A transmit/receive switch, a transmit coil array and a receive coil array for mri

Patent metadata

Field	Value
Publication number	US-2016209481-A1
Application number	US-201315023670-A
Country	US
Kind code	A1
Filing date	Sep 25, 2013
Priority date	Sep 25, 2013
Publication date	Jul 21, 2016
Grant date	—

Abstract

The invention relates to an MRI apparatus for magnetic resonance imaging of a subject of investigation, comprising: a coil arrangement ( 1 ) for transmitting an excitation signal into the subject and for receiving a response signal from the subject; a high-power radio-frequency amplifier ( 4 ) for generating the excitation signal; and a low-noise amplifier (LNA) for amplifying the response signal. The invention provides a transmit/receive switch ( 5 ) which is alternatively operable in a transmit mode or in a receive mode. In the transmit mode, the transmit/receive switch ( 5 ) transmits the excitation signal to the coil arrangement ( 1 ) and protects the low-noise amplifier (LNA) from the outgoing excitation signal. In the receive mode, the transmit/receive switch ( 5 ) routes the in coming response signal to the low-noise amplifier (LNA).

First claim

1 . A magnetic resonance imaging apparatus for magnetic resonance imaging of a subject of investigation, comprising:
a) a coil arrangement
a1) for transmitting an excitation signal into the subject thereby exciting nuclear spins within the subject and/or
a2) for receiving a response signal emitted by excited spins from the subject,
b) a high-power radio-frequency amplifier for generating the excitation signal to be transmitted into the subject, c) a low-noise amplifier for receiving and amplifying the response signal from the subject, d) a transmit/receive switch arranged between the coil arrangement on the one hand and the low-noise amplifier and the high-power radio-frequency amplifier on the other hand, wherein the transmit/receive switch is alternatively operable in
d1) a transmit mode, in which the transmit/receive switch transmits the excitation signal from the high-power radio-frequency amplifier to the coil arrangement, while the transmit/receive switch protects the low-noise amplifier from an outgoing excitation signal, and
d2) a receive mode, in which the transmit/receive switch routes an incoming response signal to the low-noise amplifier.

2 . The magnetic resonance imaging apparatus according to claim 1 , wherein
a) the transmit/receive switch comprises a receive path between the coil arrangement and the low-noise amplifier, b) a quarter-wavelength segment is arranged in the receive path of the transmit/receive switch, wherein the quarter-wavelength segment corresponds to a quarter wavelength of the Larmor frequency, and c) a diode is arranged at one end of the quarter-wavelength segment to short-circuit the receive path at said end of the quarter-wavelength segment, thereby creating an open circuit at the other end of the quarter-wavelength segment and thus preventing the outgoing excitation signal from reaching the low-noise amplifier.

3 . The magnetic resonance imaging apparatus according to claim 2 , wherein
the quarter-wavelength segment comprises a coaxial cable or a lumped network.

4 . The magnetic resonance imaging apparatus according to claim 3 , wherein the lumped network in the receive path of the transmit/receive switch comprises the following components:
a) an inductance arranged along the receive path, b) a first capacitor connected between the first end of the inductance and ground, and c) a second capacitor connected between a second end of the inductance and ground.

5 . The magnetic resonance imaging apparatus according to claim 2 , wherein an additional phase shift element is arranged in the receive path of the transmit/receive switch, the phase shift element adjusts the phase length of the receive path of the transmit/receive switch, so that a low impedance of the low-noise amplifier is transformed into a high impedance thereby creating additional protection for the low-noise amplifier.

6 . The magnetic resonance imaging apparatus according to claim 5 , wherein the phase shift element is a coaxial cable.

7 . The magnetic resonance imaging apparatus according to claim 1 , wherein the coil arrangement comprises
a) a transmit coil arrangement for transmitting the excitation signal into the subject thereby exciting nuclear spins within the subject, and b) a receive coil arrangement for receiving a induced response signal from the subject.

8 . The magnetic resonance imaging apparatus according to claim 7 , wherein
a) the transmit coil arrangement is ring-shaped and surrounds the subject of investigation, b) the transmit coil arrangement comprises several coil elements, and c) the coil elements of the transmit coil arrangement are symmetrically distributed around the circumference of the transmit coil arrangement.

