Abstract: This invention concerns a new embodiment of the instrument to measure nuclear polarization described in U.S. Pat. No. 6,356,080. The coil, that couples the nuclear polarized substance to the electronics, has been designed not to pick up ambient electromagnetic noise. The output from the low level oscillator is passed through a Schmidt trigger to reduce noise. A local oscillator beats with the output of the low level oscillator to provide an audible output. The instrument is automated, using a microprocessor with a customized downloaded program, to control the operation of the instrument and to output the results of measurement to a liquid crystal display and, if desired, to an external computer. This computer is not necessary and the instrument can act as a stand alone.

Abstract: In a method for magnetic resonance imaging of at least a portion of a body placed in a stationary and substantially homogeneous main magnetic field, the body is subjected to a sequence of RF and magnetic field gradient pulses during an interval TSE, thereby generating a plurality of spin echo signals, which are measured and processed for reconstruction of an image. Thereafter, during an interval TDRV, an additional spin echo is generated by subjecting the body to at least one further refocusing RF pulse and/or magnetic field gradient pulse, and a RF drive pulse (?X) is irradiated at the time of this additional spin echo. In order to provide a fast and reliable method for T1-weighted imaging, which gives a high T1 contrast and also a sufficient signal-to-noise ratio, the phase of the RF drive pulse (?X) is selected such that nuclear magnetization at the time of the additional spin echo is transformed into negative longitudinal magnetization.

Abstract: Multi-modal coils for coupling MRI RF signals from an anatomical region(s) to be imaged. The coil includes a segmented annular base ring conductor including a plurality of capacitances disposed between the segments, and at least one arcuate conductor symmetrically connected at each end to the base ring, one end terminating in direct contact with the base ring, the other end electrically connected to the base ring via two of the capacitive electrical connections. The RF coil is operable in multiple receiving modes in phase quadrature to establish a rotating magnetic field phasor orthogonal to the temporally constant uniform magnetic field of the magnetic resonance instrument. The RF coil can be combined with a second RF coil to simultaneously image two anatomical regions.

Abstract: An improved raster magnet driver for a linear particle beam is based on an H-bridge technique. Four branches of power HEXFETs form a two-by-two switch. Switching the HEXFETs in a predetermined order and at the right frequency produces a triangular current waveform. An H-bridge controller controls switching sequence and timing. The magnetic field of the coil follows the shape of the waveform and thus steers the beam using a triangular rather than a sinusoidal waveform. The system produces a raster pattern having a highly uniform raster density distribution, eliminates target heating from non-uniform raster density distributions, and produces higher levels of beam current.

Abstract: For the purpose of RF pulse tuning so as to effectively utilize the capacity of an RF transmission apparatus, in tuning the RF pulse for excitation use so as to make the flip angle of spins identical with its target value, the pulse width of the RF pulse is consecutively increased from its predetermined initial value until the flip angle of spins become identical with its target value (902 through 912). Further, if the flip angle fails to reach its target value even though the amplitude of the RF pulse is raised to the adjustable maximum, the next increment of the pulse width is determined according to the extent of failure to attain the target.

Abstract: At least one quantity which is characteristic of the temperature-dependent magnetic properties of magnetizable material which interacts with the magnetic fields of a magnetic resonance imaging device is determined in order to compensate the temporally varying strength of the main magnetic field of a main magnet of such a device. On the basis of this quantity a compensation signal is formed for the correction of the influence of the varying field strength on the imaging result.

Abstract: A method and an apparatus for using hyperpolarized xenon-129 and magnetic resonance imaging or spectroscopy as a probe to non-invasively and non-destructively characterize important properties of certain structures or materials with high spatial and temporal resolution, resulting in high-resolution magnetic resonance images wherein the associated signal intensities reflect a property of interest of at least one of the compartments. Hyperpolarized xenon-129 is introduced into two compartments between which xenon-129 can be exchanged, for example, into the blood vessels of mammal organs and the tissue of said organ or into compartments within inorganic objects. Due to chemical shift and applied magnetic field strength, the hyperpolarized xenon-129 introduced into the first compartment has a different resonant frequency from the hyperpolarized xenon-129 introduced into the second compartment.

