The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
T Lund - One of the best experts on this subject based on the ideXlab platform.
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a new approach to computer aided spine surgery fluoroscopy based surgical navigation
European Spine Journal, 2000Co-Authors: Lutzpeter Nolte, M Slomczykowski, U Berlemann, M J Strauss, R Hofstetter, Dietrich Schlenzka, T Laine, T LundAbstract:A new computer-based navigation system for spinal surgery has been designed. This was achieved by combining intraoperative fluoroscopy-based imaging using conventional C-arm technology with freehand surgical navigation principles. Modules were developed to automate digital X-ray image Registration. This is in contrast to existing computed tomography- (CT) based spinal navigation systems, which require a vertebra-based Registration Procedure. Cross-referencing of the image intensifier with the surgical object allows the real-time image-interactive navigation of surgical tools based on one single registered X-ray image, with no further image updates. Furthermore, the system allows the acquisition and real-time use of multiple registered images, which provides an advanced multi-directional control (pseudo 3D) during surgical action. Stereotactic instruments and graphical user interfaces for image-interactive transpedicular screw insertion have been developed. A detailed validation of the system was performed in the laboratory setting and throughout an early clinical trial including eight patients in two spine centers. Based on the resulting data, the new technique promises improved accuracy and safety in open and percutaneous spinal surgery.
Bisheng Yang - One of the best experts on this subject based on the ideXlab platform.
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nrli uav non rigid Registration of sequential raw laser scans and images for low cost uav lidar point cloud quality improvement
Isprs Journal of Photogrammetry and Remote Sensing, 2019Co-Authors: Bisheng Yang, Chi Chen, Ayman HabibAbstract:Abstract Accurate Registration of light detection and ranging (LiDAR) point clouds and images is a prerequisite for integrating the spectral and geometrical information collected by low-cost unmanned aerial vehicle (UAV) systems. Most Registration approaches take the directly georeferenced LiDAR point cloud as a rigid body, based on the assumption that the high-precision positioning and orientation system (POS) in the LiDAR system provides sufficient precision, and that the POS errors are negligible. However, due to the large errors of the low-precision POSs commonly used in the low-cost UAV LiDAR systems (ULSs), dramatic deformation may exist in the directly georeferenced ULS point cloud, resulting in non-rigid transformation between the images and the deformed ULS point cloud. As a result, Registration may fail when using a rigid transformation between the images and the directly georeferenced LiDAR point clouds. To address this problem, we proposed NRLI-UAV, which is a non-rigid Registration method for Registration of sequential raw laser scans and images collected by low-cost UAV systems. NRLI-UAV is a two-step Registration method that exploits trajectory correction and discrepancy minimization between the depths derived from structure from motion (SfM) and the raw laser scans to achieve LiDAR point cloud quality improvement. Firstly, the coarse Registration Procedure utilizes global navigation satellite system (GNSS) and inertial measurement unit (IMU)-aided SfM to obtain accurate image orientation and corrects the errors of the low-precision POS. Secondly, the fine Registration Procedure transforms the original 2D-3D Registration to 3D-3D Registration. This is performed by setting the oriented images as the reference, and iteratively minimizing the discrepancy between the depth maps derived from SfM and the raw laser scans, resulting in accurate Registration between the images and the LiDAR point clouds. In addition, an improved LiDAR point cloud is generated in the mapping frame. Experiments were conducted with data collected by a low-cost UAV system in three challenging scenes to evaluate NRLI-UAV. The final Registration errors of the images and the LiDAR point cloud are less than one pixel in image space and less than 0.13 m in object space. The LiDAR point cloud quality was also evaluated by plane fitting, and the results show that the LiDAR point cloud quality is improved by 8.8 times from 0.45 m (root-mean-square error [RMSE] of plane fitting) to 0.05 m (RMSE of plane fitting) using NRLI-UAV, demonstrating a high level of automation, robustness, and accuracy.
Lutzpeter Nolte - One of the best experts on this subject based on the ideXlab platform.
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a new approach to computer aided spine surgery fluoroscopy based surgical navigation
European Spine Journal, 2000Co-Authors: Lutzpeter Nolte, M Slomczykowski, U Berlemann, M J Strauss, R Hofstetter, Dietrich Schlenzka, T Laine, T LundAbstract:A new computer-based navigation system for spinal surgery has been designed. This was achieved by combining intraoperative fluoroscopy-based imaging using conventional C-arm technology with freehand surgical navigation principles. Modules were developed to automate digital X-ray image Registration. This is in contrast to existing computed tomography- (CT) based spinal navigation systems, which require a vertebra-based Registration Procedure. Cross-referencing of the image intensifier with the surgical object allows the real-time image-interactive navigation of surgical tools based on one single registered X-ray image, with no further image updates. Furthermore, the system allows the acquisition and real-time use of multiple registered images, which provides an advanced multi-directional control (pseudo 3D) during surgical action. Stereotactic instruments and graphical user interfaces for image-interactive transpedicular screw insertion have been developed. A detailed validation of the system was performed in the laboratory setting and throughout an early clinical trial including eight patients in two spine centers. Based on the resulting data, the new technique promises improved accuracy and safety in open and percutaneous spinal surgery.
