Bruker Biospin Mri Gmbh

Bruker Medizintechnik Gmbh

Bruker Medical Gmbh

Other

Arno Nauerth

Jurgen Hennig

Michael Heidenreich

Techniques for determining motion states of at least two bodies by an MR-device are provided, wherein the bodies each have a respective target region which is in an anatomic motion comprising a repetitive motion pattern with a motion repetition rate, and in particular, for cardiac and/or respiratory motion. A sequence of individual MR-measurements are performed on the bodies at a MR-repetition rate higher than the motion-repetition rate, wherein nuclear spins of the at least two bodies are excited during the sequence of individual MR-measurements either simultaneously or alternately at navigator times. With the individual MR-measurements, navigator signals are determined, each respective navigator signal indicative of the motion state of at least one of the motion patterns at the navigator time of the navigator signal. These techniques allow simultaneously determining motion states for imaging more than one body with a repetitive motion pattern with reduced preparation time.

Method for determining motion states of at least two bodies and method for simultaneously imaging at least two bodies

A method for determining the position of at least one ferromagnetic particle () in a liquid matrix () with an MRI system (). An MRI measurement sequence (MS, MS) is applied () to a measurement volume () in which the particle is situated. The measurement sequence includes a plurality of individual measurements (E, E), during each of which there is a spatially encoding gradient switching operation, including an excitation pulse () and signal recording (), via the MRI system. The measurement sequence has a multiplicity of measurement blocks (MB, MB), which each include one or more individual measurements and, in a pause of the spatial encoding, an intermediate gradient (ZW) switched by the MRI system. The intermediate gradients are dimensioned such that, averaged over time, the particle is kept substantially in the same position (M, M) over each measurement block.

Method for determining the position of a ferromagnetic particle and associated MRI system

A method for generating magnetic resonance (MR) images or MR spectra of at least one partial area of a moving object with at least one motion sequence that is repeated during consecutive motion states is proposed. In a learning measurement, a monitor signal of the repeating motion sequence is recorded, and MR test data of the partial area of the object are recorded under known measurement conditions, wherein the MR test data is associated with the motion states of the motion sequence. In an evaluation step, the MR test data of the motion states of the motion sequence are compared to each other with respect to at least one parameter, and the variation of the at least one parameter over the motion sequence is determined. The instantaneous motion state of the object in the motion sequence is constantly determined in a target measurement during recording of the MR images or MR spectra of the partial area via a monitor signal, and the associated variation of the at least one parameter is constantly compensated for by corresponding variation of the measurement conditions. The quality of MR measurements for recording moving objects is thereby improved, in particular, when retroactive calculation of disturbances in the measured MR data is not possible.

Interference compensation in MR measurements on moving objects through adjustment of the measurement conditions

A method for generating MR (magnetic resonance) images of a moving object with a repeating motion pattern at comparable motion states, wherein for at least one motion state, a set of MR data which is completely encoded for producing an MR image is provided from a plurality of successive individual MR measurements. The method is characterized in that at least one contiguous region of successive data points is used as indicator within the individual MR measurement, wherein this contiguous region is identically repeated for all individual MR measurements within the respective MR measuring sequence relative to irradiated RF (radio frequency) pulses and switched gradients. This provides reliable allocation of the recorded MR data with the associated motion states, wherein completely encoded sets of MR data can be determined within an optimum time.

Method for producing MR (magnetic resonance) images of a moving object using navigator signals

A method of correcting disturbing influences on MR (&equals;magnetic resonance) signals of a substance disposed in the measuring volume of an MR apparatus excited by one or more RF (&equals;radio frequency) excitation pulses, wherein an RF excitation pulse is irradiated onto the substance and a time-dependent MR signal generated thereby is detected and digitized in a phase-sensitive fashion, wherein a time dependence ( )&Dgr;&phgr; (t ) of the phase of an MR signal, relative to a predetermined reference phase &phgr; (t ) of a reference signal S (t ), is determined and digitized from a time dependence ( ) s (t ) of the detected and digitized MR signal and one or more correction or controlled variables are determined therefrom. Nearly all measuring points are used for determination of the magnetic field deviation and thus for control to guarantee considerably improved control accuracy.

