# US 8,836,332 B2 · Method and apparatus for shielding a linear accelerator and a magnetic resonance imaging device from each other > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,836,332 B2 - Document ID: US8836332B2 - Status: Granted - Kind: B2 - Application number: 12/837,309 - Filed: 2010-07-15 - Published: 2011-01-20 - Granted: 2014-09-16 - Earliest claimed: 2009-07-15 - Assignees: ViewRay Incorporated - Applicants: Shmaryu M. Shvartsman; Gordon DeMeester; James F. Dempsey; John Lester Patrick - Inventors: Shmaryu M. Shvartsman; Gordon DeMeester; James F. Dempsey; John Lester Patrick - Web page: https://patentgrep.com/patent/US8836332B2 ## CPC - G01R 33/28: Details of apparatus provided for in groups G01R33/44 - G01R33/64 - G01R 33/3806: {Open magnet assemblies for improved access to the sample, e.g. C-type or U-type magnets} - G01R 33/42: Screening - G01R 33/421: of main or gradient magnetic field - G01R 33/4808: {Multimodal MR, e.g. MR combined with positron emission tomography [PET], MR combined with ultrasound or MR combined with computed tomography [CT]} - A61N 5/1039: {using functional images, e.g. PET or MRI} - A61N 5/1049: {for verifying the position of the patient with respect to the radiation beam} - A61N 5/1081: {Rotating beam systems with a specific mechanical construction, e.g. gantries} - A61N 2005/1055: {using magnetic resonance imaging [MRI]} - A61N 2005/1088: {generated by laser radiation} - A61N 2005/1089: {Electrons} - A61N 2005/1094: {Shielding, protecting against radiation} - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) - A61N: ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY (measurement of bioelectric currents A61B; surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body A61B18/00; anaesthetic apparatus in general A61M; incandescent lamps H01K; infrared radiators for heating H05B) ## Abstract A radiation therapy system comprises a magnetic resonance imaging (MRI) system combined with an irradiation system, which can include one or more linear accelerators (linacs) that can emit respective radiation beams suitable for radiation therapy. The MRI system includes a split magnet system, comprising first and second main magnets separated by gap. A gantry is positioned in the gap between the main MRI magnets and supports the linac(s) of the irradiation system. The gantry is rotatable independently of the MRI system and can angularly reposition the linac(s). Shielding can also be provided in the form of magnetic and/or RF shielding. Magnetic shielding can be provided for shielding the linac(s) from the magnetic field generated by the MRI magnets. RF shielding can be provided for shielding the MRI system from RF radiation from the linac. ## Claims ### Claim 1 A radiation therapy system, comprising: a magnetic resonance imaging (MRI) system, the MRI system including first and second main MRI magnets separated by an MRI magnet gap, wherein the first and second main MRI magnets operate together in order to produce a magnetic field, at least a portion of the magnetic field extending along a first longitudinal axis that extends through an isocenter of the first and second main MRI magnets; a gantry positioned in the MRI magnet gap, the gantry being rotatable about the first longitudinal axis; a linear particle accelerator (linac) supported by the gantry at a first fixed radial distance from the isocenter of the first and second main MRI magnets, the linac being aligned along a second longitudinal axis and being configured to rotate with the gantry and configured to direct a radiation beam towards the isocenter of the first and second main MRI magnets; and a magnetic shield supported by the gantry at a second fixed radial distance from the isocenter of the first and second main MRI magnets, wherein the magnetic shield includes at least a first shell and a second shell, the first shell at least partially surrounding both the linac and the second shell, and wherein at least one of the first shell and the second shell is formed of a material that includes steel. ### Claim 2 (depends on 1) The radiation therapy system of claim 1, wherein the second longitudinal axis extends through the isocenter as the linac rotates about the first longitudinal axis. ### Claim 3 (depends on 1) The radiation therapy system of claim 1, wherein the second longitudinal axis remains orthogonal to the first longitudinal axis as the linac rotates about the first longitudinal axis. ### Claim 4 (depends on 1) The radiation therapy system of claim 1, wherein the second shell is coaxial to the first shell. ### Claim 5 (depends on 1) The radiation therapy system of claim 1, wherein the second shell extends along a third longitudinal axis, wherein the second and third longitudinal axes are coplanar. ### Claim 6 (depends on 5) The radiation therapy system of claim 5, further comprising a second linac at least partially surrounded by a second magnetic shield. ### Claim 7 (depends on 1) The radiation therapy system of claim 1, wherein the first and second shells are formed of respective different steels. ### Claim 8 (depends on 1) The radiation therapy system of claim 1, wherein the magnetic field produced by the first and second main MRI magnets reverses direction at a specified location from the isocenter, and wherein the magnetic shield extends from the specified location. ### Claim 9 (depends on 1) The radiation therapy system of claim 1, wherein the magnetic shield further comprises a coil. ### Claim 10 (depends on 9) The radiation therapy system of claim 9, wherein the first shell provides passive magnetic shielding and the coil of the magnetic shield provides active magnetic shielding. ### Claim 11 (depends on 1) The radiation therapy system of claim 1, wherein the gantry is rotatable about the first longitudinal axis independently of the MRI system. ### Claim 12 (depends on 1) The radiation therapy system of claim 1, wherein the first shell is cylindrical. ### Claim 13 A radiation therapy system, comprising: a magnetic resonance imaging (MRI) system, the MRI system including first and second main MRI magnets configured for generating a magnetic field, wherein the first and second main MRI magnets are separated by an MRI magnet gap, and extend radially about a first longitudinal axis; a gantry positioned in the MRI magnet gap, the gantry being rotatable about the first longitudinal axis; a linear particle accelerator (linac) supported by the gantry at a fixed radial distance from the first longitudinal axis, the linac being configured to rotate with the gantry and configured to direct a radiation beam along a second longitudinal axis towards the first longitudinal axis; and a magnetic shield supported by the gantry at a second fixed radial distance from the first longitudinal axis, wherein the magnetic shield includes at least a first shell and a second shell, the first shell extending coaxially with the linac and at least partially both the linac and the second shell, and wherein at least one of the first shell and the second shell is formed of a material that includes steel. ### Claim 14 (depends on 13) The radiation therapy system of claim 13, wherein the second longitudinal axis extends through the first longitudinal axis as the linac rotates about the first longitudinal axis. ### Claim 15 (depends on 13) The radiation therapy system of claim 13, wherein the second longitudinal axis remains orthogonal to the first longitudinal axis as the linac rotates about the first longitudinal axis. ### Claim 16 (depends on 13) The radiation therapy system of claim 13, wherein the second shell is coaxial to the first shell. ### Claim 17 (depends on 13) The radiation therapy system of claim 13, wherein the second shell extends along a third longitudinal axis, wherein the second and third longitudinal axes are coplanar. ### Claim 18 (depends on 17) The radiation therapy system of claim 17, further comprising a second linac at least partially surrounded by a second magnetic shield. ### Claim 19 (depends on 13) The radiation therapy system of claim 13, wherein the magnetic field produced by the first and second main MRI magnets reverses direction at a specified location from the first longitudinal axis, and wherein the magnetic shield extends from the specified location. ### Claim 20 (depends on 13) The radiation therapy system of claim 13, wherein the magnetic shield further comprises a coil. ### Claim 21 (depends on 13) The radiation therapy system of claim 13, wherein the gantry is rotatable about the first longitudinal axis independently of the MRI system. ### Claim 22 (depends on 13) The radiation therapy system of claim 13, wherein the first shell is cylindrical. ### Claim 23 A radiation therapy system, comprising: a magnetic resonance imaging (MRI) system, the MRI system including first and second main MRI magnets configured for generating a magnetic field, wherein the first and second main MRI magnets are separated by an MRI magnet gap, and extend radially about a first longitudinal axis; a linear particle accelerator (linac) positioned in the MRI magnet gap at a fixed radial distance from the first longitudinal axis, the linac being configured to rotate about the first longitudinal axis and configured to direct a radiation beam along a second longitudinal axis towards the first longitudinal axis; and a first magnetic shield supported by a gantry at a second fixed radial distance from the first longitudinal axis, wherein the first magnetic shield includes at least a first shell and a second shell, the first shell extending coaxially with the second longitudinal axis and at least partially surrounding both the linac and the second shell, and wherein at least one of the first shell and the second shell is formed of a material that includes steel. ### Claim 24 (depends on 23) The radiation therapy system of claim 23, wherein the second longitudinal axis extends through the first longitudinal axis as the linac rotates about the first longitudinal axis. ### Claim 25 (depends on 23) The radiation therapy system of claim 23, wherein the second longitudinal axis remains orthogonal to the first longitudinal axis as the linac rotates about the first longitudinal axis. ### Claim 26 (depends on 23) The radiation therapy system of claim 23, wherein the second shell is coaxial to the first magnetic shield. ### Claim 27 (depends on 23) The radiation therapy system of claim 23, wherein the second shell extends along a third longitudinal axis, wherein the second and third longitudinal axes are coplanar. ### Claim 28 (depends on 27) The radiation therapy system of claim 27, further comprising a second linac at least partially surrounded by a second magnetic shield. ### Claim 29 (depends on 23) The radiation therapy system of claim 23, wherein the magnetic field produced by the first and second main MRI magnets reverses direction at a specified location from the first longitudinal axis, and wherein the first magnetic shield extends