Abstract: In a measuring space of the object (1), an essential measurement region (41, 61, 71, 81, 111, 131) having a center region of the measuring space and a plurality of peripheral measurement regions (42, 62, 63, 72, 82, 112, 132) which do not have any region overlapped with the essential measurement region are set. Then, the essential measurement region is combined with a selected peripheral portion of the plurality of the peripheral measurement regions to measure in a preceding manner a nuclear magnetic resonance signal from the object as data of the measuring space. The essential measurement region is combined with the peripheral measurement region of the plurality of the peripheral measurement regions which has not been selected in the preceding measuring step to measure a nuclear magnetic resonance signal from the object as data of the measuring space.

Abstract: An NMR instrument for determining formation fluid properties includes a housing adapted to move in a wellbore; a magnet disposed in the housing adapted to induce a static magnetic field; an antenna assembly disposed in the housing adapted to resonate at a first frequency and a second frequency, the first frequency corresponding to a resonance frequency of a first nucleus, the second frequency corresponding to a resonance frequency of a second nucleus, wherein the first nucleus is different from the second nucleus; means for inducing an RF magnetic field; and means for detecting NMR signals at the first frequency. A method of NMR measurement includes inducing a static magnetic field having a selected magnetic field strength in an earth formation sample; acquiring NMR measurements having J coupling information; and deriving the J coupling information from the NMR measurements.

Abstract: In a method and processing device for a magnetic resonance tomography apparatus, with which a test bolus measurement is conducted for a subsequent angiography measurement using contrast agent, a test bolus pop-up is displayed in an interactive graphic user interface, and a time curve of at least the arterial contrast agent concentration is automatically determined from the test bolus measurement and presented in the test bolus pop-up, for time planning of the subsequent angiography measurement.

Abstract: A nuclear magnetic resonance (NMR) spectroscopy probe has a sample cell into and out of which a room temperature liquid sample may be directed. The cell is surrounded by a radio frequency coil that is used to perform NMR measurements of the liquid sample, and which is maintained at cryogenic temperatures. The coil is separated from the sample cell by a thermally insulative boundary, such as a vacuum. The sample may enter the cell through an input path, and may exit through an output path. The input path, output path and sample cell may be surrounded by a sheath through which flows room temperature gas. The ends of the sample cell may be tapered to promote thorough flow through the cell, and flow diverters may be included in the sample cell adjacent to the input and output paths to force flow to the outer wall of the sample cell.

Abstract: A 3D projection reconstruction pulse sequence is employed to acquire CEMRA data as the subject is continuously moved through the field of view of the MRI system. The acquired k-space data is phase corrected to offset the table motion and the corrected data is used to reconstruct an image over a field of view that far exceeds the size of the MRI system field of view. In one embodiment the image is formed as a set of anatomic subregion images which are concatenated to form a single image and in another embodiment a series of images of each anatomic subregion are produced to depict the dynamic inflow of contrast agent.

Abstract: A pulsed field gradient NMR (=nuclear magnetic resonance) method using stimulated echoes for determining the translational isotropic or anisotropic diffusion coefficient of a molecule or supra-molecular assembly or the flow rate and direction of fluids containing such molecules is characterized in that the molecule or supra-molecular assembly contains one or several isotopes (X) of non-zero nuclear spin other than protons having longitudinal relaxation times T1(X) that are longer than the longitudinal relaxation times T1(H) of the protons, and that the information about the localization of the molecule or supra-molecular assembly during the diffusion or flow interval is temporarily stored in the form of longitudinal magnetization of said isotope or isotopes. Thus, the determination of translational diffusion coefficients or flow rates of supra-molecular assemblies or molecules with short T1(H) values, in particular of supra-molecular assemblies or molecules with M≧50 kDa is accomplished.

Abstract: A method for magnetic resonance imaging is described.

Abstract: In a method and apparatus for improving the vessel/tissue contrast in time-of-flight angiography with a magnetic resonance tomography measurement, a sequence of radiofrequency excitation pulses is generated that each have a flip angle and a temporal spacing in the sequence defined by a repetition time, gradient pulses are generated with gradient coils such that, using an analog-to-digital converter, the magnetic resonance response signals are sampled in the frequency domain (k-space) in a slice referred to as a k-matrix, the k-matrix is sampled such that the respective distances of the measuring points from the center of the k-matrix are continuously increased (or decreased), and the repetition time is varied during the sampling, and/or the flip angle is varied during the sampling.

