Dr. Sebastian Schafer Profile

Dr. Sebastian Schafer

Scientist

SPIE Involvement:

Author

Publications (36)

SPIE Journal Paper | 15 October 2021

Three-dimensional catheter navigation of airways using continuous-sweep limited angle fluoroscopy on a C-arm

Martin Wagner, Sarvesh Periyasamy, Sebastian Schafer, Paul Laeseke, Michael Speidel

JMI, Vol. 8, Issue 05, 055001, (October 2021) https://doi.org/10.1117/12.10.1117/1.JMI.8.5.055001

KEYWORDS: Image segmentation, Fluoroscopy, X-rays, 3D modeling, X-ray imaging, 3D image processing, 3D acquisition, Navigation systems, Gold, Instrument modeling

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Proceedings Article | 15 February 2021 Presentation + Paper

Method for 3D navigation of airways on a single C-arm using multi-sweep limited angle acquisition and frame-by-frame device reconstruction

Martin Wagner, Sarvesh Periyasamy, Sebastian Schafer, Paul Laeseke, Michael Speidel

Proceedings Volume 11598, 115980O (2021) https://doi.org/10.1117/12.2580957

KEYWORDS: 3D acquisition, X-rays, X-ray imaging, 3D modeling, Tumors, Motion models, Model-based design, Image registration, Image acquisition, Gold

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Proceedings Article | 15 February 2021 Presentation + Paper

A hybrid photon counting and flat panel detector system for periprocedural hemorrhage monitoring in the angio suite

Kevin Treb, Xu Ji, Mang Feng, Ran Zhang, Sebastian Schafer, Ke Li

Proceedings Volume 11595, 115950U (2021) https://doi.org/10.1117/12.2581242

KEYWORDS: Sensors, Imaging systems, Photon counting, Computed tomography, Imaging spectroscopy, Spectroscopy, Scanners, Reliability, Photodetectors, Iodine

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Endovascular procedures performed in the angio suite have gained considerable popularity for treatment of ischemic stroke as well as aneurysms. However, new intracranial hemorrhage (ICH) may develop during these procedures, and it is highly desirable to arm the angio suite with real-time and reliable ICH monitoring tools. Currently, angio suites are equipped with scintillator-based flat panel detector (FPD) imaging systems for both planar and cone beam CT (CBCT) imaging applications. However, the reliability of CBCT for ICH imaging is insufficient due to its poor low-contrast detectability compared with MDCT and lack of spectral imaging capability for differentiating between ICH, calcifications, and iodine staining from periprocedural contrast-enhanced imaging sequences. To preserve the benefits of the FPD for 2D imaging and certain high-contrast 3D imaging tasks while adding a high quality, quantitative, and affordable CT imaging capability to the angio room for intraoperative ICH monitoring, a hybrid detector system was developed that includes the existing FPD on the C-arm gantry and a strip photon-counting detector (PCD) that can be translated into the field-of-view for high quality PCD-CT imaging at a given brain section-of-interest. The hybrid system maintains the openness and ease of use of the C-arm system without the need to remodel the angio room and without installing a slidinggantry MDCT (aka Angio CT) with orders of magnitude higher costs. Additionally, the cost of the strip PCD is much less than the cost of a large-area PCD. To demonstrate the feasibility and potential benefits of the hybrid PCD-FPD system, a series of physical phantom studies, and human cadaver studies were performed at a gantry rotation speed (7 s) and radiation dose level that closely match those of clinical CBCT acquisitions. The experimental images of C-arm PCD-CT demonstrated MDCT-equivalent low-contrast detectability of PCD-CT and significantly reduced artifacts compared with FPD-based CBCT.

