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1. Off-Grid Green Hydrogen Production Systems

Author

Ibáñez-Rioja, Alejandro, Sakas, Georgios, Järvinen, Lauri, Puranen, Pietari, Sguarezi Filho, Alfeu J., editor, Jacomini, Rogério V., editor, Capovilla, Carlos E., editor, and Casella, Ivan Roberto Santana, editor

Published
2024
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5. What is Wrong with Continual Learning in Medical Image Segmentation?

Author

Gonzalez, Camila, Lemke, Nick, Sakas, Georgios, and Mukhopadhyay, Anirban

Subjects
Computer Science - Computer Vision and Pattern Recognition, Computer Science - Machine Learning
Abstract

Continual learning protocols are attracting increasing attention from the medical imaging community. In continual environments, datasets acquired under different conditions arrive sequentially; and each is only available for a limited period of time. Given the inherent privacy risks associated with medical data, this setup reflects the reality of deployment for deep learning diagnostic radiology systems. Many techniques exist to learn continuously for image classification, and several have been adapted to semantic segmentation. Yet most struggle to accumulate knowledge in a meaningful manner. Instead, they focus on preventing the problem of catastrophic forgetting, even when this reduces model plasticity and thereon burdens the training process. This puts into question whether the additional overhead of knowledge preservation is worth it - particularly for medical image segmentation, where computation requirements are already high - or if maintaining separate models would be a better solution. We propose UNEG, a simple and widely applicable multi-model benchmark that maintains separate segmentation and autoencoder networks for each training stage. The autoencoder is built from the same architecture as the segmentation network, which in our case is a full-resolution nnU-Net, to bypass any additional design decisions. During inference, the reconstruction error is used to select the most appropriate segmenter for each test image. Open this concept, we develop a fair evaluation scheme for different continual learning settings that moves beyond the prevention of catastrophic forgetting. Our results across three regions of interest (prostate, hippocampus, and right ventricle) show that UNEG outperforms several continual learning methods, reinforcing the need for strong baselines in continual learning research.

Published
2020

6. Leveraging Spatial Uncertainty for Online Error Compensation in EMT

Author

Krumb, Henry, Hofmann, Sofie, Kügler, David, Ghazy, Ahmed, Dorweiler, Bernhard, Schmitt, Robert, Sakas, Georgios, and Mukhopadhyay, Anirban

Subjects
Electrical Engineering and Systems Science - Image and Video Processing, Electrical Engineering and Systems Science - Signal Processing
Abstract

Purpose: Electromagnetic Tracking (EMT) can potentially complement fluoroscopic navigation, reducing radiation exposure in a hybrid setting. Due to the susceptibility to external distortions, systematic error in EMT needs to be compensated algorithmically. Compensation algorithms for EMT in guidewire procedures are only practical in an online setting. Methods: We collect positional data and train a symmetric Artificial Neural Network (ANN) architecture for compensating navigation error. The results are evaluated in both online and offline scenarios and are compared to polynomial fits. We assess spatial uncertainty of the compensation proposed by the ANN. Simulations based on real data show how this uncertainty measure can be utilized to improve accuracy and limit radiation exposure in hybrid navigation. Results: ANNs compensate unseen distortions by more than 70%, outperforming polynomial regression. Working on known distortions, ANNs outperform polynomials as well. We empirically demonstrate a linear relationship between tracking accuracy and model uncertainty. The effectiveness of hybrid tracking is shown in a simulation experiment. Conclusion: ANNs are suitable for EMT error compensation and can generalize across unseen distortions. Model uncertainty needs to be assessed when spatial error compensation algorithms are developed, so that training data collection can be optimized. Finally, we find that error compensation in EMT reduces the need for x-ray images in hybrid navigation.

Published
2020
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7. Planning Nonlinear Access Paths for Temporal Bone Surgery

Author

Fauser, Johannes, Sakas, Georgios, and Mukhopadhyay, Anirban

Subjects
Computer Science - Robotics
Abstract

Purpose: Interventions at the otobasis operate in the narrow region of the temporal bone where several highly sensitive organs define obstacles with minimal clearance for surgical instruments. Nonlinear trajectories for potential minimally-invasive interventions can provide larger distances to risk structures and optimized orientations of surgical instruments, thus improving clinical outcomes when compared to existing linear approaches. In this paper, we present fast and accurate planning methods for such nonlinear access paths. Methods: We define a specific motion planning problem in SE(3) = R3 x SO(3) with notable constraints in computation time and goal pose that reflect the requirements of temporal bone surgery.We then present k-RRT-Connect: two suitable motion planners based on bidirectional Rapidly-exploring Random Trees (RRT) to solve this problem efficiently. Results: The benefits of k-RRT-Connect are demonstrated on real CT data of patients. Their general performance is shown on a large set of realistic synthetic anatomies. We also show that these new algorithms outperform state of the art methods based on circular arcs or Bezier-Splines when applied to this specific problem. Conclusion: With this work we demonstrate that pre- and intra-operative planning of nonlinear access paths is possible for minimally-invasive surgeries at the otobasis., Comment: To be published in International Journal on Computer Assisted Radiology and Surgery (IJCARS), Spl. Issue IPCAI 2018