from the specified location. ### Claim 30 (depends on 23) The radiation therapy system of claim 23, wherein the first magnetic shield further comprises a coil. ### Claim 31 (depends on 23) The radiation therapy system of claim 23, wherein the linac is rotatable about the first longitudinal axis independently of the MRI system. ### Claim 32 (depends on 23) The radiation therapy system of claim 23, wherein the first shell is cylindrical. ### Claim 33 A radiation therapy system, comprising: a magnetic resonance imaging (MRI) system, the MRI system including first and second main MRI magnets separated by an MRI magnet gap, the first and second main MRI magnets being configured to produce a magnetic field along at least a portion of a longitudinal axis of the MRI system; a gantry positioned in the MRI magnet gap, the gantry being rotatable about the longitudinal axis; a linear particle accelerator (linac) supported by the gantry at a fixed radial distance from the longitudinal axis of the MRI system, the linac being configured to rotate with the gantry and configured to direct a radiation beam towards the longitudinal axis of the MRI system, the linac being configured to produce RF radiation; and a shield supported by the gantry, the shield including at least a first shell and a second shell, the first shell at least partially surrounding both the linac and the second shell, wherein at least one of the first shell is formed of a first material that includes steel or the second shell is formed of a second material that includes steel. ### Claim 34 (depends on 33) The radiation therapy system of claim 33, wherein the first material and the second material further includes one or more of copper, aluminum, and carbon fiber. ### Claim 35 (depends on 33) The radiation therapy system of claim 33, wherein the first material further includes at least one of an RF absorbing material and an RF reflecting material. ### Claim 36 (depends on 33) The radiation therapy system of claim 33, wherein the second material further includes at least one of an RF absorbing material and an RF reflecting material. ### Claim 37 (depends on 33) The radiation system of claim 33, wherein the first material is different from the second material. ### Claim 38 (depends on 37) The radiation system of claim 37, wherein the first and second shells are concentric about a common axis. ### Claim 39 (depends on 35) The radiation system of claim 35, further comprising a cooling system that cools the shield. ### Claim 40 (depends on 35) The radiation system of claim 35, wherein the first shell includes at least one slot extending therethrough. ### Claim 41 (depends on 33) The radiation therapy system of claim 33, wherein the shield includes a combination of active and passive magnetic shielding configured for shielding the linac from at least a portion of the magnetic field produced by the main MRI magnets. ### Claim 42 (depends on 33) The radiation therapy system of claim 33, wherein the shield is configured for shielding the MRI system from at least a portion of the RF radiation. ### Claim 43 (depends on 33) The radiation therapy system of claim 33, wherein the first shell is cylindrical. ### Claim 44 A radiation therapy system, comprising: a magnetic resonance imaging (MRI) system, the MRI system including first and second main MRI magnets separated by an MRI magnet gap, the first and second main MRI magnets being configured to produce a magnetic field along at least a portion of a longitudinal axis of the MRI system; a linear particle accelerator (linac) supported at a fixed radial distance from the longitudinal axis of the MRI system, the linac being configured to direct a radiation beam towards the longitudinal axis of the MRI system, the linac being configured to produce RF radiation; and an RF shield including at least a first shell and a second shell, the first shell at least partially surrounding both the linac and the second shell, wherein at least one of the first shell is formed of a first material that includes steel or the second shell is formed of a second material that includes steel. ### Claim 45 (depends on 44) The radiation therapy system of claim 44, wherein the first material and the second material further includes one or more of: copper, aluminum, and carbon fiber. ### Claim 46 (depends on 44) The radiation therapy system of claim 44, wherein the first material further includes at least one of an RF absorbing material and an RF reflecting material. ### Claim 47 (depends on 44) The radiation therapy system of claim 44, wherein the second material further includes at least one of an RF absorbing material and an RF reflecting material. ### Claim 48 (depends on 44) The radiation system of claim 44, wherein the first material is different from the second material. ### Claim 49 (depends on 47) The radiation system of claim 47, wherein the first and second shells are concentric about a common axis. ### Claim 50 (depends on 46) The radiation system of claim 46, further comprising a cooling system that cools the RF shield. ### Claim 51 (depends on 46) The radiation system of claim 46, wherein the first shell includes at least one slot extending therethrough. ### Claim 52 (depends on 44) The radiation therapy system of claim 44, wherein the RF shield is configured for shielding the MRI system from at least a portion of the RF radiation. ### Claim 53 (depends on 44) The radiation therapy system of claim 44, wherein the first shell is cylindrical.