Siemens Aktiengesellschaft

Siemens Healthcare Gmbh

Siemens Aktiengesell Schaft

Vladimir Jellus

Stephan Kannengiesser

Timothy Hughes

Michael Szimtenings

David Grodzki

Dominik Paul

Mark A Griswold

Alto Stemmer

Mathias Nittka

David Andrew Porter

Lars Lauer

Christian Geppert

In a method for creating a composite magnetic resonance (MR) raw dataset for an MR apparatus, a first MR raw dataset is determined from a first partial section of an examination object, in which a first region of the first MR raw dataset is not filled with MR signals and in which a second region of the first MR raw dataset is filled with MR signals. An MR overview dataset is determined, which has been acquired with a number of reception coils of the MR apparatus and for which an overall field of view of the number of MR coils is larger than a reception region of the number of MR receive coils. A partial dataset is determined from the MR overview dataset, which has MR signals that originate from the first partial section of the examination object from which the first MR raw dataset originates. MR partial raw data are reconstructed for the first region of the MR raw dataset, using the partial dataset determined. The composite MR raw dataset is created from the second partial region of the first MR raw dataset and the MR partial raw data.

Method and computer use of an MR overview dataset for reconstruction of MR raw data

In a method according to optimize the noise development of a 3D gradient echo sequence in a magnetic resonance system, an optimization of at least one parameter of the gradient echo sequence, from the group including: the excitation pulse (the duration of the excitation pulse); the order of k-space lines to be scanned in k-space; and the readout direction of the k-space lines to be scanned in k-space, is implemented such that the gradients to be switched have optimally minimal slew rates, amplitudes and/or polarity changes.

Optimization of the noise development of a 3D gradient echo sequence in a magnetic resonance system

In a method processor and magnetic resonance (MR) system to generate MR slice exposures of an examination subject, measurement data for a stack of measurement slices through the examination subject are initially acquired using a series of slice measurement sequences. The series of slice measurement sequences is designed to allow a separation of a first material from a second material that has a defined chemical shift relative to said first material, and the position of a measurement slice with measurement data for the first material is spatially shifted relative to the position of a measurement slice with measurement data for the second material. Combination slice exposures are then formed by combining measurement data of the first material from at least a first slice measurement sequence with measurement data of the second material from at least one second slice measurement sequence, such that the image data of the first and second materials are spatially arranged with precise positioning relative to one another, at least within a predetermined degree of tolerance in the combination slice exposures.

Method to generate magnetic resonance slice exposures

In a methods and devices for magnetic resonance (MR) imaging, an MR data acquisition is implemented repeatedly in which an examination subject is exposed to an alternating magnetic field with a frequency before the readout sequence. The signal values acquired after the preparation of the magnetization with alternating fields of respectively different frequencies are evaluated. Magnetic field data that contain information about the curve of the basic field are used to implement the MR data acquisitions, such as to establish the frequencies, and/or in the evaluation of the signal values.

Method and device for magnetic resonance imaging

In a method and magnetic resonance system to determine a magnetic resonance (MR) image of an examination subject, wherein multiple coil-specific MR data sets that are acquired by multiple coils are used for the MR image. Each pixel of the MR image is determined from at least two coil-specific MR data sets of different coils (-), and each pixel has a pixel magnitude and a pixel phase. Multiple coil-specific base phases are determined that are respectively associated with one of the multiple coils. For each pixel multiple coil-specific pixel, magnitudes and multiple pixel phases are determined. A coil-specific pixel magnitude and a coil-specific pixel phase are respectively determined from a coil-specific MR data set of one of the multiple coils (-). The coil-specific pixel phases with the corresponding, coil-specific base phase, and the multiple coil-specific pixel magnitudes and the multiple coil-specific pixel phases are combined into the pixel magnitude and the pixel phase of the pixel.

