Abstract: A method of high-speed magnetic resonance imaging in which the object to be imaged is placed in a high static magnetic field. Nuclear spins are excited in an image area in a selected plane of the object by superimposing a slice-selection gradient along an axis and applying a pulse of radio frequency magnetic field. Following an encoding pulse sequence and rephasing of the nuclear spins by the application of a 180.degree. radio frequency pulse, mutually orthogonal phase-encoding and readout gradients are alternately applied in the image plane to effect a traversal through spatial frequency domain (k-space). In a preferred embodiment of the invention, the readout gradient is applied as a continuous sinusoidal wave, resulting in a slight overlap between the phase-encoding and readout gradients. If phase errors vary slowly in time, only a partial k-space trajectory is required.

Abstract: The invention relates to a nuclear magnetic resonance tomography method, by which in each sequence after a reading stage in which the nuclear magnetic resonance signals produced at the examination area are recorded, the magnetic gradient fields are switched on and off in such a manner that the time integral across all magnetic gradient fields is equal and different from zero for each sequence.

Abstract: The invention relates to a method of mapping the local distribution of B.sub.1 -dispersion of relaxation tim T.sub.1.rho. of the nucleus of a certain element, such as hydrogen or phosphorus of an object, such as e.g. a human body or a part of it, or the trunk of a tree. In the method of this invention, an object area is first subjected to a first excitation pulse, which tilts the magnetization of the nuclei of said object area preferably 90.degree. and thereafter to a locking pulse, whose phase and frequency are selected in a manner that relaxation with respect to the magnetic vector of this locking pulse takes place, followed by performing the required procedures by applying per se known nuclear spin imaging methods, and the above sequence of operations is repeated as many times as desired by changing the amplitude of said locking pulse.

Abstract: First and second MR (magnetic resonance) echo signals are detected from the subject by means of a spin echo method. These MR echo signals have been provided with different phase encoding data by applying the gradient magnetic fields. As a result, first and second MR echo signal data are acquired from a single Fourier plane. These MR echo signal data are amplitude-corrected and phase-corrected. Then, they are subjected to Fourier transform, thereby forming an MR image of the subject within a short time.

Abstract: A method for the determination of the spatial and of the spectral distribution of the nuclear magnetization in a region under investigation. Following a high-frequency excitation pulse, a magnetic gradient field periodically varying its polarity is actuated. The resolution is increased in that, even during the periods of time in which the gradient of this field varies, scanning values are recorded and subjected to a Fourier transformation.

Abstract: A method of finding error distribution in the static magnetic field and distribution of deviations from straight lines in the gradient magnetic fields of an NMR imaging apparatus which employs the applied spin-warp method. A phantom whose shape has been known is measured in the read-out gradient magnetic fields having different polarities to obtain two spin density distribution images. The two images are then compared with the shape of said phantom to measure the distortion distributions of the images. Error in the static magnetic field and deviations of the gradient magnetic fields from the straight lines are analyzed from the distortion distributions. From the thus obtained error distribution, furthermore, distortion induced in imaging the object is estimated, and the distortion contained in the image that is reconstructed from the spin density of the object by the spin-warp method is corrected using the thus estimated value.

Abstract: A magnetic resonance (MR) system and method for determing absolute image intensities (MR numbers) comparable to "CT" numbers by removing the dependence of the intensity measurement on system dependent parameters. The dependence of the intensity measurement on system parameters is removed by determining the absolute gain of the receiver portion of the MR system. The absolute gain is a function of the loaded gain and the unloaded gain of the receiver system, the loaded gain is divided by the unloaded gain to provide a normalization factor which is multiplied by output data to provide the absolute values of intensity of absolute MR numbers.

Abstract: A three-dimensional NMR spectroscopy capable of obtaining a plurality of two-dimensional NMR spectra by a single series of measurements. In this spectroscopy, a pulse sequence consisting of three 90.degree.-pulses and a 180.degree.-pulse is utilized. The three 90.degree.-pulses are produced at intervals. The interval between the second and the third 90.degree.-pulses is set to .tau..sub.m. The 180.degree.-pulse is produced at the middle of the interval .tau..sub.m. In a first embodiment of the invention, the interval t.sub.1 between the first and the second 90.degree.-pulses and the RF phases .phi. of the first and second 90.degree.-pulses and of the 180.degree.-pulse are taken as variables. The free induction decay signals produced after the lapse of a period of t.sub.2 subsequent to the third 90.degree.-pulse are collected to create data S (t.sub.1, t.sub.2, .phi.). In a second embodiment of the invention, the intervals t.sub.1 and .tau..sub.m are taken as variables, .tau..sub.m being rewritten as t.sub.3.

