High level workflow diagram outlining online and offline adaptive elements for adaptive brain radiotherapy. In the Online Adaption section (inside the dashed box), an onboard imager (either MRI or CBCT based) is used to acquire daily image sets, which are used to either shift the isocentre to the patient position (or vice versa) or to re-contour and re-optimize the treatment plan based on changes in anatomy via decision D1. The clinic may also wish to perform a verification scan prior to treatment (D2). The trigger for Offline Adaption (D3) may be either at a fixed time point (example after fraction 19 out of 30 fractions) or triggered by an observation at the treatment unit (e.g. swelling, mask not fitting, etc). If an offline MRI is acquired and the anatomy/disease has changed then a decision (D4) to use that scan to adapt the plan to the current anatomy and generate a new reference plan could be made, which would feed back into the online workflow. See article by Tseng et al., beginning on p. S3.