# US 5,708,360 A · Active shield gradient coil for nuclear magnetic resonance imaging apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,708,360 A - Document ID: US5708360A - Status: Granted - Kind: A - Application number: 08/528,569 - Filed: 1995-09-15 - Granted: 1998-01-13 - Earliest claimed: 1994-09-16 - Assignees: Kabushiki Kaisha Toshiba - Inventors: Masao Yui; Masafumi Kondo - Web page: https://patentgrep.com/patent/US5708360A ## CPC - G01R 33/421: of main or gradient magnetic field - G01R 33/4215: {of the gradient magnetic field, e.g. using passive or active shielding of the gradient magnetic field} - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) ## Abstract An active shield gradient coil for a nuclear magnetic resonance imaging, formed by a primary coil having a fingerprint shaped current distribution formed on an inner cylinder in which at least a part of current return lines is cut out, a shield coil having a current distribution formed on an outer cylinder, and a bridging connection member for connecting cut out part of the current return lines of the primary coil with the shield coil, in which the current distribution of the shield coil is a composition of a first shield pattern for cancelling out a magnetic field produced by the primary coil outside the outer cylinder and a second shield pattern for cancelling out a magnetic field produced by the bridging connection member outside the outer cylinder. The current distribution of the primary coil can have turn back current paths for leading the cut out part of the current return lines on one end of the gradient coil to another end of the gradient coil. ## Claims ### Claim 1 A gradient coil for nuclear magnetic resonance imaging, comprising: a primary coil having a fingerprint shaped current distribution formed on an inner cylinder in which at least a part of current return lines is cut out to form a cut out part with broken current return lines; a shield coil having a current distribution formed on an outer cylinder; and a bridging connection member for connecting the cut out part of the current return lines of the primary coil with the shield coil; wherein the current distribution of the shield coil is a composition of a first shield pattern for cancelling out a magnetic field produced by the primary coil outside the outer cylinder and a second shield pattern for cancelling out a magnetic field produced by the bridging connection member outside the outer cylinder. ### Claim 2 (depends on 1) The gradient coil of claim 1, further comprising a return connection member for connecting remaining current turns of the primary coil, the remaining current turns being current turns in the cut out part of the current return lines of the primary coil which are not connected with the shield coil by the bridging connection member, and wherein the current distribution of the shield coil is a composition of the first shield pattern, the second shield pattern, and a third shield pattern for cancelling out a magnetic field produced by the return connection member outside the outer cylinder. ### Claim 3 (depends on 2) The gradient coil of claim 2, wherein the bridging connection member and the return connection member are arranged such that a Lorentz force exerted on the bridging connection member and a Lorentz force exerted on the return connection member cancel each other. ### Claim 4 (depends on 1) The gradient coil of claim 1, wherein the fingerprint shaped current distribution of the primary coil, the current distribution of the shield coil, and a current distribution of the bridging connection member are set in a current distribution pattern for realizing a desired gradient magnetic field linearity in a desired imaging field of view within the inner cylinder. ### Claim 5 (depends on 1) The gradient coil of claim 1, wherein the inner cylinder has a pair of sectional cuttings on one end of the inner cylinder. ### Claim 6 (depends on 1) The gradient coil of claim 1, wherein a first channel coil assembly formed by a first channel part of the primary coil, a first channel part of the shield coil, and a first channel part of the bridging connection member is enclosed within a second channel coil assembly formed by a second channel part of the primary coil, a second channel part of the shield coil, and a second channel part of the bridging connection member. ### Claim 7 (depends on 1) The gradient coil of claim 1, wherein the primary coil has turn back current paths for leading the cut out part of the current return lines on one end of the gradient coil to another end of the gradient coil. ### Claim 8 (depends on 7) The gradient coil of claim 7, wherein the turn back current paths are substantially parallel to an axial direction of the gradient coil. ### Claim 9 (depends on 7) The gradient coil of claim 7, further comprising a return connection member for connecting the cut out part of the current return lines together at said another end of the gradient coil. ### Claim 10 (depends on 7) The gradient coil of claim 7, wherein the bridging connection member connects the cut out part of the current return lines and the turn back current paths of the primary coil with the shield coil. ### Claim 11 (depends on 7) The gradient coil of claim 7, wherein the fingerprint shaped current distribution and the turn back current paths of the primary coil are formed on separate layers. ### Claim 12 (depends on 7) The gradient coil of claim 7, wherein the shield coil has a current distribution in which at least a part of shield coil current return lines is cut out to form a cut out part with broken shield coil current return lines and shield coil turn back current paths for leading the cut out part of the shield coil current return lines on one end of the gradient coil to said another end of the gradient coil. ### Claim 13 (depends on 12) The gradient coil of claim 12, wherein the shield coil turn back current paths are substantially parallel to an axial direction of the gradient coil. ### Claim 14 (depends on 12) The gradient coil of claim 12, further comprising a shield coil return connection member for connecting the cut out part of the shield coil current return lines together at said another end of the gradient coil. ### Claim 15 (depends on 12) The gradient coil of claim 12, wherein the bridging connection member connects