Abstract: An MR tomograph, the magnet system (2) and gradient system of which permit access to the investigation volume along at least two essentially orthogonal axes, comprises a positioning system for the exact determination of the position of a manually guided manipulator (12) relative to the measuring object (6) which is investigated by means of imaging MR measurement and located in the investigation volume (3) of the MR tomograph (1); with a mounting frame (11) with which the manipulator (12) is connected via movable mechanics comprising a measuring means through which the respective spatial position of the manipulator (12) relative to the mounting frame (11) can be determined, wherein the measuring means of the movable mechanics does not utilize any MR signals and wherein the measured position of the manipulator (12) is displayed on the MR image. In this way, minimum-invasive operations, e.g.

Abstract: An RF coil system (1) for an MR tomograph comprising a magnet coil system and a gradient coil system is characterized in that the RF coil system is constructed of two partial systems (2, 2') which are arranged essentially laterally reversed with respect to a plane z=0 containing the centre of the measuring volume and have a distance g/2 from the plane z=0, and that each partial system (2, 2') comprises at its axial end facing the plane z=0, a compensation section (3, 3') for homogenizing the RF field drop in the measuring volume caused by the axial gap between the partial systems (2, 2') as compared with an axially continuous and undivided RF coil system (1). The RF coil system (1) in accordance with the invention allows lateral access to the investigation volume in the radial direction and/or offers the possibility to integrate in the RF coil system an adjustment, fixing or support ring surrounding the investigation volume.

Abstract: An NMR tomography magnet system (1) comprises a cryostat having a horizontal room temperature bore (2) with a diameter d between 20 cm and 40 cm having a vessel (3) filled with liquid helium. In intimate thermal contact with the liquid helium is a superconducting solenoid coil (4) with a horizontal axis (100; z=0) for the production of a static homogeneous magnetic field B in a homogeneity volume (5) within the room temperature bore (2). The center of the homogeneity volume is located at a separation l.sub.m from an axial end (z=0) of the room temperature bore (2) and the outer skin (6) of the cryostat exhibits, at the depth l.sub.m from an axial end of the room temperature bore (2) and at least in an angular region about the horizontal cryostat axis (100), minimum separations h.sub.e, h from the inside of the room temperature bore (2) whereby l.sub.m, h.sub.e <35 cm, preferentially<30 cm, and h<50 cm.

Abstract: A method for the production of a two or three-dimensional image with the assistance of magnetic resonance. The measuring data are taken according to the projection method by means of a sequential rotation of projection gradients. The image, however, is generated with 2dFT or 3dFT methods. The projection gradient is advantageously not only rotated between high frequency excitation pulses, but its strength is also changed in such fashion that the measuring points in k-space lie on squares or parallelepipeds.

Abstract: In an SPI method for the n-dimensional NMR imaging of materials with short T.sub.2 -relaxation times, for example cartilage or bones, only one single measurement point in k-space is recorded from the phase encoded FID signal following each RF excitation pulse. A pseudo spin echo (4) is derived from the extracted k-space points which has essentially the same information content as a conventional spin echo signal.

Abstract: A magnetic resonance method is utilized for taking an image of an object. An initial projection is taken by applying a gradient magnetic field having a predetermined direction .phi. and strength G, irradiating a high frequency excitation pulse and sequentially measuring a nuclear resonance signal from the object. The signal dephases under the influence of the gradient magnetic field and the signal measuring points are assigned to points in k-space lying along a vector whose direction is determined by the direction .phi. of the gradient magnetic field, and whose magnitude by the product of the strength of the gradient magnetic field and the time interval between the excitation pulse and the taking of the corresponding measuring point. A further number of n-1 (n>>1) projections are obtained by changing the direction and/or strength of the gradient magnetic field. Additional excitations and measurements are carried out for an additional n'.ltoreq.n projections having measuring points.

Abstract: A magnetic resonance probehead is disclosed comprising a split-ring coil having a ring-shaped coil body with an axial slot therein. A radio-frequency (RF) measuring field is generated within the coil body and directed in parallel to a body axis. The coil body defines a first radial plane on one axial side and a second radial plane on the opposite axial side thereof. A measuring object is surface-contacted to the first radial plane whereas an electrical mirror having an RF-conductive plate is arranged in parallel to the second radial plane and at a predetermined axial distance therefrom.

