Abstract: A nuclear magnetic resonance spectroscopic technique is applied to objects undergoing translational motion for chemical analysis of objects on a conveyor passing through a detector module. The objects are passed through the detector 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 and a radio frequency field B1 pulse transverse to the field B0. Selected nuclear magnetic resonance parameters from the objects passing through the detector module are then used to determine chemical composition or changes therein.

Abstract: An NMR system comprises an NMR probe comprising multiple NMR detection sites. Each of the multiple NMR detection sites comprises a sample holding void and an associated NMR microcoil. The NMR system further comprises a controllable fluid router operative to direct fluid sample to the multiple NMR detection sites.

Abstract: The invention relates to an MR method in which the nuclear magnetization is enhanced under the influence of a first steady magnetic field and a second steady magnetic field acts on the nuclei previously influenced by the first magnetic field. According to the invention, the two magnetic fields overlap in time and enclose an angle other than 0° relative to one another, the angle preferably amounting to 90°. The enhanced nuclear magnetization is then sustained after the activation of the first steady magnetic field while the direction of the nuclear magnetization is determined by the second steady magnetic field. The use of two mutually perpendicular magnetic fields is advantageous notably for Overhauser imaging methods, because it enables the use of mutually perpendicular RF fields for the ESR saturation and the MR excitation, thus uncoupling the coils generating such RF fields from one another.

Abstract: An image acquisition using a spoiled, gradient-recalled echo imaging pulse sequence is preceded by a magnetization preparation sequence which rapidly drives longitudinal magnetization to the steady-state equilibrium level established by the imaging pulse sequence. The preparation sequence includes an RF saturation pulse followed by a recovery period (Trec) whose length is determined by the scan parameters of the imaging pulse sequence.

Abstract: Apparatus and method for providing in-situ data of formation fluids at true reservoir conditions. The apparatus has NMR chamber of the flow-through type, so it is no longer necessary to divert a sample for the basic NMR analysis or transfer it uphole for laboratory analysis. The apparatus is preferably modular and is compatible with wireline tools configurable for a variety of sampling, testing and monitoring purposes. Fluid properties such as viscosity can be derived from diffusivities and relaxation times, as measured by NMR. Additional accuracy is provided in the downhole sampling process, and in the interpretation of NMR logs in real time at true reservoir conditions.

Abstract: An air feed device comprises a fluid motor to drive rotating vanes and blow air with high efficiency into a space accommodating a sub

Abstract: A simplified magnetic resonance flowmeter and flow measuring method, based on the dwell time of spins in the H1 Larmor radio frequency nutation field, which employs periodic H0 field gradients to phase modulate the spins so as to measure mean velocity of flow in near uniform velocity profiles or to map velocity of flow in non-uniform velocity profiles, which does not require pulse techniques and is relatively independent of relaxation and diffusion parameters consisting of a magnetizing section of pipe with a strong H0 magnetic field with a receiving section with orthogonal periodic phase modulating gradient coils, H1 Larmor radio frequency excitation (nutation) coils, and sideband receiver coils; utilizing a demodulating and cross-correlating receiver and a control system that permits concordant analysis of composition.

Abstract: In a magnetic resonance imaging system, an extended field of view through an object is realized with a magnet having a smaller homogeneous field of view by translating the object through the homogeneous field while exciting nuclear spins within the object and detecting MRI signals with a plurality of coils which translate through the homogeneous field with the object. In a preferred embodiment, the plurality of receiver coils overlap. The table and object can continuously move through the homogeneous volume during nuclear excitation and MRI signal detection. A computer adjusts the MRI signals for the effect of changes in table position between signal acquisitions and compensate for phase shift in received signals.

Abstract: An MRI apparatus having an ability of displaying images of flow in different directions in distinguishable manner. When this MRI apparatus performs multi-slice acquisition with a predetermined repetition time TR by selecting a plurality of slices approximately perpendicular to the flow direction of an object to be examined, it performs a first measurement of exciting the plurality of slices in a first order and a second measurement of exciting the same slices in the opposite order to obtain two kinds of data whose signal intensity differs depending on the flow direction. The two kinds of data obtained by two measurements are subjected to subtraction operation to obtain data with different signs depending on the flow direction. These signs combined with the signal intensity are made into images where flow in opposite directions are distinctively depicted. In the multi-slice acquisition, slices are selected so that adjacent slices partially overlap in the direction of the thickness of the slice.

