鲁棒性较高、易实现的特点，计算图像的初始平移量和旋转量，对图像进行粗配准。以粗配准的结果作为新的浮动图像，在基于互信息方法的图像配准中，由于目标函数产生局部极值的原因，采用模拟退火-单纯形的混合优化算法，以互信息作为相似性测度迭代搜索，使互信息最大，从而实现最佳配准。结果表明，采用由粗到细的配准策略，配准精度高，并且混合优化算法克服了单一优化算法的速度慢、易陷入局部极值的缺点，并且不需要人为调整待配准图像的分辨率,自动化程度高,配准速度快,能够满足脑图谱开发过程中的多模图像配准要求。     

Co-registration of magnetoencephalography with magnetic resonance imaging using bite-bar-based fiducials and surface-matching.

OBJECTIVE: To introduce a new technique for co-registration of Magnetoencephalography (MEG) with magnetic resonance imaging (MRI). We compare the accuracy of a new bite-bar with fixed fiducials to a previous technique whereby fiducial coils were attached proximal to landmarks on the skull. METHODS: A bite-bar with fixed fiducial coils is used to determine the position of the head in the MEG co-ordinate system. Co-registration is performed by a surface-matching technique. The advantage of fixing the coils is that the co-ordinate system is not based upon arbitrary and operator dependent fiducial points that are attached to landmarks (e.g. nasion and the preauricular points), but rather on those that are permanently fixed in relation to the skull. RESULTS: As a consequence of minimizing coil movement during digitization, errors in localization of the coils are significantly reduced, as shown by a randomization test. Displacement of the bite-bar caused by removal and repositioning between MEG recordings is minimal ( approximately 0.5 mm), and dipole localization accuracy of a somatosensory mapping paradigm shows a repeatability of approximately 5 mm. The overall accuracy of the new procedure is greatly improved compared to the previous technique. CONCLUSIONS: The test-retest reliability and accuracy of target localization with the new design is superior to techniques that incorporate anatomical-based fiducial points or coils placed on the circumference of the head.     

Sensor-based neuronavigation: evaluation of a large continuous patient population

Objective

Navigation systems enable neurosurgeons to guide operations with imaging data. Sensor-based neuronavigation uses an electromagnetic field and sensors to measure the positions of the patient's brain anatomy and the surgical instruments. The aim of this investigation was to determine the accuracy level of sensor-based tracking in a large patient collection.

Methods

This study covers 250 patients operated upon during a continuous 5.5-year period. The patients had a wide range of indications and surgical procedures. The operations were performed with a direct current (DC) pulsed sensor-based electromagnetic navigation system. Four kinds of errors were measured: the fiducial registration error (FRE), the target registration error (TRE), brain shift, and the position error (PE). These errors were calculated for five subgroups of indications: target determination and trajectory guidance, functional navigation, skull base and neurocranium, determination of resection volume, and transnasal and transsphenoidal access.

Results

The overall mean FRE was 1.66 mm (±0.61 mm). The overall mean TREs were 1.33 mm (±0.51 mm) centroid and 1.59 mm (±0.57 mm) lesional. The overall mean brain shift for applicable cases was 1.61 mm (±1.14 mm). The overall mean PE was 0.92 mm (±0.54 mm).

Conclusions

By and large, modern sensor-based neuronavigation operates within an acceptable and commonplace degree of error. However, the neurosurgeon must remain critical in cases of small lesions, and must exert caution not to introduce further interference from metal objects or electromagnetic devices.     

FocusDET, A New Toolbox for SISCOM Analysis. Evaluation of the Registration Accuracy Using Monte Carlo Simulation

