FIGURE 5 - uploaded by Armando Alaminos Bouza
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Computed Tomography (CT) Scanner attachments. The left image is a head-ring fixture which holds the head-ring of a patient during a CT scan acquisition. The right image shows the BrownRoberts-Wells (BRW) Localizer Frame (LF) with the Cosman-RobertsWells (CRW) system being supported by the headring fixture and restrained with brackets. This type of arrangement reduces noise during image acquisition and allows the posterior N-Localizer to be imaged well.
Source publication
Introduction: Frame-based stereotaxis has been widely utilized for precise neurosurgical procedures throughout the world for nearly 40 years. The N-localizer is an integral component of most of the extant systems. Analysis of targeting errors related to the N-localizer has not been carried out in sufficient detail. We highlight these potential erro...
Contexts in source publication
Context 1
... routine use of systems to support/suspend the stereotactic frames and suppress movement artifact optimize imaging conditions. Care during image acquisition cannot be overemphasized ( Figure 5). ...
Citations
... In practice, frame-based localization can be subject to errors that may impact surgical accuracy. As a result, error minimization is an important adjunct to stereotactic localization that obtains the best accuracy to improve the result of surgery [2]. Some factors that can impact localization accuracy include resolution of the imaging technique, imperfect detection of the centroids of the fiducials in the image, or motion of the patient during the imaging acquisition. ...
... Although this case report discusses a 3 N-localizer system, any system with greater than 3 N-localizers could also have been conceivably used to compute a 3D plane via an overdetermined method [2,7]. In contrast, a 2 N-localizer system fails to provide enough information to compute a 3D plane using diagonal bar positions. ...
Frame-based stereotactic localization is an important step for targeting during a surgical procedure. The motion may cause artifacts in this step reducing the accuracy of surgical targeting. While modeling of motion in real-life scenarios may be difficult, herein we analyzed the case where motion was suspected to impact the localization step. In this case, a scan with and without motion was performed with a 3N localizer, allowing for a thorough analysis. Pseudo-bending of straight rods was seen when analyzing the data. This pseudo-bending appears to occur because head-frame motion during imaging acquisition decreases the accuracy of the subsequent reconstruction, which depends on Digital Imaging and Communications in Medicine (DICOM) metadata to specify the slice-to-slice location that assumes embedded object stability. Comparison of single-slice and multi-slice stereotactic localization allowed for comparative errors for each slice in a volume. This comparative error demonstrated low error when the patient was under general anesthesia and presumed not to have moved, whereas a higher error was present during the scan with motion. Pseudo-bending can be corrected by using only localizer fiducial-based information to reorient the pixels in the volume, thus creating a reoriented localizer scan. Finally, targeting demonstrated a low error of 0.1 mm (+/- 0.1 mm) using this reoriented localizer scan, signifying that this method could be used to improve or recover from motion problems. Finally, it is concluded that stability and elimination of motion for all images utilized for stereotactic surgery are critical to ensure the best possible accuracy for the procedure.
... For both mask and frame immobilization SRS on the GK Icon TM system, Duggar et al. reported that the sources of uncertainty include MRI distortion, couch position and stability shifts, CBCT-MRI registration differences, and definition of stereotactic space and intrafraction motion [27]. Uncertainties unique to the mask immobilizations include errors in the definition of stereotactic space using CBCT (0.10 ± 0.05 mm) and MRI-CBCT registration uncertainty (0.62 + 0.23 mm) and is comparable to stereotactic definition with frame immobilization (root-mean-square error smaller than 0.6 to 1.5 mm) as it has been reported [27,30,31]. Carmunicci and colleagues detected an overall average motion error of less than 1 mm in the translational direction and less than or equal to 1 • in the rotational direction for both mask and frame immobilization using GK Icon TM [18]. ...
