Abstract: A shielded superconducting MRI magnet system uses a multi-layer shielded coil design. By splitting the magnet coils into a plurality of coil layers, an increased number of degrees of freedom is achieved which, in turn, permits minimization of the overall length of the magnet while nevertheless avoiding excessive magnet field and stress values in the coils. A compact coil system is thereby designed which also satisfies the plurality of MRI requirements with regard to sufficiently large investigational volume, magnet field strength, acceptable homogeneity, and magnet stray field limitation while achieving sufficiently low maximum coil B field strengths and stress values to avoid quenches and maintain the structural integrity of the magnet.

Abstract: Spatial encoding in magnetic resonance imaging (MRI) techniques is achieved by sampling the signal as a function of time in the presence of magnetic field gradients, e.g., X, Y, and Z gradients. The gradient magnets have in the past been assumed to generate a linear gradient, and typical image reconstruction techniques have relied upon this assumption. However, to achieve high speed performance, gradient magnets often sacrifice linearity for speed. This non-linearity, in turn, results in distorted images, the distortion often being sufficiently large to compromise the usefulness of MRI images for stereotaxy or longitudinal studies, where precise volumetric information is required. The disclosure provides practical methods for correcting distorted images resulting from such non-linearity in the gradient fields, as well as distortions resulting from translational, rotational, and/or winding/design errors in the field generating devices.

Abstract: Asymmetric, compact non-superconducting magnets for magnetic resonance imaging are provided. The magnets have a homogeneous region (the “dsv”) which can be located close to one end of the magnet so as to reduce the sensation of claustrophobia experienced by patients undergoing MRI procedures. The magnets can be designed using a hybrid process in which current density analysis is performed to obtain an initial coil configuration which is then refined using non-linear optimization techniques to obtain a final coil configuration. The hybrid method can incorporate various constraints, including, the location and size of the dsv, the uniformity and strength of the B0 field, stray field strengths outside of the non-superconducting magnet, and field strengths within the magnet's coils. The hybrid technique can also be used to design compact symmetric non-superconducting magnets.

Abstract: Asymmetric, compact non-superconducting magnets for magnetic resonance imaging are provided. The magnets have a homogeneous region (the “dsv”) which can be located close to one end of the magnet so as to reduce the sensation of claustrophobia experienced by patients undergoing MRI procedures. The magnets can be designed using a hybrid process in which current density analysis is performed to obtain an initial coil configuration which is then refined using non-linear optimization techniques to obtain a final coil configuration. The hybrid method can incorporate various constraints, including, the location and size of the dsv, the uniformity and strength of the B0 field, stray field strengths outside of the non-superconducting magnet, and field strengths within the magnet's coils. The hybrid technique can also be used to design compact symmetric non-superconducting magnets.

Abstract: Asymmetric, compact superconducting magnets for magnetic resonance imaging are provided. The magnets have a homogeneous region (the "dsv") which can be located close to one end of the magnet so as to reduce the sensation of claustrophobia experienced by patients undergoing MRI procedures. The magnets can be designed using a hybrid process in which current density analysis is performed to obtain an initial coil configuration which is then refined using non-linear optimization techniques to obtain a final coil configuration. The hybrid method can incorporate various constraints, including, the location and size of the dsv, the uniformity and strength of the B.sub.0 field, stray field strengths outside of the superconducting magnet, and field strengths within the magnet's coils. The hybrid technique can also be used to design compact symmetric superconducting magnets.

Abstract: Procedures for designing magnets, including superconducting magnets, shim magnets, and gradient magnets for magnetic resonance systems, are provided. The procedures involve the use of a simulated annealing procedure in which weighted spherical harmonics are included in the procedure's error function. The procedure has resulted in the development of previously unknown magnet designs. In particular, superconducting magnets have been designed which include at least one coil in which the current flow is opposite to that in adjoining coils. Such reversed flow in combination with a relatively large number of coils, e.g., more than 6 coils, have enabled the development of short, yet homogeneous, whole body magnets for use in magnetic resonance imaging (MRI).

