Abstract: A magnetic resonance examination system has an object carrier (14) to move an object to be examined relative to the field of view. A monitoring system (33) monitors examination circumstances under which magnetic resonance signals are acquired from the object within the field of view. In particular the monitoring system monitors the degree of physiological motion in the patient to be examined. A velocity control system (32) to control the velocity of the movement of the object relative to the field of view and to control the velocity on the basis of the monitored examination circumstances, i.e. the degree of physiological motion.

Abstract: A continuous moving table magnetic resonance imaging method is proposed where a ‘lateral’ read out is performed that is transverse to the direction of motion. This magnetic resonance imaging method for imaging a moving object includes spatially selective RF excitations are applied for respective phase-encodings. The sub-volume is excited by the spatially selective RF excitation moves with the motion of the object for respective subsets of primary phase-encodings. Acquisition of magnetic resonance signals is performed from a three-dimensional sub-volume of the object. The magnetic resonance signals are read encoded in a direction transverse to the direction of motion of the object and phase-encoded in at least the direction of motion of the object.

Abstract: During continuous moving of an imaging subject (12) through a scanner field of view (20), k-space data are acquired using a plurality of radio frequency coils (24, 26). The acquiring includes undersampling of k-space in at least one undersampled direction. A weighted transform (62) from k-space to real space is defined for at least one undersampled direction. The weighted transform incorporates patient position-dependent coil sensitivity weighting factors and a Fourier transform. The acquired k-space data are hybrid transformed along the direction of continuous moving to define hybrid space data having a real space dimension in the transformed direction of continuous moving and a k-space dimension in a transverse direction that is transverse to the direction of continuous moving. The hybrid space data are transformed along the transverse direction to generate a reconstructed image.

Abstract: A plurality of global receive coils (24a, 24b, 24c) are stationarily positioned around a fixed field of view (FOV) of a magnetic resonance diagnostic imaging device (10). Each global receive coil receives undersampled phase and frequency encoded data from the stationary field of view. A subject is imaged as it moves continuously through the fixed field of view such that data is collected over a virtual field of view (vFOV) of the subject which is longer than the field of view in a longitudinal direction of subject motion. Centrally encoded k-space data, acquired from each of the global receive coils, is used to generate coil sensitivity patterns (42) which are mapped (44) from the stationary field of view to the virtual field of view.

Abstract: A continuous table motion magnetic resonance imaging system includes a processor (70) for determining values of scan parameters including at least a subject velocity, a field of view length in the direction of the table velocity, and a preparation sequence time. The acquisition includes performing one or more preparatory operations (54) to manipulate image contrast or to update scanning parameters during table motion. A table (16) is provided for continuously moving a supported imaging subject at the determined velocity. A magnetic resonance imaging scanner (10) through which the table continuously moves the subject acquires magnetic resonance imaging data of the imaged subject during the continuous moving using the determined scan parameters. A reconstruction processor (30, 34, 40) reconstructs the acquired data into an image of the field of view.

Abstract: A continuous table motion magnetic resonance imaging system includes a processor (70) for determining values of scan parameters including at least a subject velocity, a field of view length in the direction of the table velocity, and a preparation sequence time. The acquisition includes performing one or more preparatory operations (54) to manipulate image contrast or to update scanning parameters during table motion. A table (16) is provided for continuously moving a supported imaging subject at the determined velocity. A magnetic resonance imaging scanner (10) through which the table continuously moves the subject acquires magnetic resonance imaging data of the imaged subject during the continuous moving using the determined scan parameters. A reconstruction processor (30, 34, 40) reconstructs the acquired data into an image of the field of view.

Abstract: A plurality of global receive coils (24a, 24b, 24c) are stationarily positioned around a fixed field of view (FOV) of a magnetic resonance diagnostic imaging device (10). Each global receive coil receives undersampled phase and frequency encoded data from the stationary field of view. A subject is imaged as it moves continuously through the fixed field of view such that data is collected over a virtual field of view (vFOV) of the subject which is longer than the field of view in a longitudinal direction of subject motion. Centrally encoded k-space data, acquired from each of the global receive coils, is used to generate coil sensitivity patterns (42) which are mapped (44) from the stationary field of view to the virtual field of view.

Abstract: A device for determining the position of a medical instrument that is introduced into an object to be examined is also used for imaging the vicinity of the medical instrument. In order to enable the acquisition of instantaneous position information and image information from the vicinity of the medical instrument for all kinds of medical instruments, a localization device that is arranged in the end zone of the medical instrument that is to be introduced determines the position of the medical instrument within the object to be examined; at the same time image information is acquired in the vicinity of the medical instrument by an image acquisition device that is arranged on the medical instrument and on the basis of the position thus determined the position of the medical instrument (3) is reproduced in a survey image of the object to be examined and images of the vicinity of the object to be examined are displayed on the basis of the image information acquired.

Abstract: The invention relates to an MR method wherein disturbing MR signals from peripheral regions outside the isocenter are suppressed in that a location-dependent, brief, steady magnetic field is produced simultaneously with an RF pulse. When the field strength of the magnetic field in the peripheral regions is either larger or smaller than that at the isocenter, it can be achieved that exclusively the nuclear magnetization in the peripheral regions is excited, which magnetization can subsequently be dephased. The subsequent MR sequence then influences only the region around the isocenter.

