206 results about "Resonance measurement" patented technology

Servo control using ferromagnetic core material and electrical windings is based on monitoring of winding currents and voltages and inference of magnetic flux, a force indication; and magnetic gap, a position indication. Third order nonlinear servo control is split into nested control loops: a fast nonlinear first-order inner loop causing flux to track a target by varying a voltage output; and a slower almost linear second-order outer loop causing magnetic gap to track a target by controlling the flux target of the inner loop. The inner loop uses efficient switching regulation, preferably based on controlled feedback instabilities, to control voltage output. The outer loop achieves damping and accurate convergence using proportional, time-integral, and time-derivative gain terms. The time-integral feedback may be based on measured and target solenoid drive currents, adjusting the magnetic gap for force balance at the target current. Incorporation of permanent magnet material permits the target current to be zero, achieving levitation with low power, including for a monorail deriving propulsion from the levitation magnets. Linear magnetic approximations lead to the simplest controller, but nonlinear analog computation in the log domain yields a better controller with relatively few parts. When servo-controlled solenoids provide actuation of a pump piston and valves, electronic LC resonance measurements determine liquid volume and gas bubble volume.

A dynamic hearing protection method and device with which a hearing protection device specific differential head related transfer function corresponding to the difference between an open ear resonance measurement of the user's ear canal or an ear canal approximating the user's ear canal without the hearing protection device being worn in the ear canal and an open ear resonance measurement with the hearing protection device being worn in the ear canal as a function of the angle of sound incidence is determined and when using the hearing protection device, a frequency-dependent gain function to the captured audio signals selected according to the presently determined angle of sound incidence with each of the gain functions is determined by inverting the previously determined HPD specific differential HRTF for the respective sound incidence angle, to compensate for the effect of the presence of the hearing protection device on the open ear resonance.

Servo controlled solenoids provide actuation of a pump piston and valves, and electronic LC resonance measurements to determine liquid volume and gas bubble volume. Third order nonlinear servo control is split into nested control loops: a fast nonlinear first-order inner loop causing flux to track a target by varying a voltage output, and a slower almost linear second-order outer loop causing magnetic gap to track a target by controlling the flux target or the inner loop. The inner loop uses efficient switching regulation, preferably based on controlled feedback instabilities, to control voltage output. The outer loop achieves damping and accurate convergence using proportional, time-integral, and time-derivative gain terms. The time-integral feedback may be based on measured and target solenoid drive currents, adjusting the magnetic gap for force balance at the target current.

A system and method are provided to detect target analytes based on magnetic resonance measurements. Magnetic structures produce distinct magnetic field regions having a size comparable to the analyte. When the analyte is bound in those regions, magnetic resonance signals from the sample are changed, leading to detection of the analyte.

Apparatus and method for varying field strength in a magnetic resonance system while keeping a relatively uniform magnetic field distribution. In an embodiment, a two-pole, generally u-shaped magnet assembly generates a static and uniform magnetic field. The magnet assembly includes two facing magnet poles separated by an air gap. Holes may be formed with the magnet poles. The field control rods may be placed at a pre-determined distance into these holes and symmetrically or asymmetrically moved across each magnet poles in a controlled manner to change the magnetic field strength while keeping the uniform magnetic field distribution. Maximum magnetic field strength may occur when the rods are removed. Minimum magnetic field strength may occur when the rods are fully inserted.

In a method and device for monitoring the physiologically effective radio-frequency exposure in at least one specific volume region of an examination subject in a magnetic resonance data acquisition scan in a magnetic resonance system, the magnetic resonance system having a radio-frequency antenna structure with a number of individually controllable radio-frequency signal channels for generation of radio-frequency field distributions in an examination volume including the examination subject, amplitude values are acquired that respectively represent, at specific acquisition points in time, a signal amplitude of the radio-frequency signals emitted or to be emitted via the radio-frequency signal channels in the course of the magnetic resonance measurement. Also, phase values are acquired that represent the phases of the appertaining radio-frequency signals at these points in time. Local exposure values are then determined on the basis of the amplitude values and phase values, these local exposure values respectively representing a physiological exposure that the radio-frequency pulses cause at the examination subject at a specific location at a specific time. Based on this, exposure control values are determined that are compared with predetermined exposure limit values. When an exposure limit values is reached or exceeded, a control signal is output.