Abstract: 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.

Abstract: Nuclear magnetic resonance methods for extracting information about a fluid in a rock are described. A system of nuclear spins in the fluid are prepared in a driven equilibrium, and a series of magnetic resonance signals generated from the fluid. The series of magnetic resonance signals is detected and analyzed to extract information about the fluid in the rock.

Abstract: An NMR method of analyzing an analyte comprises feeding an analyte sample fluid to an NMR flow cell. The NMR flow cell comprises an RF microcoil operably associated with an enlarged containment region. The mobile phase of the analyte sample flowing through the NMR flow cell has a solvent gradient greater than 10% per minute. The analyte sample fluid can be fed to the NMR flow cell from an analyte extraction chamber, e.g., operative to perform liquid chromatography, capillary electrophoresis, or the like, especially a capillary-based analyte extraction chamber integrated in an NMR probe with the NMR flow cell. A sample volume is held in the NMR flow cell for equilibration less than 1 hour, preferably less than 30 minutes prior to actuating NMR analysis of the observe volume in the microcoil.

Abstract: The present invention is a polarizing process involving a number of steps. The first step requires moving a flowing mixture of gas, the gas at least containing a polarizable nuclear species and vapor of at least one alkali metal, with a transport velocity that is not negligible when compared with the natural velocity of diffusive transport. The second step is propagating laser light in a direction, preferably at least partially through a polarizing cell. The next step is directing the flowing gas along a direction generally opposite to the direction of laser light propagation. The next step is containing the flowing gas mixture in the polarizing cell. The final step is immersing the polarizing cell in a magnetic field. These steps can be initiated in any order, although the flowing gas, the propagating laser and the magnetic field immersion must be concurrently active for polarization to occur.

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: In a magnetic resonance imaging method flow quantities and diffusion quantities are measured in the presence of temporary magnetic gradient fields (gradient pulses). Signal amplitudes of the magnetic resonance signals and/or flow and diffusion quantities calculated from the magnetic resonance signals are corrected for non-linearities in the magnetic gradient fields.

Abstract: A method and apparatus in which the limitation upon analysis caused by variation of the magnetic susceptibility of the solvent conveying a sample to an NMR spectrometer can be addressed. The solvent composition which is used to bring about elution of analyte from devices such as chromatography columns can be varied without causing a corresponding variation of the solvent composition used to transport the analyte to the NMR spectrometer. The decoupling is achieved by the summing into the chromatographic stream, post column, a solvent composition which is complementary to the instantaneous composition emerging from the column, such that the magnetic susceptibility of the summed streams remains constant.

Abstract: A method of measuring a strength of a capillary-porous chemically active material while hardening, the capillary-porous chemically active material including therein a liquid which undergoes metamorphosis and which is present in the capillary-porous chemically active material in different stages during curing, the method is effected by performing a high frequency, spin-echo nuclear magnetic resonance measurement of each stage of the liquid; and correlating the high frequency, spin-echo nuclear magnetic resonance measurement with a predetermined relationship between the strength and the high frequency, spin-echo nuclear magnetic resonance measurement.

Abstract: The invention relates to a method of imaging perfusion parameters of, for example blood in a volume of the brain in the head of a body by means of magnetic resonance, in which a contrast medium is introduced into a blood flow within the body, said contrast medium flowing, via the carotid arteries, to the volume in the head to be imaged by means of magnetic resonance. The images of the volume which are reconstructed from the magnetic resonance signals received are subsequently deconvoluted with an arterial input function of the contrast medium in a supply to the volume imaged. This arterial input function is determined according to the invention by excitation of spins and measurement of a magnetic resonance signal in an elongate part of the body which contains the carotid arteries and has a cross-section which is at least equal to a diameter of a carotid artery.