Proceedings Article | 8 March 2019 Paper

Prototype system for interventional dual-energy subtraction angiography

Michael Speidel, Christiane Burton, Ethan Nikolau, Sebastian Schafer, Paul Laeseke

Proceedings Volume 10951, 109511U (2019) https://doi.org/10.1117/12.2512956

KEYWORDS: X-rays, Switching, Angiography, 3D acquisition, X-ray detectors, X-ray imaging, Automatic exposure

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Proceedings Article | 13 March 2018 Paper

Precision blood flow measurements in vascular networks with conservation constraints

Gabe Shaughnessy, Carson Hoffman, Sebastian Schafer, Paul Laeseke, Charles Mistretta, Charles Strother

Proceedings Volume 10576, 105762Q (2018) https://doi.org/10.1117/12.2293637

KEYWORDS: Blood circulation, Data modeling, Precision measurement, In vivo imaging, Monte Carlo methods, Aneurysms, Angiography, Hemodynamics, Image-guided intervention

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Proceedings Article | 13 March 2018 Presentation + Paper

A real-time system for prosthetic valve tracking

Martin Wagner, Lindsay Bodart, Sebastian Schafer, Amish Raval, Michael Speidel

Proceedings Volume 10576, 105761A (2018) https://doi.org/10.1117/12.2293837

KEYWORDS: 3D modeling, 3D image processing, Heart, Visual process modeling, Visualization, Optical tracking, Real-time computing, Fluoroscopy, Detection and tracking algorithms, Prototyping

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Proceedings Article | 9 March 2018 Presentation + Paper

Time-resolved C-arm cone beam CT angiography using SMART-RECON: quantification of temporal resolution and reconstruction accuracy

John Garrett, Yinsheng Li, Ke Li, Sebastian Schafer, Charles Strother, Guang-Hong Chen

Proceedings Volume 10573, 105731T (2018) https://doi.org/10.1117/12.2292477

KEYWORDS: Temporal resolution, Reconstruction algorithms, Angiography, Image quality, Arteries, Veins, Computed tomography, Lithium, Error analysis, Sensors

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Proceedings Article | 2 March 2018 Presentation + Paper

Feasibility of intra-acquisition motion correction for 4D DSA reconstruction for applications in the thorax and abdomen

Martin Wagner, Paul Laeseke, Colin Harari, Sebastian Schafer, Michael Speidel, Charles Mistretta

Proceedings Volume 10574, 1057415 (2018) https://doi.org/10.1117/12.2293812

KEYWORDS: 3D acquisition, Abdomen, 3D image processing, Reconstruction algorithms, Blood circulation, Image registration, Computed tomography, Vascular diseases, 3D image reconstruction, Radiology

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Proceedings Article | 19 April 2017 Paper

Quantitative flow and velocity measurements of pulsatile blood flow with 4D-DSA

Gabe Shaughnessy, Carson Hoffman, Sebastian Schafer, Charles Mistretta, Charles Strother

Proceedings Volume 10132, 101325R (2017) https://doi.org/10.1117/12.2254143

KEYWORDS: Picosecond phenomena, Distance measurement, Medical physics, Radiology, Blood circulation, 3D metrology, Velocity measurements, Angiography, Independent component analysis, Image-guided intervention

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Proceedings Article | 22 March 2016 Paper

C-arm cone beam CT perfusion imaging using the SMART-RECON algorithm to improve temporal sampling density and temporal resolution

Yinsheng Li, Kai Niu, Ke Li, Sebastian Schafer, Kevin Royalty, Charles Strother, Guang-Hong Chen

Proceedings Volume 9783, 97830U (2016) https://doi.org/10.1117/12.2216838

KEYWORDS: Reconstruction algorithms, Temporal resolution, Algorithm development, Computer simulations, In vivo imaging, Computed tomography, Tomography, Image restoration, Denoising, Imaging systems, Tissues, X-ray computed tomography, Blood, Brain mapping, Brain

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Proceedings Article | 18 March 2016 Paper

Biplane reconstruction and visualization of virtual endoscopic and fluoroscopic views for interventional device navigation

Martin Wagner, Charles Strother, Sebastian Schafer, Charles Mistretta

Proceedings Volume 9786, 978613 (2016) https://doi.org/10.1117/12.2216538

KEYWORDS: Reconstruction algorithms, Visualization, Endoscopy, Cerebrovascular diseases, Navigation systems, Cameras, Fluoroscopy, Image segmentation, Angiography, Denoising, Glasses, 3D equipment, 3D image processing, 3D image reconstruction