Subtraction of Ictal SPECT Co-registered to MRI (SISCOM) is an imaging technique used to localize the epileptogenic focus in patients with intractable partial epilepsy. The aim of this study was to determine the accuracy of registration algorithms involved in SISCOM analysis using FocusDET, a new user-friendly application. To this end, Monte Carlo simulation was employed to generate realistic SPECT studies. Simulated sinograms were reconstructed by using the Filtered BackProjection (FBP) algorithm and an Ordered Subsets Expectation Maximization (OSEM) reconstruction method that included compensation for all degradations. Registration errors in SPECT-SPECT and SPECT-MRI registration were evaluated by comparing the theoretical and actual transforms. Patient studies with well-localized epilepsy were also included in the registration assessment. Global registration errors including SPECT-SPECT and SPECT-MRI registration errors were less than 1.2 mm on average, exceeding the voxel size (3.32 mm) of SPECT studies in no case. Although images reconstructed using OSEM led to lower registration errors than images reconstructed with FBP, differences after using OSEM or FBP in reconstruction were less than 0.2 mm on average. This indicates that correction for degradations does not play a major role in the SISCOM process, thereby facilitating the application of the methodology in centers where OSEM is not implemented with correction of all degradations. These findings together with those obtained by clinicians from patients via MRI, interictal and ictal SPECT and video-EEG, show that FocusDET is a robust application for performing SISCOM analysis in clinical practice.     

Automated alignment of perioperative MRI scans: A technical note and application in pediatric epilepsy surgery

Conventional image registration utilizing brain voxel information may be erroneous in a neurosurgical setting due to pathology and surgery‐related anatomical distortions. We report a novel application of an automated image registration procedure based on skull segmentation for magnetic resonance imaging (MRI) scans acquired before, during and after surgery (i.e., perioperative). The procedure was implemented to assist analysis of intraoperative brain shift in 11 pediatric epilepsy surgery cases, each of whom had up to five consecutive perioperative MRI scans. The procedure consisted of the following steps: (1) Skull segmentation using tissue classification tools. (2) Estimation of rigid body transformation between image pairs using registration driven by the skull segmentation. (3) Composition of transformations to provide transformations between each scan and a common space. The procedure was validated using locations of three types of reference structural landmarks: the skull pin sites, the eye positions, and the scalp skin surface, detected using the peak intensity gradient. The mean target registration error (TRE) scores by skull pin sites and scalp skin rendering were around 1 mm and <1 mm, respectively. Validation by eye position demonstrated >1 mm TRE scores, suggesting it is not a reliable reference landmark in surgical scenarios. Comparable registration accuracy was achieved between opened and closed skull scan pairs and closed and closed skull scan pairs. Our procedure offers a reliable registration framework for processing intrasubject time series perioperative MRI data, with potential of improving intraoperative MRI‐based image guidance in neurosurgical practice. Hum Brain Mapp 37:3530–3543, 2016. © 2016 Wiley Periodicals, Inc.     

Application of PET-MRI registration techniques to cat brain imaging

In positron emission tomography (PET) studies of diseased animals, it is very useful to have accurate anatomical information as a reference. In human studies, anatomical information is usually obtained from magnetic resonance imaging (MRI) of the subject with retrospective registration of the subject's PET image to the MRI. A number of PET-MRI registration techniques are used for this purpose. However, the utility of these methods has not been tested for animals image registration. This paper studies the feasibility of applying two currently used human brain PET-MRI registration techniques to cat brain images. METHODS: Three cats were anesthetized with isoflurane gas, and PET images were acquired with H(2)(15)O, benzodiazepine receptor ligand 11C-flumazemil (FMZ), dopamine receptor ligand 11C-nemonapride (NEM) and fluorodeoxy glucose (18F-FDG). The four PET scans were acquired consecutively within the same day while the cat remained fixed in the scanner. We also obtained T1-weighted and T2-weighted MRI of the cats in a 4.7 T unit. The PET images were registered to MRI using two human brain registration techniques: a semi-automatic method (SAM), which is a two-step method based on the extraction of the midsagittal plane, and an automatic method (AMIR) method that minimizes PET pixel variance within spatially connected segments determined by MRI. RESULTS: T2-weighted MRI provided better structural information than T1 MRI. FMZ did, while FDG or H(2)O PET images did not, provide a structural outline of the brain. The FMZ PET image was registered to MRI satisfactorily using SAM. The striatum visualized in nemonapride PET image re-sliced with the same parameters matched the striatum identified in T2-weighted MRI. Registration by AMIR was successful by inspection for FMZ, FDG or H(2)O PET images in only one of the three cats. The registration error of SAM was estimated to be less than 2 mm or 2 degrees. CONCLUSION: A satisfactory registration of FMZ-PET to T2-weighted MRI of the cat brain was obtained by a two-step manual registration technique. This will enhance the usefulness of PET in the field of cerebral pathophysiology.     

