Universitaetsklinikum Freiburg

Albert-ludwigs-universitaet Freiburg

Universitätsklinikum Freiburg

Other

Juergen Hennig

Maxim Zaitsev

Guobin Li

Gerrit Schultz

Daniel Gallichan

Oliver Speck

Walter Witschey

Hans Weber

Kuan Jin Lee

Steffen Glaser

Anna Welz

Jakob Asslaender

Julius Dragonu

Maxim Zaitse

A method for accelerating magnetic resonance imaging is proposed. In 3D MRI, the method utilizes two sub-echo-trains in each repetition time for the simultaneous acquisition of two contrasts. The first sub-echo-train is a turbo spin echo train and the second sub-echo-train is a gradient echo train. The method acquires two different contrasts simultaneously in a single acquisition, for example one water image plus one fat image, or one turbo spin echo image plus one susceptibility weighted image.

MRI method of hybrid acquisition in 3D TSE

A method of magnetic resonance, in which a sample introduced in a measurement volume in an external magnetic field is excited by an excitation pulse and the signal formed by the transverse magnetization thus produced is read out by a receiving coil. The method is characterized in that a prewinding pulse is used as the excitation pulse, which prewinding pulse is characterized in that the formed transverse magnetization M(&#x3c9;) of spins of different Larmor frequency &#x3c9; after the pulse has a phase &#x3c6;(&#x3c9;), wherein &#x3c6;(&#x3c9;) as a function of &#x3c9; within a predefined frequency range &#x394;&#x3c9; has an approximately linear course having negative slope, such that the spins refocus after an echo time defined by the pulse without an additional refocusing pulse being necessary.

Method of magnetic resonance with excitation by a prewinding pulse

A method of MRI for reduction of motion artifacts in 3D MR data acquisition with multiple segments comprises: the complete acquisition being divided into two parts: basic acquisition and complementary acquisition. Basic acquisition is performed at the beginning. Complementary acquisition is performed after the basic acquisition is finished. View Reordering is prepared for basic acquisition and complementary acquisition separately. Motion monitoring is performed regularly during the data acquisition. Whenever motion is detected, data acquisition stops. Image reconstruction is performed when motion occurs in the phase of complementary acquisition. The final reconstructed image is free of motion artifacts.

Method for improving robustness of 3D magnetic resonance imaging to involuntary motion

A method of MRI entails recording and storing MR signals from an object to produce an old set of data. A further measurement of the object is then initiated at a later time to record new MR data, whereby k-space is undersampled in the further measurement. The old data are corrected for changes in the new position of the object, for changes in the sensitivity and exact spatial positioning of the receiver coils as well as for changes in the actual field shimming. The old and new data are then combined to create a new, high resolution image of the object.

Method and apparatus for accelerating magnetic resonance imaging

A method is presented for accelerating magnetic resonance imaging. In 3D MRI, the k-space in the phase encoding plane is divided into two symmetric parts and three asymmetric parts. Different sampling densities are applied in different parts. Images are reconstructed by iteratively minimizing a cost function when random sampling is applied in each part. A phase constraint term is added into the cost function to improve the quality of the reconstruction by exploiting the conjugate symmetry of k-space.

Method for accelerating magnetic resonance imaging using varying k-space sampling density and phase-constrained reconstruction

A method of MR imaging applies a magnetic field Bhaving a spatially non-linear dependence to select a volume of at least one curved slice. The slice is described by its midsurface A, a volume of the selected slice being made up of n&#x3bd; partial volumes in each of which gradients of at least one pair of remaining superimposed magnetic fields B(i&#x3e;1) exhibit an angle dependence of 70&#xb0; to 110&#xb0; with respect to one another and with respect to the normal of the midsurface A. At least one superimposed magnetic field of the respective pair exhibits a spatially non-linear dependence and combinations of these pairs are used for spatial encoding. In this way, curved surfaces can be mapped efficiently in high resolution and the method can be adapted to the slice shape.

