Abstract: Disclosed is a radio frequency (RF) coil for magnetic resonance imaging (MRI), the RF coil including: a bow-tie antenna; and a loop coil.

Abstract: One example embodiment includes an atomic sensor system. The system includes a vapor cell comprising an alkali metal vapor that precesses in response to a magnetic field. The system also includes a probe laser that generates an optical probe beam that is modulated about a center frequency and which is provided through the vapor cell. A photodetector assembly generates an intensity signal corresponding to a Faraday rotation associated with a detection beam that is associated with the optical probe beam exiting the vapor cell. The system further includes a detection system configured to demodulate the intensity signal at a frequency corresponding to a modulation frequency of the optical probe beam and to generate a feedback signal based on the demodulated intensity signal. The feedback signal is provided to the probe laser to substantially stabilize the center frequency of the optical probe beam based on the feedback signal.

Abstract: A solid-state gyroscope apparatus based on ensembles of negatively charged nitrogen-vacancy (NV?) centers in diamond and methods of detection are provided. In one method, rotation of the NV? symmetry axis will induce Berry phase shifts in the NV? electronic ground-state coherences proportional to the solid angle subtended by the symmetry axis. A second method uses a modified Ramsey scheme where Berry phase shifts in the 14N hyperfine sublevels are employed.

Abstract: An atomic sensor system includes a magnetic field generator configured to generate a magnetic field along an axis and a probe laser configured to generate an optical probe beam. Beam optics direct the optical probe beam through a sensor cell comprising an alkali metal vapor such that the optical probe beam has at least a vector component along the axis. The system also includes detection optics comprising a photodetector assembly configured to measure a Faraday rotation associated with the optical probe beam exiting the sensor cell and to generate a feedback signal based on the Faraday rotation associated with the optical probe beam exiting the sensor cell. The system further includes a laser controller configured to modulate a frequency of the optical probe beam about a center frequency and to substantially stabilize the center frequency of the optical probe beam based on the feedback signal.

Abstract: The present invention relates to a vector magnetometer for measuring the components of an ambient magnetic field. This vector magnetometer comprises an optically pumped scalar magnetometer (2?), a pair of conductive windings (Ex,Ey) having distinct axes (Ox, Oy) and powered by two generators (Gx, Gy) having distinct frequencies. The RF coil (56) of the scalar magnetometer and the conductive windings (Ex,Ex) are mechanically integral with a swivel support (85) mounted on swivel means. The axis of the RF coil is in the same plane as the axes Ox, Oy. The support is swivelled so that this plane is substantially orthogonal to the ambient magnetic field.

Abstract: One embodiment of the invention includes a nuclear magnetic resonance (NMR) gyroscope system. The system includes a gyro cell that is sealed to enclose an alkali metal vapor, a first gyromagnetic isotope, and a second gyromagnetic isotope. A magnetic field generator configured to generate a magnetic field that is provided through the gyro cell to cause the first and the second gyromagnetic isotopes to precess. A magnetic field error controller configured to measure an error associated with a magnitude of the magnetic field and to generate an error signal that is fed back to the magnetic field generator to maintain the magnetic field at a desired magnitude. The system further includes a mechanization processor configured to calculate a rotation angle about a sensitive axis of the NMR gyroscope system based on a measured precession angle of at least one of the first and second gyromagnetic isotopes and the error signal.

Abstract: A system for and method of determining and compensating for the effect of a field influencing object on a field sensor, preferably a coil, that is within a navigational domain. The navigational domain contains navigational magnetic energy and disturbing magnetic energy, and the field influencing object produces the disturbing magnetic energy in response to the navigational magnetic energy. The correction system includes a first transmitter for projecting into the navigational domain field energy in a first waveform sufficient to induce a first signal value in the sensing coil. The system also includes a second transmitter for projecting into the navigational domain field energy in a second waveform sufficient to induce a second signal value in the sensing coil. The system further includes a signal processor for receiving the first signal value and for receiving the second signal value to determine the effect of the electrically conductive object on the field sensor.

