Abstract: An integrated, multi-modality imaging technique is disclosed. The embodiment described combines a split-magnet MRI system with a digital x-ray system. The two systems are employed together to generate images of a subject in accordance with their individual physics and imaging characteristics. The images may be displaced in real time, such as during a surgical intervention. The images may be registered with one another and combined to form a composite image in which tissues or objects difficult to image in one modality are visible. By appropriately selecting the position of an x-ray source and detector, and by programming a desired corresponding slice for MRI imaging, useful combined images may be obtained and displayed.

Abstract: An integrated, multi-modality imaging technique is disclosed. The embodiment described combines a split-magnet MRI system with a digital x-ray system. The two systems are employed together to generate images of a subject in accordance with their individual physics and imaging characteristics. The images may be displaced in real time, such as during a surgical intervention. The images may be registered with one another and combined to form a composite image in which tissues or objects difficult to image in one modality are visible. By appropriately selecting the position of an x-ray source and detector, and by programming a desired corresponding slice for MRI imaging, useful combined images may be obtained and displayed.

Abstract: A technique is provided for characterizing and correcting for instabilities or variations in a magnet system of an MRI scanner. The technique makes use of a navigator pulse to read out navigator echo data in the absence of phase encode, or with phase encode effects rewound. The navigator data is used to characterize several potential effects of magnet system instabilities or variations, such as zeroth order phase shifts, first order (linear) phase shifts, bulk position shifts, and amplitude effects. The effects of the instabilities can be used, then, to correct image data acquired during an examination.

Abstract: A method and system for imaging using an inhomogeneous static magnetic field is disclosed herein. The imaging includes providing the inhomogeneous static magnetic field to an object of interest located within an imaging volume. The imaging further includes providing a pulse sequence including a readout gradient pulse and a slice selection gradient pulse, both gradient pulses comprising a part of the inhomogeneous static magnetic field. The pulse sequence is configured to acquire a plurality of lines of k-space data per excitation.

Abstract: A medical imaging system includes a workstation for receiving operator inputs that prescribe a scan and a plurality of servers which control the acquisition of image data and the reconstruction of prescribed images. The workstation is programmed in Java™ to produce scan descriptions that are downloaded to the servers prior to run time using a serialization mechanism.

Abstract: The present invention relates to magnetic resonance imaging (MRI) and includes a method and apparatus to rapidly acquire T2 weighted MR images in a repetition time comparable to times usually associated with T1 weighted imaging. The invention also includes a pulse sequence for use with MR image acquisition to accomplish the foregoing. Two embodiments are disclosed, both of which have in common the use of a pulse sequence that has a first and second RF pulse, each RF pulse separated by an interval &tgr; and wherein the phase of the second and subsequent RF pulses is incremented linearly so as to spoil undesirable RF signal coherences so that the system can operate in steady state and acquire pure T2 weighted image in a time (TR) usually associated with T1 date acquisition.

Abstract: A method is provided for determining errors in MR imaging which result from translational motion of an object. In accordance with the method, an MR point source is rigidly joined to the object in selected spatial relationship, and for movement in unison therewith. An MR system is operated to acquire an overall k-space signal which represents an image of the object and of the point source collectively, the overall k-space signal being contaminated by phase errors which result from the motion. A k-space data set which represents an image of the point source alone, and which remains contaminated by the phase errors, is filtered or separated out from the overall k-space signal. The MR system is operated in selected association with the point source to acquire a reference k-space data set, which represents an image of the point source alone but which is unaffected by the phase errors resulting from the motion.

Abstract: In an MRI system a diffusion weighted fast spin echo (FSE) pulse sequence is employed to acquire data for producing an image. Each FSE pulse sequence is prefaced by a diffusion weighting pulse sequence, and components of the diffusion weighted spin magnetization that produce image artifacts are suppressed by a combination of gradient pulses and an RF pulse applied before the FSE pulse sequence is performed.

Abstract: A method is provided for correcting for effects of translational motion or movement of an object in MR imaging. In accordance with the method, an MR point source is joined to the object for translational movement in unison therewith, the point source being maintained in selectively spaced-apart relationship with the object. The method further comprises acquiring a set of k-space data representing images of the object and point source collectively, and deriving a function representing the square of the magnitude of the k-space data set. An inverse Fourier transform operation is applied to the derived function to generate a correlation function with a number of correlation components, a specified one of the correlation components comprising the cross-correlation of the object and the point source.