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Biplane fluoroscopic imaging is an important tool for minimally invasive procedures for the treatment of cerebrovascular diseases. However, finding a good working angle for the C-arms of the angiography system as well as navigating based on the 2D projection images can be a difficult task. The purpose of this work is to propose a novel 4D reconstruction algorithm for interventional devices from biplane fluoroscopy images and to propose new techniques for a better visualization of the results. The proposed reconstruction methods binarizes the fluoroscopic images using a dedicated noise reduction algorithm for curvilinear structures and a global thresholding approach. A topology preserving thinning algorithm is then applied and a path search algorithm minimizing the curvature of the device is used to extract the 2D device centerlines. Finally, the 3D device path is reconstructed using epipolar geometry. The point correspondences are determined by a monotonic mapping function that minimizes the reconstruction error. The three dimensional reconstruction of the device path allows the rendering of virtual fluoroscopy images from arbitrary angles as well as 3D visualizations like virtual endoscopic views or glass pipe renderings, where the vessel wall is rendered with a semi-transparent material. This work also proposes a combination of different visualization techniques in order to increase the usability and spatial orientation for the user. A combination of synchronized endoscopic and glass pipe views is proposed, where the virtual endoscopic camera position is determined based on the device tip location as well as the previous camera position using a Kalman filter in order to create a smooth path. Additionally, vessel centerlines are displayed and the path to the target is highlighted. Finally, the virtual endoscopic camera position is also visualized in the glass pipe view to further improve the spatial orientation. The proposed techniques could considerably improve the workflow of minimally invasive procedures for the treatment of cerebrovascular diseases.

SPIE Journal Paper | 25 January 2016 Open Access

Volumetric limiting spatial resolution analysis of four-dimensional digital subtraction angiography

Brian Davis, Erick Oberstar, Kevin Royalty, Sebastian Schafer, Charles Mistretta

JMI, Vol. 3, Issue 01, 013503, (January 2016) https://doi.org/10.1117/12.10.1117/1.JMI.3.1.013503

KEYWORDS: Spatial resolution, 3D image processing, Modulation transfer functions, Angiography, Spatial frequencies, Temporal resolution, 3D image reconstruction, Point spread functions, 3D acquisition, Medical imaging

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Proceedings Article | 18 March 2015 Paper

Volumetric limiting spatial resolution analysis of four dimensional digital subtraction angiography (4D-DSA)

Brian Davis, Erick Oberstar, Kevin Royalty, Sebastian Schafer, Charles Strother, Charles Mistretta

Proceedings Volume 9412, 94121B (2015) https://doi.org/10.1117/12.2081624

KEYWORDS: Spatial resolution, Spatial frequencies, Modulation transfer functions, Point spread functions, Computed tomography, 3D image reconstruction, 3D image processing, Temporal resolution, Image resolution, Convolution

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Proceedings Article | 18 March 2015 Paper

Ultra low radiation dose digital subtraction angiography (DSA) imaging using low rank constraint

Kai Niu, Yinsheng Li, Sebastian Schafer, Kevin Royalty, Yijing Wu, Charles Strother, Guang-Hong Chen

Proceedings Volume 9412, 94121O (2015) https://doi.org/10.1117/12.2082070

KEYWORDS: Image processing, Denoising, Data acquisition, Angiography, Medical imaging, Arteries, Algorithm development, In vivo imaging, Optimization (mathematics), Image quality

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Proceedings Article | 19 March 2014 Paper

A patient-specific scatter artifacts correction method

Wei Zhao, Stephen Brunner, Kai Niu, Sebastian Schafer, Kevin Royalty, Guang-Hong Chen

Proceedings Volume 9033, 903310 (2014) https://doi.org/10.1117/12.2043923

KEYWORDS: Monte Carlo methods, Calibration, Data modeling, X-ray computed tomography, X-ray sources, Convolution, X-rays, Image segmentation, Numerical simulations, Computed tomography

