Abstract: A process for frequency tuning microwave bridges and a device for practicing such a process. The process is characterized in that it consists in subjecting a resonator (3) to the radiation delivered by a secondary microwave source (10) sweeping a wide band of frequencies comprising particularly the frequency (F) of radiation delivered by the principal microwave source (1). The radiation reflected by the resonator (3) is displayed and the relative positions are marked along the frequency spectrum, of the frequency (F) and of the frequency of resonance (Fr) of the resonator (3). The frequency (F) of radiation delivered by the principal microwave source (1) is varied while controlling in real time the effect of this variation on the relative positions of the frequencies (F and Fr).

Abstract: A magnetic resonance imager has a magnetically permeable core and two pole pieces, each pole piece having a face. The pole pieces are arranged on the core such that the pole piece faces are in opposed relationship forming a first gap therebetween. At least one of the pole pieces is comprised of an outer element 23 connected to the core and an inner element 24 connected between the outer element and the first gap. The outer element 23 forms a cup inside which the inner element 24 is disposed. A plurality of screws 11, 12 and 13 are disposed through the outer element 23 and engage the inner element 24 such that a second gap is formed between the inner and outer element. The homogeneity of the magnetic field in the first gap is affected by adjusting the position of the inner element relative to the outer element via screws 11, 12 and 13.

Abstract: To generate a magnetic resonance image of a region comprised of two species of nuclei that have non-identical Larmor frequencies, the nuclei are excited and two read-out gradient pulses are generated. The relative phase offset between the two species of nuclei is different at the center of the first pulse than at the center of the second pulse. Data acquired during the two read-out pulses are processed in accordance with these relative phase offsets.

Abstract: A system having a battery, a battery support unit, and an electronic device provides for the exchange of information between the battery support unit and the electronic device via a mailbox in memory in the battery. When the battery is placed in the battery support unit, the battery support unit tests the battery for an error condition. If the battery support unit finds an error condition with the battery, it transmits error data to a mailbox located in the battery's memory. When the battery is then removed from the battery support unit and placed in an electronic device, the electronic device can read the error data in the mailbox and take an appropriate action. For example, the electronic device reads the mailbox and find the error data placed there by the battery support unit. In response to finding this error data, the electronic device enables an indicator, such as an indicator that informs a user that maintenance needs to be performed on the battery.

Abstract: A Z-axis magnetic field gradient coil structure for producing a desired magnetic field gradient without increasing the electrical resistance of conductors forming a coil pattern. The coil structure comprises a flexible insulative substrate to be wound on a cylindrical bobbin. The substrate is several times as long as the circumference of the bobbin. The coil pattern is formed on the substrate by etching techniques and comprises pairs of conductive strips and conductive interconnectors for interconnecting these strips. The pairs of conductive strips are symmetrical with respect to the central line of the pattern.

Abstract: The invention describes an improved NMR imaging technique having particular application in imaging of solid objects using gradient echo techniques. By applying a so called 90.degree. rf pulse substantially at zero gradient crossing it is possible to obtain frequency encoded information about an object being imaged, using a so called gradient echo technique. However, profile degradation occurs as a result of the very large magnetic fields which are used which spoil the rf pulse. By shortening the length of pulses below 90.degree. it has been possible to improve gradient echo imaging. However, this has resulted in the reduction in the signal-to-noise ratio of the echo following each pulse. The present invention overcomes this problem by providing a rapidly oscillating magnetic field gradient and applying a radio frequency pulse away from a zero gradient crossing and by substantially phase rotating the resultant profile.

Abstract: A coil element, comprising a quadrature surface coil, includes side by side loops, slightly overlapped to the degree necessary to cancel mutual inductance. A coil includes a split-capacitor configuration for balanced-to-unbalanced conversion between the coil and a coaxial cable, without interfering with the highly magnetic environment of a magnetic resonance imaging system. A coil includes multiple diodes and current stabilizing impedances in parallel, or alternatively a combination of a fast low-power PIN diode and a slow high-power diode to effectively multiply the power handling capability of fast diodes for passive decoupling in a decoupling circuit for reducing the risk to the patient over active decoupling. A coil includes a counter-rotating decoupling circuit to cancel the effects of decoupler radiation, and to prevent lowering of the quality factor of the decoupling circuit and the detection of undesirable image artifacts.