Phase-dependent magnetic-resonance imaging with multiple coils

A method is disclosed for determining an attenuation map for use in positron emission tomography and for the use of homogeneity information relating to the magnetic resonance magnetic field, in particular for the purpose of determining shim settings, within the scope of a single magnetic resonance image recording. In at least one embodiment of the method, a first and a second image data record are firstly recorded with a three-dimensional gradient echo sequence during a first and a second echo time, respectively, with the phase difference between the water and the fat signal amounting to zero during the first echo time and amounting to 180 degrees during the second echo time. The attenuation map is determined from fat/water ratios obtained from the image data records by way of a Dixon technology, in particular a 2-point Dixon technology. In at least one embodiment, all voxels with a signal intensity below a first threshold value are excluded at least for the second image data record by using a mask and only the non excluded voxels of the first and second image data record are taken into consideration in order to determine the homogeneity information from the phase differences of adjacent voxels.

Method for determining an attenuation map for use with positron emission tomography and magnetic resonance magnetic field homogeneity from a single three dimensional gradient echo sequence

In a magnetic resonance method and system to automatically differentiate whether a pixel of an MR image acquired with magnetic resonance system originated from fat-dominated tissue or water-dominated tissue, only one spin echo-based magnetic resonance signal per pixel is acquired at a point in time at which the phase of a magnetic resonance signal of aqueous tissue has a phase opposite to the phase of a magnetic resonance signal of fat tissue. The phase angle of the pixel is then calculated, a base phase at the pixel depending on the magnetic resonance system is determined, and a corrected phase angle of the pixel is determined from the phase angle and the base phase. Whether the pixel originated from fat-dominated tissue or water-dominated tissue is then determined using the corrected phase angle of the pixel.

Magnetic resonance method and device to automatically differentiate water-dominated and fat-dominated tissue with only one spin echo acquired for each pixel

In a magnetic resonance method and device for automatic differentiation of respective pixels as representing either a silicon-dominated substance, or fat-dominated tissue, or water-dominated tissue, a first magnetic resonance signal and a second magnetic resonance signal are acquired per pixel, wherein the first magnetic resonance signal per pixel is acquired at a point in time at which the phase of a magnetic resonance signal originating from water-containing tissue exhibits a phase opposite to the phase of a magnetic resonance signal originating from fat-containing tissue, and the second magnetic resonance signal is acquired per pixel at a point in time at which the phase of the magnetic resonance signal originating from water-containing tissue exhibits a phase identical to the phase of the magnetic resonance signal originating from fat-containing tissue, and the phase of a magnetic resonance signal originating from a silicon-containing substance exhibits a phase opposite to the phase of the magnetic resonance signal originating from water-containing or fat-containing tissue. A first intermediate result is determined that indicates whether the pixel represents water-dominated tissue or fat-dominated tissue on the basis of first magnetic resonance signals. A second intermediate result is determined that indicates whether the pixel represents the silicon-dominated substance on the basis of second magnetic resonance signals. The pixel is designated as representing water-dominated tissue, fat-dominated tissue or the silicon-dominated substance on the basis of the first intermediate result and the second intermediate result.

Magnetic resonance method and device to differentiate among pixels representing a silicon-dominated substance, water-dominated tissue and fat-dominated tissue

In a magnetic resonance tomography method and apparatus for separation of fat and water images according to the two-point Dixon method dependent on the T*decay, the following steps are implemented: (S) acquire three fat-water images, respectively corresponding to the echo times TE, TE, TEafter the RF excitation pulse, wherein first and third fat-water images exhibit the same phase, (S) calculate a T*map from the two equiphase images, (S) correct the T*influence in one of the two equiphase fat-water images and in the counter-phase fat-water image, and (S) reconstruct a pure T*-corrected fat image and a pure T*-corrected water image according to the two-point Dixon method on the basis of the T*-corrected equiphase and counter-phase fat-water images in Step (S).

[object Object]

A method corrects for a phase error in an MR image, in which MR signals of an examination subject are acquired, complex images of the examination subject are generated, phase differences of the phase values for various image points of the complex images are established with an averaged phase value of image points from a first surrounding region of a respective image point, and a phase correction is executed dependent on how well the phase differences correspond to a predetermined phase value, where the order of the image points in which the phase correction is implemented is dependent on how well the phase values in the image points correspond to the predetermined phase value.

