# US 12,601,800 B2 · Metamaterial slab for MRI > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,601,800 B2 - Document ID: US12601800B2 - Status: Granted - Kind: B2 - Application number: 18/362,942 - Filed: 2023-07-31 - Published: 2024-02-01 - Granted: 2026-04-14 - Earliest claimed: 2022-07-29 - Assignees: The Governors of the University of Alberta; Alberta Health Services - Applicants: The Governors of the University of Alberta; Alberta Health Services - Inventors: Adam Maunder; Nicola de Zanche; Ashwin Iyer - Web page: https://patentgrep.com/patent/US12601800B2 ## CPC - G01R 33/387: Compensation of inhomogeneities - G01R 33/5659: {caused by a distortion of the RF magnetic field, e.g. spatial inhomogeneities of the RF magnetic field (G01R33/56509, G01R33/56518, G01R33/56536 take precedence)} - G01R 33/36: Electrical details, e.g. matching or coupling of the coil to the receiver - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) ## Abstract A metamaterial (MTM) slab for a Magnetic Resonance Imaging (MRI) system passively interacts with a field generated by a transmit device to improve homogeneity of the field, specific absorption rate, and/or strength of the field. The MTM slab may also be connected to RF receive circuitry at one or more ports to act as a receiver for the MRI. The MTM slab may comprise a first layer generally defining a surface and a second layer offset from the surface generally defined by the first layer, the first layer and the second layer interacting to form a 2D transmission line supporting radio frequency (RF) current along the surface in a first direction and in a second direction transverse to the first direction, the first layer and the second layer being connected via linking capacitors. ## Claims ### Claim 1 A metamaterial structure configured to passively interact with a field generated by a transmit device within the MRI system to improve one or more of homogeneity of the field within a scan target, specific absorption rate within the scan target, and strength of the field within the scan target when the metamaterial structure is present within a bore of the MRI system with the scan target, the metamaterial structure comprising: a first layer generally defining a surface and a second layer offset from the surface generally defined by the first layer, the first layer and the second layer interacting to form a 2D transmission line supporting radio frequency (RF) current along the surface in a first direction tangential to the surface and in a second direction tangential to the surface and transverse to the first direction, the first layer and the second layer being connected via linking capacitors; the metamaterial structure being configured so that, of a set of natural resonance modes of the metamaterial structure, a natural resonance mode of the set of natural resonance mode having greatest coupling to the field generated by the transmit device has a natural frequency different from a transmit frequency of the transmit device. ### Claim 2 (depends on 1) The metamaterial structure of claim 1 comprising tuning elements that add or remove capacitance or inductance to alter a characteristic of the metamaterial structure. ### Claim 3 (depends on 2) The metamaterial structure of claim 2 in which the tuning elements include inductance tuning elements arranged to tune inductances in series with the linking capacitors. ### Claim 4 (depends on 1) The metamaterial structure of claim 1 in which the first layer comprises a grid of traces, the grid comprising first traces extending in the first direction and second traces extending in the second direction, the first traces including first capacitors between the second traces. ### Claim 5 (depends on 4) The metamaterial structure of claim 4 in which the second traces include second capacitors between the first traces. ### Claim 6 (depends on 5) The metamaterial structure of claim 5 further comprising tuning elements that add or remove capacitance or inductance to alter a characteristic of the metamaterial structure and in which the tuning elements are arranged to adjust capacitance of the second capacitors. ### Claim 7 (depends on 5) The metamaterial structure of claim 5 in which the linking capacitors connect to the second traces, the second traces also including inductors in series with the second capacitors. ### Claim 8 (depends on 1) The metamaterial structure of claim 1 in which the natural resonance mode having the greatest coupling has a 1-wavelength or multiple of unity wavelength standing wave pattern in two dimensions. ### Claim 9 (depends on 8) The metamaterial structure of claim 8 in which the natural resonance mode having the greatest coupling with the field generated by the transmit device within the MRI system is the first resonance of the HEn1 mode. ### Claim 10 (depends on 1) The metamaterial structure of claim 1 in which the metamaterial structure can be characterized as an effective medium with anisotropic permittivity and permeability. ### Claim 11 (depends