Search

DE-112014003677-B4 - Magnetic resonance transmitter

DE112014003677B4DE 112014003677 B4DE112014003677 B4DE 112014003677B4DE-112014003677-B4

Abstract

Device with a coil (102) for applying magnetic resonance (MR) pulse sequences to a substance (101), wherein the coil (102) a first coil section (202) and comprising a second coil section (204), wherein the first coil section (202) and the second coil section (204) allow current of opposite polarity to pass through, with a transmitter circuit (110) for generating the MR pulse sequences and supplying the MR pulse sequences to the coil (102), characterized in that the coil (102) comprises the first coil section (202) and the second coil section (204) along a longitudinal axis (203) of the coil (102), wherein the first coil section (202) comprises a first winding length, the second coil section (204) comprises a second winding length, and at least one section of the first winding length and at least one section of the second winding length overlap along the longitudinal axis (203) of the coil (102) and are connected to a first switch (502) coupled to the first coil section (202) and configured to selectively supply the first coil section (202) with current, and to a second switch (504) coupled to the second coil section (204) and configured to selectively supply the first coil section (202) with current. is configured to selectively supply power to the second coil section (204).

Inventors

  • Yi-Qiao Song

Assignees

  • SCHLUMBERGER TECHNOLOGY B.V.

Dates

Publication Date
20260513
Application Date
20140808
Priority Date
20130809

Claims (15)

  1. Device with a coil (102) for applying magnetic resonance (MR) pulse sequences to a substance (101), wherein the coil (102) comprises a first coil section (202) and a second coil section (204), wherein the first coil section (202) and the second coil section (204) allow current of opposite polarity to pass through, with a transmitter circuit (110) for generating the MR pulse sequences and providing the MR pulse sequences to the coil (102), characterized in that the coil (102) includes the first coil section (202) and the second coil section (204) along a longitudinal axis (203) of the coil (102), wherein the first coil section section (202) includes a first winding length segment, the second coil section (204) includes a second winding length segment, and at least one section of the first winding length segment and at least one section of the second winding length segment overlap along the longitudinal axis (203) of the coil (102) and are connected to a first switch (502) coupled to the first coil section (202) and configured to selectively supply current to the first coil section (202), and to a second switch (504) coupled to the second coil section (204) and configured to selectively supply current to the second coil section (204).
  2. Device according to Claim 1 , wherein the first switch (502) and the second switch (504) comprise transistors.
  3. Device according to Claim 1 , wherein the first switch (502) and the second switch (504) are configured to switch in less than 10 ns.
  4. Device according to Claim 1 , further comprising: a driver (112) coupled to the transmitter circuit (110) and configured to control the operation of the first switch (502) and the second switch (504).
  5. Device according to Claim 4 , wherein the operation of the first switch (502) and the second switch (504) generates the MR pulse sequences.
  6. Device according to Claim 5 , wherein the driver (112) is further configured to control the operation of the first switch (502) and the second switch (504) according to a switching logic (600).
  7. Device according to Claim 1 , further comprising: a current source (506) which is selectively coupled to the first coil section (202) via the first switch (502) and selectively coupled to the second coil section (204) via the second switch (504).
  8. Device according to Claim 1 , wherein the device is a component of a borehole surveying tool (716).
  9. A method for applying high-frequency pulses to a substance, the method comprising: applying current to a first coil section of a coil; and applying current to a second coil section of the coil, wherein current of opposite polarity flows through the coil sections, characterized in that the first coil section includes a first turn length segment, the second coil section includes a second turn length segment, and the first turn length segment and the second turn length segment superimpose along a common longitudinal axis of the coil, and wherein the current is selectively applied to the first coil section by means of a first switch and the current is selectively applied to the second coil section by means of a second switch.
  10. Procedure according to Claim 9 , whereby the operation of the first switch and the second switch generates the high-frequency pulses.
  11. Procedure according to Claim 9 , where the first switch and the second switch are transistors.
  12. Procedure according to Claim 11 , wherein the substance is a formation and the method further comprises: applying the high-frequency pulses to the formation.
  13. Magnetic resonance (MR) system comprising: a coil, comprising: a first coil section; a second coil section, wherein the first coil section and the second coil section are configured with opposite polarity; a first transistor coupled to the first coil section and configured to selectively power the first coil section; and a second transistor coupled to the second coil section and configured to selectively power the second coil section.
  14. System according Claim 13 , further comprising: a current source that is selectively coupled to the first coil section via the first switch and selectively coupled to the second coil section via the second switch.
  15. System according Claim 13 , whereby the operation of the first transistor and the second transistor generates the MR pulse sequences.

