Dekker served as a Radiotherapy Medical Physics Resident at Maastro Clinic from 2003 to 2005, later assuming the role of Medical Physics Head and Member of the Management Team until 2010. He was the Head of Information & Services, Member of the Management Team at Maastro Clinic from 2010 to 2015, and Scientific Director at Maastro Innovations from 2010 to 2018. He has served on advisory boards of organizations, including the European Society for Radiotherapy & Oncology, Hanarth Fund, MD Anderson, Novo Nordisk Foundation, Luxemburg National Research Fund and Peter Munk Cardiac Centre. He serves as the Head of Clinical Data Science at UM's Medical Center, while concurrently holding the positions of Full Professor of Clinical Data Science, Chief Scientific Officer at Medical Data Works, and Medical Physicist at Maastro Clinic.