Abstract: An NMR imaging method and apparatus according to the present invention which enables a reduction in the scanning time without lowering the contrast resolving power and the spatial resolving power is arranged such that data which belongs to a relatively low spatial frequency region is collected by an ordinary scanning method, while data which belongs to a relatively high spatial frequency region is collected by a scanning method which enables data to be collected at a relatively high frequency, and reconstruction of an image is effected on the basis of data synthesized from data collected by these two methods.

Abstract: An NMR imaging method and apparatus according to the present invention which enables collection of data to be effected within a minimum scanning time which can be desired for each object of inspection is arranged such that projection data concerning the object is collected from a plurality of directions, a direction in which the number of samples in the warp direction is minimized is obtained on the basis of the collected projection data, and then the scanning coordinate system is rotated in accordance with the obtained direction to collect data on the basis of the Fourier transformation method.

Abstract: An incomplete set of magnetic resonance image data is collected and stored in a view memory (40). The incomplete set of image data includes a central or first set of data values (42, 42') and a side or second set of data values (44, 44'). The central data set is operated on by a roll-off filter (64) and a Fourier transform (66) to create a normalized phase map (72). The first and second data sets are Fourier transformed (82) and phase corrected (86) by being multiplied with a complex conjugate (88) of the corresponding phase map data value. A third data set (46, 46') is generated (90) by determining the complex conjugate of the second or side data set. The third data set is Fourier transformed (94) and multiplied (98) by a corresponding value from the phase map to produce a second phase corrected image representation. The first and second phase corrected image representations are summed (100) and stored in a resultant image memory (102).

Abstract: A nuclear magnetic resonance tomography apparatus generates a tomographic image substantially free from artifacts caused by body movement, such as respiration, during acquisition of the tomography signals. The tomography signals are acquired and stored in the form of Fourier lines in an image matrix. For reducing image artifacts, a control unit is provided for controlling entry of the acquired tomography signals into the matrix in dependence upon a repiratory signal obtained from a sensor. The control unit insets the Fourier lines in the matrix such that Fourier lines occurring when the respiratory signal exceeds a predetermined value are alternately inserted above and below the middle of the matrix proceeding from the matrix middle, and the remaining Fourier lines are inserted into the matrix above and below the matrix middle proceeding from an edge of the matrix.

Abstract: A correction for NMR spin echo spectral data is obtained by adjusting the time origin of an extended density data set and transforming the adjusted origin data set of original density to the frequency domain.

Abstract: A set of n NMR measurements are carried out in an inhomogeneous RF field. The set is parameterized by RF pulse amplitude or duration and for half the measurements the variation of RF pulse/duration is reversed and the RF phase inverted.

Abstract: A magnetic resonance imaging apparatus includes a sequence controller. The sequence controller includes an event memory for storing a plurality of data subsets useful for applying magnetic fields and radio frequency (RF) pulses to a body under medical examination, each of the data subsets containing event data, time data for performing the event data and control data for controlling execution of the event data. It further includes a reference time generator, a comparator for comparing the reference time with the time data sequentially read from the event memory within one reference time period, and a control circuit for sequentially controlling an application of the magnetic fields and RF pulses to the body, and data acquisition based upon the event data and control data whenever the time data is coincident with the reference time data judged by the comparator.

Abstract: A magnetic resonance imaging system visualizes a tomographic image including a portion of interest by two-dimensional Fourier transformation of magnetic resonance data in readout and phase encoding directions. The system has an input section for inputting the central position of the portion of interest, and an image processing section for shifting data obtained by the Fourier transformation, so that the central position of the portion of interest is located at substantially the center of an image area, and transferring data at an end portion which falls outside the image area upon shifting into an opposite image area.

