U.S. Philips Corporation

Koninklijke Philips Corporation N.V.

Peter Van Der Meulen

Gerrit H Van Yperen

Johannes Petrus Groen

Johan Samuel Van Den Brink

Willem Christiaan Constantijn Furster

Filips Van Liere

Johannes J Cuppen

Paul Augustinus Peter Kaufholz

Antoon F Mehlkopf

Rudolf Theodoor Springorum

Marius Johannes Van Meel

Vincent Paul Quinten Van Wijk

Jan Bruijns

A magnetic resonance examination system is provided with a graphical user interface and an (software) analysis module. The analysis module is configured to analyze examination information, notably a selected examination protocol, for actions to be taken by the operator, such as connecting auxiliary equipment or radio frequency receiver coils to the magnetic resonance examination system. The analysis module supplies the actions to be taken to the (graphical) user interface at the proper instant before or during carrying-out the examination protocol. In this way the operator is guided and supported in the performance of the selected examination protocol. This improves the efficiency of workflow in performing one or more selected protocols. Preferably, the graphical user interface is provided inside the examination room and may be mounted on the gantry.

Magnetic resonance examination system with a user interface

The invention relates to a method for in vivo measurement of a periodically varying fluid flow in an object by means of magnetic resonance. The method includes a step for applying first and second additional magnetic field gradients in order to shift the phase of a reference magnetization, which phase shift relates to a net flow of the fluid during an interval between the application of the additional magnetic field gradients. According to the invention, near a phase of a period of the periodically varying fluid flow an excitation RF pulse is generated, the first additional gradient is applied and a first additional RF pulse is generated and near a corresponding phase of a second period of the periodically varying fluid flow a second additional RF pulse is generated and the second additional gradient is applied.

Magnetic resonance method and device for measuring a periodically varying fluid flow in an object

A method for magnetic resonance imaging is described in which imaging sequences, consisting of RF- and gradient magnetic field pulses (RF, G.sub.x, G.sub.y, G.sub.z) are optimized with respect to a relevant parameter (SAR, signal-to-noise, etcetera) prior to applying the RF- and gradient pulse sequence to the object or patient (7) to be imaged. This reduces the amount of different sequences to a limited number of basic sequences from which an operator has to choose and allows adaptation of the sequence to the particular image to be obtained.

Magnetic resonance imaging method with pulse sequence optimization and

In an MRI device operating according to a spin-echo method, switched gradient magnetic fields are applied in the form of slice selection, phase encoding and read gradients. The switching of the gradients causes eddy currents in metal parts of the apparatus. The eddy currents disturb the applied magnetic fields, thereby changing the phases of the precessing nuclear spins of a body to be examined and causing artefacts in a reconstructed image. The disturbing effects of the eddy currents is compensated for by supplementing a sequence of switched gradient magnetic fields with additional gradient fields. These additional fields have zero net effect but induce further eddy currents which compensate for the disturbing effects of the eddy currents generated by the regular switched gradient magnetic fields. The additional gradient fields are chosen such that the total time-integrated strength of a gradient in any interval between two RF-pulses is substantially equal to the desired value.

Eddy current compensation in magnetic resonance imaging

In an MRI device (1) operating according to a spin-echo method, switched gradient magnetic fields are applied in the form of slice selection (231-233), phase encoding (243-243, 243'243') and read gradients (252-253). The switching of the gradients causes eddy currents in metal parts of the apparatus. The eddy currents disturb the applied magnetic fields, thereby changing the phases of the precessing nuclear spins of a body (7) to be examined and causing artefacts in a reconstructed image. Another source of disturbance may be phase-distortion in the RF amplifier. By modifying a gradient (251, 231') in between the excitation pulse (221) and the first refocusing pulse to (222) in the spin-echo sequence and/or a change in phase of the RF-pulses, the effects of the disturbances can largely be compensated for. The additional gradient size is adjusted by measuring the position in time and the relative phase of spin-echo signals (162, 163) in a preparatory sequence (121-173).

