The Experts below are selected from a list of 91158 Experts worldwide ranked by ideXlab platform
Ben J M Heijmen - One of the best experts on this subject based on the ideXlab platform.
-
dosimetric investigation of lung tumor motion compensation with a robotic respiratory tracking system an experimental study
Medical Physics, 2008Co-Authors: Elena Nioutsikou, Yvette Seppenwoolde, Ben J M Heijmen, Richard J N Symondstayler, Phil M Evans, S WebbAbstract:The benefits of using Synchrony (TM) Respiratory Tracking System (RTS) in conjunction with the CyberKnife robotic treatment device to treat a "breathing tumor" in an anthropomorphic, tissue-equivalent, thoracic phantom have been investigated. The following have been studied: (a) Synchrony's ability to allow the CyberKnife to deliver accurately a planned dose distribution to the free-breathing phantom and (b) the dosimetric implications when irregularities in the breathing cycle and phase differences between internal (tumor) and external (chest) motion exist in the course of one treatment fraction. The breathing phantom PULMONE (phantom used in lung motion experiments) has been used, which can imitate regular or irregular breathing patterns. The breathing traces from two patients with lung cancer have been selected as input. Both traces were irregular in amplitude, frequency, and base line. Patient B demonstrated a phase difference between internal and external motion, whereas patient A did not. The experiment was divided into three stages: In stage I-static, the treatment was delivered to the static phantom. In stage II-motion, the phantom was set to breathe, following the breathing trace of each of the two patients. Synchrony (TM) was switched off, so no motion compensation was made. In stage III-compensation, the phantom was set to breathe and Synchrony (TM) was switched on. A linear Correspondence Model was chosen to allow for phase differences between internal and external motion. Gafchromic EBT film was inserted in the phantom tumor to measure dose. To eradicate small errors in film alignment during readout, a gamma comparison with pass criteria of 3%/3 mm was selected. For a more quantitative approach, the percentage of pixels in each gamma map that exceeded the value of 1 (P-1) was also used. For both breathing signals, the dose blurring caused by the respiratory motion of the tumor in stage II was degraded considerably compared with stage I (P-1=15% for patient A and 8% for patient B). The motion compensation via the linear Correspondence Model was sufficient to provide a dose distribution that satisfied the set gamma criteria (P-1=3% for patient A and 2% for patient B). Synchrony (TM) RTS has been found satisfactory in recovering the initial detail in dose distribution, for realistic breathing signals, even in the case where a phase delay between internal tumor motion and external chest displacement exists. For the signals applied here, a linear Correspondence Model provided an acceptable degree of motion compensation. (C) 2008 American Association of Physicists in Medicine.
-
accuracy of tumor motion compensation algorithm from a robotic respiratory tracking system a simulation study
Medical Physics, 2007Co-Authors: Yvette Seppenwoolde, R Berbeco, Seiko Nishioka, Hiroki Shirato, Ben J M HeijmenAbstract:The Synchrony™ Respiratory Tracking System (RTS) is a treatment option of the CyberKnife robotic treatment device to irradiate extra-cranial tumors that move due to respiration. Advantages of RTS are that patients can breath normally and that there is no loss of linac duty cycle such as with gated therapy. Tracking is based on a measured Correspondence Model (linear or polynomial) between internal tumor motion and external (chest/abdominal) marker motion. The radiation beam follows the tumor movement via the continuously measured external marker motion. To establish the Correspondence Model at the start of treatment, the 3D internal tumor position is determined at 15 discrete time points by automatic detection of implanted gold fiducials in two orthogonal x-ray images; simultaneously, the positions of the external markers are measured. During the treatment, the relationship between internal and external marker positions is continuously accounted for and is regularly checked and updated. Here we use computer simulations based on continuously and simultaneously recorded internal and external marker positions to investigate the effectiveness of tumor tracking by the RTS. The Cyberknife does not allow continuous acquisition of x-ray images to follow the moving internal markers (typical imaging frequency is once per minute). Therefore, for the simulations, we have used data for eight lung cancer patients treated with respiratory gating. All of these patients had simultaneous and continuous recordings of both internal tumor motion and external abdominal motion. The available continuous relationship between internal and external markers for these patients allowed investigation of the consequences of the lower acquisition frequency of the RTS. With the use of the RTS, simulated treatment errors due to breathing motion were reduced largely and consistently over treatment time for all studied patients. A considerable part of the maximum reduction in treatment error could already be reached with a simple linear Model. In case of hysteresis, a polynomial Model added some extra reduction. More frequent updating of the Correspondence Model resulted in slightly smaller errors only for the few recordings with a time trend that was fast, relative to the current x-ray update frequency. In general, the simulations suggest that the applied combined use of internal and external markers allow the robot to accurately follow tumor motion even in the case of irregularities in breathing patterns.