Abstract: Circuitry and methods are provided for reducing rise time associated with signals on an open-drain or open-collector signal line. Signal line voltage is monitored to determine if the signal line is being pulled LOW. If the signal line is not being pulled LOW, as indicated by signal line voltage exceeding a threshold level, additional pullup current is provided. The additional current may be provided gradually in relation to the signal line voltage, or may be provided in full whenever voltage exceeds the threshold. Circuitry may also be provided to monitor voltage slew rate on the signal line, and to enable the additional pullup current only when the slew rate exceeds a positive threshold level.

Abstract: An NMR device includes an NMR coil, and a sample flow path connected to a sample supply source and passing through the NMR coil. The NMR device can carry out an on-line measurement so that a portion passing through the NMR coil of the sample flow path functions as an NMR probe for measurement. A filler for absorbing a sample is provided at a position of the NMR probe in the sample flow path, and the NMR measurement is carried out in a state where the sample is absorbed by the filler. Thus, when the measurement is carried out, the sample is retained accurately at the NMR coil position while a very small quantity of sample is being concentrated.

Abstract: A bypass valve allows fast and reliable sequential transfer of samples from a 96-well plate to a flow-through nuclear magnetic resonance (NMR) probe of an NMR spectrometer. The bypass valve has three ports: an inject port connected to a first input of the flow-through probe; a load port connected to a needle capable of drawing the samples from the 96-well plate; and a hold port connected to a holding loop. The syringe pump draws a sample from the 96-well plate through the needle and the bypass valve into the holding loop. The position of the bypass valve is switched, and the sample and a dose of push solvent are pushed into the flow-through probe through the bypass valve. After NMR measurements are performed on the sample, the sample is drawn into the holding loop through the bypass valve, at the same time as air is flushed through the probe. The position of the bypass valve is again switched, and the sample is pushed out through the needle.

Abstract: A non-selective inversion pulse is applied to a plurality of slices, r.f. resonance in MR active nuclei is excited in each of those slices individually, and the slice excitation order is cycled so that the time for the non-selective inversion pulse to any particular phase-encode gradient of all the slices is the same, the time of the zero phase-encode gradient corresponding to that for zero signal from cerebro spinal or other moving fluids.

Abstract: A magnetic resonance (MR) imaging system including a method and apparatus for reducing image artifacts caused by magnet vibration is disclosed herein. The system includes a magnetic field vibration quantification and compensation scheme including quantifying a vibration error component included in the magnetic field configured to acquire k-space data corresponding to an MR image, and correcting the k-space data using the vibration error component. The vibration-induced magnetic field perturbation includes a spatially invariant magnetic field, a spatially linear readout magnetic field gradient, a spatially linear phase-encoding magnetic field gradient, and a spatially linear slice-selection magnetic field gradient.

Abstract: In a 3D magnetic resonance angiography (MRA) method, a region of interest, containing a major pulmonary vessel, is defined in an examination subject, and the subject is injected with a contrast agent bolus and a number of 3D magnetic resonance angiography data sets are obtained from the examination subject before, during and after arrival of the bolus in the region of interest. A slice from each of the data sets is selected which contains the region of interest, and an average region of interest signal as a function of time is determined and stored as a reference time curve. In the respective selected slices, a signal-time curve is identified and each signal-time curve is cross-correlated with the reference time curve. The cross-correlation results are used to form a new three-dimensional data set containing arterial and venous correlation maps.

Abstract: A magnetic imaging device, such as an MR scanner, is used to provide a modified three-dimensional gradient echo sequence having a spatial-spectral excitation in which phase-encoding lines are interleaved for the excitation of water and of fat. The phase-encoding lines are spaced by an interval equal to half of the repetition time. The resulting data are sorted for the reconstruction of water-only and fat-only images, which are realigned and combined to form water-fat combined images free of chemical shift artifacts.

Abstract: An ECG-prep scan is used to set an optimum time phase in both systole and diastole of the heart. At each of the different time phases, an imaging scan is started to acquire a plurality of sets of echo data. An artery/vein visually separated blood flow image is produced from the echo data. The imaging scan uses a half-Fourier technique, for example. This provides high-quality blood flow images with shorter scan time, without injecting a contrast medium. Additionally, with a readout gradient pulse applied substantially parallel with a direction of slowly flowing blood, a scan is performed in synchronism with an optimally determined cardiac time phase. The readout gradient pulse has a dephasing pulse for enhancing differences in a flow void effect depending on blood flow velocities. This enables slow-speed flows, such as blood flows in the inferior limb, to be depicted without fail.