Magnetic resonance imaging method and apparatus employing eddy current

In a magnetic resonance imaging method multiple refocusing RF-pulses (22-26) are applied and spin-echo signals (62-66) obtained following an excitation RF-pulse (21). Imperfections in the applied RF-pulses (21-26) and the switched gradient magnetic fields (31-36, 42-46, 51-56) cause deviations from the desired phases of the nuclear dipole moments which appear as artefacts or ghosts in a resulting image. By a suitable arrangement of the application of the phase encoding values (242-248; 342-348) imposed during the measurements and/or the addition of supplemental measurements, the effects of the phase deviations in an image are significantly reduced, resulting in images in which less artefacts and ghosts are visible. Reduction of artefacts is also obtained by weighting of measured NMR-signals.

Method and apparatus for magnetic resonance imaging

In known magnetic resonance devices shimming is applied on the basis of maps of field inhomogeneities obtained from two images of a slice of an object by formation of a ratio image thereof. This ratio image is processed in order to obtain shimming information. These known methods are time-consuming and cumbersome. The invention proposes a fast and simple shimming method which utilizes only one measuring sequence or a few measuring sequences. The shimming gradient (-dG) is determined from a time shift between an anticipated temporal position (t1) and a measured temporal position (t1') of a maximum of an echo resonance signal (ec) produced by the measuring sequence.

Magnetic resonance device

In NMR images, which are constructed from resonance signals, for example with Fourier zeugmatography, due to coherent interferences, for example, as a result of 'leak-through' of NMR signals from one sequence to a next sequence of resonance signals, artefacts can occur in the images, which, depending upon the kind of interference, become manifest in the image as interference lines, ghost images or conspicuous dots. A method is disclosed of reducing the influence of these interferences by smearing the artefacts out over the image as noise. For this purpose, the phase of the reference signals is randomly modulated between measuring cycles of the resonance signals. The reference signal is used to form excitation pulses for producing resonance signals in a body and further in synchronous detection of the resonance signals.

Method and arrangement for suppressing coherent interferences in

A method is proposed for the elimination of the effect of coherent interference signals which give rise to image artefacts in off-center imaging which usually requires roll correction in order to obtain a correct image. To this end, the image is shifted independently with respect to the artefact signal over an arbitrary distance which depends on the isocentric shift. The method is advantageous for off-center imaging where usually surface coils are used. A band of interference signals in the phase encoding direction can thus be shifted to the edge of the image.

Method of reducing MR image artefacts in off-center images

The known magnetic resonance imaging method of determining the r.f. power or pulse angle of an r.f. electromagnetic 90.degree.-pulse or 180.degree.-pulse has the drawback that the measurement inaccuracy is often high, that the experimentation time is comparatively long and that its use is limited to r.f. electromagnetic 90.degree.-pulses or 180.degree.-pulses only. In order to mitigate these drawbacks, it is proposed to determine the pulse angle of an r.f. electromagnetic pulse having a pulse angle .alpha. from two out of five echo resonance signals, including one stimulated echo resonance signal, generated by means of three r.f. electromagnetic .alpha..degree.-pulses, .alpha. having an arbitrary value (calibration phase), after which any .beta. can be adjusted by adaptation of the applied r.f. power.

Magnetic resonance imaging method, and device for determining the pulse

In known spin echo imaging examination a waiting period is customarily observed between two successive spin echo measurements in order to allow for the magnetic moment to relax in the direction of the uniform magnetic field Bo. In addition to this waiting period, the use of 180.degree. pulses also leads to a comparatively long examination time which increases the risk of image artefacts due to motions of, for example a patient to be examined. This comparatively long examination time is also unfavorable in view of the radiation load. In order to avoid these drawbacks, a method is proposed in which the electromagnetic pulses used are exclusively excitation pulses in the form of .alpha..degree. pulses, where 0&lt;.alpha.&lt;90.

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Eindhoven, Netherlands

Peter Van Der Meulen