Celina Imielinska - Academia.edu (original) (raw)

Papers by Celina Imielinska

arXiv (Cornell University), Nov 28, 2018

Augmented Reality (AR) systems add visual information to the world by using advanced display tech... more Augmented Reality (AR) systems add visual information to the world by using advanced display techniques. The advances in miniaturization and reduced costs make some of these systems feasible for applications in a wide set of fields. We present a potential component of the cyber infrastructure for the operating room of the future; a distributed AR based softwarehardware system that allows real-time visualization of 3D lung dynamics superimposed directly on the patient's body. Several emergency events (e.g. closed and tension pneumothorax) and surgical procedures related to the lung (e.g. lung transplantation, lung volume reduction surgery, surgical treatment of lung infections, lung cancer surgery) could benefit from the proposed prototype.

Proceedings of SPIE, Apr 29, 2005

The purpose of this paper is to evaluate the post-operative Magnetic Resonance Perfusion (MRP) sc... more The purpose of this paper is to evaluate the post-operative Magnetic Resonance Perfusion (MRP) scans of patients undergoing carotid endarterectomy (CEA), using a novel image-analysis algorithm, to determine if post-operative neurocognitive decline is associated with cerebral blood flow changes. CEA procedure reduces the risk of stroke in appropriately selected patients with significant carotid artery stenosis. However, 25% of patients experience subtle cognitive deficits after CEA compared to a control group. It was hypothesized that abnormalities in cerebral blood flow (CBF) are responsible for these cognitive deficits. A novel algorithm for analyzing MRperfusion (MRP) scans to identify and quantify the amount of CBF asymmetry in each hemisphere was developed and to quantify the degree of relative difference between three corresponding vascular regions in the ipsilateral and contralateral hemispheres, the Relative Difference Map (RDM). Patients undergoing CEA and spine surgery (controls) were examined preoperatively, and one day postoperatively with a battery of neuropsychometric (NPM) tests, and labeled "injured" patients with significant cognitive deficits, and "normal" if they demonstrated no decline in neurocognitive function. There are apparently significant RDM differences with MRP scans between the two hemispheres in patients with cognitive deficits which can be used to guide expert reviews of the imagery. The proposed methodology aids in the analysis of MRP parameters in patients with cognitive impairment.

We give a generalization of the hypergreedy algorithm for minimum weight perfect matching on a co... more We give a generalization of the hypergreedy algorithm for minimum weight perfect matching on a complete edge weighted graph whose weights satisfy the triangle inequality. With a modified version of this algorithm we obtain a log n-approximate perfect matching heuristic for points in the Euclidean plane, in O(n log z n) time.

Proceedings of SPIE, May 15, 2002

The purpose of this paper is to describe a framework for evaluating image segmentation algorithms... more The purpose of this paper is to describe a framework for evaluating image segmentation algorithms. Image segmentation consists of object recognition and delineation. For evaluating segmentation methods, three factors-precision (reproducibility), accuracy (agreement with truth), and efficiency (time taken)-need to be considered for both recognition and delineation. To assess precision, we need to choose a figure of merit (FOM), repeat segmentation considering all sources of variation, and determine variations in FOM via statistical analysis. It is impossible usually to establish true segmentation. Hence, to assess accuracy, we need to choose a surrogate of true segmentation and proceed as for precision. To assess efficiency, both the computational and the user time required for algorithm and operator training and for algorithm execution should be measured and analyzed. Precision, accuracy, and efficiency are interdependent. It is difficult to improve one factor without affecting others. Segmentation methods must be compared based on all three factors. The weight given to each factor depends on application.

Proceedings of the …, 1996

... Copyright notice. The VESALIUS Project: Visualization of Bronchial Tree Anataomy Lesson. Celi... more ... Copyright notice. The VESALIUS Project: Visualization of Bronchial Tree Anataomy Lesson. Celina Imielin'ska, Lisa Laino-Pepper, Richard Thumann, Carol Bean, Pat Molholt, and Derek Morris. Full text. Full text is available as a scanned copy of the original print version. ...