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Proceedings Article | 19 March 2013 Paper

Soft-tissue imaging in low-dose, C-arm cone-beam CT using statistical image reconstruction

Adam Wang, Sebastian Schafer, J. Stayman, Yoshi Otake, Marc Sussman, A. Khanna, Gary Gallia, Jeffrey Siewerdsen

Proceedings Volume 8668, 86681F (2013) https://doi.org/10.1117/12.2008421

KEYWORDS: Spatial resolution, Image quality, Head, Tissues, Bone, Sensors, Computed tomography, Image resolution, Surgery, 3D image reconstruction

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Proceedings Article | 15 March 2013 Paper

Deformable image registration with content mismatch: a demons variant to account for added material and surgical devices in the target image

S. Nithiananthan, A. Uneri, S. Schafer, D. Mirota, Y. Otake, J. Stayman, W. Zbijewski, A. Khanna, D. Reh, G. Gallia, J. Siewerdsen

Proceedings Volume 8671, 86712A (2013) https://doi.org/10.1117/12.2008410

KEYWORDS: Image registration, Image segmentation, Tissues, Distortion, Cements, Image processing, Image-guided intervention, Detection and tracking algorithms, Image processing algorithms and systems, Surgery

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Proceedings Article | 15 March 2013 Paper

Intraoperative imaging for patient safety and QA: detection of intracranial hemorrhage using C-arm cone-beam CT

Sebastian Schafer, Adam Wang, Yoshito Otake, J. Stayman, Wojciech Zbijewski, Gerhard Kleinszig, Xuewei Xia, Gary Gallia, Jeffrey Siewerdsen

Proceedings Volume 8671, 86711X (2013) https://doi.org/10.1117/12.2008043

KEYWORDS: Spatial resolution, Safety, Blood, X-ray computed tomography, Surgery, Image restoration, Visibility, 3D image reconstruction, Head, Image quality

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Proceedings Article | 8 March 2013 Paper

A gaussian mixture + demons deformable registration method for cone-beam CT-guided robotic transoral base-of-tongue surgery

S. Reaungamornrat, W. Liu, S. Schafer, Y. Otake, S. Nithiananthan, A. Uneri, J. Richmon, J. Sorger, J. Siewerdsen, R. Taylor

Proceedings Volume 8671, 86710J (2013) https://doi.org/10.1117/12.2007937

KEYWORDS: Image registration, Image segmentation, Tongue, Computed tomography, Clouds, Magnetic resonance imaging, Rigid registration, Surgery, Video, Mouth

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Purpose: An increasingly popular minimally invasive approach to resection of oropharyngeal / base-of-tongue cancer is made possible by a transoral technique conducted with the assistance of a surgical robot. However, the highly deformed surgical setup (neck flexed, mouth open, and tongue retracted) compared to the typical patient orientation in preoperative images poses a challenge to guidance and localization of the tumor target and adjacent critical anatomy. Intraoperative cone-beam CT (CBCT) can account for such deformation, but due to the low contrast of soft-tissue in CBCT images, direct localization of the target and critical tissues in CBCT images can be difficult. Such structures may be more readily delineated in preoperative CT or MR images, so a method to deformably register such information to intraoperative CBCT could offer significant value. This paper details the initial implementation of a deformable registration framework to align preoperative images with the deformed intraoperative scene and gives preliminary evaluation of the geometric accuracy of registration in CBCT-guided TORS. Method: The deformable registration aligns preoperative CT or MR to intraoperative CBCT by integrating two established approaches. The volume of interest is first segmented (specifically, the region of the tongue from the tip to the hyoid), and a Gaussian mixture (GM) mode1 of surface point clouds is used for rigid initialization (GMRigid) as well as an initial deformation (GMNonRigid). Next, refinement of the registration is performed using the Demons algorithm applied to distance transformations of the GM-registered and CBCT volumes. The registration accuracy of the framework was quantified in preliminary studies using a cadaver emulating preoperative and intraoperative setups. Geometric accuracy of registration was quantified in terms of target registration error (TRE) and surface distance error. Result: With each step of the registration process, the framework demonstrated improved registration, achieving mean TRE of 3.0 mm following the GM rigid, 1.9 mm following GM nonrigid, and 1.5 mm at the output of the registration process. Analysis of surface distance demonstrated a corresponding improvement of 2.2, 0.4, and 0.3 mm, respectively. The evaluation of registration error revealed the accurate alignment in the region of interest for base-of-tongue robotic surgery owing to point-set selection in the GM steps and refinement in the deep aspect of the tongue in the Demons step. Conclusions: A promising framework has been developed for CBCT-guided TORS in which intraoperative CBCT provides a basis for registration of preoperative images to the highly deformed intraoperative setup. The registration framework is invariant to imaging modality (accommodating preoperative CT or MR) and is robust against CBCT intensity variations and artifact, provided corresponding segmentation of the volume of interest. The approach could facilitate overlay of preoperative planning data directly in stereo-endoscopic video in support of CBCT-guided TORS.