Phase correction method

In a method, apparatus and computer-readable medium for magnetic resonance imaging of a contiguous region of a human body on the basis of partially parallel acquisition (PPA) by excitation of nuclear spins and measurement of radio-frequency signals representing the excited spins, are implemented. A k-space single channel reference image [R_kal] is calculated from the previously measured reference lines of a sub-coil series of N sub-coils with a phase-sensitive combination method. A GRAPPA coefficient matrix [W] is calculated by solving the equation system [R_kal]=[W]&#xd7;[I_kal] wherein [I_kal] represents one block from the sub-coil series. A k-space single channel image [R] is successively completed by applying [W] to successive blocks [I_z] shifted relative to one another, the blocks [I_z] being of a previously measured, under-sampled sub-coil series of the N sub-coils, and [R] is transformed into image space.

Method and device for magnetic resonance imaging on the basis of a partially parallel acquisition (PPA)

A method is for correcting inhomogeneities in an image that is recorded from an examination object. The method includes recording an image to be corrected, calculating a correction image from the image to be corrected and correcting the recorded image with the aid of the correction image in order to produce a normalized image by multiplying the correction image by the image to be corrected. When calculating the correction images, the pixels in the vicinity of the imaged examination object are identified with the aid of a signal intensity that is lower than a limiting value. Further, these pixels are allocated signal intensities that in each case are a function of the signal intensity of the pixels in the respective neighborhood.

Method for correcting inhomogeneities in an image, and an imaging apparatus therefor

In a method and apparatus for generating a magnetic resonance image of a contiguous region of a human body on the basis of partial parallel acquisition (PPA) by excitation of nuclear spins and measurement of radio-frequency signals indicating the excited spins, the spin excitation is implemented in steps with measurement of an RF response signal simultaneously in each of a number of N component coils. A number of response signals thus are acquired that, for each component coil, form an incomplete data set () of acquired RF signals. Additional acquired calibration data points exist for each incomplete data set. The N incomplete data sets are acquired to a subset of M reduced, incomplete data sets on the basis of an N&#xd7;M reduction matrix, so that M reduced, incomplete data sets are obtained, M complete data sets are formed on the basis of an N&#xd7;M reconstruction matrix with the non-measured lines of the M reduced, incomplete data sets being reconstructed from all N incomplete data sets. A spatial transformation of the completed reduced data sets is then implemented in order to form a complete image data set from each completed, reduced data set.

Method for MRT imaging on the basis of conventional PPA reconstruction methods

In a data acquisition and reconstruction method for magnetic resonance (MR) tomography, and a corresponding MR tomography apparatus, a blade-like sampling of k-space according to the PROPELLER method using a number of reception coils ensures with partial under-sampling of at least one blade of k-space such that the under-sampling ensues by regular omission of k-space lines in both boundary regions (with regard to the phase-encoding direction k) of a blade such that only data in each A-th line of said boundary regions are acquired; with no k-space lines being omitted in the central region (with regard to the k-direction) and thus at least one coil calibration line is obtained, selection of a suitable PPA method for completion of the blades and determination of the necessary coil calibration data necessary for the PPA reconstruction of a partial under-sampled blade from the central completely sampled region of said blade. PPA reconstruction via application of the selected PPA method selected in order to interpolate the non-measured or, respectively, omitted k-space lines of each blade, and execution of the PROPELLER reconstruction after the PPA reconstruction.

Multi-coil magnetic resonance data acquisition and image reconstruction method and apparatus using blade-like k-space sampling

In the operation of a magnetic resonance system, an RF excitation coil emits an excitation pulse such that nuclei in an examination subject are excited to emit of magnetic resonance signals. A number of local coils acquire the magnetic resonance signals emitted from the examination subject, with the magnetic resonance signals acquired by the local coils being coded in frequency space. An evaluation device accepts the magnetic resonance signals acquired by the local coils or accepts intermediate signals derived therefrom via one transmission channel per signal, and corrects the accepted signals using correction signals. The evaluation device uses the corrected signals reconstructing an image of the examination subject. The evaluation device determines the correction signals for all signals to be corrected using the same reference signal.

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Erlangen, Germany

Vladimir Jellus