Systems and methods for radiotherapy with magnetic resonance imaging

Abstract

Systems and methods for delivery of radiotherapy in conjunction with magnetic resonance imaging in which various conductors, shields and shims may be used to solve issues occurring when radiation therapy equipment is placed in the vicinity of an magnetic resonance imaging system.

What is claimed is: 
     
         1 . A system comprising:
 a magnetic resonance imaging system;   a gantry;   one or more radiation therapy heads fixed to the gantry;   one or more collimating devices associated with the one or more heads, including a plurality of leaves;   one or more leaf drive motors for moving the leaves, the one or more leaf drive motors including one or more position sensors, and a magnetic shield substantially surrounding the one or more position sensors;   one or more permanent magnets adjacent the one or more leaf drive motors, the one or more permanent magnets oriented so as to counteract the Mill's main magnetic field;   one or more additional conductive elements disposed around the gantry in a substantially symmetrical manner.   
     
     
         2 . The system of  claim 1  wherein the one or more collimating devices have a shape, volume and material permeability, and the one or more additional conductive elements have a shape, volume or material permeability designed to substantially match the shape, volume or material permeability of the collimating devices. 
     
     
         3 . The system of  claim 1  wherein the one or more collimating devices include outer housings and the one or more additional conductive elements are substantially similar to the outer housings of the collimating devices. 
     
     
         4 . The system of  claim 1  wherein only one radiation therapy head is fixed to the gantry and only one collimating device is associated with the one radiation therapy head and the one or more additional conductive elements comprises a single conductive element extending substantially around the portion of the gantry not occupied by the one collimating device. 
     
     
         5 . The system of  claim 1  wherein the magnetic shield is steel and a cylindrical shape. 
     
     
         6 . A system comprising:
 a magnetic resonance imaging system;   a gantry;   one or more radiation therapy heads fixed to the gantry;   one or more collimating devices associated with the one or more heads; and, one or more additional conductive elements disposed around the gantry in a substantially symmetrical manner.   
     
     
         7 . The system of  claim 6  wherein the one or more additional conductive elements are additional collimating devices. 
     
     
         8 . The system of  claim 6  wherein the one or more collimating devices include outer housings and the one or more additional conductive elements are substantially similar to the outer housings of the collimating devices. 
     
     
         9 . The system of  claim 6  wherein the one or more collimating devices have a shape, volume and material permeability, and the one or more additional conductive elements have a shape, volume or material permeability designed to substantially match the shape, volume or material permeability of the collimating devices. 
     
     
         10 . The system of  claim 6  wherein the one or more radiation therapy heads comprises three radioisotopic sources, and the one or more additional conductive elements comprise three conductors substantially similar to the outer housings of the collimating devices. 
     
     
         11 . The system of  claim 6  wherein only one radiation therapy head is fixed to the gantry and only one collimating device is associated with the one radiation therapy head and the one or more additional conductive elements comprises a single conductive element extending substantially around the portion of the gantry not occupied by the one collimating device. 
     
     
         12 . A system comprising:
 a magnetic resonance imaging system;   a gantry;   one or more radiation therapy heads fixed to the gantry;   one or more collimating devices associated with the one or more heads, including a plurality of leaves;   one or more leaf drive motors for moving the leaves, the one or more leaf drive motors including one or more position sensors and a magnetic shield substantially surrounding the one or more position sensors.   
     
     
         13 . The system of  claim 12  wherein the magnetic shield is a cylindrical shape. 
     
     
         14 . The system of  claim 12  wherein the magnetic shield is a ferromagnetic material. 
     
     
         15 . The system of  claim 12  wherein the ferromagnetic material is steel. 
     
     
         16 . A system comprising:
 a magnetic resonance imaging system;   a gantry;   one or more radiation therapy heads fixed to the gantry;   one or more collimating devices associated with the one or more heads, including a plurality of leaves;   one or more leaf drive motors for moving the leaves; and, one or more permanent magnets adjacent the one or more leaf drive motors, the one or more permanent magnets oriented so as to counteract the Mill's main magnetic field.   
     
     
         17 . The system of  claim 16  wherein a permanent magnet is placed on either side of the one or more leaf drive motors. 
     
     
         18 . The system of  claim 16  wherein the one or more permanent magnets are made from Neodymium.