Abstract: A method of high-speed imaging is employed in which less than 100% of the spatial frequency domain (k-space) is sampled. In one embodiment, the trajectory extends over the k-space origin, and the information acquired from the extension is used to compensate for any phase errors. If the same number of points are collected as in a full k-space acquisition, signal bandwidth is maintained, and spatial frequency response is increased. In a second embodiment, two or more partial k-space acquisitions are performed and then pieced together in a "mosaic" prior to Fourier transformation. In a further embodiment, partial k-space acquisitions in the direction of the readout gradient are combined with interleaved acquisitions in the direction of the phase-encoding gradient to avoid discontinuities.

Abstract: A two-dimensional nuclear magnetic resonance spectrometry which comprises the following steps to facilitate phase correction:(a) taking the Fourier transform of the set S(t.sub.1, t.sub.2) of the free induction decay signals with respect to t.sub.2 to generate the transformed data sets of S.sub.c (t.sub.1, F.sub.1) or S.sub.s (t.sub.1, F.sub.2), the signals being stored in the memory corresponding to the values of t.sub.1 ;(b) obtaining data S.sub.c (t.sub.1000, F.sub.2) and S.sub.s (t.sub.1000, F.sub.2) whose phases have been shifted by phase angle .theta..sub.2, from the initial data S.sub.c (t.sub.1000, F.sub.2) and S.sub.s (t.sub.1000, F.sub.2) contained in two Fourier components S.sub.c (t.sub.1, F.sub.2) and S.sub.s (t.sub.1, F.sub.2) derived by the Fourier transformation made in the step (a), in such a way that the peak contained in the initial data S.sub.c (t.sub.1000, F.sub.2) and S.sub.s (t.sub.1000, F.sub.

Abstract: Synchronous apparatus capable of a variety of operational states responds to a sequence of digital control words, each specifying a desired state and persistence time of the state. The control words are furnished to the apparatus from a self-clocked FIFO in accord with the persistence code. A selected sub-sequence of digital control words in ROM is placed in an auxiliary FIFO upon detection of a corresponding token in the main sequence and control is passed to the auxiliary FIFO to furnish the sub-sequence to the apparatus. At the conclusion of the sub-sequence control is returned to the main FIFO and the main sequence is resumed.

Abstract: In NMR imaging method and apparatus the free induction signal obtained from a slice in an object is detected in a quadrature receiver and is modulated in a modulator and then displayed in a video display and photographed by a camera. The photograph is viewed in coherent light and the image represents the Fourier transformation of the free induction signal and hence is an image of the NMR spin density distribution of selected nuclei in the slice. As an alternative, modulation may be produced by providing a constant offset to the main magnetic field.

Abstract: An NMR imaging method is disclosed in which an object is measured in accordance with a pulse sequence capable of expressing a difference between two of a plurality of chemical shifts by a phase difference in a signal, that is, a pulse sequence 90.degree.-.tau..sub.a -180.degree.-.tau..sub.b -spin echo (where .tau..sub.a .noteq..tau..sub.b) to obtain spin distribution data, a histogram with respect to the phase of the spin distribution data is formed to regard a phase corresponding to that one of a plurality of peaks of the histogram which exists at one end of the histogram, as a position-independent offset phase which is contained in the spin distribution data and is peculiar to an NMR imaging apparatus, and the spin distribution data is corrected using the offset value thus obtained, to extract spin density distribution data for each of the chemical shifts from the corrected spin distribution data.

Abstract: During known MRI measurements, for example spin echo and inversion recovery measurements, phase errors occur in pixels, inter alia due to eddy currents caused by the application or interruption of magnetic field gradients during a measurement. There is proposed an inversion recovery method combined with a method where the magnetization is not inverted in advance in order to determine for each pixel the phase error in an image obtained by means of an inversion recovery method, so that inversion recovery images can be obtained which do not contain phase errors.

Abstract: Method for measuring the time dependence of an oscillating field gradient and representatively its integral function with respect to time for imaging method using the field gradient such as rapid chemical shift imaging method echo planar method, etc. A uniform specimen is placed within a coil of an NMR device, in which nuclear spins are excited; a phase encoding field gradient is applied thereto; and signals are sampled under application of the field gradient to be measured. These steps are repeated and an integral function of the field gradient with respect to time is obtained by using the peak position in the series of data obtained by this repetition.