Proceedings Article | 3 March 2012 Paper

Model-based reconstruction of objects with inexactly known components

J. Stayman, Y. Otake, S. Schafer, A. Khanna, J. Prince, J. Siewerdsen

Proceedings Volume 8313, 83131S (2012) https://doi.org/10.1117/12.911202

KEYWORDS: Image registration, Signal attenuation, Spine, Image quality, Metals, Data modeling, Control systems, Visualization, Reconstruction algorithms, Image filtering

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Proceedings Article | 17 February 2012 Paper

High-performance C-arm cone-beam CT guidance of thoracic surgery

Sebastian Schafer, Yoshito Otake, Ali Uneri, Daniel Mirota, Sajendra Nithiananthan, J. Stayman, Wojciech Zbijewski, Gerhard Kleinszig, Rainer Graumann, Marc Sussman, Jeffrey Siewerdsen

Proceedings Volume 8316, 83161I (2012) https://doi.org/10.1117/12.911811

KEYWORDS: Lung, Video, Surgery, Image registration, Visibility, Tissues, Computed tomography, Visualization, Tumors, Cameras

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Proceedings Article | 17 February 2012 Paper

Automatic localization of target vertebrae in spine surgery using fast CT-to-fluoroscopy (3D-2D) image registration

Y. Otake, S. Schafer, J. Stayman, W. Zbijewski, G. Kleinszig, R. Graumann, A. J. Khanna, J. Siewerdsen

Proceedings Volume 8316, 83160N (2012) https://doi.org/10.1117/12.911308

KEYWORDS: Surgery, Fluoroscopy, Calibration, Image registration, Spine, X-rays, X-ray computed tomography, X-ray imaging, Computer simulations, Image-guided intervention

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Proceedings Article | 17 February 2012 Paper

Tracker-on-C for cone-beam CT-guided surgery: evaluation of geometric accuracy and clinical applications

S. Reaungamornrat, Y. Otake, A. Uneri, S. Schafer, D. Mirota, S. Nithiananthan, J. W. Stayman, A. J. Khanna, D. Reh, G. Gallia, R. Taylor, J. Siewerdsen

Proceedings Volume 8316, 831609 (2012) https://doi.org/10.1117/12.911454

KEYWORDS: Video, Fluoroscopy, Surgery, X-rays, Optical tracking, Visualization, Spine, Radiography, Image registration, X-ray computed tomography

