Andreas Bolke, M.Sc.

2020 [ to top ]

• Kohlhase, N., Stille, M., Bolke, A., Zvolský, M. and Rafecas, M.: Compton Camera Image Reconstruction with A-Priori Information from a Beam Tagging Hodoscope, In: 2020 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 1-4, 2020, DOI: 10.1109/NSS/MIC42677.2020.9507820.
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  @inproceedings{9507820, abstract = {Compton cameras (CC) have been proposed for range monitoring in proton therapy. The goal is to detected the prompt-gamma (PG) radiation which emerges from the patient, and estimate the underlying activation distribution by using tomographic reconstruction algorithms. The reconstructed CC images are often affected by high levels of statistical noise and other artefacts. With the aim of improving the reconstructed images, here we study various approaches able to exploit a-priori information from a beam-tagging hodoscope. The latter provides an estimation about the beam spread and its direction, so that this information can be used before or during the reconstruction in different ways, e.g. to restrict the volume-of-response assigned to each event, or to design a novel penalty function for regularized image reconstruction. We have implemented several approaches using Monte Carlo simulated data. In particular, our penalized reconstruction led to a significant improvement of the image quality. The estimated distal edge was well resolved for all tested scenarios.}, author = {Kohlhase, Nadja and Stille, Maik and Bolke, Andreas and Zvolský, Milan and Rafecas, Magdalena}, booktitle = {2020 {IEEE} Nuclear Science Symposium and Medical Imaging Conference ({NSS}/{MIC})}, keywords = {BolkeAndreas CC Compton IMT KohlhaseNadja NucI NucIRangeVerification RafecasMagdalena Simulation StilleMaik ZvolskyMilan}, month = {oct}, pages = {1-4}, title = {Compton Camera Image Reconstruction with A-Priori Information from a Beam Tagging Hodoscope}, year = 2020 }
• 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 ]

• 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 }