Abstract: Temporal B.sub.o shifts in NMR spectroscopy and/or imaging systems arising from pulsed field gradient induced eddy currents result in the distortion of free induction decay signals. A method of compensation of this distortion through modulation of the sender and/or receiver signal in opposite concert with the induced B.sub.o shifts is introduced. The method has the advantage of having a fast response and of not altering the magnetic gradient field. (FIG.

Abstract: A method serving for recording spin resonance spectra of test samples having at least two groups (CH.sub.3, CH) of nuclei of the same kind and of substantially identical chemical shift, comprises the step of suppressing the signal of the second group (CH) for the purpose of obtaining an isolated image of the signal of the first group (CH.sub.3). To this end, a pulse sequence of four r.f. pulses, preferably 90.degree. r.f. pulses (10, 12, 13, 14), are irradiated upon the sample. The first r.f. pulse (10) is a soft pulse, selective for the nuclei of the first group (CH.sub.3). The second r.f. pulse (12) is a soft pulse, selective for the nuclei of the second group (CH), and causes the magnetizations of the nuclei of the first group (CH.sub.3) and of the second group (CH) to be transferred, at least in part, to a state of multiple-quantum coherence. Immediately following the second r.f. pulse (12) the third r.f.

Abstract: A method for providing B.sub.0 homogeneity at voxels away from the magnet isocenter for use in volume selected NMR spectroscopy wherein voxels are shimmed using only first-order X, Y and Z shims to produce three dimensional shim current maps that are utilized in setting up for in vivo spectroscopy.

Abstract: A method for volume-selected NMR spectroscopy where an rf pulse of selected bandwidth, in the presence of a field gradient superimposed upon an initial homogenous magnetic field, rotates a slice of magnetization into the transverse plane, and it then uses a high power refocussing pulse to refocus the phase roll that accompanies the rf pulse. After an appropriate time, the magnetization is pulsed back to the homogenous magnetic field axis and the gradient collapsed. A read pulse is used to tip the magnetization of interest into the transverse plane for acquisition in the absence of applied gradients.

Abstract: A method for the determination of iron stores in organic tissue consists in measuring the relaxation time of deuterium included in said tissue by magnetic resonance spectroscopy.

Abstract: A method for determining the turnover of organic material stored in living organic tissue consists in that the deuterium content of the stored material is artificially modified from natural abundance and monitored as a function of time by measuring the CHD-signal by means of magnetic resonance spectroscopy. E.g., for determining the fat turnover in living beings, the deuterium content of the body fat may be increased by administering to the living being drinking water contaiing 10% D.sub.2 O for 28 days. Thereafter, the decrease of the deuterium content of the body fat is monitored while normal water is administered. The loss of .sup.2 H from body fat is an indication for the body fat turnover.

Abstract: A liquid sample comprising a system made up of two types of heteronuclei is pulsed in a particular manner in a nuclear magnetic resonance (NMR) experiment so that the resulting NMR signal from the one type of heteronucleus depends on the scalar-coupled interaction with the other type of heteronucleus. The sequence of radiofrequency pulses is such that the two types of heteronuclei interact via the phenomenon of polarization transfer and by the phenomenon of the correlated motion of the two types of heteronuclei in the transverse plane of the doubly rotating reference frame. The combination of these two phenomena in the one pulse sequence provides NMR signals which are easily made less dependent on the exact magnitude of the heteronuclear scalar coupling constant. The coupled NMR signals for polarization transfer from a system of multiple spin-half nuclei have multiplet components in the normal ratio. Consequently the pulse sequence provides an improved method for obtaining chemical structural information.

Abstract: Asymmetric, compact superconducting magnets for magnetic resonance imaging are provided. The magnets have a homogeneous region (the “dsv”) which can be located close to one end of the magnet so as to reduce the sensation of claustrophobia experienced by patients undergoing MRI procedures. The magnets can be designed using a hybrid process in which current density analysis is performed to obtain an initial coil configuration which is then refined using non-linear optimization techniques to obtain a final coil configuration. The hybrid method can incorporate various constraints, including, the location and size of the dsv, the uniformity and strength of the B0 field, stray field strengths outside of the superconducting magnet, and field strengths within the magnet's coils. The hybrid technique can also be used to design compact symmetric superconducting magnets.