9 . The magnetic resonance imaging apparatus according to claim 8 , wherein
a) the coil elements of the transmit coil arrangement are arranged in several adjacent and parallel rows, wherein the rows are arranged one behind the other along a center axis of the transmit coil arrangement, b) there is a gap in an axial direction between the adjacent rows of the transmit coil arrangement, and c) there is a gap a circumferential direction between the adjacent coil elements in each row of the transmit coil arrangement.

10 . The magnetic resonance imaging apparatus according to claim 9 , wherein
a) the gaps the transmit coil arrangement are between 10 mm and 14 mm, and b) the number of the coil elements of the transmit coil arrangement is at least 8, and c) the number of the rows of the transmit coil arrangement is at least two.

11 . The magnetic resonance imaging apparatus according to claim 9 , wherein
a) there is an angular offset in a circumferential direction between the coil elements in one of the rows relative to the coil elements in an adjacent one of the rows of the transmit coil arrangement, and b) the angular offset between the adjacent rows of the transmit coil arrangement is 180° divided by the number of the coil elements in the individual rows.

12 . The magnetic resonance imaging apparatus according to claim 8 , wherein
a) the receive coil arrangement is concave to match an outer convex contour of the subject, b) the receive coil arrangement comprises several coil elements, and c) the coil elements of the receive coil arrangement are symmetrically distributed around the circumference of the receive coil arrangement.

13 . The magnetic resonance imaging apparatus according to claim 12 , wherein
a) the coil elements of the receive coil arrangement are arranged in several adjacent and parallel rows which are arranged one behind the other along a center axis of the receive coil arrangement, and b) there is an axial overlap between the adjacent rows, so that the coil elements in one of the rows of the receive coil arrangement and the coil elements in an adjacent one of the rows of the receive coil arrangement geometrically overlap, and c) there is a gap in a circumferential direction between the adjacent coil elements in the same row of the receive coil arrangement.

14 . The magnetic resonance imaging apparatus according to claim 11 , wherein there is an angular offset in a circumferential direction between the coil elements in one of the rows relative to the coil elements in an adjacent one of the rows of the receive coil arrangement.

15 . The magnetic resonance imaging apparatus according to claim 14 , wherein
a) the rows of the receive coil arrangement are arranged one above the other with regard to the center axis of the receive coil arrangement, and b) the individual coil elements of the lower rows of the receive coil arrangement has an angular offset with respect to the upper row, each geometrically overlap with two coil elements the adjacent upper row of the receive coil arrangement.

16 . The magnetic resonance imaging apparatus according to claim 13 , wherein
a) the gaps in the receive coil arrangement are between 8 mm and 12 mm, and b) the number of the coil elements of the receive coil arrangement is at least 31 , and c) the number of the rows of the receive coil arrangement is at least four, and d) the number of the coil elements of the receive coil arrangement is greater than the number of the coil elements of the transmit coil arrangement, and e) the receive coil arrangement extends over a length of at least 180 mm along the center axis of the receive coil arrangement, and f) the individual coil elements of the receive coil arrangement are smaller than the individual coil elements of the transmit coil arrangement.

17 . The magnetic resonance i

Assignees

• Max Planck Ges Zur Förderung Der Wissenschaften E V

Inventors

• Gunamony Shajan
• Hoffmann Jens
• Scheffler Klaus
• Pohmann Rolf

Classifications

• G01R33/283

  Intercom or optical viewing arrangements, structurally associated with NMR apparatus · CPC title

• G01R33/3657

  Decoupling of multiple RF coils wherein the multiple RF coils do not have the same function in MR, e.g. decoupling of a transmission coil from a receive coil · CPC title

• G01R33/3614 Primary

  RF power amplifiers · CPC title

• G01R33/3415 Primary

  comprising arrays of sub-coils {, i.e. phased-array coils with flexible receiver channels} · CPC title

• G01R33/34007

  Manufacture of RF coils, e.g. using printed circuit board technology; additional hardware for providing mechanical support to the RF coil assembly or to part thereof, e.g. a support for moving the coil assembly relative to the remainder of the MR system · CPC title