TY - CHAP A1 - Schäfer, Stefan A1 - Plöntzke, Julia A1 - Röblitz, Susanna T1 - Mathematical Modelling of Follicular Maturation in Cows and Women T2 - 49. Jahrestagung der Physiologie und Pathologie der Fortpflanzung und gleichzeitig 41. Veterinär-Humanmedizinische Gemeinschaftstagung 2016, Leipzig. Y1 - 2016 ER - TY - CHAP A1 - Lange, Alexander A1 - Plöntzke, Julia A1 - Schäfer, Stefan A1 - Röblitz, Susanna T1 - Follicular maturation in cows: mathematical models and data T2 - 10. European Conference on Mathematical and Theoretical Biology Y1 - 2016 ER - TY - GEN A1 - Lange, Alexander A1 - Schwieger, Robert A1 - Plöntzke, Julia A1 - Schäfer, Stefan A1 - Röblitz, Susanna T1 - Follicular competition: the selection of dominant follicles as a synergistic effect N2 - The estrous cycle of mono-ovulatory species such as cows or humans, is known to show two or more waves of follicular growth and decline between two successive ovulations. Within each wave, there is one dominant follicle escorted by subordinate follicles of varying number. Under the surge of the luteinizing hormone a growing dominant follicle ovulates. Rarely the number of ovulating follicles exceeds one. In the biological literature, the change of hormonal concentrations and individually varying numbers of follicular receptors are made responsible for the selection of exactly one dominant follicle, yet a clear cause has not been identified. In this paper, we suggest a synergistic explanation based on competition, formulated by a parsimoniously defined system of ordinary differential equations (ODEs) that quantifies the time evolution of multiple follicles and their competitive interaction during one wave. Not discriminating between follicles, growth and decline are given by fixed rates. Competition is introduced via a growth-suppressing term, equally supported by all follicles. We prove that the number of dominant follicles is determined exclusively by the ratio of follicular growth and competition. This number turns out to be independent of the number of subordinate follicles. The asymptotic behavior of the corresponding dynamical system is investigated rigorously, where we demonstrate that the omega-limit set only contains fixed points. When also including follicular decline, our ODEs perfectly resemble ultrasound data of bovine follicles. Implications for the involved but not explicitly modeled hormones are discussed. T3 - ZIB-Report - 17-21 Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:0297-zib-63863 SN - 1438-0064 ER - TY - JOUR A1 - Fischer, Sophie A1 - Ehrig, Rainald A1 - Schäfer, Stefan A1 - Tronci, Enrico A1 - Mancini, Toni A1 - Egli, Marcel A1 - Ille, Fabian A1 - Krüger, Tillmann H. C. A1 - Leeners, Brigitte A1 - Röblitz, Susanna T1 - Mathematical Modelling and Simulation Provides Evidence for New Strategies of Ovarian Stimulation JF - Frontiers in Endocrinology N2 - New approaches to ovarian stimulation protocols, such as luteal start, random start or double stimulation, allow for flexibility in ovarian stimulation at different phases of the menstrual cycle which is especially useful when time for assisted reproductive technology is limited, e.g. for emergency fertility preservation in cancer patients. It has been proposed that the success of these methods is based on the continuous growth of multiple cohorts ("waves") of follicles throughout the menstrual cycle which leads to the availability of ovarian follicles for ovarian controlled stimulation at several time points. Though several preliminary studies have been published, their scientific evidence has not been considered as being strong enough to integrate these results into routine clinical practice. This work aims at adding further scientific evidence about the efficiency of variable-start protocols and underpinning the theory of follicular waves by using mathematical modelling and numerical simulations. For this purpose, we have modified and coupled two previously published models, one describing the time course of hormones and one describing competitive follicular growth in a normal menstrual cycle. The coupled model is used to test stimulation protocols in silico. Simulation results show the occurrence of follicles in a wave-like manner during a normal menstrual cycle and qualitatively predict the outcome of ovarian stimulation initiated at different time points of the menstrual cycle. Y1 - 2021 U6 - https://doi.org/10.3389/fendo.2021.613048 VL - 12 ER - TY - JOUR A1 - Lange, Alexander A1 - Schwieger, Robert A1 - Plöntzke, Julia A1 - Schäfer, Stefan A1 - Röblitz, Susanna T1 - Follicular competition in cows: the selection of dominant follicles as a synergistic effect JF - Journal of Mathematical Biology N2 - The reproductive cycle of mono-ovulatory species such as cows or humans is known to show two or more waves of follicular growth and decline between two successive ovulations. Within each wave, there is one dominant follicle escorted by subordinate follicles of varying number. Under the surge of the luteinizing hormone a growing dominant follicle ovulates. Rarely the