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US-12618923-B2 - Radio frequency coil with T-shaped connector between electrical conductors and radio frequency shield

US12618923B2US 12618923 B2US12618923 B2US 12618923B2US-12618923-B2

Abstract

A radio frequency (RF) coil comprises a lay-out of electrical conductors including several axial rung 11 s and several circumferential rings ( 12 ), in which at least one of the rung 11 s is coupled with at least one of the rings by a T-shaped connector. The T-shaped connector includes a distributed capacitive coupling between the ring ( 12 ) and the rung ( 11 ).

Inventors

  • Wouter Carel Marinus Numan
  • Eerke Holle
  • Aleksei Dubok

Assignees

  • KONINKLIJKE PHILIPS N.V.

Dates

Publication Date
20260505
Application Date
20220225
Priority Date
20210304

Claims (13)

  1. 1 . A radio frequency (RF) shield comprising: two concentric cylindrical tubes each of a conductive layers interspaced with a dielectric; a first conductive layer segmented into a set of two or more longitudinal strips; a second conductive layer segmented into a set of two or more circumferential hoops, wherein: a large mesh of smaller coupled capacitors exists in the segmented first and second conductive layers; and sets of longitudinal strips and circumferential hoops cross to form overlapping areas of a network of smaller capacitances to cause sufficient uninhibited flow of RF currents for the shield to function as an RF shield.
  2. 2 . The RF shield of claim 1 , wherein a checkerboard pattern of overlapping slits and hoops form a large cylindrical network of layered capacitors.
  3. 3 . The RF shield of claim 2 , wherein a width of a segments of each of the two or more circumferential hoops and the two or more longitudinal strops no larger than 20 mm, and the width of the overlapping slits is not larger than 1 mm.
  4. 4 . The RF shield of claim 2 , wherein each hoop is divided into at least two segments with at least one slit.
  5. 5 . The RF shield of claim 2 , further comprising a radio frequency (RF) coil comprising a lay-out of electrical conductors, the RF coil comprising: several axial rungs and several circumferential rings, in which at least one of the rungs is coupled with at least one of the rings by a T-shaped connector, which comprises: a distributed capacitive coupling between the ring and the rung, the rung and the ring comprising respective sets of overlapping axial and circumferential electrical conducting segments that form the T-shaped conductor and that are galvanically insulated from one another and the distributed capacitive coupling formed by the overlapping regions of the sets of electrical conducting segments.
  6. 6 . The RF shield of claim 5 , wherein the axial set and the circumferential set include a plurality of elongate electrical conductors that are orientated in the circumferential and axial directions, respectively.
  7. 7 . The RF shield of claim 5 , wherein the T-shaped connector has a printed-circuit board substrate and the axial and circumferential electrical conducting segments are disposed on opposite surfaces of the printed-circuit board substrate.
  8. 8 . The RF shield of claim 5 , wherein the axial and circumferential electrical conducting segments are sets of respective slitted flat elongate conductor strips orientated in the circumferential and axial directions, respectively.
  9. 9 . The RF shield of claim 5 , wherein the sets of axial and circumferential electrical conducting segments are integral with the ring and rung, respectively forming the T-shaped connector.
  10. 10 . The RF shield of claim 5 , comprising a plurality of circumferential rings and axial rung, wherein pairs of the rungs and the rings have respective sets of overlapping axial and circumferential electrical conducting segments that form the T-shaped conductor coupling the ring and rung of the pair and that are galvanically insulated from one another and the distributed capacitive coupling formed by the overlapping region of the sets of electrical conducting segments.
  11. 11 . The RF shield of claim 5 , wherein the ring and rung comprise sections that are fully slitted along their respective lengths.
  12. 12 . The RF shield of claim 11 , wherein overlapping sections of the ring and the rung form a parallel capacitor array circuit.
