Abstract: A surface coil holder for magnetic resonance imaging wherein the holder is provided with straps or tape for securing the holder to an MRI table and a body part of a patient. By preventing movement of the holder and the patient's body part during examination, image quality is maximized to thereby improve diagnostic accuracy. The holder is dimensioned for receiving a conventional 5" surface coil, and an insert is provided so that the holder can accommodate a conventional 3" surface coil.

Abstract: A method for detecting the presence of a substance in a heterogeneous sample or article (i.e., a contraband substance) in a magnetic field includes establishing a level-crossing condition (B.sub.LC) for the substance to be detected for a set time (t.sub.b), and subsequently measuring nuclear magnetic resonance (NMR) signals to detect some consequence of the level-crossing condition. A saturating signal is applied at the begining of each cyclic test. Apparatus for detecting the presence of predetermined substances is also disclosed.

Abstract: As rf quadrature coil system for a magnetic resonance examination apparatus, comprises two similar rf coils connected to an rf receiver and/or an rf transmitter and arranged so as to be offset 90.degree. with respect to one another. Each rf coil comprises several turns which are situated in mutually parallel planes. The planes of the turns of one rf coil extend perpendicular to the planes of the turns of the other rf coil. The quadrature coil system can be used in magnetic resonance examination apparatus in which the uniform, steady magnetic field required for the examination extends perpendicular to the longitudinal axis of the patient to be examined.

Abstract: An improved method of assaying local metabolite concentrations the chemical entity (CE) of interest, of a living subject by non-invasive means using magnetic resonance (MR) spectroscopy employs acquiring an MR response signal for a naturally occurring, abundant marker material of known concentration, such as water (H.sub.2 O) from the subject. An MR response signal is also acquired from the CE being assayed, e.g., adenosine triphosphate (ATP) with phosphorus (.sup.31 P) nuclei producing the MR response signal. The subject is replaced with a test phantom having a known concentration of the marker material and a reference concentration standard (e.g., phosphate) having the same resonant nuclei as the CE. Both sets of MR response signals are again acquired. The volume of tissue contributing to the CE MR response signal in the subject is deduced from the ratios of marker material MR response signals from the subject and phantom and the known concentration of the test phantom.

Abstract: A lithology-independent method of well logging the gas saturation in a reservoir containing natural gas. The method makes use of a pulsed NMR logging tool utilizing a recovery time that is greater than the relaxation time of hydrocarbon gas within the formation. In a preferred embodiment, two different NMR logs are obtained: one with a recovery time significantly shorter than the longitudinal relaxation time, T1, of the gas and one with a recovery time equal to or longer than T1. The amplitudes of the two logs are subtracted and the remainder divided by the hydrogen index of the gas at reservoir conditions to determine the pore volume occupied by gas.

Abstract: Resonance magnetometer with optical pumping using a monolithic laser. The laser (30) includes a single element (32) (crystal or fiber) whose length is modulated to provide both a wavelength and amplitude control.

Abstract: A method of Nuclear Quadrupole Resonance testing includes the steps of applying to a sample in which selected nuclei have an integral spin quantum number a series of at least three pulses of electromagnetic waves at a single radiofrequency to excite quadrupole resonance of the selected nuclei, and detecting responses at a plurality of times when echo response signals are expected to occur.

Abstract: A long RF pulse is segmented into a plurality of RF pulses segments with nuclei spin refocusing pulses provided after each RF pulse segment to maintain phase coherence off resonance and decrease nuclei spin sensitivity to magnetic field inhomogeneity. The refocusing pulses are preferably 180.degree. rectangular pulses. Magnetic gradient segments associated with the RF pulse segments have supplemental gradients at the beginning and at the end of the gradient segment to ensure that the position in k-space for the segment corresponds to the k-space position of the gradient waveform before division into segments.

Abstract: A method to display with combined color multiple quantitative images of tissue parameters obtained with nuclear magnetic resonance. The method allows an increased diagnostic accuracy, a higher sensitivity to pathologies of small extent, a standardization of acquisition sequences and a shortening of the total line required for performing the examination to be realized.

Abstract: When a pulsed nuclear magnetic resonance (NMR) well logging tool is traversing a wellbore, a NMR well logging method includes magnetizing the hydrogen nuclei in a formation traversed by the tool with a static magnetic field, waiting for a first period of time W.sub.1, energizing the formation with oscillating RF pulses, collecting a first plurality of spin echo signals, waiting a second period of time W.sub.2 which is different from the first period of time W.sub.1, energizing the formation with oscillating RF pulses, collecting a second plurality of spin echo signals, waiting a third period of time W.sub.3 which is different from both the second period of time W.sub.2 and the first period of time W.sub.1, energizing the formation with oscillating RF pulses, collecting a third plurality of spin echo signals, etc. The first, second and third, etc. plurality of spin echo signals corresponding to the different wait times are input to a signal processing apparatus disposed in the tool.