Abstract: A method of inducing tag lines in an MRI image is provided which allows adjustment of tag line width and spacing. The method includes determining a desired tag line width and then selecting a parameter of a SINC modulating function, such as main lobe bandwidth, in accordance with the desired tag line width. The method also includes determining a desired tag line separation and selecting a parameter of an RF pulse train based upon the desired tag line separation. A gradient field is applied to the specimen being imaged. The RF pulse train is modulated in accordance with the SINC modulating function and the modulated RF pulse train is applied to the specimen being imaged prior to an image acquisition operation. In one embodiment of the invention, the gradient is activated between pulses of the RF pulse train and is deactivated during the RF pulses.

Abstract: A system and method for optimally imaging the peripheral vasculature is disclosed which includes defining a given number of scan stations along a patient's peripheral vasculature and initially injecting a relatively small amount of contrast agent into the patient to pass a test bolus through the patient's peripheral vasculature, and thereafter tracking the test bolus through the patient and adjusting the patient on a moveable table within the MR imaging device from one scan station to a next station to determine a maximum travel time that the test bolus takes to travel through each of the given number of scan stations. Additional contrast agent is then injected into the patient to pass an exam bolus through the patient's peripheral vasculature, and using the test bolus travel time, MR data can be acquired from each scan station while it is known that the exam bolus is present in that station to optimize image resolution.

Abstract: The present invention provides methods and apparatus for determining flow velocity within a formation utilizing nuclear magnetic resonance (NMR) techniques in which the shape of the resonance region is restricted so that sensitivity to radial flow or vertical flow is obtained (or both when more than one NMR tool is used). Flow velocity using these NMR tools is determined using decay amplitude, frequency displacement or stimulated echoes (where the spins are stored along the magnetic field instead of the transverse plane to exploit echo decays and frequency displacements) based on the application of adiabatic pulses. Based on the described NMR measurement of flow velocity, additional wellbore parameters may be obtained such as a direct measurement of permeability, an assessment of drilling damage to the wellbore, formation pressure, invasion rate of the mud filtrate or the migration of fine mud particles during sampling operations.

Abstract: A device for measuring the rate of flow of fluids in a conduit is positioned within the conduit and includes a tube having two spaced part detectors which are separated by shielding units either side of them which are not in electrical contact with the detector units, when a variable electrical field is applied between the walls of the conduit and the shielding units the detector units detect discontinuities in the fluid, e.g., by detecting changes in the ratio of voltage to current and by correlating the movement of the discontinuities between the detector units, it is possible to measure the rate of flow of the fluid.

Abstract: In one embodiment of the present invention, a method of measuring the molecular displacement of a fluid is disclosed comprising: (a) applying a strong magnetic field gradient to the fluid; (b) applying a sequence of oscillating magnetic field pulses to the fluid wherein the sequence includes a first portion followed by a second portion, wherein the first portion spatially modulates the magnetization state of the fluid and the second portion monitors the evolution of the modulation; (c) detecting magnetic resonance signals from the fluid; and (d) analyzing the detected signals to determine the molecular displacement of the fluid. This method may be used to determine the diffusion of the fluid or the restricted diffusion of the fluid through the porous media if the fluid is within a porous media (such as earth formation, bone, wood or other material). Also disclosed is a logging tool configured to implement this methodology.

Abstract: The present invention relates to a method and system for conducting a magnetic resonance fluid flow study by conducting a labeling procedure and a control procedure and combining datasets from those procedures to create a dataset for the fluid flow study. An amplitude modulated magnetic field gradient and amplitude modulated RF irradiation may be applied during a labeling procedure. Likewise, amplitude modulated RF irradiation may be applied during a control procedure. An amplitude modulated magnetic field gradient may also be applied during the control procedure.

