Biomedical subjects

Theo van Walsum

Publications and source records attributed to Theo van Walsum.

13 recordsLinked to original sources

PubMed2006

Three-dimensional rotational X-ray navigation for needle guidance in percutaneous vertebroplasty: an accuracy study.

STUDY DESIGN: The position of a needle tip displayed on a navigation system after transpedicular introduction into a vertebral body is compared with the real position of the needle tip when using a direct navigation coupling between a three-dimensional rotational X-ray (3DRX) system and a navigation system. OBJECTIVES: To assess whether the needle tip position displayed by the navigation system corresponds to the real needle position and to quantitatively determine needle navigation accuracy in a clinically relevant setting. SUMMARY OF BACKGROUND DATA: Image-guided navigation has reportedly increased the accuracy and safety of pedicle screw insertion and decreased complication rates. In former studies, the result of image-guided navigation was mainly compared qualitatively with the result of conventional fluoroscopy-guided procedures. Previously, a direct navigation coupling between a 3DRX system and a standard navigation system was introduced that bypasses the need for explicit patient-to-image registration necessary for image-guided orthopedic surgery. In a phantom experiment, the reported accuracy of navigation with the coupling to a 3DRX system was approximately 1 mm. However, in a clinical setting, additional errors can be introduced. METHODS: Twenty-three needles were placed transpedicularly into vertebral bodies of embalmed human trunks using 3DRX-guided navigation. The navigated needle tip positions were compared with the real needle tip positions manually extracted from 3DRX volumes acquired after completion of the introduction. RESULTS: The average distance between the navigated needle tip and the real position of the needle tip extracted from a postprocedure 3DRX volume was 2.5 +/- 1.5 mm. CONCLUSIONS: Accuracy of 3DRX-guided navigation is 2.5 +/- 1.5 mm in a clinically relevant setting, which is less than the accuracy determined in phantom experiments.

Aged, 80 and over↗

PubMed2006

Navigation with three-dimensional rotational radiographic data for transpedicular percutaneous needle introduction: feasibility and comparison with fluoroscopic guidance.

PURPOSE: To investigate the feasibility of navigation with three-dimensional (3D) rotational radiographic data for transpedicular percutaneous needle introduction and to compare navigation with 3D rotational radiographic data with conventional fluoroscopic guidance. MATERIALS AND METHODS: A navigation system was coupled to a 3D rotational radiographic imaging system. In a cadaver study, 60 biopsy needles were introduced into vertebral bodies with fluoroscopic guidance or navigation with 3D rotational radiographic data by two interventionalists with different levels of experience in percutaneous procedures. Radiation exposure, fluoroscopy and introduction times, and needle position were evaluated and compared. RESULTS: For 3D rotational radiographic navigation, the needle position was equivalent for both interventionalists (7 mm). For fluoroscopic guidance, the interventionalist with less experience in percutaneous procedures had significantly more pedicle cortex violations than the other interventionalist (eight vs one). Radiation exposure measured at the operators' hand was lower for 3D rotational radiography-guided needle introductions. Radiation exposure measured at the body wall of the cadaver was equivalent between modalities (9 mGy). CONCLUSIONS: Navigation with 3D rotational radiographic image data is feasible for transpedicular percutaneous needle introduction and has two advantages compared with fluoroscopic guidance: it poses less strict requirements on the expertise of the interventionalist, and it reduces radiation exposure to the interventionalist.

Biopsy, Needle↗

PubMed2005

Direct navigation on 3D rotational x-ray data acquired with a mobile propeller C-arm: accuracy and application in functional endoscopic sinus surgery.