Abstract: According to at least one embodiment of the invention, at least two excitation fields with frequencies capable of being differently prescribed act on the object in the examination space, with the gradient field approximately vanishing in the examination space. In another embodiment, an arrangement includes a Maxwell coil pair for generating an inhomogeneous magnetic field with a prescribable magnetic field gradient, at least one device for exciting two auxiliary fields with different frequencies and a detection coil for recording the response signal.

Abstract: The present invention relates to a novel manner of measuring DC fields using a multi-channel MEG or MKG measuring instrument; and on the other hand, to a manner of eliminating from the measurement result the interference signals caused by the DC currents. The invention combines the monitoring system of a testee's movement and the method for motion correction of the measured signals so that the signals produced by the DC currents of a moving testee's are visible in the final measurement result as a static signal component in a conventional MEG or MKG measurement. In that case, in the measurement, it is not necessary to beforehand prepare oneself for measuring the DC fields.

Abstract: An apparatus in one example comprises a polarization filter and a polarization analyzer. The polarization filter comprises a first polarization axis. The polarization analyzer comprises a second polarization axis. The polarization filter is configured to polarize detection light for a nuclear magnetic resonance (NMR) cell along the first polarization axis. The polarization analyzer is configured to receive the detection light from the NMR cell and pass a portion of the detection light to a processor for determination of angular rate information. The portion of the detection light passed to the processor is based on an orientation of the second polarization axis relative to the first polarization axis. The orientation is selected to maximize a signal-to-noise ratio of the detection light.

Abstract: A system for and method of determining and compensating for the effect of a field influencing object on a field sensor, preferably a coil, that is within a navigational domain. The system includes a first and second transmitter to create signals. A signal processor is able to process the created signals. The method can include determining interference and/or a correct signal based on the two signals. Also, a shield can be provided to limit transmission of selected fields.

Abstract: A method of solving magnetoencephalographic and electroencephalographic inverse problems provides better grouping of moments of equivalent current dipoles than conventional methods. Locations of dipoles are fixed based on information using fMRI or the like. The magnitudes and orientations of the dipole moments are adjusted to fit magnetic fields and/or electrical potential distributions produced by the dipoles to magnetoencephalographically and/or electroencephalographically measured data. The method also includes grouping the dipoles in two stages, using the correlation coefficient of the magnitudes of the dipole moments as a criterion.

Abstract: The present invention relates to a method and system in which multi-coherent resonances of a microwave in which the alkali-metal atoms in the ground state are driven simultaneously by a microwave hyperfine frequency ?H and a Zeeman frequency ?Z. The driving influences on the atom can include magnetic fields or by optically pumping light modulated by a Zeeman frequency ?Z or a microwave hyperfine frequency ?H or by combinations of their harmonics or subharmonics. Multi-coherent resonances permit simultaneous measurement or control of the ambient magnetic field and measurement or control of a hyperfine resonance frequency of alkali-metal atoms. In one embodiment, the hyperfine frequency for a controlled magnetic field can serve as an atomic clock frequency.

Abstract: An NMR gyroscope in one example comprises a support structure affixed within an enclosure, an NMR cell affixed to the support structure, a plurality of permanent magnets disposed about the NMR cell to produce a magnetic field within the cell, and a field coil disposed proximate the cell to produce a modulated magnetic field transverse to the magnetic field produced by the permanent magnets.

Abstract: A system for combining electromagnetic position and orientation tracking with magnetic resonance scanner is provided. One embodiment includes a magnetic resonance scanner defining a reference coordinate system for scanning a target. Coupled to the magnetic resonance scanner is a magnetic field source which produces a magnetic field. The magnetic field is sensed by a magnetic field sensor which produces a signal proportional to the magnetic field. The magnetic field sensor has a location relative to the reference coordinate system. The location of the magnetic field sensor relative to the reference coordinate system of the magnetic resonance scanner is determined by a location tracking device using at least a line segment model of the magnetic field source and the signal from the magnetic field sensor.