We present the latest developments in modeling 3D biomedical data via the Medial Scaffold (MS), a... more We present the latest developments in modeling 3D biomedical data via the Medial Scaffold (MS), a 3D acyclic oriented graph representation of the Medial Axis (MA) [LK07, SP08]. The MS (and associated 3D MA) can be computed as the result of the singularities of a geometric wave propagation simulation. We consider here some of the potential applications of this shape model in the realm of biomedical imaging. We can reconstruct complex object surfaces and make explicit the coarse-scale structures, which are ready-to-use in a number of practical applications, including: morphological measurement for cortex or bone thickness, centerline extraction (curve skeleton) for tracheotomy or colonoscopy, surface partitioning for cortical or anatomical surface classification, as well as registration and matching of shapes of tumors or carpal bones. The MS permits to automatically and efficiently map an unorganised point cloud, i.e., simple 3D coordinates of point samples, to a coherent surface set and associated approximate MA. The derived MS is used to further recover significant medium and large scale features, such as surface ridges and main axial symmetries. The radius field of the MS provides an intuitive definition for morphological measurements, while the graph structure made explicit by the MS is useful for shape registration and matching applications.

Algorithmica, 1997

We give a class of heuristic algorithms for minimum weight perfect matching on a complete edgewei... more We give a class of heuristic algorithms for minimum weight perfect matching on a complete edgeweighted graph K (V) satisfying the triangle inequality, where V is a set of an even number, n, of vertices. This class is a generalization of the Onethird heuristics, the hypergreedy heuristic, and it possibly employs any given exact or approximate perfect matching algorithm as an auxiliary heuristic to an appropriate subgraph of K (V). In particular, by using the heuristic of Gabow et al. [3] as its auxiliary heuristic, our algorithm can obtain a solution whose weight is at most (3 2 log 3 log 3 log 3 n + 2) times the weight of the optimal solution in O(n 2 log log log n) time, or a solution with an error of 3(log 3 log 3 n) 0.125 − 1 in O(n 2) time.

Algorithmica, 1997

We give a class of heuristic algorithms for minimum weight perfect matching on a complete edgewei... more We give a class of heuristic algorithms for minimum weight perfect matching on a complete edgeweighted graph K (V) satisfying the triangle inequality, where V is a set of an even number, n, of vertices. This class is a generalization of the Onethird heuristics, the hypergreedy heuristic, and it possibly employs any given exact or approximate perfect matching algorithm as an auxiliary heuristic to an appropriate subgraph of K (V). In particular, by using the heuristic of Gabow et al. [3] as its auxiliary heuristic, our algorithm can obtain a solution whose weight is at most (3 2 log 3 log 3 log 3 n + 2) times the weight of the optimal solution in O(n 2 log log log n) time, or a solution with an error of 3(log 3 log 3 n) 0.125 − 1 in O(n 2) time.

Algorithmica, 1997

We give a class of heuristic algorithms for minimum weight perfect matching on a complete edgewei... more We give a class of heuristic algorithms for minimum weight perfect matching on a complete edgeweighted graph K (V) satisfying the triangle inequality, where V is a set of an even number, n, of vertices. This class is a generalization of the Onethird heuristics, the hypergreedy heuristic, and it possibly employs any given exact or approximate perfect matching algorithm as an auxiliary heuristic to an appropriate subgraph of K (V). In particular, by using the heuristic of Gabow et al. [3] as its auxiliary heuristic, our algorithm can obtain a solution whose weight is at most (3 2 log 3 log 3 log 3 n + 2) times the weight of the optimal solution in O(n 2 log log log n) time, or a solution with an error of 3(log 3 log 3 n) 0.125 − 1 in O(n 2) time.