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Conventional surgical tracking configurations carry a variety of limitations in line-of-sight, geometric accuracy, and mismatch with the surgeon's perspective (for video augmentation). With increasing utilization of mobile C-arms, particularly those allowing cone-beam CT (CBCT), there is opportunity to better integrate surgical trackers at bedside to address such limitations. This paper describes a tracker configuration in which the tracker is mounted directly on the Carm. To maintain registration within a dynamic coordinate system, a reference marker visible across the full C-arm rotation is implemented, and the "Tracker-on-C" configuration is shown to provide improved target registration error (TRE) over a conventional in-room setup - (0.9±0.4) mm vs (1.9±0.7) mm, respectively. The system also can generate digitally reconstructed radiographs (DRRs) from the perspective of a tracked tool ("x-ray flashlight"), the tracker, or the C-arm ("virtual fluoroscopy"), with geometric accuracy in virtual fluoroscopy of (0.4±0.2) mm. Using a video-based tracker, planning data and DRRs can be superimposed on the video scene from a natural perspective over the surgical field, with geometric accuracy (0.8±0.3) pixels for planning data overlay and (0.6±0.4) pixels for DRR overlay across all C-arm angles. The field-of-view of fluoroscopy or CBCT can also be overlaid on real-time video ("Virtual Field Light") to assist C-arm positioning. The fixed transformation between the x-ray image and tracker facilitated quick, accurate intraoperative registration. The workflow and precision associated with a variety of realistic surgical tasks were significantly improved using the Tracker-on-C - for example, nearly a factor of 2 reduction in time required for C-arm positioning, reduction or elimination of dose in "hunting" for a specific fluoroscopic view, and confident placement of the x-ray FOV on the surgical target. The proposed configuration streamlines the integration of C-arm CBCT with realtime tracking and demonstrated utility in a spectrum of image-guided interventions (e.g., spine surgery) benefiting from improved accuracy, enhanced visualization, and reduced radiation exposure.

Proceedings Article | 17 February 2012 Paper

Incorporation of prior knowledge for region of change imaging from sparse scan data in image-guided surgery

J. Lee, J. Stayman, Y. Otake, S. Schafer, W. Zbijewski, A. J. Khanna, J. Prince, J. Siewerdsen

Proceedings Volume 8316, 831603 (2012) https://doi.org/10.1117/12.910850

KEYWORDS: X-rays, Image-guided intervention, X-ray imaging, Image fusion, Surgery, Visualization, Data acquisition, Bone, Image registration, 3D image processing

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Proceedings Article | 14 February 2012 Paper

Deformable registration of the inflated and deflated lung for cone-beam CT-guided thoracic surgery

Ali Uneri, Sajendra Nithiananthan, Sebastian Schafer, Yoshito Otake, J. Webster Stayman, Gerhard Kleinszig, Marc Sussman, Russell Taylor, Jerry Prince, Jeffrey Siewerdsen

Proceedings Volume 8316, 831602 (2012) https://doi.org/10.1117/12.911440

KEYWORDS: Lung, Image registration, Surgery, Image segmentation, Tumors, Detection and tracking algorithms, Visualization, Computed tomography, Lung cancer, Image-guided intervention

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Proceedings Article | 17 March 2011 Paper

Penalized-likelihood reconstruction for sparse data acquisitions with unregistered prior images and compressed sensing penalties

J. Stayman, W. Zbijewski, Y. Otake, A. Uneri, S. Schafer, J. Lee, J. Prince, J. Siewerdsen

Proceedings Volume 7961, 79611L (2011) https://doi.org/10.1117/12.878075

KEYWORDS: Lung, Data acquisition, Image registration, Compressed sensing, Tomography, Image analysis, Data modeling, Surveillance, Signal attenuation, Signal to noise ratio

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Proceedings Article | 2 March 2011 Paper

Incorporating tissue excision in deformable image registration: a modified demons algorithm for cone-beam CT-guided surgery

S. Nithiananthan, D. Mirota, A. Uneri, S. Schafer, Y. Otake, J. W. Stayman, J. H. Siewerdsen

Proceedings Volume 7964, 796404 (2011) https://doi.org/10.1117/12.878258

KEYWORDS: Image registration, Tissues, Algorithm development, Computed tomography, Surgery, Head, Neck, 3D image processing, 3D modeling, Prototyping

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Proceedings Article | 2 March 2011 Paper

Architecture of a high-performance surgical guidance system based on C-arm cone-beam CT: software platform for technical integration and clinical translation