Abstract: A vertical field type MRI apparatus is provided with a superconducting coil system for generating a substantially homogeneous magnetic field in an imaging volume of the apparatus. The coil system includes a circular outer coil and a supplementary coil which is positioned in the same plane as and within the outer coil, which coils conduct opposite currents. The ratio Da/Do of the diameter Da of the supplementary coil to the diameter Do of the outer coil lies between 0.7 and 0.9. Further coils for making the field more homogeneous are preferably located on a conical surface within the circular outer coil and supplementary coil in such a manner that a recess is formed in which a conically shaped gradient coil system can be accommodated, with the result that the expensive outer coil and the supplementary coil can be arranged at an as short as possible distance from the space for receiving the patient to be examined.

Abstract: An MR imaging method wherein motion of an object to be imaged is examined during a preparation phase preceding the actual MR examination. The necessary sequences for the subsequent MR examination are modified during the examination to compensate for the motion based on motion parameters calculated during the preparation phase or motion parameters derived from the motion parameters calculated during the preparation phase based on a correlation between the motion parameters.

Abstract: The invention relates to a method and a device for determining the position of a medical instrument (3) that is introduced into an object (1) to be examined and for imaging the vicinity of the medical instrument (3).

Abstract: The invention relates to a vertical field type MRI apparatus that is provided with a superconducting coil system 20a, 20b for generating a substantially homogeneous magnetic field in an imaging volume 18 of the apparatus. The coil system includes a circular outer coil 28 and a supplementary coil 30 which is positioned in the same plane 32 as and within the outer coil, which coils conduct opposite currents. The ratio Da/Do of the diameter Da of the supplementary coil to the diameter Do of the outer coil lies between 0,7 and 0,9. Further coils 34 to 38, 40 to 46 for making the field more homogeneous are preferably located on a conical surface 48, 50 within the first mentioned coils 28, 30 in such a manner that a recess is formed in which a conically shaped gradient coil system 52 can be accommodated, with the result that the expensive outer coil 28 and the supplementary coil 30 can be arranged at an as short as possible distance from the space for receiving the patient to be examined.

Abstract: The invention enables the temporal variation of the magnetic field generated by a gradient coil to be derived from the measured temporal variation of the current through this gradient coil and from a pulse response which has been determined once and stored for the relevant coil. In this case an inexpensive non-linear amplifier may be used in the gradient channel, and also a gradient coil with eddy current effects, without the reconstruction or the pulse design being degraded.

Abstract: The invention relates to an MR method where the motion of an object to be imaged is examined during a preparation phase preceding the actual MR examination and where the necessary sequences for the subsequent MR examination are modified during such examination in such a manner that the motion is compensated.

Abstract: The invention relates to an MR method in which the deterioration of the image quality by the concomitant gradients is reduced or eliminated by imposing a temporal variation on the magnetic fields acting in the examination zone during the time interval between the excitation of the nuclear magnetization and the reception of the MR signal such that the spatial distribution of the phase error upon reception of the MR signal is at least approximately the same for all sequences.

Abstract: The invention relates to a method of navigating a magnetic object (11) within an object (1) which is exposed to a magnetic field, as well as to a magnetic resonance device in which this method can be carried out. The method according to the invention is particularly suitable for navigating a catheter or a flexible endoscope within the body of a patient. The magnetic object (11), preferably being provided in or on such a medical instrument (10), has a controllable magnetic moment for this purpose and the direction of movement of the object is determined by control of the magnetic moment. In the case of a magnetic resonance device whose static magnetic field is used, the object (11) is preferably includes as a coil system.

Abstract: The invention relates to an MR method and an MR device for determining the position of at least one microcoil (11, 12) which is provided in or on an object (1) to be examined which is situated in an examination zone. During the acquisition of microcoil MR signals (S), at least one variable magnetic gradient field acts on the examination zone, so that the k space is scanned at scanning points (k.sub.x (t.sub.i), k.sub.y (t.sub.i)). The position (x, y) of the microcoil (11, 12) is determined from at least three scanning values (S(t.sub.i)) of a microcoil MR signal and the associated scanning points (k.sub.x (T.sub.i), k.sub.y (t.sub.i)) for example by solving a system of equations formed from these values. The MR method can be used for various scanning modes of the k space, and the acquisition of the microcoil MR signals (S) does not require any MR sequences other than the MR sequences required for determining the nuclear magnetization distribution in the examination zone.

Abstract: In an MR method whereby artefacts can be eliminated in MR images of inclined slices which are situated outside the isocenter, the temporal variation of a phase error is calculated from the imposed (desired) variation of the magnetic gradient fields and the impulse responses of the gradient coil sub-systems generating these fields, and the measured MR signals are corrected accordingly.

Abstract: A string of input characters is recognized as one of a plurality of reference sets which are stored in predetermined groups. A set of signals representative of the correspondence of the input characters to the reference characters is generated. The input character string is identified responsive to the character correspondence signals. The character string identification comprises forming a set of signals each representative of the correspondence of the input character string to one of the predetermined groups responsive to the character correspondence signals. Jointly responsive to the character correspondence signals, the reference character sets and the group correspondence signals, the reference set that most closely corresponds to the input character string is selected.