Abstract: Two sets of time course NMR data are acquired using an EPI pulse sequence in which both gradient recalled echo NMR signals and spin-echo NMR signals are acquired after bolus injection of a contrast agent. The gradient-echo signals and spin-echo NMR signals are employed to calculate rCBV maps which are corrected for contrast leakage and used as a measure of tumor angiogenesis. Both the gradient echo and spin echo signals are employed to calculate a &Dgr;R2 weighting ratio which is also a measure of tumor angiogenesis.

Abstract: A black blood magnetic resonance angiogram is produced by exciting dipoles (52) and repeatedly inverting the resonance (541, 542, . . . ) to produce a series of magnetic resonance echoes (561, 562, . . . ). Early echoes (e.g., (561, . . . , 568)) are more heavily proton density weighted than later echoes (e.g., (569, . . . , 5616)) which are more heavily T2 weighted. The magnetic resonance echoes are received and demodulated (38) into a series of data lines. The data lines are sorted (60) between the more heavily proton density weighted data lines and T2 weighted data lines which are reconstructed into a proton density weighted image representation and a T2 weighted image representation. The proton density weighted and T2 weighted image representations are combined (90) to emphasize the black blood from the T2 weighted images and the static tissue from the proton density weighted image. The combined image is a black blood magnetic resonance angiogram.

Abstract: A magnetic resonance imaging apparatus includes a transmitting coil configured to generate RF pulses to a subject to be examined which is placed in a static field, a gradient coil configured to generate gradient magnetic field pulses to the subject, and a sequencer configured to control the transmitting coil and the gradient coil to continuously generate a plurality of echoes. Echoes are received by independent receiving coils. A computer generates a plurality of odd-numbered-echo-images respectively corresponding to the receiving coils on the basis of odd-numbered-echoes in the echos, generates even-numbered-echo images respectively corresponding to the receiving coils on the basis of even-numbered-echoes in the echos. The computer generates a first image by unfolding the odd-numbered-echo-images on the basis of sensitivity distributions of the receiving coils. The computer generates a second image by unfolding the even-numbered-echo-images on the basis of sensitivity distributions of the receiving coils.

Abstract: Increasing RF transmission power, retuning the RF transmitter and receiver coils, and increasing RF reception gain, enable MR inspection of product in a container that presents a substantial portion of an electrically conductive barrier in transverse orientation to the exciting RF magnetic field.

Abstract: For simultaneously determining the analytical NMR spectra of a number of samples placed suitably arranged in the measuring site of an NMR measuring apparatus, spatially and timely varying magnetic fields are used. The resulting signals are spatially resolved by a suited processing, for example Fourier transform. Surprisingly, from these signals, analytical NMRs of high resolution can be obtained for each sample. The method can be applied to two-dimensional arrangements of samples, for example a bundle of capillaries imitating a conventional NMR sample tube or a well plate, or three-dimensional arrangements, for example stacks of well plates. The method allows the determination of NMR spectra for analysis or for comparison with anterior spectra for long time behavior studies and quality assessment with only a fraction of time needed for measuring the samples individually.

Abstract: An artery vein visually separated MRA image and/or a higher blood/parenchyma contrast MRA image are provided by a magnetic resonance imaging system. The system comprises, in addition to a magnet generating a static magnetic field, a gradient generation unit generating magnetic gradients superimposed on the static magnetic field, a transmission/reception unit transmitting to a subject spin-exciting RF signal and receiving an MR signal emanated from the subject, a reconstruction unit reconstructing the image based on the MR, and a sequencer for performing a scan sequence of pulses through control of the gradient generation unit and the transmission/reception unit.

Abstract: A method and apparatus is disclosed to rapidly assess the severity of a stenosis using MR technology. The invention includes identifying a suspected stenotic vessel and applying a phase contrast pulse sequence to the stenotic vessel in which the MR operator is allowed to control the amplitude and direction of the flow encoding gradient. Peak flow velocity is determined in the suspected stenotic vessel by correlating the flow encoding gradient with the onset of flow velocity aliasing. In a preferred embodiment, the invention utilizes a 2D fast gradient echo pulse sequence having flow sensitizing bipolar gradient waveforms. The resulting flow sensitizing gradients are substantially coincident in time, thereby allowing rotation of the resultant flow sensitizing gradient direction. The amplitude of the flow encoding gradient is increased until the observance of flow related aliasing.