Yvette Seppenwoolde - One of the best experts on this subject based on the ideXlab platform.
-
dosimetric investigation of lung tumor motion compensation with a robotic respiratory tracking system an experimental study
Medical Physics, 2008Co-Authors: Elena Nioutsikou, Yvette Seppenwoolde, Ben J M Heijmen, Richard J N Symondstayler, Phil M Evans, S WebbAbstract:The benefits of using Synchrony (TM) Respiratory Tracking System (RTS) in conjunction with the CyberKnife robotic treatment device to treat a "breathing tumor" in an anthropomorphic, tissue-equivalent, thoracic phantom have been investigated. The following have been studied: (a) Synchrony's ability to allow the CyberKnife to deliver accurately a planned dose distribution to the free-breathing phantom and (b) the dosimetric implications when irregularities in the breathing cycle and phase differences between internal (tumor) and external (chest) motion exist in the course of one treatment fraction. The breathing phantom PULMONE (phantom used in lung motion experiments) has been used, which can imitate regular or irregular breathing patterns. The breathing traces from two patients with lung cancer have been selected as input. Both traces were irregular in amplitude, frequency, and base line. Patient B demonstrated a phase difference between internal and external motion, whereas patient A did not. The experiment was divided into three stages: In stage I-static, the treatment was delivered to the static phantom. In stage II-motion, the phantom was set to breathe, following the breathing trace of each of the two patients. Synchrony (TM) was switched off, so no motion compensation was made. In stage III-compensation, the phantom was set to breathe and Synchrony (TM) was switched on. A linear Correspondence Model was chosen to allow for phase differences between internal and external motion. Gafchromic EBT film was inserted in the phantom tumor to measure dose. To eradicate small errors in film alignment during readout, a gamma comparison with pass criteria of 3%/3 mm was selected. For a more quantitative approach, the percentage of pixels in each gamma map that exceeded the value of 1 (P-1) was also used. For both breathing signals, the dose blurring caused by the respiratory motion of the tumor in stage II was degraded considerably compared with stage I (P-1=15% for patient A and 8% for patient B). The motion compensation via the linear Correspondence Model was sufficient to provide a dose distribution that satisfied the set gamma criteria (P-1=3% for patient A and 2% for patient B). Synchrony (TM) RTS has been found satisfactory in recovering the initial detail in dose distribution, for realistic breathing signals, even in the case where a phase delay between internal tumor motion and external chest displacement exists. For the signals applied here, a linear Correspondence Model provided an acceptable degree of motion compensation. (C) 2008 American Association of Physicists in Medicine.
-
accuracy of tumor motion compensation algorithm from a robotic respiratory tracking system a simulation study
Medical Physics, 2007Co-Authors: Yvette Seppenwoolde, R Berbeco, Seiko Nishioka, Hiroki Shirato, Ben J M HeijmenAbstract:The Synchrony™ Respiratory Tracking System (RTS) is a treatment option of the CyberKnife robotic treatment device to irradiate extra-cranial tumors that move due to respiration. Advantages of RTS are that patients can breath normally and that there is no loss of linac duty cycle such as with gated therapy. Tracking is based on a measured Correspondence Model (linear or polynomial) between internal tumor motion and external (chest/abdominal) marker motion. The radiation beam follows the tumor movement via the continuously measured external marker motion. To establish the Correspondence Model at the start of treatment, the 3D internal tumor position is determined at 15 discrete time points by automatic detection of implanted gold fiducials in two orthogonal x-ray images; simultaneously, the positions of the external markers are measured. During the treatment, the relationship between internal and external marker positions is continuously accounted for and is regularly checked and updated. Here we use computer simulations based on continuously and simultaneously recorded internal and external marker positions to investigate the effectiveness of tumor tracking by the RTS. The Cyberknife does not allow continuous acquisition of x-ray images to follow the moving internal markers (typical imaging frequency is once per minute). Therefore, for the simulations, we have used data for eight lung cancer patients treated with respiratory gating. All of these patients had simultaneous and continuous recordings of both internal tumor motion and external abdominal motion. The available continuous relationship between internal and external markers for these patients allowed investigation of the consequences of the lower acquisition frequency of the RTS. With the use of the RTS, simulated treatment errors due to breathing motion were reduced largely and consistently over treatment time for all studied patients. A considerable part of the maximum reduction in treatment error could already be reached with a simple linear Model. In case of hysteresis, a polynomial Model added some extra reduction. More frequent updating of the Correspondence Model resulted in slightly smaller errors only for the few recordings with a time trend that was fast, relative to the current x-ray update frequency. In general, the simulations suggest that the applied combined use of internal and external markers allow the robot to accurately follow tumor motion even in the case of irregularities in breathing patterns.
Andreas Maier - One of the best experts on this subject based on the ideXlab platform.
