Abstract: An NMR image of a patient's heart uses SSFSE (single shot fast spin echo) type pulses to condition the body by a preparation of a phase-encoding gradient pulse whose duration differs from one sequence to another so as to define, from one sequence to another, a different effective echo time. At each sequence an image is displayed representing the discrimination of the contributions of the particles of the body as a function of their time T2 compared with this effective time. For the heart, with a single respiration on the part of the patient, lesions due to infarction and transplant rejection are revealed.

Abstract: An NMR image of a patient's heart uses SSFSE (single shot fast spin echo) type pulses to condition the body by a preparation of a phase-encoding gradient pulse whose duration differs from one sequence to another so as to define, from one sequence to another, a different effective echo time. At each sequence an image is displayed representing the discrimination of the contributions of the particles of the body as a function of their time T2 compared with this effective time. For the heart, with a single respiration on the part of the patient, lesions due to infarction and transplant rejection are revealed.

Abstract: In the acquisition of NMR signals in FSE or fast spin echo type sequences the emission phase of the 180° refocusing pulse evolves quadratically. In order to prevent problems of oscillation of the output signal, the sequence is subjected to a preparation pulses. A history is provided for the common difference of the quadratic sequence of the phase variation with respect to the first seven refocusing pulses. This history leads to an immediate thermal equilibrium.

Abstract: A method of excitation for use during an NMR examination includes the subjecting of a body (92) to an orienting magnetic field (80). The body (92) is adiabatically conditioned with a first series of RF pulses (IP1-IPn). The body (92) is excited with a second series of RF pulses (E1-Em) in a presence of gradient field pulses. A resonance signal is emitted from the body (92) in response to the second series of RF pulses (E1-Em).

Abstract: In the acquisition of NMR signals in FSE or fast spin echo type sequences the emission phase of the 180° refocusing pulse evolves quadratically. Prevention of problems of oscillation of the output signal, the sequence is subjected to a preparation pulses. A history is provided for the common difference of the quadratic sequence of the phase variation with respect to the first seven refocusing pulses. This history leads to an immediate thermal equilibrium.

Abstract: In an NMR experiment, the movements of an object are represented by carrying out a harmonic analysis of the images based on a resolution of the movement of the object into a Fourier series. There is then obtained a set of images which is representative of the Fourier components of this movement. The images are then recombined at will so as to produce either a general moving image, or an image of those parts which are motionless in the object, or finally an image of only those parts which are in motion.

Abstract: Problems of homogeneity of the resonant field of an NMR machine are solved by differentiating the polarization and resonance functions assigned to coils of the field of said machine. In order to produce a magnetization, use is made of a polarization coil which produces a high field. This polarization field does not need to be homogeneous. Before making measurements, during sequences of excitation-measurement of the electromagnetic wave within the body under examination, the polarization field is switched in order to be cancelled and the body is subjected to a resonance field. This resonance field can be of much lower strength but is on the other hand much more homogeneous. By thus making use of switching of the orienting field, it is shown that the signal-to-noise ratio of the detected signal is maintained.

Abstract: A measurement is made of the effects of eddy currents during a long period (TM) in an NMR machine by placing, in this machine, a probe possessing a material capable of magnetic resonance with a small spin-spin relaxation time, and by proceeding to make a reiteration (PR) of the electromagnetic excitation (17-19) of a resonance signal in this material and to measure the resultant de-excitation NMR signal (20-22), for as many times more as the period during which the effects of the eddy currents have to be taken into account is long. It is shown that this way of doing things enables an accurate appreciation of the corrections to be made to the real field gradient pulses (23-24).

Abstract: The acquisition of images of moving parts by NMR experiments requires the prolonged use of two series of excitation sequences. In the invention, only one sequence is enough. The radiofrequency electromagnetic excitation is itself modified to impose, from the very outset, a piece of information, representing the speed of the concerned moving parts, on the free precession signal. The imaging encodings which follow this particular excitation are standard ones. This particular excitation comprises, in principle, two excitations at 90.degree., having opposite directions, applied to one and the same axis and separated in time by a period during which a bipolar pulse of a magnetic field gradient is applied. It is shown that the magnetic moments of the fixed particles are re-aligned, at the end, with the orienting field while the magnetic moments of the moving particles are flipped with respect to this orientation, by an angle proportionate to their speed.

Abstract: In a nuclear magnetic resonance experiment, the flows are measured by causing the orientation of the magnetic moments of the particles located in a slice to flip and by subsequently causing the scattering of the phases of the magnetic resonance signals to be reflected only for particles which have migrated into a slice adjacent to the slice in which the flipping has been done. It is shown that the relative dynamic range of the measured NMR signal for the moving parts in relation to the measured signal for the fixed parts becomes infinite.

Abstract: So-called motion artifacts are removed in NMR imaging experiments by choosing a 2DFT type imaging method and by choosing a phase encoding pitch, which is a multiple of a useful encoding pitch determined by the height of the image field to be depicted. It is shown that, after the image reconstruction has been computed by Fourier transform, the central image corresponds to the depiction of the continuous components of the magnetic moments of the particles located in an examined cross-section of a body under examination, and that these continuous components are not affected by all the variations in the rate of a cyclical phenomenon which disturbs the images (in general the cardiac cycle).

Abstract: In a nuclear magnetic resonance experiment, the flows are measured by causing the orientation of the magnetic moments of the particles located in a slice to flip and by subsequently causing the scattering of the phases of the magnetic resonance signals to be reflected only for particles which have migrated into a slice adjacent to the slice in which the flipping has been done. It is shown that the relative dynamic range of the measured NMR signal for the moving parts in relation to the measured signal for the fixed parts becomes infinite.

Abstract: The present invention relates to a process for modulating the effect of the speed of the moving parts of a body. The machines or processes for measuring the density by nuclear magnetic resonance are too sensitive at the displacement speed of the parts in question. In the invention, the sensitivity of the machines or processes is reduced in such a way that the speed effect can be measured. Prior to the measurement, compensating magnetic field sequences are applied in order to counteract the effect produced by the interfering magnetic field sequences, which are necessary for performing the measurement.

Abstract: The invention proposes an imaging process by nuclear magnetic resonance in which a calculated image is given corresponding to the molecular diffusion value at each point of an investigated medium. The diffusion image is obtained by comparing images relative to same sections of the medium and acquired during two excitation sequences, whereof one is not very sensitive to the diffusion and the other is particularly sensitive thereto. These two images undergo comparison in order to produce a diffusion image.