After a Ph.D. in theoretical cosmology, Tomas Janssen started a PostDoc on treatment planning at the radiotherapy department of the Netherlands Cancer Institute (NKI) in Amsterdam in 2009. He completed his residency in 2016 and has since worked as a medical physicist at the NKI. His current work focusses on treatment planning, online adaptive radiotherapy and the clinical application of artificial intelligence and data science. Key questions he tries to answer are: - What strategies for online adaptation significantly improve the treatment? - How can we use a data-driven approach to improve contour and treatment plan quality? - How can deep learning techniques be safely and effectively introduced in daily clinical practice?