Recently, three-dimensional (3D) rotational x-ray imaging has been combined with navigation technology, enabling direct 3D navigation for minimally invasive image guided interventions. In this study, phantom experiments are used to determine the accuracy of such a navigation set-up for a mobile C-arm with propeller motion. After calibration of the C-arm system, the accuracy is evaluated by pinpointing divots on a special-purpose phantom with known geometry. This evaluation is performed both with and without C-arm motion in between calibration and registration for navigation. The variation caused by each of the individual transformations in the calibration and registration process is also studied. The feasibility of direct navigation on 3D rotational x-ray images for functional endoscopic sinus surgery has been evaluated in a cadaver navigation experiment. Navigation accuracy was approximately 1.0 mm, which is sufficient for functional endoscopic sinus surgery. C-arm motion in between calibration and registration slightly degraded the registration accuracy by approximately 0.3 mm. Standard deviations of each of the transformations were in the range 0.15-0.31 mm. In the cadaver experiment, the navigation images were considered in good correspondence with the endoscopic images by an experienced ENT surgeon. Availability of 3D localization information provided by the navigation system was considered valuable by the ENT surgeon.

Algorithms↗

PubMed2005

The reduction of endplate fractures during balloon vertebroplasty: a detailed radiological analysis of the treatment of burst fractures using pedicle screws, balloon vertebroplasty, and calcium phosphate cement.

STUDY DESIGN: In a human cadaveric burst fracture model, the amount of endplate fracture reduction after posterior instrumentation and balloon vertebroplasty was investigated quantitatively. OBJECTIVES: To assess, in a burst fracture model, the vertebral body and adjacent disc heights, in parallel sagittal planes with 3-dimensional (3D) rotational x-ray imaging, at various phases during pedicle screw fixation and subsequent balloon vertebroplasty. SUMMARY OF BACKGROUND DATA: In recent human cadaveric thoracolumbar fracture studies, it was found that vertebral body height could be restored significantly with inflatable bone tamps. However, limited quantitative data exist on the amount of fracture reduction that can be achieved and how much of the reduction will be lost after deflation and removal of the bone tamps before the cement is injected. METHODS: Twenty burst fractures were created and balloon vertebroplasty with calcium phosphate cement was performed after pedicle screw instrumentation. A 3D dataset was obtained during the following phases: intact, fractured, after reduction and stabilization with pedicle screws, after inflation of the balloons, after deflation and removal of the balloons, after injection of the cement. The fractured vertebral body and adjacent disc heights were measured from five reconstructed sagittal images and compared for the six phases of the procedure. Furthermore, the difference between the vertebral body height centrally and peripherally was calculated. RESULTS: The mean vertebral body height at the thoracic level was Tintact = 19.5 +/- 2.2 mm, Tfractured = 14.6 +/- 3.8 mm, Treduction = 17.3 +/- 2.2 mm, Tinflation = 20.1 +/- 2.0 mm, Tdeflation = 18.0 +/- 2.0 mm, and Tcement = 17.8 +/- 1.8 mm. The overall change in vertebral body height between these phases was significant (P < 0.001). At the lumbar level the mean vertebral body height was Tintact = 23.2 +/- 3.8 mm, Tfractured = 14.7 +/- 3.0 mm, Treduction = 18.4 +/- 2.5 mm, Tinflation = 23.2 +/- 3.5 mm, Tdeflation = 19.3 +/- 2.3 mm, and Tcement = 20.2 +/- 2.8 mm. The overall change in MCVBH between these phases was also significant (P < 0.001). The increase in vertebral body height resulted in a decrease of the adjacent disc height. No difference was found for the amount of endplate reduction in the center or at the periphery. No leakage of cement was detected in the spinal canal. CONCLUSIONS: Reduction of endplate fractures, both in the center and at the periphery, seems feasible and safe with combined fracture reduction and balloon vertebroplasty. The endplate fracture reduction that was gained by inflation of the bone tamps could not be maintained after deflation.

Aged↗

PubMed2005

Bone displacement and the role of longitudinal ligaments during balloon vertebroplasty in traumatic thoracolumbar fractures.