Ali Uneri, Sebastian Schafer, Daniel Mirota, Sajendra Nithiananthan, Yoshito Otake, Sureerat Reaungamornrat, Jongheun Yoo, J. Webster Stayman, Douglas Reh, Gary Gallia, A. Jay Khanna, Gregory Hager, Russell Taylor, Gerhard Kleinszig, Jeffrey Siewerdsen

Proceedings Volume 7964, 796422 (2011) https://doi.org/10.1117/12.878191

KEYWORDS: Surgery, Video, Image registration, Computer architecture, Visualization, Fluoroscopy, Endoscopy, 3D image processing, Imaging systems, Computed tomography

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Intraoperative imaging modalities are becoming more prevalent in recent years, and the need for integration of these modalities with surgical guidance is rising, creating new possibilities as well as challenges. In the context of such emerging technologies and new clinical applications, a software architecture for cone-beam CT (CBCT) guided surgery has been developed with emphasis on binding open-source surgical navigation libraries and integrating intraoperative CBCT with novel, application-specific registration and guidance technologies. The architecture design is focused on accelerating translation of task-specific technical development in a wide range of applications, including orthopaedic, head-and-neck, and thoracic surgeries. The surgical guidance system is interfaced with a prototype mobile C-arm for high-quality CBCT and through a modular software architecture, integration of different tools and devices consistent with surgical workflow in each of these applications is realized. Specific modules are developed according to the surgical task, such as: 3D-3D rigid or deformable registration of preoperative images, surgical planning data, and up-to-date CBCT images; 3D-2D registration of planning and image data in real-time fluoroscopy and/or digitally reconstructed radiographs (DRRs); compatibility with infrared, electromagnetic, and video-based trackers used individually or in hybrid arrangements; augmented overlay of image and planning data in endoscopic or in-room video; real-time "virtual fluoroscopy" computed from GPU-accelerated DRRs; and multi-modality image display. The platform aims to minimize offline data processing by exposing quantitative tools that analyze and communicate factors of geometric precision. The system was translated to preclinical phantom and cadaver studies for assessment of fiducial (FRE) and target registration error (TRE) showing sub-mm accuracy in targeting and video overlay within intraoperative CBCT. The work culminates in the development of a CBCT guidance system (reported here for the first time) that leverages the technical developments in Carm CBCT and associated technologies for realizing a high-performance system for translation to clinical studies.

Proceedings Article | 2 March 2011 Paper

High-accuracy 3D image-based registration of endoscopic video to C-arm cone-beam CT for image-guided skull base surgery

Daniel Mirota, Ali Uneri, Sebastian Schafer, Sajendra Nithiananthan, Douglas Reh, Gary Gallia, Russell Taylor, Gregory Hager, Jeffrey Siewerdsen

Proceedings Volume 7964, 79640J (2011) https://doi.org/10.1117/12.877803

KEYWORDS: Image registration, Video, Endoscopy, Surgery, 3D acquisition, 3D image processing, Computed tomography, Visualization, Optical tracking, Skull

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Proceedings Article | 23 March 2010 Paper

Off-center object of interest (OOI) imaging in filtered region of interest rotational angiography (FROI-RA)

Sebastian Schafer, Peter Noël, Alan Walczak, Andrew Kuhls-Gilcrist, Kenneth Hoffmann

Proceedings Volume 7622, 76223F (2010) https://doi.org/10.1117/12.844011

KEYWORDS: Image filtering, Angiography, X-rays, Image quality, Signal to noise ratio, Signal attenuation, X-ray imaging, Data centers, Data acquisition, Physics

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Proceedings Article | 27 March 2009 Paper

Reconstruction from a flexible number of projections in cone-beam computed tomography via active shape models

Peter Noël, Jason Corso, Jinhui Xu, Kenneth Hoffmann, Sebastian Schafer, Alan Walczak

Proceedings Volume 7259, 725949 (2009) https://doi.org/10.1117/12.811751

KEYWORDS: Reconstruction algorithms, Computed tomography, Image segmentation, Data modeling, Digital mammography, Sensors, Shape analysis, Angiography, X-rays, Bismuth

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Proceedings Article | 14 March 2009 Paper

High-contrast artifact reduction in cone beam computed tomography by using geometric techniques

