Moritz Schaar, M.Sc.

2020 [ to top ]

• Bolke, A., Zvolsky, M., Kohlhase, N., Seeger, S., Schaar, M. and Rafecas, M.: Modelling of a Bi-Modal PET / Compton-Camera System for Non-Pure Positron Emitters, In: 2020 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 1-3, 2020, DOI: 10.1109/NSS/MIC42677.2020.9507915.
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  @inproceedings{Bolke2020, abstract = {In this work, we investigate the combination of two imaging modalities, positron emission tomography (PET) and Compton-camera (CC) imaging. A prototype for simultaneous PET/CC acquisition was simulated. The design is based on the combination of two existing prototypes and allows for a first investigation of the bi-modal acquisition of the radionuclides ⁸⁹Z<inf>r</inf> and ¹²⁴I. Since the simulation framework GATE is not able to properly output coincidences of such a bi-modal system, a post-processing tool was developed. This includes custom coincidence sorting and classification of PET and CC data. Here we present our postprocessing pipeline as well as our first results, and discuss the implications of the coincidence logic and the fraction of randoms on the data. The availability of such data is the prerequisite for developing novel image reconstruction approaches.}, author = {Bolke, A. and Zvolsky, M. and Kohlhase, N. and Seeger, S. and Schaar, M. and Rafecas, M.}, booktitle = {2020 {IEEE} Nuclear Science Symposium and Medical Imaging Conference ({NSS}/{MIC})}, keywords = {BolkeAndreas CC Compton IMT KohlhaseNadja Mermaid NucI PET RafecasMagdalena SchaarMoritz SeegerSteven Simulation ZvolskyMilan}, month = {oct}, pages = {1-3}, title = {Modelling of a Bi-Modal PET / Compton-Camera System for Non-Pure Positron Emitters}, year = 2020 }
• Kohlhase, N., Wegener, T., Schaar, M., Bolke, A., Etxebeste, A., Sarrut, D. and Rafecas, M.: Capability of MLEM and OE to Detect Range Shifts with a Compton Camera in Particle Therapy, IEEE Transactions on Radiation and Plasma Medical Sciences, 4(2), 233-242, 2020, DOI: 10.1109/TRPMS.2019.2937675.
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  @article{8815866, abstract = {To identify range deviations by using Compton cameras (CC), tomographic image reconstruction of CC data is needed. Within this context, image reconstruction is usually performed using Maximum Likelihood Expectation Maximization (MLEM), and more recently, the Origin Ensemble (OE) algorithm. In this work, we investigate how MLEM and OE affect the precision and accuracy of estimated range deviations. In particular, we focus on the effects of data selection, statistical fluctuations, and artifact reduction. The use of external information of the beam path through a hodoscope was also explored. Additionally, two methods to calculate range deviations were tested. To this aim, realistic proton beams were simulated using GATE and data from single spots as well as from 7 contiguous spots of an energy layer were reconstructed. MLEM and OE reacted differently to the poor data statistics. In general, both algorithms were able to detect range shifts for single spots, particularly when multiple coincidences were also considered. Selection of events corresponding to the most relevant energy peaks decreased the identification performance due to the lower statistics. When data from several contiguous spots were jointly reconstructed, the accuracy of the results degraded significantly, and non-zero shifts were assigned when no shifts had occurred. The limited size of the cameras and the subsequent restriction in the orientation and aperture of detected cones, as well as in the number of detected events are major challenges. Future efforts should be devoted to noise regularization and compensation for data truncation.}, author = {{Kohlhase}, N. and {Wegener}, T. and {Schaar}, M. and {Bolke}, A. and {Etxebeste}, A. and {Sarrut}, D. and {Rafecas}, M.}, journal = {IEEE Transactions on Radiation and Plasma Medical Sciences}, keywords = {BolkeAndreas KohlhaseNadja NucI NucIRangeVerification RafecasMagdalena SchaarMoritz imt}, month = {March}, number = 2, pages = {233-242}, title = {Capability of MLEM and OE to Detect Range Shifts with a Compton Camera in Particle Therapy}, volume = 4, year = 2020 }

2019 [ to top ]