We compared the clinical outcomes of BM treated with mask immobilization with zero-SM (i.e., zero-PTV) to standard zero-SM frame immobilization SRS. Consecutive patients with BM, 0.5–2.0 cm in maximal diameter, treated with single-fraction SRS (22–24 Gy) during March 2019–February 2021 were included. Univariable and multivariable analysis were performed using the Kaplan–Meier method and Cox proportional hazards regression. A total of 150 patients with 453 BM met inclusion criteria. A total of 129 (28.5%) lesions were treated with a zero-SM mask immobilization and 324 (71.5%) with zero-SM frame immobilization. Frame immobilization treatments were associated with a higher proportion of gastrointestinal and fewer breast-cancer metastases (p = 0.024), and a higher number of treated lesions per SRS course (median 7 vs. 3; p < 0.001). With a median follow up of 15 months, there was no difference in FFLF between the mask and frame immobilization groups on univariable (p = 0.29) or multivariable analysis (p = 0.518). Actuarial FFLF at 1 year was 90.5% for mask and 92% for frame immobilization (p = 0.272). Radiation necrosis rates at 1 year were 12.5% for mask and 4.1% for frame immobilization (p = 0.502). For BM 0.5–2.0 cm in maximal diameter treated with single-fraction SRS using 22–24 Gy, mask immobilization with zero SM produces comparable clinical outcomes to frame immobilization. The initial findings support omitting a SM when using mask immobilization with this treatment approach on a Gamma Knife® Icon™.
... Frame-based stereotactic localization is generally constructed for single-slice image localization [1][2][3][4][5][6][7][8]. As such, each image contains all necessary fiducials required to compute single-slice stereotactic matrices (ss-SM), which allow for conversion between two-dimensional (2D) screen coordinates and three-dimensional (3D) stereotactic frame-based coordinates for that image slice. ...
... Previously, we have proposed several optimizations to the ss-SM that can reduce error [2]. Specifically, the use of overdetermined systems of equations using all fiducial data improves the solution to minimize errors. ...
... The following sections summarize important techniques for stereotactic localization as it relates to singleor multi-slice techniques. As previously published, linear methods for using an overdetermined system of equations are emphasized in the mathematics presented [2], but a non-linear solution also emerges. Stereotactic matrices are the basis for stereotactic localization, but we also utilize a plane equation which we extend from a single-to multi-slice application. ...
Frame-based stereotactic localization generally assumes that all required fiducials are present in a single-slice image which can then be used to form targeting coordinates. Previously, we have published the use of novel localizers and mathematics that can improve stereotactic localization. As stereotactic procedures include numerous imaging slices, we sought to investigate, develop, and test techniques that utilize multiple slices for stereotactic localization and provide a solution for a parallel bipanel N-localizer.
Several multi-slice equations were tested. Specifically, multi-slice stereotactic matrices (ms-SM) and multi-slice normal to parallel planes (ms-nPP) were of particular interest. Bipanel (2N) and tripanel (3N) localizer images were explored to test approaches for stereotactic localization. In addition, combination approaches using single-slice stereotactic matrices (ss-SM) and multi-slice methods were tested.
Modification of ss-SM to form ms-SM was feasible. Likewise, a method to determine ms-nPP was developed. For the special case of the parallel bipanel N-localizer, single-slice and multi-slice methods fail, but a novel non-linear solution is a robust solution for ms-nPP.
Several methods for single-slice and multi-slice stereotactic localization are described and can be adapted for nearly any stereotactic system. It is feasible to determine ms-SM and ms-nPP. In particular, these methods provide an overdetermined means to calculate the vertical Z.
, which is determined for a tripanel system using single-slice methods. In addition, the multi-slice methods can be used for extrapolation outside of the localizer space. Importantly, a novel non-linear solution can be used for parallel bipanel N-localizer systems, where other methods fail. Finally, multi-slice stereotactic localization assumes strict patient and imaging system stability, which should be carefully assessed for each case.
... Hence, for three or four SP localizers, three or four sets of coordinates are calculated respectively. Monte Carlo simulation predicts that for other types of localizers, more than three sets of coordinates improve the accuracy of image guidance [5,6]. This article reports the calculation of three sets of coordinates for each SP localizer instead of only one set; hence, for three or four SP localizers, nine or 12 sets of coordinates are calculated respectively. ...
... However, the 3D spatial orientation of the CT scan plane may be determined to greater accuracy if three sets of coordinates are calculated for each SP localizer via equations (10-12) presented in the appendices. The resulting nine sets of coordinates may then be used to create an overdetermined system of linear equations that are solved via minimization of the least-square error to obtain a three by three transformation matrix that specifies the 3D spatial orientation of the CT scan plane relative to the ZD frame [2,5]. ...
