Universitaetsklinikum Freiburg

Universitätsklinikum Freiburg

Gerrit Schultz

Maxim Zaitsev

Daniel Gallichan

Juergen Hennig

Walter Witschey

Jürgen Hennig

Hans Weber

Anna Welz

A method to compensate for the magnetic field heterogeneity inside an object of investigation in a MR device obtains an uncorrected magnetic field distribution of the object and executes an MR sequence with a desired k-space coverage by applying RF pulses to generate a transverse magnetization within the object. MR signal data is recorded, magnetic field shimming parameters are dynamically updated and MR signal data are reconstructed to produce images or localized spectroscopic data. Artifacts in a reconstructed image resulting from an uncorrected magnetic field distribution are suppressed by temporally separating MR signals originating from at least two different sub-volumes within a volume of transverse magnetization by generating a nonlinear phase distribution within the object and by dynamically updating shimming parameters to compensate for the field inhomogeneity distributions within the different sub-volumes in the volume of transverse magnetization.

Method of dynamically compensating for magnetic field heterogeneity in magnetic resonance imaging

A method for magnetic resonance (=MR) imaging, wherein non-linear gradient fields are applied for the purpose of spatial encoding to acquire images of an object to be imaged and wherein the magnet resonance signal radiated from the object to be imaged is sampled on grids in time, to thereby obtain sampling points, is characterized in that the object to be imaged is mapped completely in regions of stronger gradient fields by increasing the density of the sampling points in the center of k-space, and additional sampling points are specifically acquired in the outer regions of k-space according to a k-space sampling pattern depending on the desired distribution of the resolution in the measurement, wherein the MR measurement is calculated with the additional sampling points. An MR imaging method is thereby provided by means of which homogenized resolution is achieved in the MR measurements using non-linear gradient fields for spatial encoding.

Method for homogenizing resolution in magnet resonance tomography measurements using non-linear encoding fields

A method of MR with spatial encoding to generate an image or spectroscopic data of an object of investigation inside an MR apparatus comprises the steps of (a) selecting a volume of interest within the object of investigation, (b) applying an RF pulse to generate a transverse magnetization within the object of investigation, (c) preparing a nonlinear phase distribution within the object of investigation by application of spatially encoding magnetic fields (SEMs), the SEMs comprising of a nonlinear gradient field or a combination of linear and nonlinear gradient fields, (d) effecting primary spatial encoding through application of SEMs, and (e) recording MR signals originating from the object of investigation. Step (c) or (d) thereby comprises applying a sequence of at least two SEMs, at least one of which contains a nonlinear field gradient and at least two of the SEMs having different field geometries. The sequence of SEMs is applied at a point in time from and including the excitation of the object of interest in step (b) up to and including the recording of the MR signals in step (e), to thereby introduce a temporal shift of the signals arising from spatially different locations within the selected volume of interest, that is to thereby introduce a shift of local spatial frequency components. A sampling window for recording of the respective MR signals is set and signals originating from the volume of interest are recorded in step (e) and undesired signals originating from outside the volume of interest are suppressed.

Method of MR (=magnetic resonance) with spatial encoding to generate an image or spectroscopic data

A nuclear magnetic resonance (NMR) imaging method in which, with the aid of a gradient system, a spatially and temporally variable magnetic field Bis generated, for the at least two-dimensional spatial encoding of NMR measurement signals in a measurement sample region to be imaged, where the magnetic field Bis employed in at least two forms Band Bin the measurement sample region to be imaged during a single measurement cycle from excitation to reading of the NMR measurement signals, where the first form Bhas essentially ns poles, where ns is an even number &#x3e; 2, and has ns essentially sectorial sub-regions, in each of which the magnetic field Bis locally monotonic in one direction, where the measurement signals from the measurement sample are recorded by means of at least ns receiver coils which have different sensitivity over the ns sub-regions of the region to be imaged, is characterized in that the second form Bis essentially identical to the first form B% with the second form Bbeing rotated by an angle &#x394;&#x3c6;, where relative to the first form B. The invention provides an NMR imaging method in which a high-resolution image of the region to be imaged is obtained more quickly utilizing the advantages of NBSEMs.

Growing community of inventors

Freiburg, Germany

Gerrit Schultz