Algorithmica, 1997

We give a class of heuristic algorithms for minimum weight perfect matching on a complete edgewei... more We give a class of heuristic algorithms for minimum weight perfect matching on a complete edgeweighted graph K (V) satisfying the triangle inequality, where V is a set of an even number, n, of vertices. This class is a generalization of the Onethird heuristics, the hypergreedy heuristic, and it possibly employs any given exact or approximate perfect matching algorithm as an auxiliary heuristic to an appropriate subgraph of K (V). In particular, by using the heuristic of Gabow et al. [3] as its auxiliary heuristic, our algorithm can obtain a solution whose weight is at most (3 2 log 3 log 3 log 3 n + 2) times the weight of the optimal solution in O(n 2 log log log n) time, or a solution with an error of 3(log 3 log 3 n) 0.125 − 1 in O(n 2) time.

Wepropose aframework ofmulti-modality invariant within arigid body, under aseries of brain regist... more Wepropose aframework ofmulti-modality invariant within arigid body, under aseries of brain registration methods using symmetry plane as affinetransformations suchas rotation, theprincipal feature forgeometric matching. By translation and scaling, we prototype a bringing thesymmetry plane oftworigid objects into symmetry-based multi-modality registration coincidence, wecanpotentially matchtwoobjectsparadigm. Bybringing thesymmetry planes of approximately ifthere isnoapparent elastic distortion. tworigid objects, that werederived fromthe We illustrated thisconcept usingVisible Human same subject, intocoincidence, we can dataset, thatincluded colorcryosection, and potentially matchtwoobjects approximately if radiological data, fromwhich weextracted 3Dmesh thereisno elastic distortion. Kapouleas (2) modelsofskin, brain andskull, andaligned them proposed a waytousetheinter-hemispheric into nested bodies. Eachmodelwasgenerated with fissure planeinthreedimensions forthe different spatial o...

Communications of the ACM, 2005

The introduction of the Visible Human Project by Ackerman in 1995, described in the seminal paper... more The introduction of the Visible Human Project by Ackerman in 1995, described in the seminal paper in 1996 [9], brought a promise to anatomists that these two frozen, milled, and digitized cadavers---the Visible Male and Female---would revolutionize anatomy teaching by providing the most complete and detailed anatomical images ever. This vision could be compared to the proverbial "man on the moon" program for medical education and has proven to be much more challenging than expected. Although the ramifications of this project are not of the same scale as the shock created five centuries ago by the Padua physician Andreas Vesalius when he challenged the ancient Greek physician Galen's description of the human body, the original interest created by the availability of the Visible Human data was enormous.

… Image Computing and …, 2003

Accurate quantification of total body and the distribution of regional adipose tissue using manua... more Accurate quantification of total body and the distribution of regional adipose tissue using manual segmentation is a challenging problem due to the high variation between manual delineations. Manual segmentation also requires highly trained experts with knowledge of anatomy. We present a hybrid segmentation method that provides robust delineation results for adipose tissue from whole body MRI scans. A formal evaluation of accuracy of the segmentation method is performed. This semi-automatic segmentation algorithm reduces significantly the time required for quantification of adipose tissue, and the accuracy measurements show that the results are close to the ground truth obtained from manual segmentations.

