Radiotherapy and imaging apparatus

Abstract

A radiotherapy system comprises a patient support, moveable along a translation axis, an imaging apparatus, comprising a first magnetic coil and a second magnetic coil, the first and second magnetic coils having a common central axis parallel to the translation axis, and being displaced from one another along the central axis to form a gap therebetween, the imaging apparatus being configured to obtain an image of a patient on the patient support, a source of radiation mounted on a chassis, the chassis being rotatable about the central axis and the source being adapted to emit a beam of radiation through the gap along a beam axis that intersects with the central axis, a multi-leaf collimator comprising a plurality of elongate leaves movable between at least a withdrawn position in which the leaf lies outside the beam, and an extended position in which the leaf projects across the beam, and a radiation detector mounted to the chassis opposite the source, the radiation detector having a plurality of detector elements aligned with the elongate leaves when projected onto an isocentric plane.

1 . A radiotherapy system comprising:
 a patient support, moveable along a translation axis;   an imaging apparatus, comprising a first magnetic coil and a second magnetic coil, the first and second magnetic coils having a common central axis parallel to the translation axis, and being displaced from one another along the central axis to form a gap therebetween, the imaging apparatus being configured to obtain an image of a patient on the patient support;   a source of radiation mounted on a chassis, the chassis being rotatable about the central axis and the source being adapted to emit a beam of radiation through the gap along a beam axis that intersects with the central axis;   a multi-leaf collimator comprising a plurality of elongate leaves movable between at least a withdrawn position in which the leaf lies outside the beam, and an extended position in which the leaf projects across the beam; and   a radiation detector mounted to the chassis opposite the source, the radiation detector having a plurality of detector elements aligned with the elongate leaves when projected onto an isocentric plane.   
     
     
         2 . The radiotherapy system as claimed in  claim 1 , wherein the plurality of detector elements are arranged in columns. 
     
     
         3 . The radiotherapy system as claimed in  claim 2 , wherein each of the columns of detector elements is aligned with a respective elongate leaf. 
     
     
         4 . The radiotherapy system as claimed in  claim 2 , wherein the columns of detector elements are spaced between about 2 mm and about 10 mm apart when projected onto an isocentric plane. 
     
     
         5 . The radiotherapy system as claimed in  claim 1 , wherein the radiation detector is mounted outside the first and second magnetic coils. 
     
     
         6 . The radiotherapy system as claimed in  claim 1 , wherein the multi-leaf collimator further comprises a plurality of supports across the beam, for supporting the elongate leaves at least in their respective extended and intermediate positions. 
     
     
         7 . The radiotherapy system as claimed in  claim 1 , wherein the multi-leaf collimator further comprises a respective plurality of pneumatic or hydraulic actuators, for moving the plurality of elongate leaves. 
     
     
         8 . The radiotherapy system as claimed in  claim 1 , wherein the elongate leaves of the multi-leaf collimator are further moveable to a plurality of intermediate positions between their withdrawn and extended positions. 
     
     
         9 . The radiotherapy system as claimed in  claim 1 , wherein the multi-leaf collimator is fixed in its rotation with respect to the source of radiation. 
     
     
         10 . The radiotherapy system as claimed in  claim 1 , further comprising a control means for the source adapted to control the source so as to deliver a therapeutic radiation dose to a patient on the patient support, the control means being adapted to receive magnetic resonance images from the imaging apparatus during delivery of the dose. 
     
     
         11 . The radiotherapy system as claimed in  claim 1 , in which the chassis is continuously rotatable about the central axis.