... The minimum allowed height of the CT scan plane is greater for a tilt than for a tilt so that the CT scan plane does not intersect the base of the ZD stereotactic frame posteriorly. In view of the improved accuracy predicted for the attachment of a fourth SP localizer to the posterior aspect of the ZD stereotactic frame, the accuracy of the four SP localizer configuration was compared to the accuracy of a four N-localizer configuration that is the most accurate of all N-localizer configurations [5]. In this four N-localizer configuration, an N-localizer is attached to each of the anterior, posterior, left lateral, and right lateral aspects of a stereotactic frame in a configuration similar to the attachment of four SP localizers to the ZD frame. ...
A novel and more stable solution of the stereotactic image registration problem for systems equipped with Sturm-Pastyr (SP) localizer is presented by the authors. The metric of such mathematical stability is the RMS-error in the presence of image noise, which is the case of real clinical application.
Alaminos-Bouza and Brown propose formulas to calculate three sets of (x,y,z) coordinates for each SP localizer. Monte Carlo simulation compares the accuracy of the new formulation to the accuracy of the original SP formulation that calculates only one set of (x,y,z) coordinates for each SP localizer. Monte Carlo simulation reveals that the calculation of three sets of (x,y,z) coordinates instead of only one set improves the accuracy of image guidance.
Sturm-Pastyr localizers are used in ZD and RM stereotactic systems manufactured by inomed (Inomed Medizintechnik GmbH, Emmendingen, Germany)
... Image-guidance for frame-based stereotaxis is facilitated by incorporating three to four N-localizers or Sturm-Pastyr localizers into a stereotactic frame [1,2]. Monte Carlo (MC) simulation [3] predicts that the attachment of one N-localizer to each of the anterior, posterior, and left and right lateral faces of a rectangular stereotactic frame affords the highest accuracy [4]. To avoid contact with the computed tomography (CT) scanner couch, the posterior N-localizer is often omitted, which results in a configuration that comprises three N-localizers [4]. ...
... Monte Carlo (MC) simulation [3] predicts that the attachment of one N-localizer to each of the anterior, posterior, and left and right lateral faces of a rectangular stereotactic frame affords the highest accuracy [4]. To avoid contact with the computed tomography (CT) scanner couch, the posterior N-localizer is often omitted, which results in a configuration that comprises three N-localizers [4]. Moreover, to promote patient comfort and minimize claustrophobia, the omission of both the anterior and posterior N-localizers results in a configuration that includes only two N-localizers [5]. ...
... This article reports root mean square errors (RMSe) calculated via MC simulation for the two and four Vlocalizer configurations. These RMSe are compared to the RMSe for the M-localizer, the Z-localizer, a four Nlocalizer configuration, and the Brown-Roberts-Wells (BRW) localizer that embodies a three N-localizer configuration [1,4,7]. MC simulation models random fluctuations of the coordinates of the centroids of fiducials in a CT image. ...
Image-guidance for frame-based stereotaxis is facilitated by incorporating three to four N-localizers or Sturm-Pastyr localizers into a stereotactic frame. An extant frame that incorporates only two N-localizers violates the fundamental principle of the N-localizer, which requires three non-colinear points to define a plane in three-dimensional space. Hence, this two N-localizer configuration is susceptible to error. The present article proposes the V-localizer that comprises multiple diagonal bars to provide four or more non-colinear points to minimize erro
... Four N-localizer panels affixed to its anterior, posterior, and lateral sides afford the smallest errors. Due to practical considerations, the posterior Nlocalizer panel is often omitted, resulting in a configuration that comprises three N-localizer panels [3]. In order to promote patient comfort, minimize claustrophobia, and simplify the design, the removal of the anterior and posterior N-localizer panels creates a configuration that comprises only two N-localizer panels, wherein one N-localizer panel is affixed to each lateral side of a rectangular frame [4]. ...
... This stereotactic matrix converts 3D coordinates to two-dimensional (2D) coordinates or 2D to 3D. It has been shown previously that the use of an overdetermined system of equations affords an incremental minimization of error at a given target [3]. However, with the introduction of a 2-panel (bipanel) localizer system, the ability to localize a single image yields insufficient information because only two of the three required 3D points are present ( Figure 1). ...
... Moreover, the Z-localizer has supporting vertical bars to which 10 diagonal bars abut; these supporting vertical bars are not intended for use in stereotactic calculations. All of these new localizer panels (M, F, and Z) are arranged in an "antiparallel" manner (i.e., one panel inverted compared to the opposite panel) that was found previously to minimize errors [3]. Each diagonal bar is bracketed by parallel, vertically oriented bars and can therefore exploit N-localizer mathematics to calculate the (x,y,z)(x,y,z) coordinates of a point along a diagonal bar, given the (u,v)(u,v) coordinates of 3 fiducials in a CT or MRI image [6]. ...