Academic Radiology, 2008

Rationale and Objectives. An automated method for identification and segmentation of acute/subacu... more Rationale and Objectives. An automated method for identification and segmentation of acute/subacute ischemic stroke, using the inherent bi-fold symmetry in brain images, is presented. An accurate and automated method for localization of acute ischemic stroke could provide physicians with a mechanism for early detection and potentially faster delivery of effective stroke therapy. Materials and Methods. Segmentation of ischemic stroke was performed on magnetic resonance (MR) images of subacute rodent cerebral ischemia. Eight adult male Wistar rats weighing 225-300 g were anesthetized with halothane in a mix of 70% nitrous oxide/30% oxygen. Animal core temperature was maintained at 37°C during the entire surgical procedure, including occlusion of the middle cerebral artery (MCA) and the 90-minute post-reperfusion period. To confirm cerebral ischemia, transcranial measurements of cerebral blood flow were performed with laser-Doppler flowmetry, using 15-mm flexible fiberoptic Doppler probes attached to the skull over the MCA territory. Animal MR scans were performed at 1.5 T using a knee coil. Three experts performed manual tracing of the stroke regions for each rat, using the histologicstained slices to guide delineation of stroke regions. A strict tracing protocol was followed that included multiple (three) tracings of each stroke region. The volumetric MR image data were processed for each rat by computing the axis of symmetry and extracting statistical dissimilarities. A nonparametric Wilcoxon rank sum test operating on paired windows in opposing hemispheres identified seeds in the pixels exhibiting statistically significant bi-fold mirror asymmetry. Two brain reference maps were used for analysis: an absolute difference map (ADM) and a statistical difference map (SDM). Although an ADM simply displays the absolute difference by subtracting one brain hemisphere from its reflection, SDM highlights regions by labeling pixels exhibiting statistically significant asymmetry. Results. To assess the accuracy of the proposed segmentation method, the surrogate ground truth (the stroke tracing data) was compared to the results of our proposed automated segmentation algorithm. Three accuracy segmentation metrics were utilized: true-positive volume fraction (TPVF), false-positive volume fraction (FPVF), and false-negative volume fraction (FNVF). The mean value of the TPVF for our segmentation method was 0.8877; 95% CI 0.7254 to 1.0500; the mean FPVF was 0.3370, 95% CI-0.0893 to 0.7633; the mean FNVF was 0.1122, 95% CI-0.0502 to 0.2747. Conclusions. Unlike most segmentation methods that require some degree of manual intervention, our segmentation algorithm is fully automated and highly accurate in identifying regions of brain asymmetry. This approach is attractive for numerous neurologic applications where the operator's intervention should be minimal or null.

Ieee Transactions on Information Technology in Biomedicine, 2007

Augmented Reality (AR) systems add visual information to the world by using advanced display tech... more Augmented Reality (AR) systems add visual information to the world by using advanced display techniques. The advances in miniaturization and reduced costs make some of these systems feasible for applications in a wide set of fields. We present a potential component of the cyber infrastructure for the operating room of the future; a distributed AR based softwarehardware system that allows real-time visualization of 3D lung dynamics superimposed directly on the patient's body. Several emergency events (e.g. closed and tension pneumothorax) and surgical procedures related to the lung (e.g. lung transplantation, lung volume reduction surgery, surgical treatment of lung infections, lung cancer surgery) could benefit from the proposed prototype.

Visualization tools using Augmented Reality Environments are effective in applications related to... more Visualization tools using Augmented Reality Environments are effective in applications related to medical training, prognosis and expert interaction. Such medical visualization tools can also provide key visual insights on the physiology of deformable anatomical organs (e.g. lungs). In this paper we propose a deformation method that facilitates physically-based elastostatic deformations of 3D highresolution polygonal models. The implementation of the deformation method as a pre-computation approach is shown for a 3D high-resolution lung model. The deformation is represented as an integration of the applied force and the local elastic property assigned to the 3D lung model. The proposed deformation method shows faster convergence to equilibrium as compared to other physically-based simulation methods. The proposed method also accounts for the anisotropic tissue elastic properties. The transfer functions are formulated in such a way that they overcome stiffness effects during deformations.