Abstract: At least one quantity which is characteristic of the temperature-dependent magnetic properties of magnetizable material which interacts with the magnetic fields of a magnetic resonance imaging device is determined in order to compensate the temporally varying strength of the main magnetic field of a main magnet of such a device. On the basis of this quantity a compensation signal is formed for the correction of the influence of the varying field strength on the imaging result.

Abstract: In order to nullify the adverse effect of an external magnetic field on a static magnetic field generated in an MRI system, small-size coils are used to generate a compensation magnetic field. Thus, the component of the static magnetic field to be applied to a magnetic sensor is canceled. The magnetic sensor can therefore detect the external magnetic field highly precisely. A correction current proportional to the external magnetic field detected highly precisely is fed to BO correction coils. Eventually, the external magnetic field that adversely affects the static magnetic field is canceled.

Abstract: The present invention relates to devices and method for melting solid polarised sample while retaining a high level of polarisation. In an embodiment of the present invention a sample is polarised in a sample-retaining cup (9) in a strong magnetic field in a polarising means (3a, 3b, 3c) in a cryostat (2) and then melted inside the cryostat (2) by melting means such as a laser (8) connected by an optical fibre (4) to the interior of the cryostat.

Abstract: For the purpose of efficiently correcting a quadratic term component of a static magnetic field, when an inhomogeneity error of a static magnetic field generated by a pair of magnets (102) supported by yokes (202, 204) so that the magnets face each other across a space is to be corrected, a quadratic term component of the static magnetic field is corrected by a quadratic term component of a magnetic field generated by a pair of circular loop coils (104), and a zero-th order term component of the magnetic field from the pair of circular loop coils is compensated by a zero-th order term component of a magnetic field generated by coils (114) wound around the yokes (204).

Abstract: A magnetic resonance method is described for forming a fast dynamic image with an automatically generated grid of essentially orthogonally arranged grid lines by a saturation information induced over the object to be imaged. Therefore a first set of parallel saturation planes is obtained by applying a first nonselective RF pulse with a flip angle of 90°, an intermediate magnetic field gradient pulse in direction of the spatial modulation, and a second nonselective RF pulse with a flip angle of 90°. A subsequent spoiler gradient pulse is applied in the direction of the magnetic field gradient for slice selection. Subsequently a second set of parallel saturation planes is obtained in the same manner by inverting one second RF pulse with respect to the first RF pulse. Further the first and the sets of saturation planes are subtracted from each other to obtain a grid free of any contribution of relaxation components of magnetization.

Abstract: An MR imaging pulse sequence provides a method for simultaneous data acquisition from more than one independently prescribed volume while providing optimized field uniformity during both the magnetization preparation and data acquisition parts of the acquisition. The method is based on the use of a multi-element array coil where individual RF coil elements are more sensitive to one of the separate volumes of interest than to the other volumes. In the example of breast imaging, one scenario would have two coil elements that are designed to be most sensitive to the signal from the left breast, and two coil elements that are designed to be most sensitive to the signal from the right breast. An optimized pulse sequence and reconstruction technique is used to simultaneously acquire two separate sagittal imaging volumes corresponding to the left and right breasts with optimized fat suppression.

Abstract: A combustionless BTU meter utilizes Nuclear Magnetic Resonance (NMR) spectroscopy to measure the concentrations of the component parts of a heterogeneous gas. Measurement of the gas component concentrations allow for subsequent calculations of British Thermal Unit/Cubic Foot (BTU/CF) from the measured component parts. Static pressure and temperature are also measured. Gas concentrations are preferably combined with static pressure and temperature, to calculate other characteristics of British Thermal Unit/Pound (BTU/lb), molar mass, relative density, and absolute gas density. A method for measuring heat production is also disclosed.

Abstract: At least one quantity which is characteristic of the temperature-dependent magnetic properties of magnetizable material which interacts with the magnetic fields of a magnetic resonance imaging device is determined in order to compensate the temporally varying strength of the main magnetic field of a main magnet of such a device. On the basis of this quantity a compensation signal is formed for the correction of the influence of the varying field strength on the imaging result.

Abstract: In a method for prescribing an essentially linear ramp with a prescribable slope by a quantity, and which is clock-pulse-controlled and which describes the ramp by an increment per clock interval, the ramp is described by a number of regular increments and by at least one first and one second irregular increment. The regular increments exhibit a value corresponding to the prescribable slope. The irregular increments exhibit a value deviating from the prescribable slope. The first irregular increment is a first increment describing the ramp and the second irregular increment is a last increment describing the ramp.

