ASP-based approaches for solving the nuclear medicine scheduling problem

The Nuclear Medicine Scheduling (NMS) problem consists of assigning patients to a day, on which the patient will undergo the medical check, the preparation and the actual image detection process. The schedule should consider the different requirements of the patients and the available resources, e.g. varying time required for different diseases and radiopharmaceuticals used, number of injection chairs and tomographs available. In this paper, we present two solutions to the NMS problem based on Answer Set Programming (ASP). The first solution is a direct ASP encoding, which is then processed by an ASP solver, while the second solution employs a Logic-based Bender Decomposition (LBBD) approach implemented through the usage of multi-shot solving. Experiments employing real data show that the direct encoding provides overall satisfying results in terms of solutions quality in a relatively short time, and that the LBBD approach also helps in improving scalability.