International Journal of Computer Assisted Radiology and Surgery, Jun 19, 2007

Validation of a new protocol for computer-assisted evaluation of kinematics of double-bundle ACL ... more Validation of a new protocol for computer-assisted evaluation of kinematics of double-bundle ACL reconstruction. Clin Biomech 21(3):279-287 13. Hoff WA, Komistek RD, Dennis DA, Gabriel SM, Walker SA (1998) Three-dimensional determination of femoraltibial contact positions under in vivo conditions using fluoroscopy. Clin Biomech 13(7):455-472

arXiv (Cornell University), Nov 28, 2018

Augmented Reality (AR) systems add visual information to the world by using advanced display tech... more Augmented Reality (AR) systems add visual information to the world by using advanced display techniques. The advances in miniaturization and reduced costs make some of these systems feasible for applications in a wide set of fields. We present a potential component of the cyber infrastructure for the operating room of the future; a distributed AR based softwarehardware system that allows real-time visualization of 3D lung dynamics superimposed directly on the patient's body. Several emergency events (e.g. closed and tension pneumothorax) and surgical procedures related to the lung (e.g. lung transplantation, lung volume reduction surgery, surgical treatment of lung infections, lung cancer surgery) could benefit from the proposed prototype.

Proceedings of SPIE, Apr 29, 2005

The purpose of this paper is to evaluate the post-operative Magnetic Resonance Perfusion (MRP) sc... more The purpose of this paper is to evaluate the post-operative Magnetic Resonance Perfusion (MRP) scans of patients undergoing carotid endarterectomy (CEA), using a novel image-analysis algorithm, to determine if post-operative neurocognitive decline is associated with cerebral blood flow changes. CEA procedure reduces the risk of stroke in appropriately selected patients with significant carotid artery stenosis. However, 25% of patients experience subtle cognitive deficits after CEA compared to a control group. It was hypothesized that abnormalities in cerebral blood flow (CBF) are responsible for these cognitive deficits. A novel algorithm for analyzing MRperfusion (MRP) scans to identify and quantify the amount of CBF asymmetry in each hemisphere was developed and to quantify the degree of relative difference between three corresponding vascular regions in the ipsilateral and contralateral hemispheres, the Relative Difference Map (RDM). Patients undergoing CEA and spine surgery (controls) were examined preoperatively, and one day postoperatively with a battery of neuropsychometric (NPM) tests, and labeled "injured" patients with significant cognitive deficits, and "normal" if they demonstrated no decline in neurocognitive function. There are apparently significant RDM differences with MRP scans between the two hemispheres in patients with cognitive deficits which can be used to guide expert reviews of the imagery. The proposed methodology aids in the analysis of MRP parameters in patients with cognitive impairment.

We give a generalization of the hypergreedy algorithm for minimum weight perfect matching on a co... more We give a generalization of the hypergreedy algorithm for minimum weight perfect matching on a complete edge weighted graph whose weights satisfy the triangle inequality. With a modified version of this algorithm we obtain a log n-approximate perfect matching heuristic for points in the Euclidean plane, in O(n log z n) time.

Proceedings of SPIE, May 15, 2002

The purpose of this paper is to describe a framework for evaluating image segmentation algorithms... more The purpose of this paper is to describe a framework for evaluating image segmentation algorithms. Image segmentation consists of object recognition and delineation. For evaluating segmentation methods, three factors-precision (reproducibility), accuracy (agreement with truth), and efficiency (time taken)-need to be considered for both recognition and delineation. To assess precision, we need to choose a figure of merit (FOM), repeat segmentation considering all sources of variation, and determine variations in FOM via statistical analysis. It is impossible usually to establish true segmentation. Hence, to assess accuracy, we need to choose a surrogate of true segmentation and proceed as for precision. To assess efficiency, both the computational and the user time required for algorithm and operator training and for algorithm execution should be measured and analyzed. Precision, accuracy, and efficiency are interdependent. It is difficult to improve one factor without affecting others. Segmentation methods must be compared based on all three factors. The weight given to each factor depends on application.

Proceedings of the …, 1996

... Copyright notice. The VESALIUS Project: Visualization of Bronchial Tree Anataomy Lesson. Celi... more ... Copyright notice. The VESALIUS Project: Visualization of Bronchial Tree Anataomy Lesson. Celina Imielin'ska, Lisa Laino-Pepper, Richard Thumann, Carol Bean, Pat Molholt, and Derek Morris. Full text. Full text is available as a scanned copy of the original print version. ...