STUDY DESIGN: In a human cadaveric burst fracture model with and without longitudinal ligament damage, the amount of anterior and posterior bone displacement (ABD, PBD) during balloon vertebroplasty after pedicle-screw instrumentation was investigated quantitatively. OBJECTIVES: To investigate, in a burst fracture model with and without longitudinal ligament damage, the amount of ABD, PBD, and cement leakage at various phases during balloon vertebroplasty in combination with pedicle-screw instrumentation. SUMMARY OF BACKGROUND DATA: The role of intact longitudinal ligaments in traumatic spine fractures, for prevention of bone retropulsion and subsequent reduction, has been discussed in several studies but is still up for debate. In a recent human cadaveric burst fracture study, inflatable bone tamps and calcium phosphate cement were used for the augmentation of the anterior column after pedicle-screw instrumentation. The additional balloon vertebroplasty procedure was found to be feasible and safe, but no data pertaining to unwarranted bone displacement or cement leakage during the procedure are available for burst fractures with damaged longitudinal ligaments. METHODS: Ten thoracic and 10 lumbar burst fractures, with rotation or flexion components, were created, and balloon vertebroplasty with calcium phosphate cement was performed after pedicle-screw instrumentation. Volumetric datasets (using the 3-dimensional (3D) rotational x-ray imaging technique) of the fractures were obtained during the following phases: intact, fractured, after reduction and stabilization with pedicle-screws, after inflation of the balloons, after deflation and removal of the balloons, and after injection of the cement. The amount of ABD and PBD was measured on reconstructed sagittal images and recorded together with the presence of extracorporal cement leakage. The continuity of the longitudinal ligaments was assessed after anatomic dissection. RESULTS: During the balloon vertebroplasty procedure, a significant (P < 0.05) increase of ABD (at both thoracic and lumbar level) and PBD (thoracic level) occurred after inflation of the balloons. After deflation and subsequent injection of the cement, however, the ABD and PBD returned to the preinflation levels. The absolute amount of ABD and PBD (<1 mm) during inflation was considered of little clinical importance. No differences in ABD or PBD were observed for specimens with or without continuity of the corresponding longitudinal ligament, irrespective of the level, at any of the phases during the experiment (P > 0.5 in all cases). A small amount of cement leakage was observed in the psoas compartment of one specimen with intact longitudinal ligaments. CONCLUSIONS: It is suggested that balloon vertebroplasty after pedicle-screw instrumentation may safely be used, in terms of bone displacement and cement leakage, in fracture types where damage to longitudinal ligaments is to be expected.

Aged↗

PubMed2005

Accuracy evaluation of direct navigation with an isocentric 3D rotational X-ray system.

Minimally invasive interventions are often performed under fluoroscopic guidance. Drawbacks of fluoroscopic guidance are the fact that the presented images are 2D projections and that both the patient and the clinician are exposed to radiation. Image-guided navigation using pre-interventionally acquired 3D MR or CT data is an alternative. However, this often requires invasive anatomical landmark-based, marker-based or surface-based image-to-patient registration. In this paper, a coupling between an image-guided navigation system and an intraoperative C-arm X-ray device with 3D imaging capabilities (3D rotational X-ray (3DRX) system) that enables direct navigation without invasive image-to-patient registration on 3DRX volumes, is described and evaluated. The coupling is established in a one-time preoperative calibration procedure. The individual steps in the registration procedure are explained and evaluated. The acquired navigation accuracy using this coupling is approximately one millimeter.

Algorithms↗

PubMed2005

Three-dimensional rotational X-ray imaging for spine surgery: a quantitative validation study comparing reconstructed images with corresponding anatomical sections.

STUDY DESIGN: A validation study was done in which reconstructed three-dimensional rotational x-ray images were quantitatively compared with corresponding anatomic sections. OBJECTIVES: To assess the accuracy of reconstructed images acquired on a three-dimensional rotational x-ray imaging device. SUMMARY OF BACKGROUND DATA: Minimally invasive procedures have proven quite successful as alternatives for a multitude of open treatments. An unfavorable property of this type of procedure is a lack of direct vision of the operating area. Three-dimensional rotational x-ray imaging may be able to merge the advantages of computed tomography and fluoroscopy: real-time two-dimensional projections for fast visual feedback and three-dimensional reconstructions for detailed volumetric imaging of complex anatomy. METHODS: Twenty traumatic thoracolumbar burst fractures were created and underwent pedicle screw instrumentation and balloon vertebroplasty. Subsequently, a three-dimensional dataset was obtained, and the midsagittal image was reconstructed. The specimens were sliced, and photographs were obtained. Multiple parameters on the reconstructed images and photographs were measured two times by two observers using a graphical method. The differences and standard deviations were calculated for the corresponding parameters and for the intraobserver data. RESULTS: The mean difference between the corresponding values ranged between -1.1 and 2.1 mm for all parameters. The standard deviation for the differences per parameter ranged between 1.2 and 3.2 mm. The intraobserver differences ranged from -0.8 to 1.4 mm, and the standard deviation varied between 0.4 and 2.4 mm. CONCLUSIONS: The reconstructed midsagittal images were accurate in all measured parameters. The three-dimensional rotational x-ray technique may prove to be valuable for less invasive spine surgery.