Method of correcting disturbing influences on the MR signals of a substance disposed in the measuring volume of an MR apparatus

The invention concerns a method for correcting linear field inhomogeneities in a magnetic resonance apparatus. After an excitation pulse and application of a phase gradient in a predetermined direction, a data point is taken after a fixed, predetermined time t . This is repeated for systematically changed strengths of the phase gradient and constant t . The phase gradient with maximum measuring signal corresponds to a field correction gradient in the corresponding direction.

Method of correcting linear field inhomogeneities in a magnetic resonance apparatus

The invention concerns a method of correcting field inhomogeneities of higher order in a magnetic resonance apparatus After an excitation pulse and action of a phase gradient in a predetermined direction p, a data point is recorded after two predetermined times t and t . This is repeated for systematically modified strengths of the phase gradient and constant t and t , and two sets of signal dependences in the p direction are obtained. The two phase dependences of the two Fourier transformed data sets in the p direction are subtracted. The profile of the difference phase in the p direction corresponds to a field error profile. The method is repeated for several p directions, and coefficients of higher order of a series expansion of the field inhomogeneities in spherical harmonic functions are obtained.

Method of correcting higher order field inhomogeneities in a magnetic resonance apparatus

A method for the production of a two or three-dimensional image with the assistance of magnetic resonance. The measuring data are taken according to the projection method by means of a sequential rotation of projection gradients. The image, however, is generated with 2dFT or 3dFT methods. The projection gradient is advantageously not only rotated between high frequency excitation pulses, but its strength is also changed in such fashion that the measuring points in k-space lie on squares or parallelepipeds.

Magnetic resonance imaging with combined back projection and fourier

In an SPI method for the n-dimensional NMR imaging of materials with short T.sub.2 -relaxation times, for example cartilage or bones, only one single measurement point in k-space is recorded from the phase encoded FID signal following each RF excitation pulse. A pseudo spin echo (4) is derived from the extracted k-space points which has essentially the same information content as a conventional spin echo signal. In order to prevent excessive noise development when switching the gradients, the gradients are also applied during the waiting time between the recording of individual points, and the stepwise change of the gradient fields from one point to the next is done in such a fashion that at least one of the gradient fields is not fully switched-off between two individual points rather only changed, in each case, by an increment value which is very small compared to the maximum value of the corresponding gradient fields, whereby the size of the increment value corresponds to one to z-times the separation between two neighboring points in k-space, and preferentially z&lt;5.

Low-noise NMR imaging method with single point recording (SPI)

A magnetic resonance method is utilized for taking an image of an object. An initial projection is taken by applying a gradient magnetic field having a predetermined direction .phi. and strength G, irradiating a high frequency excitation pulse and sequentially measuring a nuclear resonance signal from the object. The signal dephases under the influence of the gradient magnetic field and the signal measuring points are assigned to points in k-space lying along a vector whose direction is determined by the direction .phi. of the gradient magnetic field, and whose magnitude by the product of the strength of the gradient magnetic field and the time interval between the excitation pulse and the taking of the corresponding measuring point. A further number of n-1 (n&gt;&gt;1) projections are obtained by changing the direction and/or strength of the gradient magnetic field. Additional excitations and measurements are carried out for an additional n'.ltoreq.n projections having measuring points. The gradient strengths and the waiting time t.sub.w ' of the additional excitations are adjusted and the image is reconstructed from the total number measuring points.

Magnetic resonance imaging with combined single point and back

For recording a nuclear magnetic resonance tomogram according to a Fourier-transform method, a Carr-Purcell-Gill-Meiboom pulse sequence is used for the excitation of a body to produce a sequence of spin-echo signals. A time-limited phase-encoding magnetic gradient field G.sub.X is imposed between each pair of 180.degree. pulses of the sequence. The phase-encoding magnetic gradient field is modified after every 180.degree. pulse so that every spin-echo signal corresponds to a different projection of the body. The magnetic gradient fields used in the recording are regulated in intensity and duration in such a way that a spin-phase condition at each 180.degree. pulse of the pulse sequence remains effectively constant. Thereby, it is possible to construct a complete tomographic recording with a single pulse-sequence excitation, so that the time required for such recordings can be reduced to a fraction of the time needed for recording nuclear-magnetic-resonance tomograms conventionally.

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Erlenbach, Germany

Arno Nauerth