We present the latest developments in modeling 3D biomedical data via the Medial Scaffold (MS), a... more We present the latest developments in modeling 3D biomedical data via the Medial Scaffold (MS), a 3D acyclic oriented graph representation of the Medial Axis (MA) [LK07, SP08]. The MS (and associated 3D MA) can be computed as the result of the singularities of a geometric wave propagation simulation. We consider here some of the potential applications of this shape model in the realm of biomedical imaging. We can reconstruct complex object surfaces and make explicit the coarse-scale structures, which are ready-to-use in a number of practical applications, including: morphological measurement for cortex or bone thickness, centerline extraction (curve skeleton) for tracheotomy or colonoscopy, surface partitioning for cortical or anatomical surface classification, as well as registration and matching of shapes of tumors or carpal bones. The MS permits to automatically and efficiently map an unorganised point cloud, i.e., simple 3D coordinates of point samples, to a coherent surface set and associated approximate MA. The derived MS is used to further recover significant medium and large scale features, such as surface ridges and main axial symmetries. The radius field of the MS provides an intuitive definition for morphological measurements, while the graph structure made explicit by the MS is useful for shape registration and matching applications.

Algorithmica, 1997

We give a class of heuristic algorithms for minimum weight perfect matching on a complete edgewei... more We give a class of heuristic algorithms for minimum weight perfect matching on a complete edgeweighted graph K (V) satisfying the triangle inequality, where V is a set of an even number, n, of vertices. This class is a generalization of the Onethird heuristics, the hypergreedy heuristic, and it possibly employs any given exact or approximate perfect matching algorithm as an auxiliary heuristic to an appropriate subgraph of K (V). In particular, by using the heuristic of Gabow et al. [3] as its auxiliary heuristic, our algorithm can obtain a solution whose weight is at most (3 2 log 3 log 3 log 3 n + 2) times the weight of the optimal solution in O(n 2 log log log n) time, or a solution with an error of 3(log 3 log 3 n) 0.125 − 1 in O(n 2) time.

Algorithmica, 1997

We give a class of heuristic algorithms for minimum weight perfect matching on a complete edgewei... more We give a class of heuristic algorithms for minimum weight perfect matching on a complete edgeweighted graph K (V) satisfying the triangle inequality, where V is a set of an even number, n, of vertices. This class is a generalization of the Onethird heuristics, the hypergreedy heuristic, and it possibly employs any given exact or approximate perfect matching algorithm as an auxiliary heuristic to an appropriate subgraph of K (V). In particular, by using the heuristic of Gabow et al. [3] as its auxiliary heuristic, our algorithm can obtain a solution whose weight is at most (3 2 log 3 log 3 log 3 n + 2) times the weight of the optimal solution in O(n 2 log log log n) time, or a solution with an error of 3(log 3 log 3 n) 0.125 − 1 in O(n 2) time.

Algorithmica, 1997

We give a class of heuristic algorithms for minimum weight perfect matching on a complete edgewei... more We give a class of heuristic algorithms for minimum weight perfect matching on a complete edgeweighted graph K (V) satisfying the triangle inequality, where V is a set of an even number, n, of vertices. This class is a generalization of the Onethird heuristics, the hypergreedy heuristic, and it possibly employs any given exact or approximate perfect matching algorithm as an auxiliary heuristic to an appropriate subgraph of K (V). In particular, by using the heuristic of Gabow et al. [3] as its auxiliary heuristic, our algorithm can obtain a solution whose weight is at most (3 2 log 3 log 3 log 3 n + 2) times the weight of the optimal solution in O(n 2 log log log n) time, or a solution with an error of 3(log 3 log 3 n) 0.125 − 1 in O(n 2) time.