-
robust multi view 2 d 3 d registration using point to plane Correspondence Model
IEEE Transactions on Medical Imaging, 2020Co-Authors: Roman Schaffert, Jian Wang, Andreas Maier, Peter Fischer, Anja BorsdorfAbstract:In minimally invasive procedures, the clinician relies on image guidance to observe and navigate the operation site. In order to show structures which are not visible in the live X-ray images, such as vessels or planning annotations, X-ray images can be augmented with pre-operatively acquired images. Accurate image alignment is needed and can be provided by 2-D/3-D registration. In this paper, a multi-view registration method based on the point-to-plane Correspondence Model is proposed. The Correspondence Model is extended to be independent of the used camera coordinates and different multi-view registration schemes are introduced and compared. Evaluation is performed for a wide range of clinically relevant registration scenarios. We show for different applications that registration using Correspondences from both views simultaneously provides accurate and robust registration, while the performance of the other schemes varies considerably. Our method also outperforms the state-of-the-art method for cerebral angiography registration, achieving a capture range of 18 mm and an accuracy of 0.22±0.07 mm. Furthermore, investigations on the minimum angle between the views are performed in order to provide accurate and robust registration, while minimizing the obstruction to the clinical workflow. We show that small angles around 30° are sufficient to provide reliable registration results.
-
An MR-Based Model for Cardio-Respiratory Motion Compensation of Overlays in X-Ray Fluoroscopy
IEEE Transactions on Medical Imaging, 2018Co-Authors: Peter Fischer, Andreas Maier, Anthony Faranesh, Thomas Pohl, Toby Rogers, Kanishka Ratnayaka, Robert Lederman, Joachim HorneggerAbstract:In X-ray fluoroscopy, static overlays are used to visualize soft tissue. We propose a system for cardiac and respiratory motion compensation of these overlays. It consists of a 3-D motion Model created from real-time magnetic resonance (MR) imaging. Multiple sagittal slices are acquired and retrospectively stacked to consistent 3-D volumes. Slice stacking considers cardiac information derived from the ECG and respiratory information extracted from the images. Additionally, temporal smoothness of the stacking is enhanced. Motion is estimated from the MR volumes using deformable 3-D/3-D registration. The motion Model itself is a linear direct Correspondence Model using the same surrogate signals as slice stacking. In X-ray fluoroscopy, only the surrogate signals need to be extracted to apply the motion Model and animate the overlay in real time. For evaluation, points are manually annotated in oblique MR slices and in contrast-enhanced X-ray images. The 2-D Euclidean distance of these points is reduced from 3.85 to 2.75 mm in MR and from 3.0 to 1.8 mm in X-ray compared with the static baseline. Furthermore, the motion-compensated overlays are shown qualitatively as images and videos.
-
dynamic 2 d 3 d rigid registration framework using point to plane Correspondence Model
IEEE Transactions on Medical Imaging, 2017Co-Authors: Jian Wang, Anja Borsdorf, Roman Schaffert, Benno Heigl, Xiaolin Huang, Joachim Hornegger, Andreas MaierAbstract:In image-guided interventional procedures, live 2-D X-ray images can be augmented with preoperative 3-D computed tomography or MRI images to provide planning landmarks and enhanced spatial perception. An accurate alignment between the 3-D and 2-D images is a prerequisite for fusion applications. This paper presents a dynamic rigid 2-D/3-D registration framework, which measures the local 3-D-to-2-D misalignment and efficiently constrains the update of both planar and non-planar 3-D rigid transformations using a novel point-to-plane Correspondence Model. In the simulation evaluation, the proposed method achieved a mean 3-D accuracy of 0.07 mm for the head phantom and 0.05 mm for the thorax phantom using single-view X-ray images. In the evaluation on dynamic motion compensation, our method significantly increases the accuracy comparing with the baseline method. The proposed method is also evaluated on a publicly-available clinical angiogram data set with “gold-standard” registrations. The proposed method achieved a mean 3-D accuracy below 0.8 mm and a mean 2-D accuracy below 0.3 mm using single-view X-ray images. It outperformed the state-of-the-art methods in both accuracy and robustness in single-view registration. The proposed method is intuitive, generic, and suitable for both initial and dynamic registration scenarios.
Xiaoou Tang - One of the best experts on this subject based on the ideXlab platform.