Abstract: A method and apparatus is disclosed for MR perfusion acquisition using a notched RF saturation pulse. In acquiring such MR data, a volume of slice locations is selected in which MR data is to be acquired. Each given slice is prepared with a notched RF saturation pulse which has a stop-band between a pair of pass-bands. The stop-band is designed to not affect the spins in the next slice in which MR data is to be acquired thereby effectively increasing the TI and increasing SNR and contrast simultaneously. Since the notched saturation pulse saturates all the spins outside of the notched stop-band, the blood in the ventricular chamber is effectively saturated so that the resulting perfusion images have blood pool suppression. Additionally, the use of a 90° presaturation RF pulse provides a high level of immunity to the effects of arrhythmias or other variations in the patient's heart rate.

Abstract: For the purpose of reducing degradation of image quality due to attenuation of signal intensity, or satisfactorily rendering blood flow even when fast blood flow and slow blood flow are simultaneously present in an imaged region, an imaged region A is divided into a plurality of adjacent slabs S1-S6; RF pulses are transmitted with a flip angle profile whose flip angle &agr; varies with respect to the thickness direction in each of the slabs S1-S6 and whose average flip angle differs for each of the slabs S1-S6, to collect NMR signals; and blood flow imaging is conducted based on the NMR signals.

Abstract: For the purpose of acquiring the magnetic resonance signal having a small Maxwell term, a flow encode gradient Gr having the first half and the second half in which the gradient of the respective halves is reversed and having an equal absolute value of the gradient is applied in the readout gradient direction in a time period coincident with the time period when the spin is rephased by means of the slice gradient, and a flow encode gradient having the first half and the second half in which the gradient of the respective halves is reversed and having an equal absolute value of the gradient is applied in the slice gradient direction in a time period coincident with the time period when the spin is dephased by means of the readout gradient.

Abstract: Nuclear magnetic resonance measurement of a medium are made using a tool with a static magnetic field having a gradient. The nuclear spins of the medium are magnetically polarized using the static magnetic field. Data are acquired from at least three sensitive volumes of the medium using an interleaved sequence of pulses at three different non-overlapping frequencies. At each frequency, a number of sub-sequences of a saturation pulse, a recovery pulse and at least one refocusing pulse are used. The saturation times between the saturation pulse and the recovery pulse for the sub-sequences are selected from a distribution of values between a minimum time to a maximum time to enable determination of T1 and T2 spectra over a wide range of values. Repetitions of sub-sequences having the same saturation at one or more frequencies may be carried out with phase alternation of the recovery pulse phases.

Abstract: A magnetic resonance imaging method includes acquiring a baseline magnetic resonance image of a region of interest in the absence of a contrast agent and simulating an increase in image intensity of a subregion of interest within the region of interest which is subject to increased image intensity in the presence of a contrast agent. The magnetic resonance k-space signal intensity is correlated with contrast agent concentration in the subregion and a contrast agent is administered to the subject. As k-space data for the region of interest is acquired, the signal intensity is monitored to derive contrast agent concentration information. When the peak contrast agent concentration is detected from the monitored k-space data signal intensity, the phase encoding is adjusted so that k-space data with zero phase encoding is acquired. In a further aspect, a magnetic resonance imaging apparatus is also provided.

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: An imaging apparatus particularly suitable for nuclear magnetic imaging has a transmitter coil generating a plurality a first rf pulse and a second rf pulse having a repetition time therebetween. A first gradient coil is used to generate a first gradient waveform substantially centered within the repetition time. A second gradient is used to generate a second gradient waveform substantially centered within the repetition time. A receiver coil receives a resonance signal substantially centered within the repetition time. A controller is coupled to the receiver coil and forms an image in response to said resonance signal.

Abstract: A method and apparatus for detecting displacement of an object using navigator echoes is presented. For motion that is linear in 3D, a linear regression on k-space data is performed by fitting a straight line to the motion-induced phase shift using a k-space weighted least squares minimization to find the displacement. For general motion due to rotation, dilation, and displacement, a rotation angle and dilation scaling factors are determined from the magnitude k-space data by a weighted least squares minimization. A displacement vector is then obtained from the phase data in k-space using a weighted least squares minimization. The weighting factor takes into account that the noise in k-space is inversely proportional to the signal to noise ration. For motion of coronary arteries, the k-space data is acquired in one embodiment using selective volumetric excitation and sampling the resulting excited signal with a trajectory sensitized to the motion of interest.

