A journey to understand SFRT

Abstract This article tells the story of a medical physicist's journey to understand SFRT which started by accident more than 15 years ago. For decades, clinical application and preclinical research have shown that spatially fractionated radiation therapy (SFRT) can achieve a magically high therapeutic index. However, only recently, SFRT received well‐deserved attention from mainstream radiation oncology. Today, our understanding of SFRT remains limited, which significantly hinders the advancement of SFRT for patient care. In this article, the author intends to shed some light on several important but unanswered SFRT research questions, including what is the essence of SFRT, which dosimetric parameters have clinical relevance and which do not, how does SFRT spare normal tissue but not tumor, and why radiobiological models developed for conventional radiation therapy may not be suitable for SFRT.