Peter Noël, Jinhui Xu, Kenneth Hoffmann, Jason Corso, Sebastian Schafer, Alan Walczak

Proceedings Volume 7258, 72583A (2009) https://doi.org/10.1117/12.811679

KEYWORDS: Reconstruction algorithms, Computed tomography, Sensors, Image quality, Metals, Visibility, CT reconstruction, Computer simulations, X-rays, Diagnostics

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Proceedings Article | 13 March 2009 Paper

Toward region of interest computer tomography

Sebastian Schafer, Peter Noël, Alan Walczak, Kenneth Hoffmann

Proceedings Volume 7258, 72582N (2009) https://doi.org/10.1117/12.811542

KEYWORDS: Image filtering, X-rays, Signal attenuation, Angiography, Computed tomography, X-ray imaging, Head, X-ray computed tomography, Gadolinium, Tomography

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Computed Tomography (CT) is widely used in the modern clinical settings. In certain procedures, the region of interest (ROI) is often considerably smaller than the imaged field of view (FOV), thereby subjecting the patient to extra dose. For these procedures, we propose a method of filtered region-of-interest (FROI) CT. In this procedure, a predetermined ROI is imaged with standard x-ray intensity, while surrounding areas are imaged using a substantial lower x-ray intensity by interposing an x-ray attenuator in the beam. For the FROI-CT acquisitions in this study, a gadolinium filter with a circular central opening is placed in the x-ray beam of a standard clinical rotational angiography system. The resulting image contains a high intensity ROI, a low intensity region surrounding the ROI, and a transition region between these two. Three-dimensional reconstruction using these images would result in artifacts. Therefore, the intensities in the images are equalized prior to reconstruction. To equalize the intensities, first two images are obtained, one unfiltered and one with a filter in place. The corresponding data in the two images are used in a linear least-squares fit to determine the equalization function. The transition region is equalized using a radial filter technique, based on a comparison of the data on either side of the transition region after intensity equalization. The technique was evaluated using rotational angiographic sequences of a head phantom obtained with and without the filter in place. Differences between conventional (unfiltered) and FROI-equalized images of the head phantom were approximately 5%. Differences in reconstructed images (conventional and FROI) were 7% on average inside the reconstructed ROI. These results are comparable to those obtained for two separate standard acquisitions. A 50% dose reduction was obtained for a 50% FOV radius for the filter. These results indicate that FROI-CT can provide the physician with the image detail comparable to conventional image acquisition while reducing dose to the patient.

Proceedings Article | 26 March 2008 Paper

3D-3D alignment using particle swarm optimization

Sebastian Schafer, Kenneth Hoffmann, Peter Noël, Christina Bloebaum

Proceedings Volume 6914, 691431 (2008) https://doi.org/10.1117/12.771685

KEYWORDS: Particle swarm optimization, Particles, Head, Teeth, Data acquisition, Alignment procedures, Data fusion, Optimization (mathematics), X-rays, Tomography

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Proceedings Article | 29 March 2007 Paper

Linear programming approach to optimize 3D data obtained from multiple view angiograms

Peter Noël, Jinhui Xu, Kenneth Hoffmann, Vikas Singh, Sebastian Schafer, Alan Walczak

Proceedings Volume 6511, 65112F (2007) https://doi.org/10.1117/12.709499

KEYWORDS: Angiography, Calibration, Computer programming, Imaging systems, 3D image processing, Cerebrovascular diseases, Visualization, Error analysis, Scientific programming, Data centers

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Proceedings Article | 22 March 2007 Paper

Planning image-guided endovascular interventions: guidewire simulation using shortest path algorithms

Sebastian Schafer, Vikas Singh, Kenneth Hoffmann, Peter Noël, Jinhui Xu

Proceedings Volume 6509, 65092C (2007) https://doi.org/10.1117/12.709519

KEYWORDS: Computer simulations, Arteries, Angiography, 3D modeling, Surgery, X-rays, Data modeling, Instrument modeling, Data acquisition, Signal attenuation

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