-
stereo Correspondence with occlusion handling in a symmetric patch based graph cuts Model
IEEE Transactions on Pattern Analysis and Machine Intelligence, 2007Co-Authors: Yi Deng, Qiong Yang, Xueyin Lin, Xiaoou TangAbstract:A novel patch-based Correspondence Model is presented in this paper. Many segment-based Correspondence approaches have been proposed in recent years. Untextured pixels and boundaries of discontinuities are imposed with hard constraints by the discontinuity assumption that large disparity variation only happens at the boundaries of segments in the above approaches. Significant improvements on performance of untextured and discontinuity area have been reported. But, the performance near occlusion is not satisfactory because a segmented region in one image may be only partially visible in the other one. To solve this problem, we utilize the observation that the shared edge of a visible area and an occluded area corresponds to the discontinuity in the other image. So, the proposed Model conducts color segmentation on both images first and then a segment in one image is further cut into smaller patches corresponding to the boundaries of segments in the other when it is assigned with a disparity. Different visibility of patches in one segment is allowed. The uniqueness constraint in a segment level is used to compute the occlusions. An energy minimization framework using graph-cuts is proposed to find a global optimal configuration including both disparities and occlusions. Besides, some measurements are taken to make our segment-based algorithm suffer less from violation of the discontinuity assumption. Experimental results have shown superior performance of the proposed approach, especially on occlusions, untextured areas, and near discontinuities
-
a symmetric patch based Correspondence Model for occlusion handling
International Conference on Computer Vision, 2005Co-Authors: Yi Deng, Qiong Yang, Xueyin Lin, Xiaoou TangAbstract:Occlusion is one of the challenging problems in stereo. In this paper, we solve the problem in a segment-based style. Both images are segmented, and we propose a novel patch-based stereo algorithm that cuts the segments of one image using the segments of the other, and handles occlusion areas in a proper way. A symmetric graph-cuts optimization framework is used to find Correspondence and occlusions simultaneously. The experimental results show superior performance of the proposed algorithm, especially on occlusions, untextured areas and discontinuities
Hattori G - One of the best experts on this subject based on the ideXlab platform.
-
An implicit non-ordinary state-based peridynamics with stabilised Correspondence material Model for finite deformation analysis.
'Elsevier BV', 2020Co-Authors: Hashim, Nur A., Coombs W.m., Augarde C.e., Hattori GAbstract:This paper is devoted to the development of a stabilised implicit non-ordinary state-based peridynamics approach. We propose a geometrically nonlinear implicit approach focusing on quasi-static analyses. Since the construction of the Jacobian matrix is the most time consuming step in conducting this nonlinear analysis, we formulate an analytical expression based on the equation of motion of non-ordinary state-based peridynamics to ensure optimum convergence of the global residual force. The implicit formulation can adopt fairly large time increments, making it a good choice for analyses of finite deformation. Another important extension presented in this paper is the modification of the Correspondence material Model to remove zero-energy mode instabilities and reduce the spurious oscillations, as proposed by Silling (2017). The derivative of the additional stabilisation term with respect to displacement is included in the formulation of the Jacobian for the first time. Computational examples of 2D finite deformation problems with a stabilised Correspondence Model are presented. We assess the eectiveness of dierent values of the stabilisation parameter, G in terms of the particles’ spacings and horizon sizes for dierent problems. This allows the non-ordinary state-based peridynamics approach to Model material behaviour with greater accuracy where Correspondence materials have previously failed due to instabilities. In this paper, a damage Model is also proposed, which provides for the first time an implicit approach for the static solution of crack propagation problems for non-ordinary state-based peridynamics. This paper lays the groundwork for nonordinary state-based peridynamics to be used for a much greater variety of solid mechanics problems than is currently possible and at the same time satisfying the stability condition
-
An implicit non-ordinary state-based peridynamics with stabilised Correspondence material Model for finite deformation analysis
2020Co-Authors: Hattori G, Na Hashim, Wm Coombs, Ce AugardeAbstract:© 2020 Elsevier B.V. This paper is devoted to the development of a stabilised implicit non-ordinary state-based peridynamics approach. We propose a geometrically nonlinear implicit approach focusing on quasi-static analyses. Since the construction of the Jacobian matrix is the most time-consuming step in conducting this nonlinear analysis, we formulate an analytical expression based on the equation of motion of non-ordinary state-based peridynamics to ensure optimum convergence of the global residual force. The implicit formulation can adopt fairly large time increments, making it a good choice for analyses of finite deformation. Another important extension presented in this paper is the modification of the Correspondence material Model to remove zero-energy mode instabilities and reduce the spurious oscillations, as proposed by Silling (2017). The derivative of the additional stabilisation term with respect to displacement is included in the formulation of the Jacobian for the first time. Computational examples of 2D finite deformation problems with a stabilised Correspondence Model are presented. We assess the effectiveness of different values of the stabilisation parameter, G in terms of the particles’ spacings and horizon sizes for different problems. This allows the non-ordinary state-based peridynamics approach to Model material behaviour with greater accuracy where Correspondence materials have previously failed due to instabilities. In this paper, a damage Model is also proposed, which provides for the first time an implicit approach for the static solution of crack propagation problems for non-ordinary state-based peridynamics. This paper lays the groundwork for non-ordinary state-based peridynamics to be used for a much greater variety of solid mechanics problems than is currently possible and at the same time satisfying the stability condition