Abstract: A method and an apparatus are disclosed for detecting an atomic structure of a sample along a surface thereof. The method comprises arranging the sample in a constant magnetic field (B.sub.0) of predetermined field strength and high homogeneity and irradiating a high-frequency magnetic field (B.sub.1) of a predetermined frequency on the sample, wherein the fields (B.sub.0) and (B.sub.1) are oriented perpendicularly to each other. The method further comprises providing a force-sensitive sensor having a paramagnetic tip comprising a paramagnetic material. The sensor is placed in close vicinity to the sample such that the paramagnetic tip is in atomic interaction with the sample surface which means that the distance between the tip and the surface is in the order of between 1 and 10 .ANG.. The predetermined field strength and the predetermined frequency are set such that electron paramagnetic resonance (EPR) is excited within the tip paramagnetic material.

Abstract: The invention relates to a method of determining prefocused pulses with sufficiently low power and short duration to allow multi-slice in-vivo spectroscopic imaging of humans. The method has two main stages, analytic and numerical. In the analytic stage a magnetization response is selected with certain desired characteristics such as prefocused time. During the numerical stage, the response is then transformed into an RF pulse for use in magnetic resonance imaging. The theoretical response to the RF pulse is evaluated and characteristics such as duration and amplitude may be altered to meet further requirements. The theoretical response is then transformed into an RF pulse for use in magnetic resonance imaging or for further application of the numerical stage.

Abstract: Improvement of the ability to detect selected resonant frequencies associated with the position of the piston in a piston position sensing system using electromagnetic waves in the fluid in a hydraulic cylinder is achieved by positioning the electric signal input and output probes with 90 degree separation around the circumferential periphery of the cylinder to suppress coupling into unwanted modes that diminish detectability of particular resonant frequency signals, In a coaxial sensing system "dummy" probes at 90 degree separation to each other and 90 degree separation to the input and output probes operate to improve symmetry and resonance shape and to suppress unwanted modes.

Abstract: A fast and robust method for correcting magnetic resonance image distortion due to field inhomogeneity is applied to spiral k-space scanning. The method includes acquiring a local field map, finding the best fit to a linear map, and using the linear field map to deblur the image distortions due to local frequency variations. The linear field map is determined using a maximum likelihood estimator with weights proportional to the pixel intensity. The method requires little additional computation and is robust in low signal regions and near abrupt field changes. The application of this method is illustrated in conjunction with a multi-slice, T2-weighted, breath-held spiral scan of the liver.

Abstract: A superconducting magnet (10) generates a uniform, static magnetic field through a central bore (12) along its longitudinal or z-axis. An insertable coil assembly (40) is inserted into the bore with a radio frequency shield (76, 84) for providing a radio frequency shield between the insertable coil assembly and a surrounding, whole body radio frequency coil assembly (32) and a whole body gradient magnetic field coil assembly (30). The insertable coil includes a gradient coil (44a) including conductors (52) mounted on a dielectric former (50) with a dielectric constant below 4.0. The conductors are relatively narrow and spaced relatively far apart to minimize capacitive coupling with a closely adjacent insertable radio frequency coil (70a). Filters (60, 64) are connected with the conductors of the gradient coil to prevent the gradient coil conductors from supporting radio frequency signals while permitting ready support of kHz frequency currents.

Abstract: One aspect of the present invention is a method for detecting a class of target species containing quadrupolar nuclei in a specimen by nuclear quadrupole resonance, comprising: (a) generating a random or pseudo-random train of rf pulses; (b) irradiating the specimen with the train of rf pulses; (c) detecting an NQR signal in response to irradiating the specimen; (d) cross-correlating the NQR signal with the random or pseudo-random train of rf pulses, thereby generating a free induction decay signal; and (e) converting the free induction decay signal into a frequency domain signal. Another aspect of the present invention is an apparatus for carrying out the method of the invention.