  13. 13 . The RF shield of claim 5 , wherein the overlapping regions of the sets of extensions overlap each other entirely.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is a U.S. national phase application of International Application No. PCT/EP2022/054757 filed Feb. 25, 2022, which claims the benefit of EP Application Serial No. 21160678.5 filed on Mar. 4, 2021 and EP Application Serial No. 21190253.1 filed on Aug. 9, 2021, each of which is incorporated herein by reference. FIELD OF THE INVENTION The invention pertains to a radio frequency (RF) coil comprising a lay-out of electrical conductors including several axial rungs and several circumferential rings coupled by a T-shaped connector. BACKGROUND OF THE INVENTION Such an RF coil is known form the US-patent application US2009/0219026. The known RF coil is a birdcage type multi-channel transmit/receive RF coil and has a set of coil units forming a cylindrical shape having a circumference and opposite ends. The coil units are connected in succession along circumferential direction of the cylindrical shape at the respective opposite ends of the cylindrical shape. Each coil unit comprises at least one capacitor. The capacitance value of the capacitor in each coil unit is selected primarily to achieve primary mode coil RF resonance at the desired frequency. The capacitors are respectively connected in the coil units at an edge of one end face of the cylindrical shape. SUMMARY OF THE INVENTION An object of the present invention is to provide an RF coil, in particular for a magnetic resonance examination system that has improved electromagnetic properties. This object is achieved by the RF coil as defined in Claim 1. An insight of the present invention is that the distributed capacitive coupling in the T-shaped connector where rings and rungs meet each other forms a parallel circuit capacitor array. This achieves multiple independent electrical current paths of similar impedance which distributes electrical current so as to reduce the proximity effect, lowers local RF heating and suppresses eddy current generation due to gradient switching in the magnetic resonance examination system. The configuration of the distributed capacitive coupling further has larger impedance transitions predominantly concentrated radially and between the capacitor plates, so that electrical field fanning into the magnetic resonance examination system's examination region (i.e. towards the patient to be examined) is reduced. Moreover, the RF coil of the invention is simpler and less expensive to manufacture, notably because there is no need to mount a large number of lumped capacitors. The invention achieves improved electromagnetic properties notably in that the RF coil has improved gradient field decoupling and RF performance. The invention may be employed in a magnetic resonance examination system comprising an RF transmit antenna to generate RF fields in the examination zone and a gradient system to generate gradient magnetic field pulses. The RF fields and the gradient magnetic fields manipulate nuclear spins so as the generated magnetic resonance signals that are encode for particular contrast and spatial resolution. When employed in an magnetic resonance examination system the invention provides for a T-section with low gradient coupling in particular for laminate RF coils. It is noted that in the framework of this application the term T-shape encompassed any geometrical arrangement in which electrical conductors meet from different directions, often at right angles, but other transverse orientations may be employed. Thus, the T-shape may be straight or skewed and may or may not be part of a more elaborate geometric combination of conductors, such as in the shape of a +-sign or X-sign that can be regarded of a combination of several (two) strict T-shapes. An insight of the present invention is that in order to achieve better capacitive coupling without the use of discrete capacitive elements, the conductive overlapping were to be increased, while on the other hand larger overlapping conductive area have increased susceptibility for eddy currents. According to the invention, overlapping areas of structured separate galvanically isolated conductors of both the ring and rung achieve both improved capacitive coupling and reduced eddy current susceptibility and hence less heat generation. The invention may be applied in RF receiver coils for receiving (RF) magnetic resonance signals, as well as in RF transmit coils that generate RF (B1+)-fields and also in RF transmit-/receive coils that can operate in a transmit mode and in a receive mode. These and other aspects of the invention will be further elaborated with reference to the embodiments defined in the dependent Claims. In a preferred embodiment of the RF coil of the invention, the rung and the ring have respective sets of axially and circumferentially overlapping axial and circumferential electrical conducting segments that form the T-shaped conductor and that are galvanically insulated from one another and the distributed capacitive cou