Abstract: Each view of a magnetic resonance image is phase encoded with one of a plurality of phase encode gradients which vary from each other by a multiple of a phase encode gradient interval or step. For a given field of view, the resolution is determined by the upper and lower limit phase encode gradient angles. The larger the limit angle, the finer the resolution. When the imaged subject is shorter in dimension along the phase encode axis than the dimension of the field of view of the image along the phase encode axis, a portion of dead space other than the subject is imaged. To shorten the imaging time, the number of views is reduced in accordance with the ratio of the object dimension to the field of view. The size of the phase encode gradient steps or intervals are increased by the same ratio such that a reduced number of views spans the same upper and lower phase encode gradient angle limits. This stretches the resultant image.

Abstract: A method and apparatus provides complete mensuration of two-dimensional Fourier components of a nuclear spin property thereby permitting undistorted image reconstruction. In spite of an unavoidable phase factor which originates from basic field inhomogeneities and drifts and from non-perfect electronics adjustment, an optimum sectional image is obtained from half measurements of the sampled resonance signals which are complex conjugate pairs. The image is obtained by determining the phase and then eliminating it from a spatial Fourier transform of the spin density distribution.

Abstract: In an improved NMR imaging method for forming images of a subject by determining the relative densities of nuclei within the subject, three orthogonal gradient fields are generated by digitally storing three gradient waveforms for each orthogonal direction, with each waveform being individually compensated and calibrated with respect to an axis with which it is associated. Nine associated matrix multiplying functions which determine the coordinates of a desired slice in its rotated plane are also stored by an external input (by computer or by the clinician operating the system.) Then, in a sequential fashion, digital words for each gradient waveform are read out, multiplied by pairs with the appropriate multiplying function and the three terms are added to form a digital word. These words are converted to an analog value and applied to the respective gradient coils.

Abstract: Reception signal processing apparatus in nuclear magnetic resonance diagnostic apparatus to display as an image the distribution of the spin density or relaxation time of specific atomic nuclei existing in an object utilizing nuclear magnetic resonance phenomena including a phase demodulator for phase demodulating a nuclear magnetic resonance signal evoked by nuclear magnetic resonance phenomena in accordance with two reference waves, the phases of which are different by 90.degree., an analog-to-digital convertor for digitalizing the separated two signals obtained by the phase demodulator, and a noise correction processor for eliminating the low frequency component noises included in the demodulated signals from the phase demodulator to obtain an image without artifacts.

Abstract: In an imaging method called spin warp method in which a measuring sequence inclusive of nuclear spin excitation, application of phase-encoding gradient field, and measurement of NMR signals under the application of read-out gradient field, is repeated while changing the phase-encoding amount, and a data train thus obtained is subjected to the two-dimensional inverse Fourier transformation to reconstruct a magnetization distribution image of an object, wherein an NMR imaging method is characterized in that measurement of NMR signals is repeated a plural number of times for a particular phase-encoding amount only among many phase-encoding amounts, a plurality of NMR signals thus obtained are added up together and are averaged, and the data obtained by the addition and averaging is subjected to the two-dimensional inverse Fourier transformation.

Abstract: A method for providing spin density distribution images of an object, discriminated with respect to plural chemical shifts. This method is performed by repeating a measurement sequence in a spin warp imaging method, of the spin data plural times, with a time difference .DELTA..tau. between a time interval .tau..sub.1 from spin excitation to a 180.degree. RF pulse and a time interval .tau..sub.2 from the 180.degree. RF pulse to a peak of a spin echo, altering .DELTA..tau. in the ways corresponding the number of chemical shifts to be discriminated from one another, subjecting the respective spin data to two-dimensional Fourier transform to provide plural sets of spin data for respective coordinates in a spatial domain, and solving simultaneous equations of the sets of spin data to provide spin densities corresponding to the respective chemical shifts.

Abstract: In order to make an accurate display possible even in case image data having been subjected to a Fourier transformation have negative values, the sampling timing deviations of measured signals having phase errors based on various factors are detected from the gradient of the linear components of the image data having been subjected to the Fourier transformation, and the density values of the image having the detected timing deviations corrected are displayed.