Hongjian You - One of the best experts on this subject based on the ideXlab platform.
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an automatic and novel sar image Registration algorithm a case study of the chinese gf 3 satellite
Sensors, 2018Co-Authors: Yuming Xiang, Feng Wang, Hongjian YouAbstract:The Chinese GF-3 satellite launched in August 2016 is a Synthetic Aperture Radar (SAR) satellite that has the largest number of imaging modes in the world. It achieves a free switch in the spotlight, stripmap, scanSAR, wave, global observation and other imaging modes. In order to further utilize GF-3 SAR images, an automatic and fast image Registration Procedure needs to be done. In this paper, we propose a novel image Registration technique for GF-3 images of different imaging modes. The proposed algorithm consists of two stages: coarse Registration and fine Registration. In the first stage, we combine an adaptive sampling method with the SAR-SIFT algorithm to efficiently eliminate obvious translation, rotation and scale differences between the reference and sensed images. In the second stage, uniformly-distributed control points are extracted, then the fast normalized cross-correlation of an improved phase congruency model is utilized as a new similarity metric to match the reference image and the coarse-registered image in a local search region. Moreover, a selection strategy is used to remove outliers. Experimental results on several GF-3 SAR images of different imaging modes show that the proposed algorithm gives a robust, efficient and precise Registration performance, compared with other state-of-the-art algorithms for SAR image Registration.
P.i. Adriaanse - One of the best experts on this subject based on the ideXlab platform.
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development of scenarios for drinking water produced from groundwater and surface water for use in the pesticide Registration Procedure of ethiopia
2015Co-Authors: P.i. Adriaanse, M M S Ter Horst, Berhan M Teklu, J W Deneer, A Woldeamanuel, J J T I BoestenAbstract:In the Pesticide Risk Reduction Programme Ethiopia the evaluation of risks of pesticides present in drinking water for man and cattle was selected as a priority protection goal. In cooperation with the Plant Health Regulatory Department of the Ministry of Agriculture of Ethiopia and other Ethiopian stakeholders Alterra developed a Procedure to assess the risks for drinking water caused by pesticides, used according to Good Agricultural Practices (GAP). To do so, ‘realistic worst case’ scenarios were developed, that intend to protect man and cattle in 99% of all possible situations in Ethiopia. For groundwater three scenarios representing wells in aquifers in the Ethiopian highlands or Rift Valley margins were developed and for surface water three scenarios representing small rivers in the highlands or temporay stagnant ponds were developed. The scenarios were linked to crops on which pesticides are used that score high on acute, chronic or local chronic risk for man. In addition other agro-environmental conditions were defined, such as precipitation, soil, and land use management. The groundwater scenarios were parameterised in the EuroPEARL metamodel to calculate leaching concentrations to groundwater, whereas the surface water scenarios make use of the runoff model PRZM, the EU-FOCUS spray drift deposition table and the surface water model TOXSWA to calculate the concentration in the small river or pond scenarios
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proposed standard scenarios for a surface water model in the dutch authorization Procedure of pesticides method to define standard scenarios for determining exposure concentrations simulated by the tosxwa model
1999Co-Authors: W H J Beltman, P.i. AdriaanseAbstract:The TOXSWA model will be used to estimate exposure concentrations for aquatic organisms in the Dutch pesticide Registration Procedure. Applying a model in the Registration Procedure requires standard scenarios. A gross number of 24 scenarios were defined, based on worst case values of three sensitive system parameters (water depth, flow velocity, and macrophyte mass). In concurrency with developments at EU level on standard `waterbodies' we here propose scenarios representing ditches with a water depth of 0.30 m, without macrophytes, and a flow velocity of 10 m d-1 for spring and summer and 100 m d-1 for autumn. For these standard scenarios graphs have been constructed in which the momentary exposure concentration is given as a function of the coefficient describing sorption to sediment and suspended solids, based on the organic matter content. Other graphs give the average exposure concentrations as a function of the dissipation half-life (comprising transformation in water and volatilization).