Abstract: MRI scans typically have higher resolution within a slice than between slices. To improve the resolution, two MRI scans are taken in different, preferably orthogonal, directions. The scans are registered by maximizing a correlation between their gradients and then fused to form a high-resolution image. Multiple receiving coils can be used. When the images are multispectral, the number of spectral bands is reduced by transformation of the spectral bands in order of image contrast and using the transformed spectral bands with the highest contrast.

Abstract: MRI scans typically have higher resolution within a slice than between slices. To improve the resolution, two MRI scans are taken in different, preferably orthogonal, directions. The scans are registered by maximizing a correlation between their gradients and then fused to form a high-resolution image. Multiple receiving coils can be used. When the images are multispectral, the number of spectral bands is reduced by transformation of the spectral bands in order of image contrast and using the transformed spectral bands with the highest contrast.

Abstract: A vectorial magnetometer (1), measures the components of a magnetic field in three directions (Oxyz) using a scalar magnetometer (2). The field is periodically modulated in each of the directions by generators (Gx, Gy, Gz) which have a specific frequency for each direction and that power coils (Ex, Ey, Ez). Synchronous demodulation of the of the output signal of the scalar magnetometer (2) for each of the three frequencies permits the relative continuous component of each axis to be found. The vectorial magnetometer (1) is characterized in that it has means (Dx D?x, Dy D?y, Dz D?z) that can carry out a double demodulation for phase and quadrature for each of the frequencies and processing means (70) that use the continuous component modules for phase and quadrature to calculate a transfer function of the scalar magnetometer at the frequency in question, and to apply this function to the correction of the components.

Abstract: The present invention provides a high sensitivity atomic magnetometer and methods of measuring low intensity magnetic fields that relate to the use of an alkali metal vapor and a buffer gas; increasing the magnetic polarization of the alkali metal vapor thereby increasing the sensitivity of the alkali metal vapor to a low intensity magnetic field; probing the magnetic polarization of the alkali metal vapor, the probing means providing an output from the alkali metal vapor, the output including characteristics related to the low intensity magnetic field; and measuring means that receives the output, determines the characteristics of the low intensity magnetic field, and provides a representation of the low intensity magnetic field. In addition, the invention relates to a magnetometer and methods that provide a representation of a first magnetic field originating within a sample volume. The sample volume may be part or all of a subject, such as a human subject.

Abstract: A magnetic resonance imaging apparatus includes a calculator that calculates the quantity of heat generated (or to be generated) in a gradient magnetic field coil as a function of current supplied (or to be supplied) to the gradient magnetic field coil and at least one other factor such as eddy currents induced in a shield body used for shielding gradient field leakage flux from the imaged volume and/or delayed measurement of actual coil temperature. Such improved more timely temperature prediction and/or measurement is used to effect protective actions to better prevent permanent coil damage due to overheating.

Abstract: The invention describes a system, method, and means for an MRI guidewire that can be visible on an MRI, can act as an antenna and receive MRI signals from surrounding subject matter, and can allow the use of multiple interventional tools without removal of the guidewire from a subject.

Abstract: Apparatus and method for detecting and quantifying magnetic field gradients by measuring the magnetic force acting on a mechanical oscillator with an attached spin-containing material (any material that displays a magnetic moment in the presence of a magnetic field) having a modulated magnetic moment with a temporal response that matches the resonance frequency of the mechanical oscillator. Modulation of the magnetic moment in the direction of the measurement is achieved by the action of a spatially uniform polarizing field with a temporal response that matches the resonance frequency of the mechanical oscillator.

Abstract: A method for use during a procedure on a body. The method generates a display representing relative positions of two structure during the procedure.

Abstract: A method of performing synthetic aperture magnetometery on the signals from a target organ using an array of biomagnetic sensors positioned in a predetermined manner around the target organ, each sensor in the array having a position vector and an orientation vector relative to a common coordinate system encompassing the target organ.

Abstract: A magnetometer for, among other things, measuring a magnetic field, associated with nuclear magnetic spins or electron spins receives a specimen of a material that exhibits nuclear magnetic resonance or electron spin resonance at a resonant frequency &ggr;·Bm that is dependent on a magnetic flux density Bm of the magnetic field to be measured. The magnetometer has a transmission device for emitting a transmission signal into the specimen at at least one prescribable transmission frequency &ohgr;1 that has a frequency spacing from the resonant frequency &ggr;·Bm, and a reception device for receiving a mixed signal with mixed frequencies containing the resonant frequency &ggr;·Bm and the transmission frequency &ohgr;1 and for filtering out the resonant frequency &ggr;·Bm from at least one of the mixed frequencies as an indicator for the magnetic flux density Bm.

