Treatment technique for cardiac targets

A radiotherapy device comprising: a radiation source to generate a beam to treat a subject; a detector to detect a motion 500 of the subject, the motion comprising a first and second physiological motion component 502 and a controller coupled with the radiation source and the detector. The controller generates a beam shaping control signal based upon the first physiological motion 502 and also generates a beam gating control signal based upon the second physiological motion 504. Preferably, the first physiological motion 502 comprises a pseudo-periodic component. The first physiological motion 502 may comprise a respiratory motion. The second physiological 504 motion may comprise a cardiac motion. The detector may comprise first and second detectors to respectively detect the first and second physiological motions. The radiotherapy device may comprise a collimator, where the controller transmits the beam shaping control signal to the collimator. The controller may transmit the beam gating control signal to the radiation source. The detecting means may comprise a magnetic resonance imaging apparatus. The beam shaping control signal and/or the beam gating control signal may comprise time-varying instructions. The radiotherapy device may irradiate a cardiac target with the beam.