Abstract: A digital frequency generating device is comprised of a first digital frequency generator which generates a first output signal at a first frequency and a second digital frequency generator which generates a second output signal at a second frequency independent of the first frequency. Both the first and the second frequency generators run continuously and either can be connected to the generating device output by means of a multiplexer. Apparatus is provided to synchronize the two generators so that a continuous phase transition is maintained when the generating device output switches from the first output signal to the second output signal. This arrangement allows the device output to be shifted from a first frequency to a second frequency and then return to the first frequency output while maintaining the phase position of the first frequency output and is particularly useful in nuclear magnetic resonance applications.

Abstract: In a method for the generation of a nuclear magnetic resonance (NMR) spectrum from a measuring volume, which is exposed to a highly homogeneous stationary magnetic field B.sub.0, a radio frequency (RF)-pulse is irradiated in a first run into the measuring volume in order to excite the concerned nuclear spins; at least one magnetic gradient field G is switched, for example for selecting a certain slice from the measuring volume and after switching off the magnetic gradient field G, a first data set is recorded which contains the observable measuring signals from the measuring volume, subsequently the method is repeated in a second run with a magnetic gradient field -G which has the opposite polarity to the magnetic gradient field G, whereas the remaining experimental parameters of the first run are maintained, wherein after switching off the magnetic gradient field -G a second data set is recorded and added to the first data set.

Abstract: A method for obtaining a time sequence of nuclear magnetic resonance (NMR) tomograms of a certain sectional plane in a measuring volume for observation of variations with time of signal intensities from the sectional plane. The method where k data sets f.sup.'k =f.sub.1.sup.'k . . . f.sub.n.sup.'k are recorded for NMR-tomograms with a low spatial resolution characterized by a parameter n in a time sequence with a waiting time t.sub.w between the acquisition of each data set f.sup.'k. The method where, in terms of time before k data sets f.sup.'k, a data set f=f.sub.1 . . . f.sub.m is recorded for an NMR-tomogram of the same sectional plane with a high spatial resolution characterized by a parameter m (i.e. m>>n). Subsequently, by means of said primarily recorded data set, new data sets f.sup.'k are reconstructed from the successively recorded k data sets f.sup.'k for NMR-tomograms of the sectional plane with a high resolution in space and time.

Abstract: An apparatus serves to excite and/or measure magnetic resonance in samples, in particular in relation to whole body tomography. A probehead (10) incorporates a high frequency system to transmit and/or to detect a high frequency magnetic field of a predetermined measuring frequency. The probehead (10) further incorporates a coil system to produce a magnetic field of predetermined inhomogeneity inside an inner space (13) of the probehead (10) varying according to a predetermined time program. Elements of the high frequency system are combined with elements of the coil system into common construction units. In addition, a signal processing unit for measured resonance signals is provided for. The construction units are in the form of hollow bodies (20). Coils (33) of the coil system are located inside the hollow bodies (20). Conductive outer walls (21) of the hollow bodies (20) form the high frequency system.

Abstract: A sample head for the NMR tomography is disclosed. The sample head has at least two hollow-cylindrical housings, arranged beside each other along a common axis. Each of the housings has an outer cylindrical wall consisting of essentially continuous, electrically conductive material and has an inner cylindrical wall surrounding a sample area. The inner cylindrical walls are provided with a plurality of parallel electrical conductors extending parallel to an axis of the sample head. The sample head, further, has a coupling device for generating rf electrical currents within the conductors.

Abstract: A method serves for recording spin resonance spectra of test samples having at least three groups of spins. A first group is coupled to a second group, while a third group is uncoupled relative to the second group but has a spectral position, e.g. chemical shift, which is substantially identical only to that of the first group. For obtaining an isolated image of the signal of the first group, one suppresses the signal of the third group. A pulse sequence of three r.f. pulses (10, 13, 17) are irradiated upon the sample in a manner known as such. The second r.f. pulse (13 ) is applied in such a way that the magnetization of the spins of the first group and of the second group is transferred to a state of double-quantum coherence by coherence transfer. Then, a first magnetic gradient field pulse (15) of a predetermined pulse surface (.epsilon..sub.2), with dephasing effect for the double-quantum coherence, is exerted upon the sample. The third r.f.