Aged↗

PubMed2005

Multispectral MR to X-ray registration of vertebral bodies by generating CT-like data.

A new method for MR to X-ray registration is presented. Based on training data, consisting of registered multispectral MR and CT data, a function is defined that maps multispectral MR data to CT-like data. For new subjects for which multispectral MR data have been acquired, the mapping function is used to generate a corresponding CT-like dataset. The CT-like image is subsequently used for registration to X-ray data, using gradient-based registration. Preliminary experiments indicate that MR to X-ray registration using this method is more accurate and has a larger capture range than gradient-based registration applied directly to MR data.

Algorithms↗

PubMed2005

Guide wire reconstruction and visualization in 3DRA using monoplane fluoroscopic imaging.

A method has been developed that, based on the guide wire position in monoplane fluoroscopic images, visualizes the approximate guide wire position in the three-dimensional (3-D) vasculature, that is obtained prior to the intervention with 3-D rotational X-ray angiography (3DRA). The method assumes the position of the guide wire in the fluoroscopic images is known. A two-dimensional feature image is determined from the 3DRA data. In this feature image, the guide wire position is determined in a two-step approach: a mincost algorithm is used to determine a suitable position for the guide wire, and subsequently a snake optimization technique is applied to move the guide wire to a better position. The resulting guide wire can then be visualized in 3-D in combination with the 3DRA dataset. The reconstruction accuracy of the method has been evaluated using a 3DRA image of a vascular phantom filled with contrast, and monoplane fluoroscopic images of the same phantom without contrast and with a guide wire inserted. The evaluation has been performed for different projection angles, and with different parameters for the method. The final result does not appear to be very sensitive to the parameters of the method. The average mean error of the estimated 3-D guide wire position is 1.5 mm, and the average tip distance is 2.3 mm. The effect of inaccurate C-arm geometry information is also investigated. Small errors in geometry information (up to 1 degrees) will slightly decrease the 3-D reconstruction accuracies, with an error of at most 1 mm. The feasibility of this approach on clinical data is demonstrated.

Algorithms↗

PubMed2005

Standardized evaluation methodology for 2-D-3-D registration.

In the past few years, a number of two-dimensional (2-D) to three-dimensional (3-D) (2-D-3-D) registration algorithms have been introduced. However, these methods have been developed and evaluated for specific applications, and have not been directly compared. Understanding and evaluating their performance is therefore an open and important issue. To address this challenge we introduce a standardized evaluation methodology, which can be used for all types of 2-D-3-D registration methods and for different applications and anatomies. Our evaluation methodology uses the calibrated geometry of a 3-D rotational X-ray (3DRX) imaging system (Philips Medical Systems, Best, The Netherlands) in combination with image-based 3-D-3-D registration for attaining a highly accurate gold standard for 2-D X-ray to 3-D MR/CT/3DRX registration. Furthermore, we propose standardized starting positions and failure criteria to allow future researchers to directly compare their methods. As an illustration, the proposed methodology has been used to evaluate the performance of two 2-D-3-D registration techniques, viz. a gradient-based and an intensity-based method, for images of the spine. The data and gold standard transformations are available on the internet (http://www.isi.uu.nl/Research/Databases/).

Algorithms↗

PubMed2004

Noninvasive magnetic resonance to three-dimensional rotational x-ray registration of vertebral bodies for image-guided spine surgery.