• Schaar, M. and Rafecas, M.: Modelling of Scatter in the System Matrix for 3D PET Image Reconstruction: a Comparative Study, In: 2019 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2019, DOI: 10.1109/nss/mic42101.2019.9059797.
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  @inproceedings{Schaar2019, author = {Schaar, M. and Rafecas, M.}, booktitle = {2019 {IEEE} Nuclear Science Symposium and Medical Imaging Conference ({NSS}/{MIC})}, keywords = {CTPET IMT MLEM NucI OE RafecasMagdalena SSS SchaarMoritz scatter}, month = {oct}, publisher = {{IEEE}}, title = {Modelling of Scatter in the System Matrix for 3D PET Image Reconstruction: a Comparative Study}, year = 2019 }
• Zvolsky, M., Schreiner, N., Seeger, S., Schaar, M., Rakers, S. and Rafecas, M.: Digital Zebrafish Phantom based on Micro-CT Data for Imaging Research, In: 2019 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2019, DOI: 10.1109/nss/mic42101.2019.9059702.
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  @inproceedings{Zvolsky2019, author = {Zvolsky, M. and Schreiner, N. and Seeger, S. and Schaar, M. and Rakers, S. and Rafecas, M.}, booktitle = {2019 {IEEE} Nuclear Science Symposium and Medical Imaging Conference ({NSS}/{MIC})}, keywords = {IMT MERMAID NucI RafecasMagdalena SchaarMoritz SeegerSteven ZvolskyMilan}, month = {oct}, publisher = {{IEEE}}, title = {{Digital Zebrafish Phantom based on Micro-CT Data for Imaging Research}}, year = 2019 }
• Zvolsky, M., Seeger, S., Schaar, M., Schmidt, C. and Rafecas, M.: MERMAID - A PET Prototype for Small Aquatic Animal Imaging, In: 2019 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2019, DOI: 10.1109/nss/mic42101.2019.9059687.
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  @inproceedings{Zvolsky2019a, author = {Zvolsky, M. and Seeger, S. and Schaar, M. and Schmidt, C. and Rafecas, M.}, booktitle = {2019 {IEEE} Nuclear Science Symposium and Medical Imaging Conference ({NSS}/{MIC})}, keywords = {IMT MERMAID NucI RafecasMagdalena SchaarMoritz SeegerSteven ZvolskyMilan}, month = {oct}, publisher = {{IEEE}}, title = {{MERMAID - A PET Prototype for Small Aquatic Animal Imaging}}, year = 2019 }
• Kohlhase, N., Wegener, T., Schaar, M., Bolke, A. and Rafecas, M.: Bildrekonstruktion von Compton-Kamera Daten unter Verwendung eines Hodoskops für die Reichweitenverifikation in der Partikeltherapie, In: 50. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik (DGMP) - Abstractband, 317, 2019.
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  @inproceedings{kohlhase2019bildrekonstruktion, author = {Kohlhase, N and Wegener, T and Schaar, M and Bolke, A and Rafecas, M}, booktitle = {50. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik (DGMP) - Abstractband}, editor = {Gromoll, Christian and Wegner, Niels}, keywords = {BolkeAndreas KohlhaseNadja NucI NucIRangeVerification RafecasMagdalena SchaarMoritz imt}, organization = {Deutsche Gesellschaft für Medizinische Physik}, pages = 317, title = {Bildrekonstruktion von Compton-Kamera Daten unter Verwendung eines Hodoskops für die Reichweitenverifikation in der Partikeltherapie}, year = 2019 }
• Wegener, T., Kohlhase, N., Schaar, M., Bolke, A. and Rafecas, M.: Stochastic behavior of the Origin-Ensemble Algorithm – effect on ange verification in proton therapy using Compton-Cameras, In: 50. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik (DGMP) - Abstractband, 240, 2019.
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  @inproceedings{wegener2019stochastic, author = {Wegener, T and Kohlhase, N and Schaar, M and Bolke, A and Rafecas, M}, booktitle = {50. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik (DGMP) - Abstractband}, editor = {Gromoll, Christian and Wegner, Niels}, keywords = {BolkeAndreas KohlhaseNadja NucI NucIRangeVerification RafecasMagdalena SchaarMoritz imt}, organization = {Deutsche Gesellschaft für Medizinische Physik}, pages = 240, title = {Stochastic behavior of the Origin-Ensemble Algorithm – effect on ange verification in proton therapy using Compton-Cameras}, year = 2019 }
• Zvolský, M., Seeger, S., Schmidt, C., Bruhn, D., Schaar, M., Weller, D. and Rafecas, M.: Nukleare in-vivo Bildgebung von Zebrafischen, In: 50. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik (DGMP) - Abstractband, 35, 2019.
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  @inproceedings{zvolsky2019nukleare, author = {Zvolský, M and Seeger, S and Schmidt, C and Bruhn, D and Schaar, M and Weller, D and Rafecas, M}, booktitle = {50. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik (DGMP) - Abstractband}, editor = {Gromoll, Christian and Wegner, Niels}, keywords = {MERMAID NucI RafecasMagdalena SchaarMoritz SeegerSteven ZvolskyMilan imt}, pages = 35, title = {Nukleare in-vivo Bildgebung von Zebrafischen}, year = 2019 }

2017 [ to top ]

• Schaar, M., Buzug, T. M. and Rafecas, M.: PET image reconstruction using the Origin Ensemble algorithm and geometric constraints, In: Current Directions in Biomedical Engineering, 549-553, 2017, DOI: 10.1515/cdbme-2017-0115.
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  @inproceedings{schaar2017oebmt, author = {Schaar, Moritz and Buzug, Thorsten M. and Rafecas, Magdalena}, booktitle = {Deutsche Gesellschaft für Biomedizinische Technik Jahrestagung, Dresden, Sept. 10--13, 2017}, journal = {Current Directions in Biomedical Engineering}, keywords = {BuzugThorsten CTPET MLEM NucI OE PET RafecasMagdalena SSS SchaarMoritz imt scatter}, number = 2, pages = {549-553}, publisher = {De Gruyter}, title = {PET image reconstruction using the Origin Ensemble algorithm and geometric constraints}, type = {Publication}, volume = 3, year = 2017 }

2013 [ to top ]

• Schaar, M. and Erhardt, J.: Segmentation of Anatomical Structures using Statistical Shape Models based on Level Sets, In: Student Conference Medical Engineering Science, 2013.
  [ BibTeX ]
   
  @inproceedings{Schaar2013, author = {Schaar, M. and Erhardt, J.}, booktitle = {Student Conference Medical Engineering Science}, keywords = {SchaarMoritz}, title = {Segmentation of Anatomical Structures using Statistical Shape Models based on Level Sets}, year = 2013 }