Algorithmica, 1997

We give a class of heuristic algorithms for minimum weight perfect matching on a complete edgewei... more We give a class of heuristic algorithms for minimum weight perfect matching on a complete edgeweighted graph K (V) satisfying the triangle inequality, where V is a set of an even number, n, of vertices. This class is a generalization of the Onethird heuristics, the hypergreedy heuristic, and it possibly employs any given exact or approximate perfect matching algorithm as an auxiliary heuristic to an appropriate subgraph of K (V). In particular, by using the heuristic of Gabow et al. [3] as its auxiliary heuristic, our algorithm can obtain a solution whose weight is at most (3 2 log 3 log 3 log 3 n + 2) times the weight of the optimal solution in O(n 2 log log log n) time, or a solution with an error of 3(log 3 log 3 n) 0.125 − 1 in O(n 2) time.

Wepropose aframework ofmulti-modality invariant within arigid body, under aseries of brain regist... more Wepropose aframework ofmulti-modality invariant within arigid body, under aseries of brain registration methods using symmetry plane as affinetransformations suchas rotation, theprincipal feature forgeometric matching. By translation and scaling, we prototype a bringing thesymmetry plane oftworigid objects into symmetry-based multi-modality registration coincidence, wecanpotentially matchtwoobjectsparadigm. Bybringing thesymmetry planes of approximately ifthere isnoapparent elastic distortion. tworigid objects, that werederived fromthe We illustrated thisconcept usingVisible Human same subject, intocoincidence, we can dataset, thatincluded colorcryosection, and potentially matchtwoobjects approximately if radiological data, fromwhich weextracted 3Dmesh thereisno elastic distortion. Kapouleas (2) modelsofskin, brain andskull, andaligned them proposed a waytousetheinter-hemispheric into nested bodies. Eachmodelwasgenerated with fissure planeinthreedimensions forthe different spatial o...

Communications of the ACM, 2005

The introduction of the Visible Human Project by Ackerman in 1995, described in the seminal paper... more The introduction of the Visible Human Project by Ackerman in 1995, described in the seminal paper in 1996 [9], brought a promise to anatomists that these two frozen, milled, and digitized cadavers---the Visible Male and Female---would revolutionize anatomy teaching by providing the most complete and detailed anatomical images ever. This vision could be compared to the proverbial "man on the moon" program for medical education and has proven to be much more challenging than expected. Although the ramifications of this project are not of the same scale as the shock created five centuries ago by the Padua physician Andreas Vesalius when he challenged the ancient Greek physician Galen's description of the human body, the original interest created by the availability of the Visible Human data was enormous.

… Image Computing and …, 2003

Accurate quantification of total body and the distribution of regional adipose tissue using manua... more Accurate quantification of total body and the distribution of regional adipose tissue using manual segmentation is a challenging problem due to the high variation between manual delineations. Manual segmentation also requires highly trained experts with knowledge of anatomy. We present a hybrid segmentation method that provides robust delineation results for adipose tissue from whole body MRI scans. A formal evaluation of accuracy of the segmentation method is performed. This semi-automatic segmentation algorithm reduces significantly the time required for quantification of adipose tissue, and the accuracy measurements show that the results are close to the ground truth obtained from manual segmentations.

