System and method for low-field, multi-channel imaging

Patent metadata

Field	Value
Publication number	US-2017074956-A1
Application number	US-201515125514-A
Country	US
Kind code	A1
Filing date	Mar 13, 2015
Priority date	Mar 14, 2014
Publication date	Mar 16, 2017
Grant date	—

Abstract

A system and method for performing parallel magnetic resonance imaging (pMRI) process using a low-field magnetic resonance imaging (IfMRI) system includes a substrate configured to follow a contour of a portion of a subject to be imaged by the IfMRI system using a pMRI process. A plurality of coils are coupled to the substrate. Each coil in the plurality of coils has a number of turns and an associated decoupling mechanism selected to operate the plurality of coils to effectuate the pMRI process using the IfMRI system.

First claim

1 . A coil system for performing a parallel magnetic resonance imaging (pMRI) process using a low-field magnetic resonance imaging (IfMRI) system, the system comprising:
a substrate configured to follow a contour of a portion of a subject to be imaged by the IfMRI system using a pMRI process; and a plurality of coils coupled to the substrate, each coil in the plurality of coils having a number of turns and an associated decoupling mechanism selected to operate the plurality of coils to effectuate the pMRI process using the IfMRI system.

2 . The coil system of claim 1 wherein the number of turns and the associated decoupling mechanism selected to operate with a magnetic field strength of 6.5 mT.

3 . The coil system of claim 1 wherein the plurality of coils are passively decoupled.

4 . The coil system of claim 3 wherein transmit coils are passively decoupled using crossed diodes arranged in series.

5 . The coil system of claim 3 wherein receive coils are passively decoupled using crossed diodes arranged in parallel.

6 . The coil system of claim 1 wherein the each of the coils in the plurality of coils is tuned to 276.0 kHz

7 . The coil system of claim 1 wherein the each of the coils in the plurality of coils is matched to at least −27 dB.

8 . The coil system of claim 1 wherein the each of the coils in the plurality of coils is geometrically decoupled from their nearest neighbors by at least −30 dB.

9 . The coil system of claim 8 wherein decoupling from next-nearest neighbors is at least −6 dB.

10 . A magnetic resonance imaging (MRI) system, comprising:
a magnet system configured to generate a low-field static magnetic field about at least a region of interest (ROI) of a subject arranged in the MRI system; a plurality of gradient coils configured to establish at least one magnetic gradient field with respect to the low-field static magnetic field; a radio frequency (RF) system including a local coil comprising:
a substrate configured to follow a contour of a portion of the subject including the ROI; and
a plurality of coils coupled to the substrate, each coil in the plurality of coils having a number of turns and an associated decoupling mechanism selected to operate the plurality of coils to effectuate a parallel imaging process using the low-field static magnetic field.

11 . The MRI system of claim 10 wherein magnetic field strength is 6.5 mT.

12 . The MRI system of claim 10 wherein the number of turns and the associated decoupling mechanism selected to operate with the low-field static magnetic field.

13 . The MRI system of claim 10 wherein the plurality of coils are passively decoupled.

14 . The MRI system of claim 13 wherein transmit coils are passively decoupled using crossed diodes arranged in series.

15 . The MRI system of claim 13 wherein receive coils are passively decoupled using crossed diodes arranged in parallel.

16 . The MRI system of claim 10 wherein the each of the coils in the plurality of coils is tuned to 276.0 kHz

17 . The MRI system of claim 1 wherein the each of the coils in the plurality of coils is matched to at least −27 dB.

18 . The MRI system of claim 1 wherein the each of the coils in the plurality of coils is geometrically decoupled from their nearest neighbors by at least −30 dB.

19 . The MRI system of claim 18 wherein decoupling from next-nearest neighbors is at least −6 dB.

20 . The MRI system of claim 10 wherein the coils in the plurality of coils are arranged in a tiling geometry to be aligned about the ROI and either longitudinally or transversely to low-field static magnetic field.

21 . A parallel receive coil array for use in low-field magnetic resonance imaging, the parallel receive coil array comprising:
a plurality of receive coils arranged in a three-dimensional geometry about a region of interest, each of the plurality of receive coils having a respective plurality of turns.

22 . The parallel receive coil array of claim 21 , wherein each of the plurality of receive coils overlaps at least one adjacent receive coil.

23 . The parallel receive coil array of claim 21 , wherein each of the plurality of receive coils is formed by winding wire according to the respective plurality of turns.

24 . The parallel receive coil array of claim 23 , wherein the wire is a Litz wire.

25 . The parallel receive coil array of claim 21 configured for a portion of human anatomy, wherein the plurality of receive coils, when operated in conjunction with performing magnetic resonance of the portion of the human anatomy of a subject, is capable of detecting emitted magnetic resonance signals in a direction substantially parallel to a longitudinal axis of the subject's body.

26 . The parallel receive coil array of claim 21 , wherein each of the plurality of receive coils is connected to a passive decoupling circuit to decouple the respective receive coil from a transmit coil.

27 . The parallel receive coil array of claim 26 , wherein the passive decoupling circuit comprises a pair of crossed diodes connected in parallel with the respective receive coil.

28 . The parallel receive coil array of claim 21 , wherein the number of turns for at least one of the plurality of receive coils is greater than 10.

29 . The parallel receive coil array of claim 21 , wherein the number of turns for at least one of the plurality of receive coils is greater than 20.

30 . The parallel receive coil array of claim 23 , wherein the length of the wire for at least one of the plurality of receive coils is greater than 100 cm.

30 . The parallel receive coil array of claim 23 , wherein the length of the wire for at least one of the plurality of receive coils is greater than 200 cm.

31 . The parallel receive coil array of claim 23 , wherein the plurality of receive coils are tuned to detect frequencies characteristic of a B0 field of 0.2 T or less.

32 . A method of reducing signal-to-noise ratio in a low-field magnetic resonance imaging system, the method comprising:
providing an excitation pulse sequence to a region of interest; detecting magnetic resonance measurements emitted in response to the excitation pulse sequence using a plurality of receive coils to obtain an increased number of measurements in parallel; utilizing the increased number of measurements obtained in parallel to increase the number of measurements averaged to obtain a value for each location in the region of interest.

33 . The method of claim 32 , wherein the increased number of measurements is utilized in part to increase the number of measurement averaged and in part to reduce a total acquisition time.

Assignees

• Massachusetts Gen Hospital

Inventors

• Rosen Matthew S
• Wald Lawrence L
• Lapierre Cristen

Classifications

• G01R33/5635

  Angiography, e.g. contrast-enhanced angiography [CE-MRA] or time-of-flight angiography [TOF-MRA] · CPC title

• G01R33/5611

  Parallel magnetic resonance imaging, e.g. sensitivity encoding [SENSE], simultaneous acquisition of spatial harmonics [SMASH], unaliasing by Fourier encoding of the overlaps using the temporal dimension [UNFOLD], k-t-broad-use linear acquisition speed-up technique [k-t-BLAST], k-t-SENSE (structural details of arrays of sub-coils G01R33/3415) · CPC title

• G01R33/5673

  Gating or triggering based on a physiological signal other than an MR signal, e.g. ECG gating or motion monitoring using optical systems for monitoring the motion of a fiducial marker · CPC title

• G01R33/34046 Primary

  Volume type coils, e.g. bird-cage coils; Quadrature bird-cage coils; Circularly polarised coils · CPC title

• G01R33/365

  Decoupling of multiple RF coils wherein the multiple RF coils have the same function in MR, e.g. decoupling of a receive coil from another receive coil in a receive coil array, decoupling of a transmission coil from another transmission coil in a transmission coil array · CPC title