Introduction:
The N-localizer is generally utilized in a 3-panel or, more rarely, a 4-panel system for computing stereotactic positions. However, a stereotactic frame that incorporates a 2-panel (bipanel) N-localizer system with panels affixed to only the left and right sides of the frame offers several advantages: improved ergonomics to attach the panels, reduced claustrophobia for the patient, mitigation of posterior panel contact with imaging systems, and reduced complexity. A bipanel system that comprises two standard N-localizer panels yields only two three-dimensional (3D) coordinates, which are insufficient to solve for the stereotactic matrix without further information. While additional information to determine the stereotactic positions could include scalar distances from Digital Imaging and Communications in Medicine (DICOM) metadata or 3D regression across the imaging volume, both have risks related to noise and error propagation. Therefore, we sought to develop new stereotactic localizers that comprise only lateral fiducials (bipanel) that leave the front and back regions of the patient accessible but that contain enough information to solve for the stereotactic matrix using each image independently. Methods: To solve the stereotactic matrix, we assumed the need to compute three or more 3D points from a single image. Several localizer options were studied using Monte Carlo simulations to understand the effect of errors on the computed target location. The simulations included millions of possible combinations for computing the stereotactic matrix in the presence of random errors of 1mm magnitude. The matrix then transformed coordinates for a target that was placed 50mm anterior, 50mm posterior, 50mm lateral, or 50mm anterior and 50mm lateral to the centre of the image. Simulated cross-sectional axial images of the novel localizer systems were created and converted into DICOM images representing computed tomography (CT) images. Results: Three novel models include the M-localizer, F-localizer, and Z-localizer. For each of these localizer systems, optimized results were obtained using an overdetermined system of equations made possible by more than three diagonal bars. In each case, the diagonal bar position was computed using standard N-localizer mathematics. Additionally, the M-localizer allowed adding a computation using the Sturm-Pastyr method. Monte Carlo simulation demonstrated that the Z-localizer provided optimal results.
Conclusion:
The three proposed novel models meet our design objectives. Of the three, the Z-localizer produced the least propagation of error. The M-localizer was simpler and had slightly more error than the Z-localizer. The F-localizer produced more error than either the Z-localizer or M-localizer. Further study is needed to determine optimizations using these novel models.
... Até esta data existem dois tipos de localizadores que predominam no mercado da estereotaxia: Localizadores do tipo Note-se que embora os sistemas de planejamento suportem ambos os tipos de localizadores, cada modelo deve ser utilizado na melhor condição possível para garantir acurácia perante ruido nas imagens, angulação do estereotáxico em relação com o plano de imagem e manter nossos alvos na melhor altura para cada modelo de localizador. Estes detalhes podem ser consultados na literatura [12,13]. Em particular recomendamos manter o paralelismo entre aro e plano de imagem nos sistemas baseados em localizadores em V, pois está demostrado que neste caso existe menos estabilidade numérica das soluções [12]. ...
English:
An introductory lecture that presents the basic functionalities of a modern system for planning stereotactic and functional neurosurgery. We highlight actions to be observed to ensure the safety and accuracy of surgical procedures based on computerized planning. We recommend a bibliography for those interested in delving into the topics covered.
An in-depth study of any specific planning system is outside the scope of this talk. It is essential that before operating any software of this nature, the interested party must go through a specific course for this purpose or be assisted by a suitably qualified operator.
Portugues:
Palestra introdutória que apresenta as funcionalidades básicas de um sistema moderno para planejamento de neurocirurgia estereotáxica e funcional. Destacamos ações a serem observadas para garantir a segurança e acurácia dos procedimentos cirúrgicos baseados no planejamento computadorizado. Recomendamos bibliografia para aqueles interessados em aprofundar-se nos tópicos abordados.
Um estudo em profundidade de qualquer sistema de planejamento específico fica fora do escopo desta palestra. É imprescindível que antes de operar qualquer software desta natureza o interessado passe por um curso específico para tal ou seja assistido por um operador devidamente qualificado.
Basic ideas regarding neuroimaging and its relation with stereotactic surgery and neuronavigation.
XXXIII Congresso Brasileiro de Neurocirurgia - CBN 2022
Curso Pre-Congresso. Neurocirurgia Funcional.