the cut out part of the current return lines and the turn back current paths of the primary coil with the shield coil current return lines and the shield coil turn back current paths. ### Claim 16 (depends on 12) The gradient coil of claim 12, wherein the current distribution and the turn back current paths of the shield coil are formed on separate layers. ### Claim 17 A gradient coil for nuclear magnetic resonance imaging, comprising: a primary coil having a fingerprint shaped current distribution formed on an inner cylinder in which at least a part of current return lines is cut out to form a cut out part with broken current return lines, and turn back current paths for leading the cut out part of the current return lines on one end of the gradient coil to another end of the gradient coil; and a shield coil having a current distribution formed on an outer cylinder for cancelling out a magnetic field produced by the primary coil outside the outer cylinder. ### Claim 18 (depends on 17) The gradient coil of claim 17, wherein the turn back current paths are substantially parallel to an axial direction of the gradient coil. ### Claim 19 (depends on 17) The gradient coil of claim 17, further comprising a return connection member for connecting the cut out part of the current return lines together at said another end of the gradient coil. ### Claim 20 (depends on 17) The gradient coil of claim 17, further comprising a bridging connection member for connecting the cut out part of the current return lines and the turn back current paths of the primary coil with the shield coil. ### Claim 21 (depends on 17) The gradient coil of claim 17, wherein the fingerprint shaped current distribution and the turn back current paths of the primary coil are formed on separate layers. ### Claim 22 (depends on 17) The gradient coil of claim 17, wherein the shield coil has a current distribution in which at least a part of shield coil current return lines is cut out to form a cut out part with broken shield coil current return lines and shield coil turn back current paths for leading the cut out part of the shield coil current return lines on one end of the gradient coil to said another end of the gradient coil. ### Claim 23 (depends on 22) The gradient coil of claim 22, wherein the shield coil turn back current paths are substantially parallel to an axial direction of the gradient coil. ### Claim 24 (depends on 22) The gradient coil of claim 22, further comprising a shield coil return connection member for connecting the cut out part of the shield coil current return lines together at said another end of the gradient coil. ### Claim 25 (depends on 22) The gradient coil of claim 22, further comprising a bridging connection member for connecting the cut out part of the current return lines and the turn back current paths of the primary coil with the shield coil current return lines and the shield coil turn back current paths. ### Claim 26 (depends on 22) The gradient coil of claim 22, wherein the current distribution and the turn back current paths of the shield coil are formed on separate layers. ### Claim 27 (depends on 17) The gradient coil of claim 17, wherein a first channel coil assembly formed by a first channel part of the primary coil and a first channel part of the shield coil is enclosed within a second channel coil assembly formed by a second channel part of the primary coil and a second channel part of the shield coil. ### Claim 28 A nuclear magnetic resonance imaging apparatus, comprising: a gradient coil including a primary coil having a fingerprint shaped current distribution formed on an inner cylinder in which at least a part of current return lines is cut out to form a cut out part with broken current return lines; a shield coil having a current distribution formed on an outer cylinder; and a bridging connection member for connecting the cut out part of the current return lines of the primary coil with the shield coil; wherein the current distribution of the shield coil is a composition of a first shield pattern for cancelling out a magnetic field produced by the primary coil outside the outer cylinder and a second shield pattern for cancelling out a magnetic field produced by the bridging connection member outside the outer cylinder; and imaging means for imaging a body to be examined placed in a homogeneous static magnetic field by applying a radio frequency magnetic field onto the body to be examined and operating the gradient coil to apply gradient magnetic fields onto the body to be examined according to a pulse sequence, detecting nuclear magnetic resonance signals emitted from the body to be examined in response to the radio frequency magnetic field and the gradient magnetic fields, and processing the nuclear magnetic resonance signals to construct nuclear magnetic resonance images. ### Claim 29 (depends on 28) The apparatus of claim 28, further comprising a return connection member for connecting remaining current turns of the primary coil, the remaining current turns being current turns in the cut out part of the current return lines of the primary coil which are not connected with the shield coil by the bridging connection member, and wherein the current distribution of the shield coil is a composition of the first shield pattern, the second shield pattern, and a third shield pattern for cancelling out a magnetic field produced by the return connection member outside the outer cylinder. ### Claim 30 (depends on 29) The apparatus of claim 29, wherein the bridging connection member and the return connection member are arranged such that a Lorentz force exerted on the bridging connection member and a Lorentz force exerted on the return connection member cancel each other. ### Claim 31 (depends on 28) The apparatus of claim 28, wherein the fingerprint shaped current distribution of the primary coil, the current distribution of the shield coil, and a current distribution of the bridging connection member are set in a current distribution pattern for realizing a desired gradient magnetic field linearity in a desired imaging field of view within the inner cylinder. ### Claim 32 (depends on 28) The apparatus of claim 28, wherein the inner cylinder has a pair of sectional cuttings on one end of the inner cylinder. ### Claim 33 (depends on 28) The apparatus of claim 