Published
2018

11. Visual Comparison of 3D Medical Image Segmentation Algorithms Based on Statistical Shape Models

Author

Geurts, Alexander, Sakas, Georgios, Kuijper, Arjan, Becker, Meike, Landesberger, Tatiana von, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Weikum, Gerhard, Series editor, and Duffy, Vincent G., editor

Published
2015
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12. Intraoperative Registration for Liver Tumor Ablation

Author

Oyarzun Laura, Cristina, Drechsler, Klaus, Erdt, Marius, Keil, Matthias, Noll, Matthias, De Beni, Stefano, Sakas, Georgios, Solbiati, Luigi, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Yoshida, Hiroyuki, editor, Sakas, Georgios, editor, and Linguraru, Marius George, editor

Published
2012
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13. FIST: Fast Interactive Segmentation of Tumors

Author

Steger, Sebastian, Sakas, Georgios, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Yoshida, Hiroyuki, editor, Sakas, Georgios, editor, and Linguraru, Marius George, editor

Published
2012
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14. Path Planning for Multi-port Lateral Skull Base Surgery Based on First Clinical Experiences

Author

Becker, Meike, Hansen, Stefan, Wesarg, Stefan, Sakas, Georgios, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Kobsa, Alfred, Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Nierstrasz, Oscar, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Weikum, Gerhard, Series editor, Erdt, Marius, editor, Linguraru, Marius George, editor, Oyarzun Laura, Cristina, editor, Shekhar, Raj, editor, Wesarg, Stefan, editor, González Ballester, Miguel Angel, editor, and Drechsler, Klaus, editor

Published
2014
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15. Absolute Orientation of Stereoscopic Cameras by Aligning Contours in Pairs of Images and Reference Images

Author

Selby, Boris Peter, Sakas, Georgios, Groch, Wolfgang-Dieter, Stilla, Uwe, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Nierstrasz, Oscar, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Sudan, Madhu, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Vardi, Moshe Y., Series editor, Weikum, Gerhard, Series editor, Stilla, Uwe, editor, Rottensteiner, Franz, editor, Mayer, Helmut, editor, Jutzi, Boris, editor, and Butenuth, Matthias, editor

Published
2011
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24. Prospective Head Motion Compensation for MRI by Updating the Gradients and Radio Frequency During Data Acquisition

Author

Dold, Christian, Zaitsev, Maxim, Speck, Oliver, Firle, Evelyn A., Hennig, Jürgen, Sakas, Georgios, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Dough, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Duncan, James S., editor, and Gerig, Guido, editor

Published
2005
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26. Epilog

Author

Sakas, Georgios, Zentrum fär Graphische Datenverabeitung e.V. Darmstadt (ZGDV), and Sakas, Georgios

Published
1993
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27. Literatur

Author

Sakas, Georgios, Zentrum fär Graphische Datenverabeitung e.V. Darmstadt (ZGDV), and Sakas, Georgios

Published
1993
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28. Implementierungen

Author

Sakas, Georgios, Zentrum fär Graphische Datenverabeitung e.V. Darmstadt (ZGDV), and Sakas, Georgios

Published
1993
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33. Stand der Technik

Author

Sakas, Georgios, Zentrum fär Graphische Datenverabeitung e.V. Darmstadt (ZGDV), and Sakas, Georgios

Published
1993
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34. Prolog

Author

Sakas, Georgios, Zentrum fär Graphische Datenverabeitung e.V. Darmstadt (ZGDV), and Sakas, Georgios

Published
1993
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35. Modeling and Simulation : Working Group Results

Author

Encarnação, José L., Sakas, Georgios, Peitgen, Heinz-Otto, Englert, Gabriele, ZGDV, Zentrum für Graphische Datenverarbeitung e. V., Encarnação, José L., editor, Sakas, Georgios, editor, Peitgen, Heinz-Otto, editor, and Englert, Gabriele, editor

Published
1992
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41. Random Fractals : Working Group Results

Author

Encarnação, José L., Sakas, Georgios, Peitgen, Heinz-Otto, Englert, Gabriele, ZGDV, Zentrum für Graphische Datenverarbeitung e. V., Encarnação, José L., editor, Sakas, Georgios, editor, Peitgen, Heinz-Otto, editor, and Englert, Gabriele, editor

Published
1992
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