Combined mri and radiation therapy equipment

Abstract

In a combined MRI and radiation therapy system, a magnet structure and radiation therapy equipment are provided. The magnet structure comprises a single substantially cylindrical field coil structure comprising a number of superconducting coils joined by a support structure and extending axially of a central region. An outer vacuum chamber encloses the field coil structure in an evacuated volume. A cooling arrangement comprising cooling tubes is in thermal contact with the superconducting coils and receives a cryogen flowing through the cooling tubes. The radiation therapy equipment comprises a gamma radiation source rotatable about an axis of the field coil structure to direct a radiation beam substantially radially through the field coil structure. Parts of the field coil structure and the outer vacuum chamber are transparent to radiation emitted by the gamma radiation source whereby the radiation beam is directed through the field coil structure and the outer vacuum chamber without substantial interference.

I claim as my invention: 
     
         1 . A combined MRI and radiation therapy system, comprising:
 a magnet structure and radiation therapy equipment;   the magnet structure comprising
 a single substantially cylindrical field coil structure comprising a number of superconducting coils joined by a support structure and extending axially either side of a central region, 
 an outer vacuum chamber enclosing the field coil structure in an evacuated volume, and 
 a cooling arrangement comprising cooling tubes arranged in thermal contact with the superconducting coils and arranged to receive a cryogen flowing through the cooling tubes; and 
   the radiation therapy equipment comprising
 a gamma radiation source arranged to rotate about an axis of the substantially cylindrical field coil structure in the central region so as to direct a radiation beam along a selected path substantially radially through the substantially cylindrical field coil structure, and 
 parts of the field coil structure and the outer vacuum chamber in the central region within any path of the radiation beam which is selected are transparent to radiation emitted by the gamma radiation source, whereby the radiation beam is directed through the field coil structure and the outer vacuum chamber without substantial interference from the field coil structure and the outer vacuum chamber. 
   
     
     
         2 . The combined MRI and radiation therapy system according to  claim 1  wherein the gamma radiation source is further arranged to tilt, whereby the radiation beam is directed along a selected path at a selected angle from a true radial direction. 
     
     
         3 . The combined MRI and radiation therapy system according to  claim 1  wherein a gimbal arrangement is provided to allow motion of the gamma radiation source. 
     
     
         4 . The combined MRI and radiation therapy system according to  claim 1  wherein a thermal radiation shield is provided between the field coil structure and the outer vacuum chamber, and parts of the thermal radiation shield in the central region within any path of the radiation beam which is selected are transparent to the radiation emitted by the gamma radiation source, whereby the radiation beam is directed through the thermal radiation shield without substantial interference from the thermal radiation shield. 
     
     
         5 . The combined MRI and radiation therapy system according to  claim 1  wherein the magnet structure further comprises shield coils of greater diameter than the field coil structure located away from the central region toward axial ends of the field coil structure. 
     
     
         6 . The combined MRI and radiation therapy system according to  claim 1  wherein an axially central portion of the outer vacuum chamber has a lesser outer diameter than an outer diameter of axially outer portions of the outer vacuum chamber thereby defining a toroidal cavity, and the gimbal arrangement and the gamma source are substantially accommodated within the toroidal cavity. 
     
     
         7 . The combined MRI and radiation therapy system according to  claim 1  provided with looks covers to enclose the entire system in an aesthetically attractive outer cover. 
     
     
         8 . The combined MRI and radiation therapy system according to  claim 1  wherein the parts which are transparent to the radiation emitted by the gamma radiation source comprise beryllium, carbon, or aluminum. 
     
     
         9 . The combined MRI and radiation therapy system according to  claim 1  wherein the parts which are transparent to the radiation emitted by the gamma radiation source comprise resin-impregnated carbon fiber. 
     
     
         10 . The combined MRI and radiation therapy system according to  claim 1  wherein the cooling arrangement comprises upper and lower manifolds which extend through the central region and parts of the manifolds in the central region within any path of the radiation beam which is selected are transparent to the radiation emitted by the gamma radiation source, whereby the radiation beam is directed through the manifolds without substantial interference from the manifolds. 
     
     
         11 . The combined MRI and radiation therapy system according to  claim 10  wherein the parts which are transparent to the radiation emitted by the gamma radiation source comprise a ceramic.