Abstract: In imaging methods represented by the echo-planar method, i.e., in a method including a step of measuring the spin echos while applying a fixed gradient magnetic field to an object and applying a gradient field G.sub.Y periodically inverted in sense to the object and a step of obtaining the spin distribution image in the spatial domain by applying two-dimensional Fourier transform to the measured data, measurement is repeated a plurality of times while altering the phase of the applied waveform of G.sub.X, and the spin density image is derived by applying two-dimensional Fourier transform to a plurality of sets of data groups thus obtained.

Abstract: An NMR imaging apparatus of the present invention which is provided with an improved data acquiring means 16 and which is useful for enhancement of the speed of reconstruction of an image in NMR imaging by a multislice multiecho method is characterized in that a raw data memory 18 which is provided for storing raw data for the maximum number of slices that can be acquired in one scanning separately from the memory 10 of a computer system 6, and an address converter 19 for converting the addressses of the measured data supplied subsequently in accordance with the sequence of the multislice multiecho method and for storing the measured data in the raw data memory 18 in the arrangement different from the order of acquisition are disposed in a data acquiring device, so that a data block for each slice is formed in the raw data memory 18.

Abstract: A complete data set of complex-valued NMR signal responses (sufficient to determine an NMR image) is conventionally acquired. Thereafter, using such time domain signals and/or a one-dimensional Fourier transform of same, synthesized NMR signals are derived using assumed complex conjugate symmetry relationships between the desired NMR signal components. Such synthesized data is then averaged (e.g. with the actually acquired data) to result in averaged data having an improved signal-to-noise ratio (e.g. up to 100% improvement or more is theoretically possible). Such improvement is made possible because the noise signal components (unlike the desired signal components) do not actually exhibit complex conjugate symmetry. Accordingly, noise signals add incoherently while desired signals add coherently when the synthesized data is averaged. Once an averaged data set is thus derived having improved signal-to-noise ratio, it may be conventionally transformed to an NMR image (e.g.

Abstract: A pulse sequencer (40) controls a resonance excitation controls circuit (22), an inversion pulse controls circuit (24), a slice select gradient controls circuit (32), a read gradient controls circuit (34), and a phase encode gradient controls circuit (36) to cause an appropriate gradient pulse imaging sequence to be generated in the image region. The operator selects an appropriate imaging sequence such as a spin echo, inversion recovery, multi-echo, radient echo, or other conventional imaging sequence and the parameters, such as the number of repetitions, from an image pulse sequence and motion desensitization memory (44, 46). In the exemplary pulse sequences of FIGS. 2-4, this memory directs the formation of RF pulses (62, 66), slice selection pulses (60, 64) and read gradient pulse (70), phase encode gradient pulse (72), and the appropriate additional gradient pulses for rephasing signals from one or more of static, constant velocity, accelerating, and pulsatilitory tissue in the image region.

Abstract: An NMR imaging method using a rotating field gradient is disclosed in which transverse magnetization is prepared in a portion of an object to be inspected, by the 90.degree.-180.degree. RF pulse excitation, a rotating field gradient is generated to perform a sampling operation for an output signal in a state that the position of signal in a phase space is revolved, the intensity or rotational speed of the rotating field gradient is varied stepwise or continuously to obtain data arranged on concentric circles or a spiral in the phase space, and the data thus obtained undergoes Fourier transformation in each of a plurality of radial directions or two-dimensional Fourier transformation, to form an image of spin distribution.

Abstract: In order to measure a static field distribution with one scanning operation and to make image distortion corrections with the static field distribution and a gradient field distribution simultaneously considered, an image is reconstructed using a spin echo signal produced under the condition that a time interval between a 90.degree. pulse and a 180.degree. pulse differs from an interval between the 180.degree. pulse and the time origin of the spin echo signal, the static field distribution is evaluated from the relation of distortions to phase errors free from a phase distortion attributed to the characteristic of a detecting part and a phase distortion attributed to the dynamic characteristic of the gradient field, a relations existing between the spatial distortion and phase distortion of the reconstructed image and a magnetic field distribution including the gradient field is obtained, and the distortion magnitude of the reconstructed image is evaluated from the measured magnetic field distribution.