on 1) The metamaterial structure of claim 1 being connected to RF receive circuitry at a port to act as a receiver for the MRI system. ### Claim 12 (depends on 11) The metamaterial structure of claim 11 in which the port is arranged to connect the RF receive circuitry to the metamaterial structure at a location selected to generally correspond to a current minimum of a current distribution induced by the passive interaction of the metamaterial structure with the field generated by the transmit device. ### Claim 13 (depends on 11) The metamaterial structure of claim 11 further comprising one or more additional ports connected to the RF receive circuitry or to additional RF receive circuitry to act as multiple receive elements for the MRI system. ### Claim 14 (depends on 13) The metamaterial structure of claim 13 in which the port is arranged to connect the RF receive circuitry to the metamaterial structure at a location selected to generally correspond to a current minimum of a current distribution induced by the passive interaction of the metamaterial structure with the field generated by the transmit device and in which the one or more additional ports are arranged to connect the RF receive circuitry to the metamaterial structure at one or more additional locations selected to generally correspond to one or more additional current minima of the current distribution induced by the passive interaction of the metamaterial structure with the field generated by the transmit device. ### Claim 15 A metamaterial structure configured to passively interact with a field generated by a transmit device within the MRI system to improve one or more of homogeneity of the field within a scan target, specific absorption rate within the scan target, and strength of the field within the scan target when the metamaterial structure is present within a bore of the MRI system with the scan target, the metamaterial structure comprising: a first layer generally defining a surface and a second layer offset from the surface generally defined by the first layer, the first layer and the second layer interacting to form a 2D transmission line supporting radio frequency (RF) current along the surface in a first direction tangential to the surface and in a second direction tangential to the surface and transverse to the first direction, the first layer comprises a grid of traces, the grid comprising first traces extending in the first direction and second traces extending in the second direction, the first traces including first capacitors between the second traces and the second traces include second capacitors between the first traces, the first layer and the second layer being connected via linking capacitors, in which the linking capacitors connect to the second traces, the second traces also including inductors in series with the second capacitors. ### Claim 16 (depends on 15) The metamaterial structure of claim 15 in which the metamaterial further comprises tuning elements that add or remove capacitance or inductance to alter a characteristic of the metamaterial structure and in which the tuning elements are arranged to adjust capacitance of the second capacitors. ### Claim 17 A metamaterial structure configured to passively interact with a field generated by a transmit device within the MRI system to improve one or more of homogeneity of the field within a scan target, specific absorption rate within the scan target, and strength of the field within the scan target when the metamaterial structure is present within a bore of the MRI system with the scan target, the metamaterial structure comprising: a first layer generally defining a surface and a second layer offset from the surface generally defined by the first layer, the first layer and the second layer interacting to form a 2D transmission line supporting radio frequency (RF) current along the surface in a first direction tangential to the surface and in a second direction tangential to the surface and transverse to the first direction, the first layer and the second layer being connected via linking capacitors, the metamaterial structure comprising tuning elements that add or remove capacitance or inductance to alter a characteristic of the metamaterial structure, the tuning elements including inductance tuning elements arranged to tune inductances in series with the linking capacitors. ### Claim 18 (depends on 17) The metamaterial structure of claim 17 in which the first layer comprises a grid of traces, the grid comprising first traces extending in the first direction and second traces extending in the second direction, the first traces including first capacitors between the second traces. ### Claim 19 (depends on 18) The metamaterial structure of claim 18 in which the second traces include second capacitors between the first traces. ### Claim 20 (depends on 19) The metamaterial structure of claim 19 in which the tuning elements include capacitance tuning elements arranged to adjust capacitance of the second capacitors.