Abstract: A scan using an NMR imaging system is carried out while applying an oscillating voltage to the subject being imaged. The applied voltage may produce an electric field which moves charged particles in the subject, or it may produce a current that moves ions in the subject. An alternating magnetic field gradient synchronized with the applied voltage is employed in the NMR imaging pulse sequence to detect and measure synchronous spin motion throughout the field of view. The direction of the alternating gradient and/or the applied voltage may be changed to measure and image the properties of the subject.

Abstract: In magnetic resonance imaging, a pulse sequence is used to obtain both water-only and fat-only signals within a single acquisition time. Pulses and readout gradients are applied to take a proton-density-weighted image of the water, a proton-density-weighted image of the fat, and a T2-weighted image of the water. Between the first water readout gradient and the fat readout gradient, a spoiling gradient is applied to spoil the first water echo. Between the fat readout gradient and the second water readout gradient, a refocusing gradient is applied to refocus the second water echo. The proton-density-weighted images of water and fat are combined to form water-plus-fat images free of in-plane and through-plane chemical-shift artifacts.

Abstract: NMR methods for extracting information about a fluid in rock and logging apparatuses for implementing such methods in a borehole environment are provided. The methods involve generating at least two different magnetic field pulse sequences. The magnetic field pulse sequences include a first portion and a second portion. A magnetic field pulse sequence is generated, and magnetic resonance signals are detected using the second portion of the sequence. The first portion of the sequence is modified, and again the sequence generated and magnetic resonance signals detected using the second portion. The magnetic resonance signals are analyzed, and information about, for example, diffusion coefficient, viscosity, composition, saturation in a rock, pore size, pore geometry and the like, extracted from the analyzed signals.

Abstract: The present invention is a technique of, and system for, imaging vascular anatomy over distance considerably greater than the maximum practical field of view of a magnetic resonance imaging system while using substantially one contrast agent injection. The technique and system of the present invention acquires image data of a plurality of image volumes which are representative of different portions of the patient's body. The image data of each image volume includes image data which is representative of the center of k-space. The acquisition of image data which is representative of the center of k-space is correlated with a concentration of contrast agent in the artery(ies) residing in the image volume being substantially greater than the concentration of contrast agent in veins and background tissue adjacent to the artery(ies).

Abstract: A magnetic resonance apparatus has a controllable device with which at least a part of the magnetic resonance apparatus can be fixed in a first control statue and with which the part can be held isolated with respect to mechanical oscillations in a second control statue.

Abstract: Calibration data is acquired during a prescan in an MRI system from each local coil in a coil array. The calibration data is used to calculate a sensitivity matrix S which is employed in a SENSE technique to reconstruct an MR image acquired with the same local coils.

Abstract: An apparatus and method for making NMR measurements uses an electromagnet for producing the static magnetic field. When used in well logging applications, the absence of a strong permanent magnet eliminates almost completely the amount of ferromagnetic debris picked up on the logging tool when passed through casing. The absence of debris results in the static magnetic field being substantially in conformance with design. The electromagnet is designed to give a static field of 0.6-6 mT (10-100 times the earth's magnetic field). Free induction decay or spin echo measurements may be made to give low resolution measurements of bulk properties of earth formations. The same coil configuration may be used to estimate body fat measurements of a human body. An alternate embodiment of the invention uses a capacitive discharge through an electromagnet with a time varying magnetic field with the receiver operating at a different frequency from the transmitter.

Abstract: Magnetic resonance temperature change monitoring of a heated portion of a tissue mass undergoing thermal treatment is more accurately accomplished by compensating for false temperature change measurements caused by movement of the mass and/or temporal changes of the magnetic field during the thermal MR Imaging, wherein the compensation is based on subtracting out “apparent temperature change” measurements of one or more unheated portions of the tissue mass located in a neighborhood of the heated portion, which form a temperature bias map of the tissue mass region.

Abstract: A magnetic resonance angiogram (MRA) is acquired using a contrast enhancement method in which a series of low resolution NMR images are rapidly acquired during a time resolved phase of the examination in which the contrast bolus makes a first pass through the arteries and veins. Additional, high spatial resolution NMR image data is acquired in a subsequent steady-state phase of the examination. The low resolution NMR image is segmented and masked to depict only arteries, and the central k-space region of this data is combined with the peripheral k-space data portion of the high resolution NMR data to produce one or more images.