Abstract: An MRI system performs a scan to acquire NMR signals from which an image can be reconstructed. The NMR signals are compressed prior to digitization by a nonlinear preamplifier, and after digitization, the signal is restored to the correct amplitude by a decompression process. The SNR of the reconstructed image is improved without increasing the size of the analog to digital converter.

Abstract: An MRI system includes a gradient compensation system which appends magnetization reset gradient waveforms to imaging gradient waveforms produced during a scan. The magnetization compensation gradients maintain the residual magnetization in the MRI system at a constant level which reduces image artifacts.

Abstract: An MRI system produces magnetic field gradients along physical axes during a patient scan. The gradients are specified as logical gradient waveforms in a pulse sequence and these are stored in a logical vector table. A physical vector table is produced by rotating amplitude values in the logical vector table, and the resulting rotated amplitude values are used to calculate the heating in each gradient axis of the MRI system.

Abstract: A medical appliance for use in magnetic resonance imaging procedures. A guidewire for vascular procedures is formed by a coaxial cable acting as antenna in a magnetic resonance imaging system.

Abstract: In localized carbon MR spectroscopy, three slice selective pulses which influence the nuclear magnetization in only one slice are generated before a subsequence which is suitable for polarization transfer.

Abstract: In the presence of a stationary homogeneous magnetic field a number of generated pulse sequences act on an object examination region, of which sequence each sequence comprises three 180.degree. high-frequency pulses following one another at the same temporal interval, which are preceded by at least one high-frequency pulse which produces a transverse magnetization. An apparatus for carrying out the method includes providing an echo time independent of the J-coupling of the object. The first and third of the three 180.degree. high-frequency pulses and the preceding high-frequency pulse are generated as slice-selective pulses, which excite three slices, the second 180.degree. high-frequency pulse is a frequency-selective pulse which is so shaped that it excites only one of two mutually coupled components of the object, and the nuclear resonance signal produced from the sectional area of the three slices is then processed in order to determine its spectrum.

Abstract: MR spectroscopy method and apparatus in which an examination zone is exposed, preferably repeatedly, to a sequence which comprises a first binomial 90.degree. RF pulse, a 180.degree. RF pulse and a second binomial 90.degree. RF pulse which sequence enables separate demonstration of the presence of either lactic acid or lipids in the presence of water. The periods in time between the two binomial RF pulses and the 180.degree. RF pulse are equal and are approximately at least to the reciprocal value of four times the scalar coupling constant of lactic acid.

Abstract: The invention relates to a volume selective magnetic resonance spectroscopy method. Volume selection is performed after excitation by means of three layer-selective 180.degree. rf pulses which excite the nuclear magnetization in three mutually perpendicular layers. The distance between the three selective 180.degree. rf pulses can be chosen to be as small as possible.

Abstract: The invention relates to a method of generating a selective 180.degree. rf pulse is formed by means of two selective 90.degree. rf pulses. Halfway between the two rf pulses there is generated a non-selective 180.degree. rf pulse which ensures that the excited nuclear magnetization is independent of the homogeneity of the steady magnetic field of the magnetic resonance examination apparatus.

Abstract: Apparatus and method of determining the spectral distribution of the nuclear magnetization in a limited volume, in which the nuclear magnetization is excited in three mutually perpendicular layers by means of three successive high-frequency pulses. The stimulated echo signal generated at the area of intersection of the three layers is subjected to a Fourier transformation. The spin resonance signals additionally generated by the three high-frequency pulses are suppressed in that magnetic gradient fields are activated during the three intervals between the high-frequency pulses and between the last high-frequency pulse and the stimulated echo signal.

Abstract: The invention relates to a method of determining the spectral distribution of the nuclear magnetization in a limited volume range. For this purposes, a sequence is used, which comprises a first 90.degree. high-frequency pulse and three succeeding 180.degree. high-frequency pulse, whose relative time spacing is equal and smaller than the time spacing of the first high-frequency pulse from the first of the 180.degree. high-frequency pulses. The spectral distribution then obtained is strongly independent of the influence of eddy currents.