STUDY DESIGN: Magnetic resonance (MR) and three-dimensional rotational x-ray (3DRX) images of cadaveric spinal segments were registered using a conventional point-based technique and a noninvasive technique called maximization of mutual information (MMI). OBJECTIVES: To assess the feasibility and accuracy of MMI-based registration in comparison with point-based registration as a new noninvasive image-to-patient registration technique for use in minimally invasive image-guided spine surgery. SUMMARY OF BACKGROUND DATA: In image-guided orthopedic surgery, correspondence between before surgery acquired images and the patient is required. Currently, this necessitates an invasive registration step, in which anatomic landmarks on the bone surface have to be physically touched by a pointer. To overcome this invasive procedure, we propose using a calibrated 3DRX system, a modality that can visualize high contrast objects intraoperatively and that provides a direct correspondence between the image data and the patient. A noninvasive voxel-based technique is used to register the intraoperative 3DRX image to a before surgery acquired MR image. METHODS: Cadaveric thoracic and lumbar spine segments were implanted with markers, which were used as landmarks. The accuracy of the landmark-based registration was compared with MMI-based registration using the residual errors on the marker positions. RESULTS: The errors made using the point-based registration technique were compared with the errors made with MMI. The results show a statistically significant lower error (P < 0.01) for the proposed MMI method. CONCLUSIONS: Noninvasive MMI registration of intraoperative 3DRX images to preoperative MR images is more accurate than point-based registration in cadaveric spine segments. It is therefore a promising technique for replacing the invasive landmark-based registration that is currently used in image-guided spine surgery.

Humans↗

PubMed2003

Endpoint localization in guide wire tracking during endovascular interventions.

RATIONALE AND OBJECTIVES: A method is presented to track guide wires during endovascular interventions under X-ray fluoroscopy. Accurate guide wire tracking can be used to improve guide wire visualization in the low quality fluoroscopic images, and to estimate the position of the guide wire in world coordinates for navigation purposes. MATERIALS AND METHODS: A two-step procedure is used to track the guide wire in subsequent frames. First, the position of the guide wire is obtained by fitting a spline to the image. Subsequently, the spline is iteratively moved toward the tip of the guide wire for accurate tip localization. For both steps, a feature image is used in which line-like structures are enhanced. The method is validated using a reference standard, obtained by manual tracings of three observers. RESULTS: The method is evaluated on 20 image sequences, 10 sequences with a J-tipped guide wire and 10 with a straight guide wire. The tracking success was 96% for J-tipped and 100% for straight guide wires, whereas accurate endpoint localization could be performed in 91.3% and 94.4% of the frames respectively, with a tip localization error of less than 1.5 mm. CONCLUSIONS: Accurate endpoint localization can be performed for both J-tipped and straight guide wires and therefore the presented tracking method can be used for navigation purposes.

Algorithms↗

PubMed2003

Three-dimensional guide-wire reconstruction from biplane image sequences for integrated display in 3-D vasculature.

Using three-dimensional rotational X-ray angiography (3DRA), three-dimensional (3-D) information of the vasculature can be obtained prior to endovascular interventions. However, during interventions, the radiologist has to rely on fluoroscopy images to manipulate the guide wire. In order to take full advantage of the 3-D information from 3DRA data during endovascular interventions, a method is presented that yields an integrated display of the position of the guide wire and vasculature in 3-D. The method relies on an automated method that tracks the guide wire simultaneously in biplane fluoroscopy images. Based on the calibrated geometry of the C-arm, the 3-D guide-wire position is determined and visualized in the 3-D coordinate system of the vasculature. The method is evaluated in an intracranial anthropomorphic vascular phantom. The influence of the angle between projections, distortion correction of the projection images, and accuracy of geometry knowledge on the accuracy of 3-D guide-wire reconstruction from biplane images is determined. If the calibrated geometry information is used and the images are corrected for distortion, a mean distance to the reference standard of 0.42 mm and a tip distance of 0.65 mm is found, which means that accurate guide-wire reconstruction from biplane images can be performed.

Algorithms↗