Abstract: Disclosed herein are methods for determining the location of a moving target region (e.g., a tumor) based on the location of the center of its range of motion and the location of a target region surrogate, during a radiotherapy treatment session or a quality assurance (QA) session. These methods comprise characterizing the motion range of the target region, calculating the location of the center of the motion range, and determining a correlation between the position of the target region surrogate and the displacement of the target region from the center of the motion range as the target region moves.

Abstract: Described herein are methods and systems for generating a MV detector image for evaluating the quality of radiation delivery according to a radiotherapy treatment plan. The MV detector image is generated from MV detector measurements of a small number of multi-leaf collimator (MLC) leaf openings.

Abstract: Disclosed herein are systems and methods for rapidly delivering high doses of radiation, also known as, flash dose radiotherapy or flash radiotherapy. One variation of a system for flash radiotherapy has a plurality of therapeutic radiation sources on a support structure (e.g., a gantry or arm) and configured to toward a patient target region, and a controller in communication with all of the therapeutic radiation sources. The controller is configured to activate the plurality of therapeutic radiation sources simultaneously so that the patient target region rapidly receives a high dose of radiation, e.g. the entire prescribed dose of radiation. In some variations, a flash radiotherapy system has a pulsed, high-power source that may be used to generate an X-ray pulse that delivers a dose having a dose rate from about 7.5 Gy/s to about 70 Gy/s. Flash radiotherapy systems may also include one or more imaging systems mounted on the support structure.