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: An MRI system repeatedly performs a pulse sequence during a time interval &Dgr;T in which a surge of blood flows through a vessel whose compliance is to be measured. Two spaced-apart slices are simultaneously excited by each pulse sequence and the transverse magnetization is flow-encoded before an NMR signal is acquired in the presence of a readout gradient pulse. The change in phase of the NMR signal is used to detect when the wave arrives at each slice location, and from this information blood vessel compliance may be calculated.

Abstract: A technique for MRI or the like employs optimized orthogonal gradients. For a device having a peak physical magnetic field gradient strength G0, the gradients are optimized if, in physical space, one gradient has a value −0.5G0 while the two gradients orthogonal thereto have the value G0. That is equivalent to an optimized orthogonal gradient space in which one gradient has a value 1.5G0 while the two gradients orthogonal thereto have the value zero. The gradients are cycled over a sequence of six gradient pulses to provide enough data to calculate the diffusion tensor.

Abstract: The invention relates to a magnetic resonance method for determining a perfusion image of a portion, which method comprises the following steps: generation of a control pulse sequence in a first portion of the body and measurement of a control data set by generation of an MR-image sequence for imaging of an third portion of the body, generation of a labelling pulse sequence in a second portion of the body wherein a fluid flows towards the third portion, and measurement of the labelled data set by generation of the MR-image sequence for imaging the third portion of the body, and reconstruction of the perfusion image of the fluid in a mass of the third portion of the body from a combination of the control data set and the labelled data set.

Abstract: A technique is described for correction of phase errors in bipolar readout gradient examination sequences, such as EPI pulse sequences. The technique employs short reference pulse sequences associated with each readout pulse train. Reference data is collected for positive and negative lobes of the reference sequence. Each reference sequence is employed to estimate a phase error of an associated readout sequence. Data collected in the readout sequence is then corrected based upon the estimated errors. Phase errors resulting from changes in scan orientation are thereby corrected for each frame of k-space data without significantly increasing the data acquisition time.

Abstract: An MRI system produces a series of real-time images by repeatedly acquiring image data and repeatedly reconstructing images from the acquired image data. The effective latency period between acquisition of the image data and display of the reconstructed images is minimized by acquiring image data in a reverse-centric view order in which low spatial frequencies are acquired last.

Abstract: The invention relates to a method for imaging diffusion parameters of a body by means of magnetic resonance. The method involves an adjustment pulse sequence and an imaging pulse sequence. The adjustment pulse sequence measures preparation MR signals. The imaging pulse sequence measures position-dependent MR signals. The imaging pulse sequence is adjusted on the basis of information from the preparation MR signals measured during the adjustment pulse sequence.

Abstract: Interventional MRI imaging leads to the development of open magnets such as for example C-magnet 1, in which it is correspondingly more difficult to generate a large field in order to obtain a good signal-to-noise ratio. To overcome this, a pre-polarizing unit 7 is provided which utilizes a HTSC magnet, for example of YBCO, which is brought adjacent to the patient to assist in generating the main field, and then rapidly withdrawn to position 8, in order to enable the r.f. signals to be detected in the presence of the field of the C-magnet 1.

Abstract: A magnetic resonance technique to measure perfusion of fluid to tissue by inverting all the spins in fluid water hydrogen nuclei of the subject with a non-spatially-selective radiofrequency (RF) pulse and immediately reinverting the spins in an imaging plane of interest such that the spins in the imaging plane experience minimal perturbation of their magnetization while the spins outside the plane (extraslice) are inverted (tagged). To account for signal loss effects of magnetization transfer (MT), a control image is obtained by applying two non-selective inversion pulses and creating a perfusion-weighted image by subtracting the tagged image from the control image. When this tagged image is subtracted from a “control” image, the resulting intensity arises solely from the tagged spins that have flowed into the imaging plane. This resultant image is referred to as a perfusion weighted image, because its intensity is a function of the rate of perfusion into the imaging plane.