Abstract: A method of oscillating dual-equilibrium steady-state angiography (ODESSA), utilizes a modified steady state free precession (SSFP) pulse sequence. The SSFP sequence is modified such that flowing material reaches a steady state which oscillates between two equilibrium values, while stationary material attains a standard, non-oscillatory steady state. When alternating sequences are employed, subtraction of adjacent echoes results in large, uniform signal from all flowing spins and zero signal from stationary spins. Venous signal can be suppressed based on its reduced T2. ODESSA arterial signal is more than three times as large as that of traditional phase-contrast angiography (PCA) in the same scan time, and also compares favorably with other techniques of MR angiography. Pulse sequences are implemented in 2D, 3D, and volumetric projection modes. Angiograms of the lower leg, generated in as few as 5 s, show high arterial SNR and full suppression of other tissues.

Abstract: A nuclear magnetic resonance imaging technique is applied to objects undergoing translational motion for analysis of objects on a conveyor passing through an imaging unit. The objects are passed through the imaging module at a predetermined velocity (v), in which there is provided: a spatially uniform, constant magnetic field (B0) substantially parallel to the direction of the velocity (v); a linear magnetic field gradient (Gz) substantially parallel to the direction of the velocity (v); and a radiofrequency field (Bz) pulse transverse to field B0. Selected nuclear magnetic resonance parameters from said objects are then detected for subsequent imaging and analysis.

Abstract: A method of oscillating dual-equilibrium steady-state angiography (ODESSA), utilizes a modified steady state free precession (SSFP) pulse sequence. The SSFP sequence is modified such that flowing material reaches a steady state which oscillates between two equilibrium values, while stationary material attains a standard, non-oscillatory steady state. When alternating sequences are employed, subtraction of adjacent echoes results in large, uniform signal from all flowing spins and zero signal from stationary spins. Venous signal can be suppressed based on its reduced T2. ODESSA arterial signal is more than three times as large as that of traditional phase-contrast angiography (PCA) in the same scan time, and also compares favorably with other techniques of MR angiography. Pulse sequences are implemented in 2D, 3D, and volumetric projection modes. Angiograms of the lower leg, generated in as few as 5 s, show high arterial SNR and full suppression of other tissues.

Abstract: The present invention provides methods and apparatus for determining flow velocity within a formation utilizing nuclear magnetic resonance (NMR) techniques in which the shape of the resonance region is restricted so that sensitivity to radial flow or vertical flow is obtained (or both when more than one NMR tool is used). Flow velocity using these NMR tools is determined using decay amplitude, frequency displacement or stimulated echoes (where the spins are stored along the magnetic field instead of the transverse plane to exploit echo decays and frequency displacements) based on the application of adiabatic pulses. Based on the described NMR measurement of flow velocity, additional wellbore parameters may be obtained such as a direct measurement of permeability, an assessment of drilling damage to the wellbore, formation pressure, invasion rate of the mud filtrate or the migration of fine mud particles during sampling operations.

Abstract: The present invention provides methods and apparatus for determining flow velocity within a formation utilizing nuclear magnetic resonance (NMR) techniques in which the shape of the resonance region is restricted so that sensitivity to radial flow or vertical flow is obtained (or both when more than one NMR tool is used). Flow velocity using these NMR tools is determined using decay amplitude, frequency displacement or stimulated echoes (where the spins are stored along the magnetic field instead of the transverse plane to exploit echo decays and frequency displacements) based on the application of adiabatic pulses. Based on the described NMR measurement of flow velocity, additional wellbore parameters may be obtained such as a direct measurement of permeability, an assessment of drilling damage to the wellbore, formation pressure, invasion rate of the mud filtrate or the migration of fine mud particles during sampling operations.

Abstract: The present invention provides methods and apparatus for determining flow velocity within a formation utilizing nuclear magnetic resonance (NMR) techniques in which the shape of the resonance region is restricted so that sensitivity to radial flow or vertical flow is obtained (or both when more than one NMR tool is used). Flow velocity using these NMR tools is determined using decay amplitude, frequency displacement or stimulated echoes (where the spins are stored along the magnetic field instead of the transverse plane to exploit echo decays and frequency displacements) based on the application of adiabatic pulses. Based on the described NMR measurement of flow velocity, additional wellbore parameters may be obtained such as a direct measurement of permeability, an assessment of drilling damage to the wellbore, formation pressure, invasion rate of the mud filtrate or the migration of fine mud particles during sampling operations.

