Magnetic resonance (MR) performance in MR-guided ultrasound systems
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Publication Number
US-12151125-B2
Publication Date
2024-11-26
Expiration Date
Abstract
Ultrasound transducers adjust the B1+ and/or B1− field distribution in an MRI apparatus to improve the signal sensitivity and homogeneity at a region of interest. Approaches employed include strategic placement of field-altering features such as slots and/or dipoles along the exterior surface or, in some cases, the interior of the transducer. In various embodiments, the field-altering features are (or behave as) passive resonators.
Core Innovation
An ultrasound transducer for use with an MRI unit having at least one transmit coil and at least one receive coil includes a dielectric layer and a first conductive layer conforming to at least a portion of the dielectric layer. The first conductive layer has at least one passive resonator thereon or therethrough, and the passive resonator has a geometry and dimensions selected to allow RF waves to penetrate the first conductive layer and rearrange a B1 field inside the transducer.
The selected geometry and dimensions are used to achieve an optimized B1+ and/or B1− magnetic field distribution within a field of view of the MRI transmit and/or receive coil. The passive resonator is configured as RF-wave-penetrating structures that perturb or rearrange the B1 field inside the transducer to improve signal sensitivity and homogeneity at a region of interest.
The document further discloses passive resonator geometries such as elongated slots, cruciform slot pairs, dipoles, and loop/figure-8 shapes, and includes metamaterial-like resonator regions. Constructions include conforming conductive layers and multilayer membrane arrangements with conductive layers and polymer/water chambers, with placement options including exterior surfaces, interior surfaces at dielectric interfaces, and surrounding head base ring structures.
Claims Coverage
The patent content includes one independent claim. It covers an ultrasound transducer construction where passive resonator geometry and dimensions are selected to allow RF wave penetration and rearrangement of the B1 field, producing an optimized B1+ and/or B1− magnetic field distribution within the MRI coils’ field of view.
Rf-penetrating passive resonator on a conductive layer for optimized B1+ and/or B1− field
An ultrasound transducer for use with an MRI unit having at least one transmit coil and at least one receive coil, including a dielectric layer and a first conductive layer conforming thereto, where the first conductive layer has at least one passive resonator thereon or therethrough whose geometry and dimensions allow RF waves to penetrate the first conductive layer and rearrange a B1 field inside the transducer to achieve an optimized B1+ and/or B1− magnetic field distribution within a field of view of the MRI transmit and/or receive coil.
Adjustable passive resonator geometry, location, and/or orientation guided by initial MRI images
The geometry, location, and/or orientation of the at least one passive resonator is adjustable to improve the B1+ and/or B1− magnetic field distribution in a region of interest in response to one or more initial MRI images.
Dielectric constant greater than 10 with elongated-slot passive resonator through a conductive layer
The transducer includes passive resonators with a dielectric constant greater than 10, and at least one passive resonator is formed as an elongated slot through the first conductive layer and extending across part of it.
Cruciform slot pair resonator geometry
The transducer includes at least one slot implemented as a pair of slots arranged in a cruciform configuration.
Multilayer transducer with a second conductive layer spaced from the first with dielectric between
The transducer includes a second conductive layer spaced from the first conductive layer, with both conductive layers conforming to the dielectric layer such that the dielectric layer is positioned between the first and second conductive layers in a multilayer single transducer structure.
Interior-surface placement at a dielectric medium interface
The ultrasound transducer includes at least one passive resonator positioned on an interior surface of the transducer at an interface with a dielectric medium.
Across the provided claim material, the core coverage centers on an MRI-compatible ultrasound transducer whose first conductive layer includes a passive resonator configured to permit RF-wave penetration and to rearrange the B1 field to achieve optimized B1+ and/or B1− distribution within the MRI transmit/receive field of view. Dependent refinements specify adjustable resonator geometry/location/orientation guided by initial MRI images, resonator geometries including cruciform slot pairs and elongated slots, multilayer conductive/dielectric stacking, dielectric-constant constraints, and resonator placement on interior surfaces at dielectric interfaces.
Stated Advantages
Optimized B1+ and/or B1− magnetic field distribution within a field of view of the MRI transmit and/or receive coil.
Improved signal sensitivity and homogeneity at a region of interest.
Documented Applications
MR-guided focused ultrasound, where an ultrasound transducer is used with an MRI unit having transmit and receive coils to achieve optimized B1+ and/or B1− magnetic field distribution within a field of view.
Use in a region of interest to improve signal sensitivity and homogeneity.
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