Abstract
Laser photocoagulation is a technique applied in the treatment of retinal disease, which is often done manually or using simple control schemes. We pursue an optimization-based approach, namely Model Predictive Control (MPC), to enforce bounds on the peak temperature and, thus, to ensure safety during the medical treatment procedure – despite the spot-dependent absorption of the tissue. The desired laser repetition rate of 1 kHz is renders the requirements on the computation time of the MPC feedback a major challenge. We present a tailored MPC scheme using parametric model reduction, an extended Kalman filter for the parameter and state estimation, and suitably tuned stage costs and verify its applicability both in simulation and experiments with porcine eyes. Moreover, we give some insight on the implementation specifically tailored for fast numerical computations.
Zusammenfassung
Laserphotokoagulation ist eine Technik, die bei der Behandlung von Netzhauterkrankungen eingesetzt wird. Während dies oft manuell oder mit einfachen Kontrollschemata geschieht, verfolgen wir einen optimierungsbasierten Ansatz mittels Modellprädiktiver Regelung (Model Predictive Control; MPC), um Schranken für die Spitzentemperatur und damit für die Sicherheit während des medizinischen Behandlungsverfahrens zu erzwingen – trotz der vom Behandlungspunkt abhängigen Absorption des Gewebes. Zu diesem Zweck ist eine Wiederholungsrate von 1 kHz wünschenswert, was die Echtzeitanforderungen zu einer großen Herausforderung macht. Wir stellen ein maßgeschneidertes MPC-Schema mittels einer parametrischen Modellreduktion, einem erweiterten Kalman-Filter für die Parameter-und Zustandsschätzung, sowie geeignet konstruierte Stufenkosten vor und verifizieren seine Anwendbarkeit sowohl in Simulation als auch in Experimenten mit Schweineaugen. Außerdem geben wir einen Einblick in die Implementierung, die speziell für schnelle numerische Berechnungen zugeschnitten ist.
Acknowledgment
The collaborative project “Temperature controlled retinal laser treatment” is funded by the German Research Foundation (DFG) under the project number 430154635 (MU 3929/3-1, WO 2056/7-1, BR 1349/6-1). Karl Worthmann gratefully acknowledges funding by the German Research Foundation (DFG; grant WO 2056/6-1, project number 406141926).
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Author contributions: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.
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Research funding: None declared.
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Conflict of interest statement: The authors declare no conflicts of interest regarding this article.
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