Abstract: A portion of a subject (22) which is undergoing respiratory or other motion is disposed in an image region (20) to be examined. A respiratory or other motion monitor (50) monitors the cyclic respiratory motion and provides output signals indicative of chest expansion. A phase encoding gradient selector (60) selects the phase encoding gradient that is to be applied by a gradient magnetic field controller (40) and coil (42). A central phase encoding gradient is selected corresponding to a chest relaxation extreme and minimum and maximum phase encoding gradients are selected corresponding to a chest expansion extreme (FIG. 2). Intermediate degrees of monitored physical movement cause the selection of corresponding intermediate phase encoding gradients. Resonance signals collected during each phase encoding gradient are Fourier or otherwise transformed (80) into a corresponding view.

Abstract: A nuclear magnetic resonance tomography apparatus, and a method for operating such an apparatus, generate a tomographic image by projecting acquired signals corresponding to the nuclear spins on a frequency axis as a Fourier line, and the image of the examined slice is calculated by Fourier transformation of the Fourier lines. In the method and apparatus, a number of echo sequences are acquired after excitation of the nuclear spins in the axamination subject by a high frequency pulse. Each echo sequence consists of a selected number of individual echoes occurring in succession within each sequence. In the method and apparatus, entry of these individual echoes into a matrix having a central zero line is controlled such that the first-occuring echoes from each sequence are entered in the matrix on alternating sides of the zero line, i.e., above and below the zero line, at increasing distances from the zero line.

Abstract: A shimming magnetic field control (22) causes shimming magnetic fields for improving uniformity of a main magnetic field generated by main magnets (10). A resonance excitation control (32) selectively applies a resonance excitation pulse (34) and inversion pulse (36) for inverting the spin magnetization of water and lipid dipoles. A phase sensitive detector (30) selectively receives resonance signal components which are transformed by a transform algorithm (70) into a real image (72) and an imaginary image (74). The inversion pulse (36) is shifted by a time such that the water and lipid spin magnetizations are out of phase by a predetermined amount. With a 90.degree. phase difference, the real image represents water and the imaginary represents lipid. A phase image (80) is derived from a reference image pair (76, 78). A phase unwrap circuit (82) removes ambiguities attributable to the spin magnetizations becoming dephased by multiples of 2.pi. to create a phase map (84).

Abstract: In a system for reducing artifacts in a desired image due to substantially periodic variations in the imaging signal detected from a portion of an object under examination, a method and apparatus for generating from a signal y(t) related to the variations and whose values are not equally likely, a signal .phi.(t) whose values are substantially equally likely for use in distributing events substantially evenly over the variations. In order to provide the signal .phi.(t), an apparatus is disclosed for executing the following steps: (a) establishing a historical data base derived from values of the signal y(t) for a period of time preceding the present time, (b) measuring parameters related to the present value of the signal y(t); and (c) producing a value for .phi.(t) using the present measured parameters and the historical data base; wherein the values of .phi.(t) are more evenly distributed than the values of y(t).

Abstract: A signal processing unit which employs a constant, continuous and automatic error correction. The prior manual calibration to eliminate errors is eliminated. An echo signal is employed for ease of design.

Abstract: A method and apparatus for determining the chemical structure of an unknown substance wherein spectral data of the unknown substance is detected, a point-assessment is calculated which expresses the degree of possibility of partial structures being contained in the unknown substance based on the spectral data and prememorized chemical shift values corresponding to the partial structures of known substances, it is judged whether the point-assessment is a predetermined threshold value or more and the partial structures with a large possibility of being contained in the unknown substance based on the output of the judgement results are found and displayed. The partial structures thus found are used to determine a molecular structure of the unknown substance.

Abstract: A method of obtaining a separate data contribution from first and second spectral components during a single magnetic resonance scan. The method uses a scan sequence causing the data from the first and second spectral components to be 90 degrees out of phase. This shift of the data along with a measurement of the inhomegeneities of the field initiates two output signals which are used to provide all of the data required for imaging the two spectral components and/or correcting images for chemical shifts.