Abstract: Microcoils can be used in medical devices to enhance RF response signals and to create fields to enhance imaging capability in MRI imaging systems. An improved microcoil design includes a device to be inserted into a patient comprising a solid body having at least one pair of radially opposed microcoils physically associated with the solid body, each microcoil having an outside microcoil diameter of 6 mm or less, individual windings of each microcoil together defining a geometric plane for each microcoil, and the plane of each microcoil being parallel to the plane of another microcoil in the pair of radially opposed microcoils.

Abstract: A method of, an and apparatus for, creating an image of currents flowing through current paths in a microelectronic circuit such that the image of the currents has improved spatial resolution using filters. The filters increase the spatial resolution and eliminate noise and edge artifacts in magnetic field and electric field images of electronic circuits. In accordance with the method, a magnetic field image is created with a scanning SQUID microscope. A magnetic inversion technique is then used to convert the magnetic field image into a current density image. The current density image is filtered based upon known restrictions on the wiring geometry of the microelectronic circuit being imaged. The technique can also be applied to convert electric fields of a circuit from a scanning single electron transistor microscope into images of the voltage levels on the wires in the circuit.

Abstract: Microcoil designs are provided that enable unique RF response Field profiles that are particularly useful in MRI imaging procedures, particularly where fields of view outside of the medical device are desirable. These devices are particulatly for use within an organism, the device comprising an element having at least one RF receiver, the coils of said microcoils defining a cross-section that lies in a plane oriented at 0 to 90 (or 0 to 80) degrees to the longest axis of the device. Another way of describing the device is as a device for use in an organism, the device comprising an element having at least one wound microcoil with at least three windings on the microcoil. Each winding has an aspect ratio of greater than one. The aspect ratio of each winding is measured as the ratio of longest to shortest dimension in a cross section situated approximately transverse to the winding axis of the coil windings, the winding axis also being transverse to the longest axis of said device.

Abstract: In a method for correcting artifacts in magnetic resonance images that are caused, in a magnetic resonance device, by transverse magnetic field components that are oriented transverse to a basic magnetic field of the magnetic resonance device, wherein the magnetic resonance device has a gradient coil system for generating magnetic gradient fields and a high frequency transmitter for exciting magnetic resonance signals, during a measurement sequence a frequency correction value is fed to the high frequency transmitter for a correction area, this frequency correction value being determined dependent on the transverse magnetic field components, and/or an additional gradient field is produced for compensating the transverse magnetic field components.

Abstract: A method for reducing ringing in nuclear magnetic resonance measurements is disclosed. The method includes inducing a static magnetic field in a sensitive volume to orient nuclear magnetic spins of nuclei in the sensitive volume. The nuclear spins are reoriented by a first selected angle. An amplitude of the static magnetic field is then adjusted to cause a first selected phase shift in a spin echo signal measured subsequently to the reorienting by the first angle. The spins are then reoriented by a second selected angle, and a first spin echo signal is detected. After a selected wait time, reorienting by the first selected angle is repeated. Adjusting the amplitude of the static magnetic field is then repeated to cause a second selected phase shift in a subsequently measured spin echo. The first and second selected phase shifts have a difference between them of an odd numbered multiple of 180 degrees. Reorienting by the second selected and detecting a second spin echo signal are then repeated.

Abstract: A method for eliminating then on-MG component in RARE imaging that does not require a poor slice profile or discarding a substantial number of echoes (FIG. 2). This method relies upon the observation that the magnetization in each component is determined by the phase at one half of the echo time before the first refocusing pulse. A ninety degree pulse applied at this time will rotate one of the components to the longitudinal axis where it will be invisible in the subsequent sequence, (b RF). If the phase of the ninety degree pulse is the same as that of the refocusing pulses, then it will be the non-MG component that is eliminated. The combination of the tailored RF train and this ninety degree pulse permits acquisition of data from the very first echo without artifact (FIGS. 2, 4).