Description

The application relates to a device with a coil for applying magnetic resonance (MR) pulse frequencies to a substance according to the preamble of claim 1. The application further relates to a method for applying high-frequency pulses to a substance and a magnetic resonance (MR) system. TECHNICAL AREA A device with a coil for applying magnetic resonance (MR) pulses to a substance according to the preamble of claim 1 is known from US 5,903,150 A. Magnetic resonance (MR) systems and in particular MR transmitters are also known from US 7,117,752 B2 , US 5,047,992 A , US 201110127999 A1 , US 2012/0001629 A1 and US 2013/0234705 A1 . GENERAL STATE OF THE ART Magnetic resonance (MR) systems can be used to determine the properties of a substance. One example of an MR system is a nuclear magnetic resonance (NMR) system. An NMR system performs an NMR measurement by applying a static magnetic field to the substance. The static magnetic field induces an initial magnetization of atomic nuclei within the substance. The NMR system also includes an NMR transmitter with a coil that applies an oscillating magnetic field at a specific frequency to the substance. The oscillating field consists of a sequence of pulses that move the magnetization of the atomic nuclei away from the initial magnetization. The NMR pulse sequence can be arranged such that the pulses and the static field interact with the nuclei to generate a resonance signal, consisting of "echoes," within at least a portion of the substance. The resonance signal is detected and then used to determine NMR properties such as T1 relaxation time, T2 relaxation time, and signal attenuation due to molecular diffusion. These NMR properties can be used to determine the properties of the substance. In some cases, NMR pulse sequences of different frequencies are applied to the substance to study different parts of a substance in an inhomogeneous magnetic field or to investigate different atomic nuclei. To switch between frequencies, narrowband NMR transmitters use rows of fixed capacitors and mechanical switches coupled to the coil. The mechanical switches tune the coil to different frequencies between a predetermined number of fixed capacitors. These narrowband transmitters have several disadvantages. First, the switching process is slow (e.g., switching times of 10–100 ms). Second, the switches in the capacitor rows introduce noise into the NMR measurement. Third, a predetermined, separate set of narrowband frequencies can be established, since each frequency depends on separate capacitors. Fourth, the frequency-switching process introduces dynamics and may not maintain the phase coherence of the pulse sequence waveform. Consequently, narrowband NMR transmitters do not switch between frequencies efficiently and effectively. SUMMARY Illustrative embodiments of the present disclosure relate to a transmitter for a magnetic resonance (MR) system, such as a nuclear magnetic resonance (NMR) system. The transmitter includes a coil for applying NMR pulse sequences to a substance. The coil comprises a first coil section and a second coil section. The first coil section and the second coil section allow current of opposite polarity to pass through. In some embodiments, the transmitter may include a transmitter circuit for generating and supplying the MR pulse sequences to the coil. The transmitter circuit includes a first switch that selectively energizes the first coil section and a second switch that selectively energizes the second coil section. The operation of the first and second switches generates the MR pulse sequences. Several embodiments of the present disclosure also relate to a method for applying MR pulse sequences to a substance. The method involves applying current to a first coil section and applying current to a second coil section. The current flows through the coil sections with opposite polarity. In some embodiments, the current is selectively applied to the first coil section by means of a first switch, and the current is selectively applied to the second coil section by means of a second switch. The operation of the first switch and the second switch generates the MR pulse sequences. Further illustrative embodiments of the present disclosure relate to a magnetic resonance (MR) system. The system comprises a coil with a first coil section and a second coil section. The first coil section and the second coil section are wound with opposite polarity. The system also includes a first transistor coupled to the first coil section, selectively supplying current to the first coil section, and a second transistor coupled to the second coil section, selectively supplying current to the second coil section. BRIEF DESCRIPTION OF THE DRAWINGS For experts, the advantages of different embodiments will become clearer with reference to the following description of illustrative embodiments, which are discussed with reference to the drawings briefly described below. 1 shows an NM