Systems and methods for radiotherapy with magnetic resonance imaging
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.
1. A system comprising:
a magnetic resonance imaging system;
a gantry having a circumference around a patient couch within the magnetic resonance imaging system;
a radiation therapy head fixed to the gantry;
a collimating device associated with the head, including a plurality of leaves;
a leaf drive motor for moving the leaves, the leaf drive motor including one or more position sensors, and a magnetic shield substantially surrounding the one or more position sensors;
a permanent magnet adjacent the leaf drive motor, the permanent magnet oriented so as to counteract a main magnetic field of the magnetic resonance imaging system; and
a conductive element disposed around the gantry such that the conductive element and the radiation therapy head are arranged in a substantially symmetrical pattern about the circumference of the gantry.
2. The system of claim 1 wherein the collimating device has a shape, a volume, and a material permeability, and the conductive element matches at least one of the shape, the volume, and the material permeability of the collimating device.
3. The system of claim 1 wherein the collimating device includes a housing and the conductive element is substantially similar to the housing of the collimating device.
4. The system of claim 1 wherein the radiation therapy head is fixed to the gantry and conductive element is a single conductive element extending substantially around a portion of the gantry not occupied by the collimating device.
5. The system of claim 1 wherein the magnetic shield comprises steel and has a cylindrical shape.
6. A system comprising:
a magnetic resonance imaging system;
a gantry having a circumference around a patient couch within the magnetic resonance imaging system;
a radiation therapy head fixed to the gantry;
a collimating device associated with the head, the collimating device comprising:
a housing;
multi-leaf collimator leaves; and
multi-leaf collimator motors; and
a conductive element disposed around the circumference to form a substantially symmetrical pattern with the collimating device, the conductive element shaped substantially similar to the housing and constructed from a material which, in combination with the shape of the conductive element, substantially mimics eddy-current properties of the collimating device, wherein the conductive element is not a duplicate of the collimating device.
7. The system of claim 6 wherein the conductive element comprises an additional collimating device.
8. The system of claim 6 wherein the collimating device has a shape, a volume, and a material permeability, and the conductive element matches at least one of the shape, the volume, and the material permeability of the collimating device.
9. The system of claim 6 further comprising:
two additional radiation therapy heads, each of which comprises a radioisotopic source;
two additional collimating devices, each of which is associated with one of the two additional radiation therapy heads, and each of which includes an additional housing; and
two additional conductive elements, each of which is associated with one of the two additional radiation therapy heads, and each of which comprises a conductor substantially similar to the additional housing of the two additional collimating devices; and
wherein the substantially symmetrical pattern includes the collimating device, the two additional collimating devices, the conductive element, and the two additional conductive elements arranged substantially symmetrically around the circumference of the gantry.
10. The system of claim 6 wherein the radiation therapy head is fixed to the gantry and the conductive element is a single conductive element extending substantially around a portion of the gantry not occupied by the collimating device.
11. The system of claim 6 further comprising:
a plurality of radiation therapy heads, wherein the radiation therapy head is included in the plurality of radiation therapy heads;
a plurality of collimating devices, wherein:
the collimating device is included in the plurality of collimating devices,
each of the plurality of collimating devices is associated with one of the plurality of radiation therapy heads, and
each of the plurality of collimating devices includes a housing; and
a plurality of conductive elements, wherein:
each of the plurality of conductive elements is associated with one of the plurality of radiation therapy heads, and
each of the plurality of conducting elements comprise conductor substantially similar to the housing of the associated collimating device; and
wherein the substantially symmetrical pattern about the circumference of the gantry includes the plurality of conductive elements and the plurality of collimating devices arranged in the substantially symmetrical pattern.
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;
a plurality of leaf drive motors for moving the leaves, each of the plurality of leaf drive motors including at least one position sensor; and
a plurality of magnetic shields for each of the plurality of leaf drive motors, each magnetic shield substantially surrounding the at least one position sensor of one of the plurality of leaf drive motors.
13. The system of claim 12 wherein the plurality of magnetic shields have a cylindrical shape.
14. The system of claim 12 wherein the plurality of magnetic shields comprise a ferromagnetic material.
15. The system of claim 14 wherein the ferromagnetic material comprises 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 MRI's main magnetic field.
17. The system of claim 16 wherein the one or more permanent magnets comprises permanent magnets placed on opposite sides of the one or more leaf drive motors.
18. The system of claim 16 wherein the one or more permanent magnets comprise Neodymium.