Abstract: An MRI apparatus and method for reducing wrap around artifacts during image reconstruction is provided. An RF coil and control configuration includes a center coil and at least one pair of end RF coils configured to encode and excite spins over an adjustable field-of-view (FOV). The adjustable FOV has at least two size designations in response to an FOV size request input. The control connected to the RF coil assembly is capable of switching between the FOV size designations by switching power to activate a center coil alone or the center coil in conjunction with the end coils in unison.

Abstract: A plurality of magnetic field induction coils and a radio frequency (RF) detection coil are supported by a frame which is inserted into the bore of an MRI system to detect magnetic fields produced by gradient pulses and RF pulses produced during a scan. The detected magnetic fields are processed to produce gradient waveforms and RF pulse waveforms that are displayed to the user.

Abstract: A magnetic field imaging apparatus for sensing a magnetic field generated by current flowing in the semiconductor device includes a pair of sensing devices which may be focused at a chosen depth in a semiconductor device. The sensing devices may be movable so that they may be focused at different focal points. The apparatus may also include three or more sensing devices, which can be chosen to operate in tears to define a variety of focus depths in a semiconductor device.

Abstract: A device for measuring the polarization of a hyperpolarized resonant substance; in a particular embodiment a hyperpolarized noble gas. A specimen of the hyperpolarized substance is made one component of a coupled oscillator, the other component being a resonant electric circuit. Such a coupled system has, in general, two stable modes of oscillation, and their frequencies are related to various parameters of the system, including the polarization of the specimen of hyperpolarized substance. The polarization can therefore be deduced from these frequencies.

Abstract: An apparatus for tuning and/or matching a RF coil in a NMR probe comprising a first variable capacitor electrically connected to the coil and a first motor capable of coupling to the first variable capacitor. The first motor when coupled to the first capacitor adjusts a capacitance associated with the first capacitor. The first motor is capable of operating in a strong magnetic field and is capable of not disturbing homogeneity of said magnetic field when said motor is not operating. The apparatus may further include a second variable capacitor and a second motor. The first motor is further capable of coupling to the second capacitor for adjusting a capacitance associated with the second capacitor. The second motor moves the first motor between coupling with the first capacitor and coupling with the second capacitor. The mechanism may be employed to manipulate variable inductive loads for tuning and/or matching.

Abstract: A magnet assembly for a magnetic resonance imaging apparatus, has a magnet with a patient receptacle therein, the magnet producing a basic magnetic field having a homogeneity volume within the patient receptacle. Auxiliary components in the form of coils or ferromagnetic elements are disposed relative to the magnet to selectively spatially displace the homogeneity volume, either by selectively activating current flowing through the respective coils, or by selective positioning of the ferromagnetic elements.

Abstract: A pair of gradient field pulses of the same applied time and the same intensity are applied before and after a radio-frequency (RF) refocusing pulse (180.degree. pulse) as additional gradient field pulses to enhance the phase shift of a transverse magnetization spin, caused by the diffusion of a molecule including a target nuclide. To compensate for image deterioration caused by an unnecessary field distribution which is produced by the additional gradient field pulses, a compensation gradient field pulse dGcp and a compensation offset gradient field dGoffset are applied and a center frequency at the time of receiving and detecting an echo signal is shifted by df.sub.0.

Abstract: An MRI system performs a calibration prescan in which NMR projections are produced using either a spiral acquisition pulse sequence (FIG. 3) or a series of pulse sequences at a corresponding series of projection angles. The signal energies of the projections are summed to produce NMR calibration data. The signal energy in a prescribed region of interest may be calculated to provide the optimal RF transmit power when using local coils.

Abstract: Determining the magnitude of the calibration RF pulse using the signal phase rather than the signal amplitude.

Abstract: This invention includes methods for analyzing data generated by various solid-state NMR experiments, including rotational echo double resonance (REDOR), transferred echo double resonance (TEDOR), dipolar recoupling at the magic angle (DRAMA), dipolar recoupling with a windowless sequence (DRAWS), and melding of spin-locking and DRAMA (MELODRAMA). The methods are based alternately on a new analytical transform or the maximum entropy method and their multi-dimensional extensions. They permit simultaneous, multiple distance measurements of high accuracy and precision, even from nuclei with identical chemical shifts. By providing high quality easily obtained distance measurement from disordered solid state materials, this invention also improves drug discovery and design through fast determination of structures of pharmaceutical lead compounds, drug molecules, or their targets.