Abstract: A method serves for recording nuclear resonance spectra of test samples having at least three groups of spins. A first group is coupled to a second group, while a third group is uncoupled relative to the second group but has a spectral position, e.g. chemical shift, which is substantially identical only to that of the first group. For obtaining an isolated image of the signal of the first group, one suppresses the signal of the third group. A pulse sequence of three r.f. pulses (10, 13, 22) are irradiated upon the sample in a manner known as such. The second r.f. pulse (13) is applied in such a way that the magnetization of the spins of the first group is transferred to the spins of the second group by polarization transfer. Then, a first magnetic gradient field pulse (17, 23), with dephasing effect for the spins of the said second group, is exerted upon the sample. The third r.f.

Abstract: A nuclear magnetic resonance tomograph comprises a magnet surrounding a measuring space for receiving an object under test, e.g. a human body. A coil is provided for generating a high-frequency magnetic field within the measuring space. The coil is fed by a transmitter comprising a stage for adjusting the amplitude of a high-frequency current generated by the transmitter. A high-frequency magnetic field sensor is arranged at a predetermined calibration location outside the measuring space for measuring the high-frequency magnetic field strength prevailing at the predetermined calibration location. For calibrating the high-frequency magnetic field strength during a tomography measurement, the coil with the object under test inside is subjected to a test current and the resulting high-frequency magnetic field amplitude is sensed.

Abstract: A method is disclosed for a multi-dimensional measurement of magnetic resonance in defined small volume regions of solid-state samples. The samples are arranged in a uniform homogeneous magnetic field and, in a predetermined manner, irradiated with a sequence of high frequency pulses as well as exposed to a sequence of gradient magnetic field pulses. This is done in such a way that the spin magnetization to be measured is maintained for a time interval which is longer then the amount of time needed to switch-off the gradient magnetic field pulses. Initially, in a first time interval, the magnetization of a single slice only of the sample is transferred into a transverse magnetization tilted by 90.degree. with respect to the direction of the constant homogeneous magnetic field. Thereupon, in a second time interval, volume selective gradient magnetic field pulses are irradiated on the sample.

Abstract: A sample head (1) with cage resonator includes an insert (51) which can be introduced into the cavity formed by the conductor sections (22) of the cage conductor and which increases the electric length of the cage resonator in such a manner that the cage resonator containing the insert assumes a resonant state at a second predetermined operating frequency f.sub.1, whereas without the insert introduced, it is resonant at a first predetermined operating frequency f.sub.o. By introducing or withdrawing the insert (51), it is therefore possible to operate a sample head of this type selectively with two different frequencies corresponding to the resonance frequencies of different nuclear species, for example the proton and the fluorine resonance.

Abstract: A probe head is provided for nuclear magnetic resonance (NMR) measurements, in particular for use in NMR tomography.

Abstract: In nuclear spin tomography disturbances are encountered as a result of the insertion of the gradient fields, which disturbances are due to the generation of eddy currents and lead to field distortions making themselves felt, among other things, in the rapid decay of the echo signals of spin echo pulse sequences, i.e. in disturbances of the rephasing conditions. According to the invention, the rephasing conditions required for generating spin echo impulse sequences can be established either by varying the value of the static magnetic field between the excitation pulse and the next following rf pulse of a spin echo pulse sequence, or else by adjusting the interval between the excitation pulse and the next following rf pulse to a value different from half the interval between the subsequent rf pulses.

Abstract: For recording a nuclear magnetic resonance tomogram according to a Fourier-transform method, a Carr-Purcell-Gill-Meiboom pulse sequence is used for the excitation of a body to produce a sequence of spin-echo signals. A time-limited phase-encoding magnetic gradient field G.sub.X is imposed between each pair of 180.degree. pulses of the sequence. The phase-encoding magnetic gradient field is modified after every 180.degree. pulse so that every spin-echo signal corresponds to a different projection of the body. The magnetic gradient fields used in the recording are regulated in intensity and duration in such a way that a spin-phase condition at each 180.degree. pulse of the pulse sequence remains effectively constant. Thereby, it is possible to construct a complete tomographic recording with a single pulse-sequence excitation, so that the time required for such recordings can be reduced to a fraction of the time needed for recording nuclear-magnetic-resonance tomograms conventionally.