Abstract: An RF front end unit (32) for a magnetic resonance imaging (MRI) system (20) has transmit and receive channels to which a plurality of coils (22) can remain attached during operation (including RF coils having differing types of matching circuits), and facilitates switching between a plurality of attached coils. Methods and apparatus are additionally provided for selectively tuning differing RF coils, including both high power coils (22B, 22C) and varactor-tuned coils (22D). The tuning of a high power coil involves using a remote impedance match tuning network (RTU) (26) for a coarse tuning operation and, if necessary, a fine tuning operation. In performing the coarse tuning operation separately for In-Phase ("I") and Quadrature ("Q") channels, a tuning controller (60) determines the effective load impedance of each of the RF coil channels by quadrature demodulation of their reflected signals.

Abstract: A quadrature coil system which includes the following elements. (1) First and second electric main conductors which are situated at a distance from one another in a first plane and a second plane, respectively, and each of which is formed as a loop with an opening, the main conductors having mainly the same orientation. (2) First and second connection conductors, each of which constitutes an electric connection between the free ends of the first and second main conductors, which free ends are situated to corresponding sides of the opening. (3) An electric connection device which is connected to the conductors so that first and second sets of turns are formed which are suitable to generate and/or receive first and second magnetic fields, respectively, which are mutually orthogonally directed.

Abstract: An MRI probe/transmitter coil has a pair of concentric cylinders with a plurality of inductively coupled freely rotating resonant elements radially mounted between the two cylinders. The coil can be tuned both symmetrically by pivoting all the resonant elements uniformly or asymmetrically by tuning them individually. The coil is driven in quadrature by a quad-hybrid circuit. A substantial part of the electromagnetic energy is stored in the resonant elements outside of the loading region of the coil to reduce perturbation in the coil operation due to the characteristics of the test subject.

Abstract: Process for the excitation and acquisition of NMR signals, particularly for the analysis of molecules dispersed in a solvent, such as for example water. A specimen to be analyzed is first subjected to a series of impulses (1) corresponding to a high resolution NMR test to be carried out. Then there is applied to the specimen a first pulsed field gradient (2) in a given direction, and then the specimen is subjected to a 180.degree. selective pulsed radiofrequency field (3) affecting all the spectrum except the resonance frequency of the water or corresponding solvent. Then a second pulsed field gradient (4) identical to the first is applied to the specimen. Then the acquisition and processing of the resulting NMR signals are effected.

Abstract: A high-frequency apparatus for nuclear spin tomography includes a high-frequency transmitter for exciting nuclear spin in a body to be imaged and a high-frequency receiver for detecting B-field components resulting from the nuclear spin. The high-frequency receiver includes a galvanically-separated local coil device having two antenna loops between which an amplifier unit is connected. The local coil device radiates new B-field components in response to the original B-field components caused by the nuclear spin excitation, with the new B-field components oriented substantially orthogonal to the original B-field components. The new B-field components are then received by an external receiving antenna for subsequent signal processing, ultimately resulting in an image of the body.

Abstract: An antenna arrangement for a magnetic resonance imaging apparatus is composed of an array having at least three linearly polarized local coils which mutually overlap to such an extent that they are geometrically decoupled. Each local coil is separately connected to a combination network wherein a complex operation between the output signals of the respective local coils is produced such that a radio-frequency signal corresponding to a circular polarization is obtained.

Abstract: When image information obtained on the basis of an NMR signal, e.g. MRI, is acquired, a radio frequency pulse is set so that a strong signal can be obtained particularly from a portion of interest among the sample. To accomplish this object, the occurrence of signals from portions of the sample other than the selected portion of interest is inhibited in advance of obtaining information (an image) of the sample. Various radio frequency pulses are then irradiated to the sample and a suitable radio frequency pulse is determined on the basis of the resulting signal.

Abstract: An assembly which generates a magnetic field in a working volume spaced from the assembly. The assembly includes first and second magnets, each having a north and a south pole and a respective magnet axis which joins the north and south poles, the first and second magnets being positioned so that the respective magnet axes are along a main axis of the assembly and a pole of the first magnet faces a like pole of the second magnet.

Abstract: A motion imaging method uses magnetic resonance to detect acceleration, and an velocity distribution within moving materials in a subject. Acceleration encoding is performed by computing differences of data obtained with modulated motion-encoding magnetic field gradient pulses. Distributions of velocity are measured responsive to a motion sensitive phase-encoding gradient pulse.

Abstract: An antenna arrangement for a nuclear magnetic resonance apparatus, the apparatus having a magnet which generates a basic magnetic field between two pole plates, includes a sub-antenna disposed at each pole plate, each sub-antenna being composed of a closed, grounded shielding facing toward the pole plate and a planar conductor structure disposed a distance from the shielding and substantially parallel thereto, into which a high-frequency current is fed.