28, wherein a first channel coil assembly formed by a first channel part of the primary coil, a first channel part of the shield coil, and a first channel part of the bridging connection member is enclosed within a second channel coil assembly formed by a second channel part of the primary coil, a second channel part of the shield coil, and a second channel part of the bridging connection member. ### Claim 34 (depends on 28) The apparatus of claim 28, wherein the primary coil has turn back current paths for leading the cut out part of the current return lines on one end of the gradient coil to another end of the gradient coil. ### Claim 35 (depends on 34) The apparatus of claim 34, wherein the turn back current paths are substantially parallel to an axial direction of the gradient coil. ### Claim 36 (depends on 34) The apparatus of claim 34, further comprising a return connection member for connecting the cut out part of the current return lines together at said another end of the gradient coil. ### Claim 37 (depends on 34) The apparatus of claim 34, wherein the bridging connection member connects the cut out part of the current return lines and the turn back current paths of the primary coil with the shield coil. ### Claim 38 (depends on 34) The apparatus of claim 34, wherein the fingerprint shaped current distribution and the turn back current paths of the primary coil are formed on separate layers. ### Claim 39 (depends on 34) The apparatus of claim 34, wherein the shield coil has a current distribution in which at least a part of shield coil current return lines is cut out to form a cut out part with broken shield coil current return lines and shield coil turn back current paths for leading the cut out part of the shield coil current return lines on one end of the gradient coil to said another end of the gradient coil. ### Claim 40 (depends on 39) The apparatus of claim 39, wherein the shield coil turn back current paths are substantially parallel to an axial direction of the gradient coil. ### Claim 41 (depends on 39) The apparatus of claim 39, further comprising a shield coil return connection member for connecting the cut out part of the shield coil current return lines together at said another end of the gradient coil. ### Claim 42 (depends on 39) The apparatus of claim 39, wherein the bridging connection member connects the cut out part of the current return lines and the turn back current paths of the primary coil with the shield coil current return lines and the shield coil turn back current paths. ### Claim 43 (depends on 39) The apparatus of claim 39, wherein the current distribution and the turn back current paths of the shield coil are formed on separate layers. ### Claim 44 A nuclear magnetic resonance imaging apparatus, comprising: a gradient coil including a primary coil having a fingerprint shaped current distribution formed on an inner cylinder in which at least a part of current return lines is cut out to form a cut out part with broken current return lines, and turn back current paths for leading the cut out part of the current return lines on one end of the gradient coil to another end of the gradient coil; and a shield coil having a current distribution formed on an outer cylinder for cancelling out a magnetic field produced by the primary coil outside the outer cylinder; and imaging means for imaging a body to be examined placed in a homogeneous static magnetic field by applying a radio frequency magnetic field onto the body to be examined and operating the gradient coil to apply gradient magnetic fields onto the body to be examined according to a pulse sequence, detecting nuclear magnetic resonance signals emitted from the body to be examined in response to the radio frequency magnetic field and the gradient magnetic fields, and processing the nuclear magnetic resonance signals to construct nuclear magnetic resonance images. ### Claim 45 (depends on 44) The apparatus of claim 44, wherein the turn back current paths are substantially parallel to an axial direction of the gradient coil. ### Claim 46 (depends on 44) The apparatus of claim 44, further comprising a return connection member for connecting the cut out part of the current return lines together at said another end of the gradient coil. ### Claim 47 (depends on 44) The apparatus of claim 44, further comprising a bridging connection member for connecting the cut out part of the current return lines and the turn back current paths of the primary coil with the shield coil. ### Claim 48 (depends on 44) The apparatus of claim 44, wherein the fingerprint shaped current distribution and the turn back current paths of the primary coil are formed on separate layers. ### Claim 49 (depends on 44) The apparatus of claim 44, wherein the shield coil has a current distribution in which at least a part of shield coil current return lines is cut out to form a cut out part with broken shield coil current return lines and shield coil turn back current paths for leading the cut out part of the shield coil current return lines on one end of the gradient coil to said another end of the gradient coil. ### Claim 50 (depends on 49) The apparatus of claim 49, wherein the shield coil turn back current paths are substantially parallel to an axial direction of the gradient coil. ### Claim 51 (depends on 49) The apparatus of claim 49, further comprising a shield coil return connection member for connecting the cut out part of the shield coil current return lines together at said another end of the gradient coil. ### Claim 52 (depends on 49) The apparatus of claim 49, further comprising a bridging connection member for connecting the cut out part of the current return lines and the turn back current paths of the primary coil with the shield coil current return lines and the shield coil turn back current paths. ### Claim 53 (depends on 49) The apparatus of claim 49, wherein the current distribution and the turn back current paths of the shield coil are formed on separate layers. ### Claim 54 (depends on 44) The apparatus of claim 44, wherein a first channel coil assembly formed by a first channel part of the primary coil and a first channel part of the shield coil is enclosed within a second channel coil assembly formed by a second channel part of the primary coil and a second channel part of the shield coil.