AUTHOR=Kerkmeijer Linda G. W. , Valentini Vincenzo , Fuller Clifton D. (Dave) , Slotman Ben J. TITLE=Editorial: Online Adaptive MR-Guided Radiotherapy JOURNAL=Frontiers in Oncology VOLUME=11 YEAR=2021 URL=https://www.frontiersin.org/journals/oncology/articles/10.3389/fonc.2021.748685 DOI=10.3389/fonc.2021.748685 ISSN=2234-943X