Academic Radiology, 2008

Rationale and Objectives. An automated method for identification and segmentation of acute/subacu... more Rationale and Objectives. An automated method for identification and segmentation of acute/subacute ischemic stroke, using the inherent bi-fold symmetry in brain images, is presented. An accurate and automated method for localization of acute ischemic stroke could provide physicians with a mechanism for early detection and potentially faster delivery of effective stroke therapy. Materials and Methods. Segmentation of ischemic stroke was performed on magnetic resonance (MR) images of subacute rodent cerebral ischemia. Eight adult male Wistar rats weighing 225-300 g were anesthetized with halothane in a mix of 70% nitrous oxide/30% oxygen. Animal core temperature was maintained at 37°C during the entire surgical procedure, including occlusion of the middle cerebral artery (MCA) and the 90-minute post-reperfusion period. To confirm cerebral ischemia, transcranial measurements of cerebral blood flow were performed with laser-Doppler flowmetry, using 15-mm flexible fiberoptic Doppler probes attached to the skull over the MCA territory. Animal MR scans were performed at 1.5 T using a knee coil. Three experts performed manual tracing of the stroke regions for each rat, using the histologicstained slices to guide delineation of stroke regions. A strict tracing protocol was followed that included multiple (three) tracings of each stroke region. The volumetric MR image data were processed for each rat by computing the axis of symmetry and extracting statistical dissimilarities. A nonparametric Wilcoxon rank sum test operating on paired windows in opposing hemispheres identified seeds in the pixels exhibiting statistically significant bi-fold mirror asymmetry. Two brain reference maps were used for analysis: an absolute difference map (ADM) and a statistical difference map (SDM). Although an ADM simply displays the absolute difference by subtracting one brain hemisphere from its reflection, SDM highlights regions by labeling pixels exhibiting statistically significant asymmetry. Results. To assess the accuracy of the proposed segmentation method, the surrogate ground truth (the stroke tracing data) was compared to the results of our proposed automated segmentation algorithm. Three accuracy segmentation metrics were utilized: true-positive volume fraction (TPVF), false-positive volume fraction (FPVF), and false-negative volume fraction (FNVF). The mean value of the TPVF for our segmentation method was 0.8877; 95% CI 0.7254 to 1.0500; the mean FPVF was 0.3370, 95% CI-0.0893 to 0.7633; the mean FNVF was 0.1122, 95% CI-0.0502 to 0.2747. Conclusions. Unlike most segmentation methods that require some degree of manual intervention, our segmentation algorithm is fully automated and highly accurate in identifying regions of brain asymmetry. This approach is attractive for numerous neurologic applications where the operator's intervention should be minimal or null.

Ieee Transactions on Information Technology in Biomedicine, 2007

Augmented Reality (AR) systems add visual information to the world by using advanced display tech... more Augmented Reality (AR) systems add visual information to the world by using advanced display techniques. The advances in miniaturization and reduced costs make some of these systems feasible for applications in a wide set of fields. We present a potential component of the cyber infrastructure for the operating room of the future; a distributed AR based softwarehardware system that allows real-time visualization of 3D lung dynamics superimposed directly on the patient's body. Several emergency events (e.g. closed and tension pneumothorax) and surgical procedures related to the lung (e.g. lung transplantation, lung volume reduction surgery, surgical treatment of lung infections, lung cancer surgery) could benefit from the proposed prototype.

Visualization tools using Augmented Reality Environments are effective in applications related to... more Visualization tools using Augmented Reality Environments are effective in applications related to medical training, prognosis and expert interaction. Such medical visualization tools can also provide key visual insights on the physiology of deformable anatomical organs (e.g. lungs). In this paper we propose a deformation method that facilitates physically-based elastostatic deformations of 3D highresolution polygonal models. The implementation of the deformation method as a pre-computation approach is shown for a 3D high-resolution lung model. The deformation is represented as an integration of the applied force and the local elastic property assigned to the 3D lung model. The proposed deformation method shows faster convergence to equilibrium as compared to other physically-based simulation methods. The proposed method also accounts for the anisotropic tissue elastic properties. The transfer functions are formulated in such a way that they overcome stiffness effects during deformations.

International Journal of Computer Assisted Radiology and Surgery, Jun 19, 2007

Validation of a new protocol for computer-assisted evaluation of kinematics of double-bundle ACL ... more Validation of a new protocol for computer-assisted evaluation of kinematics of double-bundle ACL reconstruction. Clin Biomech 21(3):279-287 13. Hoff WA, Komistek RD, Dennis DA, Gabriel SM, Walker SA (1998) Three-dimensional determination of femoraltibial contact positions under in vivo conditions using fluoroscopy. Clin Biomech 13(7):455-472