Title: NMR, MRI, and spectroscopic MRI in inhomogeneous fields

Abstract

A method for locally creating effectively homogeneous or "clean" magnetic field gradients (of high uniformity) for imaging (with NMR, MRI, or spectroscopic MRI) both in in-situ and ex-situ systems with high degrees of inhomogeneous field strength. THe method of imaging comprises: a) providing a functional approximation of an inhomogeneous static magnetic field strength B.sub.0({right arrow over (r)}) at a spatial position {right arrow over (r)}; b) providing a temporal functional approximation of {right arrow over (G)}.sub.shim(t) with i basis functions and j variables for each basis function, resulting in v.sub.ij variables; c) providing a measured value .OMEGA., which is an temporally accumulated dephasing due to the inhomogeneities of B.sub.0({right arrow over(r)}); and d) minimizing a difference in the local dephasing angle .phi.({right arrow over (r)},t)=.gamma..intg..sub.0.sup.t{square root over (|{right arrow over (B)}.sub.1({right arrow over (r)},t')|.sup.2+({right arrow over (r)}{right arrow over (G)}.sub.shimG.sub.shim(t')+.parallel.{right arrow over (B)}.sub.0({right arrow over (r)}).parallel..DELTA..omega.({right arrow over (r)},t'/.gamma/).sup.2)}dt'-.OMEGA. by varying the v.sub.ij variables to form a set of minimized v.sub.ij variables. The method requires calibration of the static fields prior to minimization, but may thereafter be implemented without such calibration, may be used in open or closed systems, and potentially portable systems.

Inventors:

Demas, Vasiliki; Pines, Alexander; Martin, Rachel W; Franck, John; Reimer, Jeffrey A

Issue Date:

2013-12-24

Research Org.:

Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE

OSTI Identifier:

1111464

Patent Number(s):

8614575

Application Number:

11/917,639

Assignee:

The Regents of the University of California (Oakland, CA)

Patent Classifications (CPCs):

G - PHYSICS G01 - MEASURING G01R - MEASURING ELECTRIC VARIABLES

G - PHYSICS G01 - MEASURING G01N - INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES

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G - PHYSICS G01 - MEASURING G01R - MEASURING ELECTRIC VARIABLES

G01R33/485 - based on chemical shift information {CSI or spectroscopic imaging, e.g. to acquire the spatial distributions of metabolites}
G01R33/3808 - {Magnet assemblies for single-sided MR wherein the magnet assembly is located on one side of a subject only

G - PHYSICS G01 - MEASURING G01N - INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES

G01N24/084 - {Detection of potentially hazardous samples, e.g. toxic samples, explosives, drugs, firearms, weapons}

G - PHYSICS G01 - MEASURING G01R - MEASURING ELECTRIC VARIABLES

G01R33/445 - {MR involving a non-standard magnetic field B0, e.g. of low magnitude as in the earth's magnetic field or in nanoTesla spectroscopy, comprising a polarizing magnetic field for pre-polarisation, B0 with a temporal variation of its magnitude or direction such as field cycling of B0 or rotation of the direction of B0, or spatially inhomogeneous B0 like in fringe-field MR or in stray-field imaging}
G01R33/56563 - {caused by a distortion of the main magnetic field B0, e.g. temporal variation of the magnitude or spatial inhomogeneity of B0
G01R33/4833 - {using spatially selective excitation of the volume of interest, e.g. selecting non-orthogonal or inclined slices}

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DOE Contract Number:  

AC02-05CH11231

Resource Type:

Patent

Country of Publication:

United States

Language:

English

Subject:

47 OTHER INSTRUMENTATION