Abstract: A nuclear magnetic resonance probe is provided comprising a high frequency resonator (14, 16) having a resonant frequency, a first coaxial conductor (20) connected to the high frequency resonator, and a high frequency supply which supplies the first coaxial conductor (20) the resonant frequency of the high frequency resonator (14, 16). The high frequency supply includes a conductive sampling loop (40) at least partly placed in the high frequency resonator (14, 16) and a broad band, high frequency, amplifier (56) having an input (E) connected to the sampling loop (40) by a second coaxial conductor (50) and an output (S) connected to the first coaxial conductor (20). The assembly forming a high frequency loop oscillator locked to the resonant frequency of the high frequency resonator (14, 16).

Abstract: The magnetometer according to the invention comprises a logic unit (50) receiving a resonance detection signal, a digital processor (60) supplying a number N, a digital-analog converter converting said number into current for establishing a feedback. The measurement of the field is directly digitally given by the processor.Use in magnetometry.

Abstract: A permanent magnet for nuclear magnetic resonance imaging that provides an intense and highly homogeneous magnetic magnetic field is disclosed. The magnet is made up of a set of rings having two sub-sets of rings of permanently magnetized polygonal blocks, wherein the rings of a sub-set of rings are substantially concentric. In addition, the rings of the two sub-sets are complementary in terms of magnetization. Each ring of a sub-set is separated from its complementary ring by a space that is substantially the same for all pairs of complementary rings. The rings have a regular polygonal structure and are made up of blocks that also have regular polygonal shapes.

Abstract: A method and an apparatus are disclosed serving to localize proton-poor objects situated in aqueous surroundings, in particular to localize submarines or sea mines in an ocean or an inland water. By using a nuclear magnetic proton resonance technique, a magnetic disturbance caused by the proton-poor object in relation to its proton-rich aqueous surroundings is detected. The apparatus comprises at least one transmission coil for exciting the nuclear resonance by means of an alternating electromagnetic field and comprises detection means for detecting nuclear magnetic resonance signals. The transmission coil generates conditions in the aqueous surroundings in which water proton nuclear magnetic resonance occurs in a volume region of more than 50 cubic meters, preferably considerably more than 1000 cubic meters of water. The volume region is monitored for the presence of nuclear magnetic resonance signals and a predetermined decrease in such resonance signals is detected.

Abstract: A magnetometer for precise measurement of weak magnetic fields involves a system which injects a plurality of light beams into a gas containing cell. An optical multiplexer receives the light beams emitted by a source and successively supplies a plurality of light beams which traverse a corresponding number of polarizers. The beams are subsequently injected into the cell 10 in the plurality of different directions in order to optically pump the gas. A detection device detects an electrical resonance signal and supplies a plurality of signals corresponding to the optical pumping beams.

Abstract: A magnetometer having three trirectangular trihedron windings (20x, 20y, 20z) which are put into service successively by a multiplexer (50). The means frequency (F.sub.m) of the three measurement signals is independent of the orientation of the weak magnetic field which is to be measured.

Abstract: An improved optical pumping magnetometer with sequential polarization for measurement of weak magnetic fields involves a device which sequentially modifies the polarization either in the direction of the polarization or from clockwise to counterclockwise circular polarization. As a result of the sequential modification of the polarization, the magnetometer for measurement of the weak magnetic fields has excellent isotropy while still retaining a simple construction and a small overall dimension to the device by using only a single cell.