Abstract: A coil for bucking out undesired ambient time varying magnetic fields in the region of the gap in an MRI magnet structure is energized by a servo loop controlled by a Flux Lock Circuit having, in turn, a closed loop circuit controlled by a magnetic sensor. The sensor has a pair of windings energized in parallel by a 2 KHz oscillator, the windings being oppositely poled to induce zero voltage in a third winding to which feedback signals are supplied. Extraneous fields cause an asymmetry in the current passing through the pair of windings which asymmetry is accompanied by the generation of second harmonic components which are detected and fed back to the third winding for restoring symmetry. The signal fed back to the third winding is also used for controlling the current supplied to the field bucking coil.

Abstract: A single-tuned rf-gradient saddle coil is used for an internal NMR lock in a high-field NMR probe. The non-dipolar lock coil geometry is chosen such that its filling factor and Q are maximized subject to the constraint that its coupling coefficient to two orthogonal saddle coils is zero. Various quadrupolar and octopolar rf coils are disclosed for use in NMR probes having three or four sample coils for multi-nuclear triple resonance or homonuclear decoupling.

Abstract: A bipolar, phase-encoding, pre-phaser pulse is employed in each shot of a multi-shot EPI pulse sequence to smooth the phase-encoding gradient first moment throughout the scan. The first moment of the pre-phaser pulse is calculated for each shot in the scan and is played out at the beginning of each shot after the RF excitation.

Abstract: A method (100) of automatically tuning a radio frequency transmitter (24) and receiver (38) in a magnetic resonance imaging apparatus to an optimum frequency includes generating and acquiring (104) a magnetic resonance signal. The magnetic resonance signal is transformed to the frequency domain and spectral magnitude of the signal is computed (106). A center of gravity interpolation is performed (110) on the spectral magnitude to obtain a desired frequency sampling. A model function is generated based upon a strength of a main magnetic field which has peaks separated by the same separation as that for fat and water signals. The spectral magnitude is correlated (112) with the model function and a peak having the greatest magnitude is located therefrom. The location of a species peak along the spectral magnitude is estimated (114) from empirically derived information, the strength of the main magnetic field and the location of the correlation peak.

Abstract: A microwave spectrometer includes a sensing chamber into which is introduced a gas or constituent to be analyzed. Microwave radiation is introduced into the chamber and any of the chamber resonant frequency, the microwave frequency, and the center frequency of the absorption peak are varied independently. The resultant variation in intensity of the microwave radiation in the chamber is monitored to determine the concentration of the gas within said chamber. The spectrometer may include a frequency measuring and reference system for measuring the resonant frequency of the chamber.

Abstract: A prescan for an MRI system (FIG. 1) automatically sets the rf power level to produce an excitation field that nutates spins in the image plane the amount prescribed by the scan. Nutation angle is measured with a pulse sequence comprised of three slice selective excitation pulses that produce a set of frequency encoded NMR echo signals (E.sub.1, S.sub.1, E.sub.2, E.sub.23, E.sub.13). Nutation angle is calculated at locations in the image slice from the Fourier transformation of these signals and the maximum nutation angle is employed to calculate the final rf power level setting for the scan.

Abstract: An NMR scanner performs a prescan before each NMR scan sequence in which the optimal RF excitation frequency is automatically determined and applied to the scanner's transceiver. The prescan sequence includes a pair of NMR measurements which provide data that allows the precise RF excitation frequency to be determined.

Abstract: In addition to the usual winding of an MRI RF receive coil, a second, opposite sense, winding is connected to the same pair of RF output terminals and linked to at least part of the same space as the first winding. One or more serially connected RF switches in the second winding selectively connect it in circuit only during transmission of NMR RF nutation pulses. Under these conditions, any transmitted RF fields linked to the first winding are also linked to the second winding. Accordingly, any induced RF currents flowing in the receive coil windings produce self-cancelling effects in the tissue being imaged (thereby reducing possible distortion of the desired transmit fields being used for NMR nutation purposes).

Abstract: An actuating drive for controllable adjustment of a plurality of actuators in a nuclear resonance spectrometer is characterized in that the actuating drive has a drive train with a drive shaft (9) that can be driven by an electric drive motor (3) and with a plurality of drive train outputs, for coupling to the actuators, each of which can be individually coupled to the drive shaft by means of a changeover device. This enables the actuators to be adjusted automatically.