Abstract: In accordance with the invention, two detection periods t.sub.2 and t.sub.2 ' are set by the use of a pulse train essentially consisting of three pulses. Free induction decay signals FIDa and FIDb obtained during the two periods, respectively, are stored in respective data files. The measurement is repeated a plurality of times while putting at least one of the three pulses of the pulse train out of phase with the others. The free induction decay signals FIDa and FIDb derived by each measurement are stored in their respective data files. After the measurements, a linear combination of the data items which are stored in the data files assigned either to the signals FIDa or to FIDb is formed. The resultant data is subjected to double Fourier transformation to obtain a two-dimensional NMR spectrum. The manner in which the data items are linearly combined is appropriately selected to obtain a desired kind of two-dimensional NMR spectrum.

Abstract: An NMR imaging apparatus, wherein a 180.degree. RF pulse is applied shortly after the termination of the 90.degree. RF pulse, and wherein after such 180.degree. pulse application, to collection of spins and after collection of spins to dispersion of spins are sampled asymmetrically, whereby Fourier transformation takes place by interpolating missing data on a Fourier plane, and by operating on the data, image is accurately reconstructed. The novel pulse sequence improves the S/N ratio and reduces deterioration of images.

Abstract: An NMR method for producing a sequence of images throughout the cardiac cycle is disclosed. A fast scan NMR pulse sequence is continuously and asynchronously applied during successive cardiac cycles, and a phase encoding magnetic field gradient is incremented between cardiac cycles to acquire NMR data which is reconstructed using a 2DFT technique. The phase encoding magnetic field gradient is stepped in subincrements, and the odd and even phase encoding views are acquired in separate segments of the procedure in order to eliminate image distortion due to disturbance of the residual transverse magnetization.

Abstract: A two dimensional Fourier transform magnetic resonance imaging method produces a series of scan lines in Fourier space using quadrature demodulation of a series of radio frequency echo signals from an object being observed with a reference signal. Fourier transforming the scan line data provides visual image data through a section of the object. Limitations in the hardware performance introduces unknown, time varying, phase errors into the scan line data, proportional to the phase difference between the reference signal and the echo signals as each is demodulated. Improved visual imaging results from the introduction of an additional sensitive line scan through Y=0 in Fourier space, having a calculable phase error which is used to correct the unknown phase errors in the remaining scan lines. The phase term of the sensitive line data is corrected for the phase error which is known at Y=0. Magnetic resonance imaging scan line data are next generated for a slice through the object.

Abstract: A method of suppressing at least one undesired resonance response signal while facilitating reception of at least one other desired NMR response signal from a coupled spin resonance in NMR spectroscopy, utilizes a pair of alternating sequences of RF signal pulses, with each sequence having an initial .pi./2 RF pulse, followed by a .pi. RF signal pulse having a temporal midpoint at a time interval T after the temporal midpoint of the initial pulse (where T=n/4J, with n being an odd integer and J being the spin coupling constant of the hydrogen nuclei) and a final .pi. RF signal pulse with a temporal midpoint at twice the time interval T after the temporal midpoint of the first .pi. RF signal pulse in that sequence. Only one of the pair of sequences is provided with a polarization transfer narrowband .pi. RF signal pulse symmetrically disposed about a temporal midpoint located at substantially a time interval T after the first .pi.

Abstract: An NMR imaging method for measuring a magnetization distribution of an article under test, particularly the magnetization distribution including a longitudinal relaxation effect, by a Fourier imaging method with identification of polarity of the magnetization distribution.A homogeneous phantom is measured by the Fourier imaging method and image-reconstructed so that a reference image data which reflects a phase rotation inherent to an NMR imaging apparatus is obtained. Then, a magnetization distribution of an article under test is obtained in a similar measurement and image reconstruction sequence, and products of the reference image data and the image data of the article under test are stored as the signs to represent the polarity of magnetization of the article under test.

Abstract: A method of calculating the intrinsic parameters including the spin-lattice relaxation time T1 and the spin-spin relaxation time T2 for Nuclear Magnetic Resonance (NMR) technique which utilizes calculations of derived algorithms by a series of passthroughs of a digital video processor. The use of a digital video processor to accomplish the algorithm construction provides a significant increase in the speed with which the intrinsic parameters can be calculated.