In a method and device for monitoring the physiologically effective radio-frequency exposure in at least one specific volume region of an examination subject in a magnetic resonance data acquisition scan in a magnetic resonance system, amplitude values are acquired that respectively represent, at specific acquisition points in time, a signal amplitude of the radio-frequency signals emitted or to be emitted via the radio-frequency signal channels. Also, phase values are acquired that represent the phases of the appertaining radio-frequency signals at these points in time. Local exposure values are then determined on the basis of the amplitude values and phase values, respectively representing a physiological exposure that the radio-frequency pulses cause at the examination subject at a specific location at a specific time. Based on this, exposure control values are determined that are compared with predetermined exposure limit values. When an exposure limit values is reached or exceeded, a control signal is output.

A method of MR imaging and spectroscopy reduces artifacts occurring due to the motion of an object to be represented, wherein the object position is determined quasi-continuously during the runtime of the MR acquisition, which includes one or more partial acquisitions (TA), and wherein motion correction is performed, which comprises dynamic adaptation of the frequency and phase settings of the RF system of the tomograph and of the orientation and amplitudes of the gradients during the runtime of the MR acquisition according to the current object position. The motion correction is thereby applied during a signal weighting period, during a signal read-out period, or between and / or during the two stated periods and the adaptations for motion correction are performed without interrupting or slowing the temporal progression of the MR acquisition. In this way, artifacts due to motion of the object to be represented can be further reduced.

Nuclear magnetic resonance systems and methods of use thereof are provided. The systems employ implantable radiofrequency coils (105) and optionally implantable magnets (101). The systems can employ weak permanent magnets and / or permanent magnets that provide magnetic fields that are much less homogeneous than in conventional systems. This allows, for example, for inexpensive and simple probeheads for nuclear magnetic resonance relaxometry with suitable biosensors. The methods of the present invention allow in-vivo magnetic resonance measurements and, in particular, monitoring of analytes and determination of medical diagnostic information, for example, based on determined magnetic resonance parameters.

In a method and device for monitoring a radio-frequency transmit device of a magnetic resonance tomography system, having a transmitter antenna system that has a number of transmit channels, during a magnetic resonance measurement of an examination subject, a reference scattering parameter matrix of the transmitter antenna system is determined in the unloaded state, and a subject-specific scattering parameter matrix of the transmitter antenna system is determined in a state loaded with the subject of examination. Moreover, transmitter amplitude vectors are determined in time-dependent fashion that represent the radio-frequency voltage amplitudes on the individual transmit channels. On the basis of the subject-specific scattering parameter matrix, the reference scattering parameter matrix, and the transmit amplitude vectors, radio-frequency power values absorbed at particular transmit times in the subject are determined. Based on a large number of the determined radio-frequency power values, a number of monitoring values are formed. The radio-frequency transmit device is limited in its functioning when a monitoring value reaches or exceeds a prespecified boundary monitoring value.

A magnet assembly and a magnetic field configuration are disclosed for the generation of a magnetic field in a defined volume, with the field being homogeneous over a pre-determined portion of the volume and not homogeneous over the rest. The disclosed magnetic assembly has a plurality of spaced-apart magnets arranged in pairs. The magnets of each pair are be positioned diametrically opposite each other with respect to an enclosed volume. In different embodiments magnets may all be arranged such that their magnetization directions are substantially aligned, or could alternatively be arranged to have magnetizations pointing in different directions. The angular spacing between the magnets is selected in the range of approximately 13°-17° and could be as large as the size of the magnets. The assembly generates a homogeneous magnetic field within an inner portion of the defined volume, and a second magnetic field, substantially different from the homogeneous magnetic field throughout the remainder, i.e., in the periphery of the defined volume.