Abstract: The quadrature channels of an RF generator in an NMR spectrometer are aligned relative to one another by applying pulse sets to pairs of channels that are 180.degree. out of phase. The effect of the pulses in one channel is the opposite of the pulses in the other channel. As a result, the magnetization of the sample returns to the direction in which it started when the amplitudes of the pulses applied to each channel are equal. The magnetization returns to the initial direction even in the presence of RF inhomogeneities. The characteristic magnetization pattern can be easily observed and used to adjust the relative pulse amplitudes equal and the absolute pulse amplitudes to .pi./2.

Abstract: External field compensation is provided for MRI apparatus which is in a magnetically noisy environment such as that caused by nearby subway trains. By means of a magnetometer type sensor, the external field fluctuation is sensed and after being adjusted for the filtering effect of the magnet structure of the MRI device itself, the master oscillator of the MRI device is adjusted to compensate for the external field fluctuation. Alternatively the current of the magnet coil is adjusted.

Abstract: A radio frequency coil for use in MR imaging applications includes a series of conducting segments aligned with the longitudinal, static magnetic field of the MR magnet. A hybrid power splitter/combiner feeds to and receives from each axial segment a phased signal to generate or receive a transverse circularly polarized magnetic field. The power splitter combiner isolates the axial segments to reduce magnetic field distortions produced by capacitive coupling between the imaged object and the radio frequency coil. Each segment may be disabled by an associated solid state switch so as to isolate the radio frequency coil from other radio frequency coils that may be used in conjunction with it either for specialized transmitting or receiving functions.

Abstract: An NMR imaging system includes a prescan procedure in which the RF transmit power level is calibrated to produce an optimal, uniform RF field. Pulse sequences are conducted at a series of RF power levels and from the resulting acquired NMR data the power level which produces the most uniform signal across the extent of the subject being imaged is determined.

Abstract: A pattern generator and controller arrangement operates for controlling the component parts of an MRI system. The arrangement comprises a plurality of channels including a main control channel and output channels. The arrangement receives instructions from the system CPU which then leaves the control and outputting to the arrangement, thereby avoiding the necessity of a large expensive CPU to operate the system with versatility and speed.

Abstract: A sample (80) is disposed in an examination region (10) through which a strong, uniform magnetic field is generated. A gradient pulse (24, 82) is created across the magnetic field. After the gradient field has been turned off, a rapid succession of radio frequency pulses (52, 84) are applied. Each radio frequency pulse is followed by a free induction decay signal (54, 86). For each free induction decay signal, the evolution of phase vs. time is determined (60) because the slope of the changing phase vs. changing time curve is proportional to resonance frequency (66) and the resonance frequency is proportional to magnetic field strength (68). For each free induction decay signal, the magnetic field strength and the time since the determination of the gradient field pulse are determined and stored (70). From the plurality of free induction decay signals, a decaying curve (28) representing eddy current induced gradient field strength vs. time is produced.

Abstract: Static B.sub.o field strength is measured during each TR interval of an MRI sequence providing field calibration data used to compensate for rapid variations in B.sub.o during the MRI sequence.

Abstract: A device and method are provided for adjusting a radiofrequency antenna of a nuclear magnetic resonance apparatus. In the invention, using capacities preset in the factory, the antenna detuning of an NMR apparatus is limited to a range such that the standing wave rate of a high frequency line which conveys the radiofrequency signal is limited. This line is cut and, at a short distance, a tuning adjustment circuit is inserted. This circuit may be automated: the electric adjustment motors, thus spaced away, do not disturb the magnetic fields of the apparatus. By measuring the real part of the admittance at the input of the adjustment circuit and the phase shift between voltage and current this circuit can be adjusted.

Abstract: A head or body coil assembly for picking up signals in an MRI system is provided. It includes a band of conductive material which surrounds the specimen to be tested but which forms a gap substantially parallel to the axis of the curved band. An overlapping conductive section overlaps the gap at the adjacent ends to form respective capacitors with these ends. A ground connection in taken off from the overlapping section and a signal output lead is attached to one of the ends. Auxiliary variable capacitors are provided for balancing the system and for tuning it into resonance.