Abstract: The present invention provides methods and apparatus for determining flow velocity within a formation utilizing nuclear magnetic resonance (NMR) techniques in which the shape of the resonance region is restricted so that sensitivity to radial flow or vertical flow is obtained (or both when more than one NMR tool is used). Flow velocity using these NMR tools is determined using decay amplitude, frequency displacement or stimulated echoes (where the spins are stored along the magnetic field instead of the transverse plane to exploit echo decays and frequency displacements) based on the application of adiabatic pulses. Based on the described NMR measurement of flow velocity, additional wellbore parameters may be obtained such as a direct measurement of permeability, an assessment of drilling damage to the wellbore, formation pressure, invasion rate of the mud filtrate or the migration of fine mud particles during sampling operations.

Abstract: The present invention provides methods and apparatus for determining flow velocity within a formation utilizing nuclear magnetic resonance (NMR) techniques in which the shape of the resonance region is restricted so that sensitivity to radial flow or vertical flow is obtained (or both when more than one NMR tool is used). Flow velocity using these NMR tools is determined using decay amplitude, frequency displacement or stimulated echoes (where the spins are stored along the magnetic field instead of the transverse plane to exploit echo decays and frequency displacements) based on the application of adiabatic pulses. Based on the described NMR measurement of flow velocity, additional wellbore parameters may be obtained such as a direct measurement of permeability, an assessment of drilling damage to the wellbore, formation pressure, invasion rate of the mud filtrate or the migration of fine mud particles during sampling operations.

Abstract: A detecting method and detector expands the capabilities of Nuclear Magnetic Resonance (NMR) analysis. A Rotational Exchange Gradient Imager (REGI) allows for real-time, in situ investigation of materials subjected to the effects of centrifugal force by NMR analysis. The REGI comprises a cylindrical stator formed of an electrically conductive, non-magnetic material, a rotor contained in the cylindrical stator formed of an electrically non-conductive, non-magnetic material, and a conductor located along a central axis of the cylindrical stator. A sample is contained within the rotor. The stator and central conductor serve to generate the RF magnetic field for NMR analysis. The rotor containing the sample is rotated within a stable air bearing formed between the cylindrical stator and rotor.

Abstract: The present invention provides methods and apparatus for determining flow velocity within a formation utilizing nuclear magnetic resonance (NMR) techniques in which the shape of the resonance region is restricted so that sensitivity to radial flow or vertical flow is obtained (or both when more than one NMR tool is used). Flow velocity using these NMR tools is determined using decay amplitude, frequency displacement or stimulated echoes (where the spins are stored along the magnetic field instead of the transverse plane to exploit echo decays and frequency displacements) based on the application of adiabatic pulses. Based on the described NMR measurement of flow velocity, additional wellbore parameters may be obtained such as a direct measurement of permeability, an assessment of drilling damage to the wellbore, formation pressure, invasion rate of the mud filtrate or the migration of fine mud particles during sampling operations.

Abstract: The present invention provides met hods and apparatus for determining flow velocity within a formation utilizing nuclear magnetic resonance (NMR) techniques in which the shape of the resonance region is restricted so that sensitivity to radial flow or vertical flow is obtained (or both when more than one NMR tool is used). Flow velocity using these NMR tools is determined using decay amplitude, frequency displacement or stimulated echoes (where the spins are stored along the magnetic field instead of the transverse plane to exploit echo decays and frequency displacements) based on the application of adiabatic pulses. Based on the described NMR measurement of flow velocity, additional wellbore parameters may be obtained such as a direct measurement of permeability, an assessment of drilling damage to the wellbore, formation pressure, invasion rate of the mud filtrate or the migration of fine mud particles during sampling operations.