number of ovulating follicles exceeds one. In the biological literature, the change of hormonal concentrations and individually varying numbers of follicular receptors are made responsible for the selection of exactly one dominant follicle, yet a clear cause has not been identified. In this paper, we suggest a synergistic explanation based on competition, formulated by a parsimoniously defined system of ordinary differential equations (ODEs) that quantifies the time evolution of multiple follicles and their competitive interaction during one wave. Not discriminating between follicles, growth and decline are given by fixed rates. Competition is introduced via a growth-suppressing term, equally supported by all follicles. We prove that the number of dominant follicles is determined exclusively by the ratio of follicular growth and competition. This number turns out to be independent of the number of subordinate follicles. The asymptotic behavior of the corresponding dynamical system is investigated rigorously, where we demonstrate that the ω-limit set only contains fixed points. When also including follicular decline, our ODEs perfectly resemble ultrasound data of bovine follicles. Implications for the involved but not explicitly modeled hormones are discussed. Y1 - 2018 U6 - https://doi.org/https://doi.org/10.1007/s00285-018-1284-0 ER - TY - JOUR A1 - Li, Jianning A1 - Pimentel, Pedro A1 - Szengel, Angelika A1 - Ehlke, Moritz A1 - Lamecker, Hans A1 - Zachow, Stefan A1 - Estacio, Laura A1 - Doenitz, Christian A1 - Ramm, Heiko A1 - Shi, Haochen A1 - Chen, Xiaojun A1 - Matzkin, Franco A1 - Newcombe, Virginia A1 - Ferrante, Enzo A1 - Jin, Yuan A1 - Ellis, David G. A1 - Aizenberg, Michele R. A1 - Kodym, Oldrich A1 - Spanel, Michal A1 - Herout, Adam A1 - Mainprize, James G. A1 - Fishman, Zachary A1 - Hardisty, Michael R. A1 - Bayat, Amirhossein A1 - Shit, Suprosanna A1 - Wang, Bomin A1 - Liu, Zhi A1 - Eder, Matthias A1 - Pepe, Antonio A1 - Gsaxner, Christina A1 - Alves, Victor A1 - Zefferer, Ulrike A1 - von Campe, Cord A1 - Pistracher, Karin A1 - Schäfer, Ute A1 - Schmalstieg, Dieter A1 - Menze, Bjoern H. A1 - Glocker, Ben A1 - Egger, Jan T1 - AutoImplant 2020 - First MICCAI Challenge on Automatic Cranial Implant Design JF - IEEE Transactions on Medical Imaging N2 - The aim of this paper is to provide a comprehensive overview of the MICCAI 2020 AutoImplant Challenge. The approaches and publications submitted and accepted within the challenge will be summarized and reported, highlighting common algorithmic trends and algorithmic diversity. Furthermore, the evaluation results will be presented, compared and discussed in regard to the challenge aim: seeking for low cost, fast and fully automated solutions for cranial implant design. Based on feedback from collaborating neurosurgeons, this paper concludes by stating open issues and post-challenge requirements for intra-operative use. Y1 - 2021 U6 - https://doi.org/10.1109/TMI.2021.3077047 SN - 0278-0062 VL - 40 IS - 9 SP - 2329 EP - 2342 ER - TY - GEN A1 - Ehrig, Rainald A1 - Dierkes, Thomas A1 - Schäfer, Stefan A1 - Röblitz, Susanna A1 - Tronci, Enrico A1 - Mancini, Toni A1 - Salvo, Ivano A1 - Alimguzhin, Vadim A1 - Mari, Federico A1 - Melatti, Igor A1 - Massini, Annalisa A1 - Krüger, Tillmann H. C. A1 - Egli, Marcel A1 - Ille, Fabian A1 - Leeners, Brigitte T1 - An Integrative Approach for Model Driven Computation of Treatments in Reproductive Medicine N2 - We present an overview of the current status of the European collaborative project PAEON. The challenge of PAEON is to provide specialists in reproduc- tive medicine with a computerised model of the menstrual cycle under normal and various pathological conditions, which will allow them to get further in- sight in fertility dynamics. This model also enables the simulation of treatment protocols, which were used within in vitro fertilization. By the definition of virtual patients through biologically admissible parametrizations our approach allows not only the evaluation of a given treatment strategy in silico, but also the design and optimization of such protocols. Once a protocol is formalized in the virtual hospital, the success can be controlled by a treatment execution monitor, which works then as a clinical decision support system. All these tools will be combined in a virtual hospital environment, enabling the access to the PAEON services through the web. T3 - ZIB-Report - 16-04 Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:0297-zib-57103 SN - 1438-0064 ER - TY - CHAP A1 - Ehrig, Rainald A1 - Dierkes, Thomas A1 - Schäfer, Stefan A1 - Röblitz, Susanna A1 - Tronci, Enrico A1 - Mancini, Toni A1 - Salvo, Ivano A1 - Alimguzhin, Vadim A1 - Mari, Federico A1 - Melatti, Igor A1 - Massini, Annalisa A1 - Krüger, Tillmann H. C. A1 - Egli, Marcel A1 - Ille, Fabian A1 - Leeners, Brigitte T1 - An integrative approach for model driven computation of treatments in reproductive medicine T2 - BIOMAT - Proceedings of the 15th International Symposium on Mathematical and Computational Biology, Rorkee, India Y1 - 2016 ER -