Method of magnetic resonance imaging for the selection and recording of curved slices

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 method for accelerating data acquisition in MRI with N-dimensional spatial encoding has a first method step in which a transverse magnetization within an imaged object volume is prepared having a non-linear phase distribution. Primary spatial encoding is thereby effected through application of switched magnetic fields. Two or more RF receivers are used to simultaneously record MR signals originating from the imaged object volume, wherein, for each RF receiver, an N-dimensional data matrix is recorded which is undersampled by a factor Rper selected k-space direction. Data points belonging to a k-space matrix which were not recoded by a selected acquisition schema are reconstructed using a parallel imaging method, wherein reference information concerning receiver coil sensitivities is extracted from a phase-scrambled reconstruction of the undersampled data matrix. The method generates a high-resolution image free of artifacts in a time-efficient manner by improving data sampling efficiency and thereby reducing overall data acquisition time.

Method for data acquisition acceleration in magnetic resonance imaging (MRI) with N-dimensional spatial encoding using two or more receiver coil arrays and non-linear phase distributions

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.

NMR tomography method based on NBSEM with 2D spatial encoding by two mutually rotated multipole gradient fields

A magnetic resonance (NMR) method for fast, dynamic, spatially resolved measurement of the temporal changes in NMR signals by means of repeated data acquisition in individual measurements (Acq) with measuring sequences which are sensitive to a parameter to be observed, in an NMR apparatus with shim coils for correcting the magnetic field is characterized in that during data acquisition of each individual measurement (Acq) in acquisition steps (SS) with a time lag, the magnetic field distribution in the NMR apparatus is measured, technically or physiologically based changes in the magnetic field distribution are determined therefrom in a calculation step (S) as well as a change in the currents in the magnetic field required for compensation thereof, and the dynamic changes in the magnetic field distribution are compensated for by means of the correspondingly changed shim currents. The inventive method permits dynamic detection of the changes in the magnetic field distribution through the above-mentioned factors during the measurement and compensation thereof through corresponding re-calculation of &#x394;y(x,y,z) or &#x394;B(x,y,z) and adjustment of the shim currents to render the magnetic field distribution for subsequent measurements again preferably identical to the initial magnetic field distribution.

Method for dynamic detection and change in the magnetic field distribution in magnetic resonance (NMR) measurements

A nuclear magnetic resonance (NMR) method for spatially resolved measurement of the distribution of signals of metabolites of different resonance frequencies by application of a sequence of radio-frequency pulses and switched magnetic fields, wherein the generated signals are generated by application of read gradients in a spatially encoded manner in the direction of these gradients, is characterized in that, after a time interval TR/2, the initially excited magnetization is subjected to a sequence of several radio frequency pulses, which are equally spaced by time intervals TR, and the used magnetic field gradients in each TR interval are applied such that the originally excited magnetization is repeatedly refocused in several TR intervals and thereby read out several times, several signals are generated within one TR interval by multiple inversion of the read gradient, and the signals which are read-out several times are each identically spatially encoded by application of phase encoding gradients and therefore differ only with respect to dephasing given by the respective resonance frequency, such that the individual signals at any read-out time can subsequently be associated with the signal contributions of the examined substances of different resonance frequencies. This method permits chemical shift selective measurement of hyperpolarized metabolites.

Method for measuring the nuclear magnetic resonance (NMR) of substances having hyperpolarized nuclei using continuously refocused multiecho spectroscopic imaging

A method of spatially resolved magnetic resonance spectroscopy according to the principle of chemical shift imaging (&equals;CSI) in which, through application of an excitation pulse, spins in a measuring volume are excited and a metabolite signal thereof is read out, wherein between the excitation pulse and the recording of the signal, spatial encoding of the signal is effected by means of a gradient pulse in at least one spatial direction, wherein said spatial encoding gradient is varied between each recording step, such that one obtains spatial allocation of the recorded signals in the partial volume of the measuring volume, is characterized in that a reference signal is recorded in addition to the signal of the recorded metabolites, which comprises the same spatial encoding as the metabolite signal, wherein the recording of the two signals is effected in a convoluted manner. This method enables the correction of the local effects without considerable increase of the recording time in order to obtain in this manner standardized and comparable results independently of occurring imperfections during the recording.

Growing community of inventors

Freiburg, Germany

Juergen Hennig