An apparatus having a combined magnetic resonance apparatus is proposed. The magnetic resonance apparatus features at least one main magnet for generating a main magnetic field in an examination space for a magnetic resonance measurement, and a radiation therapy apparatus, which is provided to generate a particle beam and which features a beam guide. The magnetic resonance apparatus features an essentially magnetic-field-free region and the beam guide for the particle beam runs along the essentially magnetic-field-free region.

The invention provides a method for measuring track corrugation by utilizing axle box vibration and impact information. A vibration and impact information acquisition device contains a rotating speed sensor S arranged on a wheel set shaft of an operating vehicle, a vibration and impact detection sensor A1 and a vibration and impact detection sensor A2 which are arranged on an axle box bearing block at the two ends of a wheel set, an online monitoring device JKQ and a corrugation ground analysis system DMXT, wherein the rotating speed sensor S, the vibration and impact detection sensor A1 and the vibration and impact detection sensor A2 are connected with the online monitoring device JKQ, and detection, acquisition, diagnosis, analysis and decision of vehicular corrugation information of the operating vehicle are realized by virtue of the online monitoring device JKQ or by downloading data of the online monitoring device JKQ to the corrugation ground analysis system DMXT. The method for measuring the track corrugation by utilizing the axle box vibration and impact information has the advantages that the axle box vibration and impact information of the operating vehicle are acquired, based on a generalized resonance measurement principle, vehicular real-time track corrugation wave length and wave depth measurement and analysis or track corrugation wave length and wave depth measurement and analysis after downloading is completed are realized, and the manual workload is greatly reduced.

In a method for adjustment of the field strength of radio-frequency pulses as well as a magnetic resonance measurement system, radio-frequency pulses are emitted by a radio-frequency antenna of a magnetic resonance measurement system in a magnetic resonance measurement A test volume slice is initially excited by emission of radio-frequency pulses with a defined pulse amplitude by the appertaining radio-frequency antenna and one-dimensional, spatially-resolved characteristic values are determined along an extent direction of the test volume slice. The one-dimensional, spatially-resolved characteristic values respectively represent a local field strength of the B1 field in strips of the test volume slice running perpendicular to the extent direction. An average value of the determined characteristic values is then formed over at least over one determined segment along the extent direction of the test volume slice. A pulse amplitude of the radio-frequency pulses that is to be set for the magnetic resonance measurement to be implemented is determined on the basis of the average value.

In a magnetic resonance method and apparatus, a) data points of a physiological signal are detected, b) a trigger condition is evaluated depending on the detected physiological data points, c) a preparation module is executed to suppress unwanted signals in the time period in which the trigger condition has not yet been satisfied, d) after satisfying the trigger condition, an acquisition phase of predetermined duration is started, that includes at least two similar preparation modules to suppress unwanted signals and a respective following acquisition module to acquire measurement data, and e) after the acquisition phase, a) through d) are repeated until all desired measurement data have been acquired, with a time interval between two successive preparation modules being the same after a first execution of a preparation module in c) until the end of the acquisition phase in a subsequent d).

A magnetic resonance apparatus has an examination region to accommodate a patient to be examined, and a body coil that circumferentially encompasses the examination region and is designed for magnetic resonance examination of the patient. A gradient coil circumferentially encompasses the examination region and the body coil and is designed to detect the position of magnetic resonance measurement values. A basic field magnet is designed to form a basic magnetic field in the examination region for a patient examination to be conducted. The basic field magnet at least partially encompasses the examination region, the body coil and the gradient coil. A shim device is used that is designed to influence the basic magnetic field. Components of the shim device and components of the body coil are associated to exhibit a common distance relative to the longitudinal axis of symmetry of the examination region and thus encompass the examination region.

A method of MR imaging and spectroscopy to reduce artifacts occurring due to the motion of an object to be represented, wherein the object position is determined quasi-continuously during the runtime of the MR acquisition, which includes one or more partial acquisitions (TA), and wherein motion correction is performed, which comprises dynamic adaptation of the frequency and phase settings of the RF system of the tomograph and of the orientation and amplitudes of the gradients during the runtime of the MR acquisition according to the current object position. The motion correction is thereby applied during a signal weighting period, during a signal read-out period, or between and / or during the two stated periods and the adaptations for motion correction are performed without interrupting or slowing the temporal progression of the MR acquisition. In this way, artifacts due to motion of the object to be represented can be further reduced.