Abstract: A technique is described for correcting phase errors in a bipolar readout gradient MRI imaging sequence, such as an EPI examination. The technique employs alternating sets of oscillating readout gradient pulses. Each readout pulse train has a polarity which is inverted with respect to an immediately preceding and an immediately succeeding readout sequence. The collected data then incorporates both image data and data which is used to correct for phase errors. Following data acquisition, correction factors may be determined from the k-space frames for correction of successive k-space data. K-space frames may be reformatted to inherently correct for phase errors, followed by combination of hybrid k-space data frames to obtain a corrected image.

Abstract: A magnetic resonance imaging system includes a gradient hardware subsystem (36), a radio frequency transmission hardware subsystem (30), and a data sampling and digitization hardware subsystem (40) A sequence control processor (20) applies control signals or pulses to the hardware subsystems to cause the implementation of a selected EPI imaging sequence. Due to inductive loads, analog filters, and other circuit constructions within the hardware subsystems, each of the hardware subsystems has a different inherent delay between receipt of a control signal and actually achieving the controlled function such as applying a gradient or RF pulse or sampling data. Due to these different inherent delays, the imaging sequence occurs with timing variations from the intended sequence. Echo planar imaging sequences are very sensitive to phase errors caused by these relative delays, which phase errors manifest themselves in the form of Nyquist ghosts.

Abstract: An imaging apparatus particularly suitable for nuclear magnetic imaging has a transmitter coil generating a plurality a first rf pulse and a second rf pulse having a repetition time therebetween. A first gradient coil is used to generate a first gradient waveform substantially centered within the repetition time. A second gradient is used to generate a second gradient waveform substantially centered within the repetition time. A receiver coil receives a resonance signal substantially centered within the repetition time. A controller is coupled to the receiver coil and forms an image in response to said resonance signal.

Abstract: The present invention provides methods and apparatus for determining flow velocity within a formation utilizing nuclear magnetic resonance (NMR) techniques in which the shape of the resonance region is restricted so that sensitivity to radial flow or vertical flow is obtained (or both when more than one NMR tool is used). Flow velocity using these NMR tools is determined using decay amplitude, frequency displacement or stimulated echoes (where the spins are stored along the magnetic field instead of the transverse plane to exploit echo decays and frequency displacements) based on the application of adiabatic pulses. Based on the described NMR measurement of flow velocity, additional wellbore parameters may be obtained such as a direct measurement of permeability, an assessment of drilling damage to the wellbore, formation pressure, invasion rate of the mud filtrate or the migration of fine mud particles during sampling operations.

Abstract: In order to provide a magnetic resonance signal collection method and apparatus that suppress false images caused by motion of an imaged object, the order of selecting trajectories a-p is randomized. Alternatively, the angular difference is set at 90° between first and next trajectories, and then new trajectories are defined so that the angular difference between adjacent trajectories is a repeatedly bisected angle in sequence.

Abstract: The echo time in an MR pulse sequence is optimized in accordance with the application desired. Advantageously, the echo time is selected to cause a partial volume signal cancellation from veins as compared with background tissue, and the MR pulse sequence is of a velocity-compensated type. MR data are acquired from gradient echoes. Multiple echoes may be used to extract information (such as volume content and susceptibility) about the material under investigation.

Abstract: The invention includes a technique for efficient multi-slice fast spin echo image acquisition with black blood contrast in cardiac imaging. The technique includes applying a non-selective inversion pulse, followed by a re-inversion pulse that is slice-selective over a region encompassing a plurality of slice selections. Execution of a series of RF excitation pulses with fast spin echo readout is timed such that signal from blood is near a null point before acquiring data for each spatial slice. For greater contrast consistency, the flip angles for the excitation pulses occurring before the null point can be reduced, and those occurring after the null point can be increased.

Abstract: A method of MRI includes supporting a subject in an examination region of an MRI scanner, and setting up a spin system with a net magnetization. An inversion pulse is applied which inverts the magnetization of the spin system in a selected volume of the subject. As the magnetization re-grows, a first set of raw data is generated by acquiring MR signals from a series of regions within the selected volume. For the first set of raw data, the series of regions are acquired in a first temporal order with respect to the inversion pulse. The inversion pulse is re-applied, and as the magnetization re-grows, a second set of raw data is generated in similar fashion to the first. However, for the second set of raw data, the series of regions are acquired in a second temporal order with respect to the inversion pulse. The second temporal order is different from the first temporal order. From the first and second sets of raw data, respectively, first and second sets of complex image data are generated.