Abstract: An inspection method by means of an inspection apparatus using nuclear magnetic resonance and having magnetic field generating apparatus for generating a static magnetic field, gradient magnetic fields and an RF magnetic field; magnetic field generating apparatus by means of additional shim coils, which vary homogeneity of the static magnetic field by varying current flowing therethrough; signal detecting apparatus for detecting nuclear magnetic resonance signals from an object to be inspected; an apparatus for processing signals detected by the signal detecting apparatus; and control apparatus for controlling currents flowing through the shim coils, which method using nuclear magnetic resonance comprises a step of storing shim currents corresponding to each of a plurality of slices, capable of improving homogeneity of the static magnetic field for each of the plurality of slices, and a step of switching over the shim currents to those corresponding to a relevant slice to be measured prior to measurements of

Abstract: A single-mode semiconductor laser for optical pumping in H.sup.e and .sup.4 He and high-sensitivity magnetometers based upon these systems. A distributed Bragg reflection (DBR) or distributed feedback (DFB) single mode, preferably InGaAs laser diode (1) which obviates the need for optomechanical arrangements and their inherent instabilities as required by the prior art laser pumped magnetometers. By constructing a DBR or DFB region (28) within the laser diode structure, the laser is forced to operate within a single-mode at a wavelength that is jointly determined by the gain of the laser medium and feedback from the Bragg grating. This wavelength is controllable in one of three ways: (1) temperature control (13) of the laser diode junction and grating, (2) injection current control (12) within the gain region, (3) current control (11) of the Bragg grating region or any combination of the three.

Abstract: In a magnetic resonance imaging apparatus, a radio frequency coil (40) is disposed closely adjacent the patient's head. The radio frequency coil includes a first annular ring (80, 114) around the patient's head from which a first plurality of legs (82, 116) extend. Opposite legs are interconnected equidistant from the first annular ring to form a virtual ground connection (84, 118). In the embodiment of FIG. 6, a second annular ring (120) is disposed parallel to the first annular ring with a second plurality of legs (122) extending between the first and second annular rings. By adjusting a ratio .rho. of the current flow in the loops defined by the first legs, the first annular ring and virtual ground relative to the current loops defined by the second legs and the first and second annular rings, the linearity of the B.sub.1 field within the head coil is selectively adjustable (FIG. 8).

Abstract: In a magnetic resonance imaging system, a read gradient scaler (102) scales the amplitude and width of read gradients (78, 82, 84). A sampling rate control (104) controls the sampling rate of the resonance signals received from corresponding magnetic resonance echoes (80 54, 86). For example, when the amplitude of the gradient pulse is doubled and its width halved, the sampling rate of the resultant magnetic resonance signal is doubled, e.g., from a bandwidth of 32 MHz to a bandwidth of 64 MHz. In this manner, some echoes are read-out over a longer period of time with a lower bandwidth to produce lower signal-to-noise data lines; whereas, other echoes are much shorter and are read-out more quickly, but with a lower signal-to-noise ratio.

Abstract: In a magnetic resonance apparatus including a transducer (25, 31 ) positioned in the examination region of the apparatus, the transducer is connected with equipment (49) outside the examination region by way of a lead (47) which is grounded (51, 53) to signals of the frequency of the RF field applied to a subject (5) in the examination region to excite magnetic resonance in the subject, at a distance along the lead from the transducer equal to a quarter wavelength at the RF field frequency (or an odd multiple thereof). Distortion of the RF field due to loading by the transducer is thereby reduced. The transducer may, for example, be a microphone or loudspeaker, e.g. incorporated in an intercom or active noise reduction arrangement, or a sensor for sensing a condition of a patient being examined.

Abstract: A low power, low cost, millimeter wave (MMW) proximity sensor that provides over a 6:1 increase in minimum detection range (55 mm minimum) compared to standard 18 mm inductive proximity sensors preferably includes a low cost MMW Gunn oscillator, MMW detector and analog processing/driver circuitry. The sensor is preferably designed for 3-wire operation and will fit in a standard 18 mm tube.

Abstract: The invention provides a cavity resonator for an electron spin resonance device in which modulation coils for generating a modulation magnetic field to be applied to a sample in the cavity resonator are arranged at an exterior of the cavity resonator. The cavity resonator comprises a body being rectangular-defined by predetermined length, width and height. The body has a pair of side walls being vertical to the modulation magnetic field. The side wall respectively have at least thin portions of a thickness being nearly equal to or less than a skin depth of a skin effect appearing at the side walls. The modulation coils are arranged on the thin portions so as to have the modulation magnetic field be transmitted through the thin portions into the interior of the cavity resonator. Alternatively, it is possible that inner walls of the body are overlaid with metallic foils having at least sufficiently smaller thickness than a skin depth of a skin effect appearing at the walls.