Abstract: Various flowmeters (10, 70, 110, 120) each have an ESR sensor (13, 73, 112, 121) for measuring the crude oil fraction and/or velocity of a fluid containing crude oil. In combination with an NMR sensor or other sensors, a complete set of flow fraction, flow velocity, and flow rate measurements can be obtained for multiphase fluids containing gas, oil, water or any combination thereof.

Abstract: An MRI image is corrected for motion artifacts using an iterative, autocorrection process in which corrections are tried and the quality of the resulting reconstructed image is measured. Different metrics for evaluating image quality are used during the autocorrection process to take advantage of their different attributes.

Abstract: A method and a system for magnetic resonance imaging using echo planar method enable obtaining MRI images reduced in ghost artifacts. The magnetic resonance imaging system realizing the magnetic resonance imaging method includes a gradient coil for fast switching (inverting) a gradient magnetic field in a magnetostatic field applied to an object to be analyzed by a magnetostatic field generator, a receiver for receiving magnetic resonant signals from atomic nuclei of the object to be analyzed as echo signals necessary for filling a k-space, k-space data developer for developing the signals converted into a digital form over the a k-space as echo data, data collector for collecting echo data of the same phase encoding data in two frequency encoding directions for about half the k-space, and imager for making an image by classifying the echo data by frequency encoding direction, performing Fourier transformation separately to obtain images, and adding absolute number processed images to improve S/N.

Abstract: A chemometric method for predicting unknown properties in polymers using an on-line NMR system comprising the steps of producing a predictive data set and using the predictive data set to obtain unknown amounts of properties in a polymer. In a preferred embodiment, the process begins by obtaining free induction decays for samples of polypropylene with measured concentrations of xylene soluble polypropylene from a xylene soluble polypropylene data set to produce a free induction decay data set. The free induction decay data set is analyzed using PCA to produce a principle component data set. The principle component data set, the xylene soluble polypropylene data set, and the free induction decay data set, are analyzed using partial-least squares analysis to produce a training data set and the training data set is subsequently validated to produce a predictive data set.

Abstract: A chemometric technique for predicting styrene content in Butadiene-Styrene resin (K-Resin) using an on-line NMR system comprising the steps of producing a predictive data set and using the predictive data set to obtain unknown concentrations of styrene in samples of K-Resin. The predictive data set is generated by obtaining free induction decays for samples of K-Resin with measured concentrations of styrene to produce a free induction decay data set; analyzing the free induction decay data set using PCA to produce a principle component data set; analyzing the styrene concentrations, the free induction decay data set and the principle component data set using PLS to produce a training data set; and validating the training data set to produce a predictive data set. Using the predictive data set involves the steps of obtaining free induction decays of samples of K-Resin with unknown concentrations of styrene and applying the free induction decays to the predictive data set to predict the unknown concentrations.

Abstract: A dynamic MRA study of a subject is performed using a 3D fast gradient-recalled echo pulse sequence after the subject is injected with a contrast agent. The sampling of k-space is synchronized with the peak of the contrast enhancement profile by sampling in an inward spiral pattern during the rise in enhancement and by sampling in an outward spiral pattern after peak enhancement occurs.

Abstract: A dynamic MRA study of a subject is performed using a 3D fast gradient-recalled echo pulse sequence after the subject is injected with a contrast agent. The flip angle of an rf excitation pulse in the pulse sequence is modulated during the acquisition as a function of contrast agent concentration in the region of interest. In one embodiment the flip angle is updated by interleaving measurement pulse sequences which measure in real-time contrast agent concentration. In another embodiment the contrast concentration profile is determined in advance and a corresponding table of optimal flip angles are calculated and played out during the image acquisition.

Abstract: A dynamic MRA study is performed using a 3D fast gradient recalled echo pulse sequence. A signal strength indicator for each acquired k-space data set is calculated and these indicator values are employed to produce a contrast curve. This contrast curve is used to select data for use in forming a CONTRAST k-space data set and a MASK k-space data set. The MASK is subtracted from the CONTRAST data set and the result is used to reconstruct an image.