Clinical application of neuro-navigation in a series of single burr-hole procedures

With recent developments in computer technology and the improvement of neuroimaging, modern optical neuro-navigation systems are increasingly being used in neurosurgery. In this study, we present our experience with 51 operations using a frameless optical navigation system in a variety of single burr-hole procedures. The procedures include neuroendoscopic surgery, frameless stereotactic biopsy, cyst aspiration and catheter placement. Both the VectorVision and the VectorVision(2) neuro-navigation systems (BrainLab AG, Munich, Germany) were used. The reliability and accuracy of the neuro-navigation system, postoperative complications and the clinical usefulness of image-guidance were analyzed. The navigation system worked properly in all 51 neurosurgical cases. Exact planning of the approach and determination of the ideal trajectory were possible in all cases. The mean registration error of the system, given as a computer-calculated value, was 2.1 mm (0.4-3.1 mm). Postoperative clinical evaluations and imaging were performed on every patient in order to confirm the success of the surgical procedure. All patients recovered well and without any postoperative complications. We conclude that image guidance in single burr-hole procedures provides a high degree of accuracy in lesion targeting, permits good anatomical orientation and minimizes brain trauma. The navigation system has proven to be a helpful tool since it increases the safety of single burr-hole procedures.     

和平方舟号医院船16排移动CT头部扫描报告

目的检测16排移动CT在和平方舟号医院船上对健康志愿者进行头部轴位平扫的成像质量、电磁干扰影响以及无线信息传输的稳定性。 方法随机选择96例健康志愿者，分为航行组和停泊组。航行组58例，在医院船正常航行状态下进行头部轴位平扫；停泊组38例，在医院船航行结束返回码头停泊状态进行头部轴位平扫成像。比较2组头部轴向扫描的成像质量、电磁干扰影响，以及无线信息传输的稳定性。 结果16排移动CT与医院船上大功率仪器之间相互无电磁干扰，影像信息传输系统性能稳定。在医院船航行和停泊状态下骨窗位成像质量稳定，显示颅骨、眼眶、鼻蝶窦等骨性结构良好；头窗位成像质量良好，显示眼球及视神经、脑干、脑皮质及沟回等软组织结构清晰。2组受检者在颅底扫描时，一部分层面发生线条状运动伪影，航行组发生运动伪影的比率（15.52%）高于停泊组（5.26%），但2组间差异无统计学意义（P=0.191），对临床诊断无明显影响。 结论16排移动CT装配在医院船上进行头部平扫，成像质量优良、性能可靠、使用便捷，移动CT与医院船之间无电磁干扰，无线信息传输稳定性好。     

Automatic alignment of EEG/MEG and MRI data sets.

OBJECTIVEs: We developed a new technique of fully automatic alignment of brain data acquired with scalp sensors (e.g. electroencephalography/evoked potential (EP) electrodes, magnetoencephalography sensors) with a magnetic resonance imaging (MRI) volume of the head. METHODS: The method uses geometrical features (two sets of head points: digitized from the subject and extracted from MRI) to guide the alignment. It combines matching on 3 dimensional (3D) geometrical moments that perform the initial alignment, and 3D distance-based alignment that provides the final tuning. To reduce errors of the initial guessed computation resulting from digitization of the head surface points we introduced weights to compute geometrical moments, and a procedure to remove outliers to eliminate incorrectly digitized points. RESULTS: The method was tested on simulated (Monte Carlo trials) and on real data sets. The simulations demonstrated that for the number of test points within the range of 0.1-1% of the total number of head surface points and for the digitization error in the range of -2-2 mm the average map error was between 0.7 and 2.1 mm. The average distance error was less than 1 mm. Tests on real data gave the average distance error between 2.1 and 2.5 mm. CONCLUSIONS: The developed technique is fast, robust and comfortable for the patient and for medical personnel. It registers scalp sensor positions with MRI head volume with accuracy that is satisfactory for localization of biological processes examined with a commonly used number of scalp sensors (32, 64, or 128).