Abstract: A multi level multileaf collimator employs leaves with leaf tips having a non-square shape in a beam's eye view to improve beam shaping effect and penumbra performance. The multi level multileaf collimator includes a first multileaf collimator in a first level comprising beam blocking leaves longitudinally movable in a first direction, and a second multileaf collimator in a second level comprising beam blocking leaves longitudinally movable in a second direction. The first direction may be generally parallel with the second direction and the leaves of the first multileaf collimator may laterally offset the leaves of the second multileaf collimator. The beam blocking leaves of the first multileaf collimator may comprise an end portion having a non-square shape in a beam's eye view.

Abstract: A radiation system includes a radiation source having an accelerator, the radiation source having a magnetic field associated therewith that is resulted from an operation of the accelerator, and a magnetic field source configured to provide a compensating magnetic field to at least partially counteract against the magnetic field that is resulted from the operation of the accelerator. A radiation system includes a radiation device having a radiation source, a patient support, and a protective guard located between the radiation source and the patient support, wherein the protective guard is moveably coupled to the radiation device or the patient support. A radiation system includes a particle generator for generating a particle, an accelerator for accelerating the particle, and a magnetic source for changing a trajectory of the particle, wherein the magnetic source comprises a permanent magnet.