Abstract: It is used for measuring a magnetic-field Hlex, which is the projection, in a given direction, of a field Hex and which incorporates a sample (2) containing resonant spins, first means (4) for exciting the resonance and detecting the latter, second means (32) for producing a polarization field Hb in accordance with the direction and compensating Hlex, processing and closed loop control means (6, 8, 16 to 20, 34 to 38, 48 to 52, 40, 44), which are connected to the first and second means and which make it possible to obtain voltages proportional to Hb-Ho+hlex and to Ho-Hb+Hlex in the vicinity of the resonance, Ho being the value of the field at resonance, with Ho being well above Hex, and a pulsed square-wave current for inducing Hb and for supplying a voltage proportional to Hlex in particular to the second magnetic means.

Abstract: An improved shielded magnetometer including a resonant probe containing a magnetically resonating material held in a resonator. The magnetometer has a spherical electromagnetic shield which exhibits improvements in the sensitivity characteristics by removing the effects of interference fields when the magnetometer is rotated about its axis.

Abstract: A conventional magnetometer produces an output signal (10) which comprises a series of pulses (12, 14, 16). Each of these pulses has a beat frequency maximum. These pulses are input to a comparator (50) which makes a comparison to a threshold voltage V.sub.0 to produce a bi-level detected signal at a line (62). The detected signal is input to an integrator (52) which produces a series of pulses (78, 80, 82) corresponding respectively with the magnetometer output signal pulses (12, 14, 16). The two states of the detected signal corresponding to positive and negative integration. The time period for the positive integration is proportional to the beat frequency maximum time width period for the corresponding magnetometer output signal pulse. Thus the integrated pulses (78, 80, 82) have an amplitude which is a measure of the maxima time width periods for the corresponding magnetometer signal pulses.

Abstract: A nuclear magnetic resonance gyroscope which derives angular rotation thef from the phases of precessing nuclear moments utilizes a single-resonance cell situated in the center of a uniform DC magnetic field. The field is generated by current flow through a circular array of coils between parallel plates. It also utilizes a pump and readout beam and associated electronics for signal processing and control. Encapsulated in the cell for sensing rotation are odd isotopes of Mercury Hg.sup.199 and Hg.sup.201. Unpolarized intensity modulated light from a pump lamp is directed by lenses to a linear polarizer, quarter wave plate combination producing circularly polarized light. The circularly polarized light is reflected by a mirror to the cell transverse to the field for optical pumping of the isotopes. Unpolarized light from a readout lamp is directed by lenses to another linear polarizer.

Abstract: In order to provide an all-angle gradient magnetometer, first and second magnetic resonance cells are mounted to a common base and separated by a predetermined distance. Circularly polarized pumping light is passed through the two cells orthogonally. Mixed with the circularly polarized pumping light is readout light which is linearly polarized. At the output of the cells appropriate filters are provided to filter out the pumping light whereafter the modulated readout light is detected in push-pull manner and fed back to modulate the pumping beams and at the same time fed to signal processing means to permit detecting phase differences between the outputs of the separated cells.

Abstract: A magnetic field detector for determining the presence of a magnetic field disturbance in the vicinity of the apparatus senses the difference in magnetic fields at two spaced-apart locations. A pair of field sensors, each including a body of polarizable liquid and a probing coil, are connected in series and provide an output signal that is produced in the coils by the free procession of the protons of the liquid bodies in the earth's magnetic field. A timer circuit controls a relay to alternately connect the magnetometer coils to a source of polarizing current during a polarizing period, and to detection circuitry during a listening period. The detection circuitry includes a high gain signal channel comprising a multi-stage, high input impedance preamplifier and a bandpass amplifier tuned to the frequency range of the signals generated in the probing coils.

Abstract: A cryogenic nuclear gyroscope comprises a cylinder of niobium cooled within a helium cryostat so as to be superconducting and to provide a trapped, substantially homogeneous magnetic field, a helium-3 sample contained within a spherical pyrex cell having nuclei possessing a net magnetic moment, coils provided to polarize the sample to provide that net magnetic moment, a SQUID magnetometer coupled to the sample by a pick-up coil of a transformer and frequency sensitive means coupled to the SQUID to detect changes in the precession of the nuclear moments of the sample caused by rotation of the gyroscope about an axis parallel to the direction of the homogeneous magnetic field. A superconducting lead shield isolates the helium-3 sample from external magnetic fields.