A magnetic resonance measurement technique is provided which shortens the measurement time while suppressing artifacts caused by body movement of a measuring object and enables high-speed imaging. An excitation pulse which excites a plurality of slice planes and an excitation pulse which excites slice planes perpendicular to the slice planes are applied and a plurality of substantially parallel linear crossing areas are simultaneously measured. Spatial information of a linear direction of the crossing areas is acquired by modulating a magnetic resonance signal from the crossing areas by a gradient magnetic field. A spatial information of a direction perpendicular to the linear direction is acquired by changing the position of the plane and an image is reconstructed.

A method for performing magnetic resonance measurements on a sample includes applying a first predetermined number of pulse trains for excitation, each pulse train having a constant amplitude and including a second predetermined number of pulses spaced by a predetermined time interval. The pulse trains are modulated by a bent function. After each pulse, data is sampled. Preferably a square number of pulses is generated being constant in power, and the Walsh transform of the sequence of their phases is constant in power, so that the power of the excitation in time and frequency domain is constant. The method can reduce power requirements and may permit undercutting specific absorption rate (SAR) limits due to the small excitation power necessary to create time signals with reasonable signal to noise ratio.

The invention relates to a hydrocarbon polluted shallow groundwater magnetic resonance detection device and a hydrocarbon polluted shallow groundwater magnetic resonance detection method. According to the detection device, a computer is respectively connected with a transmission logic and control unit, an MCU (Microprogrammed Control Unit) and a signal acquisition card; a 24V battery is connected with a signal regulation circuit by virtue of a DCDC (Direct Current Direct Current) module, a transmission logic and control unit, the MCU and the signal acquisition card; an energy storage transmission unit is connected with the transmission logic and control unit; the energy storage transmission unit is connected with the signal regulation circuit by virtue of a voltage-current acquisition unit 7 and the MCU. By adopting the detection device, non-intrusive quantitative qualitative measurement is achieved, and testing result can be rapidly obtained on site. The intensity of a local magnetic field is improved by virtue of a permanent magnet, magnetic resonance measurement can be carried out at places with intensive electric power interference, the signal to noise ratio can be effectively improved, the constraint that the magnetic resonance exploration cannot be carried out because of intensive electric power interference is broken, and the defect that the result is not correct because of nonuniform magnetic field can be effectively overcome by use of spin echo pulse. Hydrocarbon pollution within 5m underground can be rapidly and accurately detected.

In a method for controlling a radio-frequency device, and a magnetic resonance tomography system and a radio-frequency control device wherein the method is implemented, the RF device of a magnetic resonance tomography system is emitted during a magnetic resonance measurement of an examination subject that is moving relative to the transmission field of the RF device. The RF device emits RF pulses at chronological intervals, and measurement values are measured at chronological intervals. At chronological intervals, position values are determined that represent a current position of the examination subject relative to the transmission field. On the basis of the measurement values and the position values, exposure values are determined that represent a physiological degree of effectiveness that the RF pulses have on the subject exposed to the RF pulses. Based on a multiplicity of exposure values, exposure control values are respectively formed. The RF device is limited in its functioning if an exposure control value reaches or exceeds an exposure limit value.

Radiation damping (RD) is employed to hasten the recovery of longitudinal magnetization after RF excitation and signal readout in a magnetic resonance measurement cycle. A switch driven by the pulse sequence that performs the measurement cycle energizes a feedback RF coil driven by an amplified and phase shifted portion of the received MR signal. The recovery of longitudinal magnetization is thus under direct control of the MR system and enables the reduction of the otherwise inefficient waiting times that are required for natural T1 recovery of the excited spin magnetization. This enables shortened acquisition times, improved sensitivity, better spatial and temporal resolution, and reduction of motion artifacts that result from long acquisition times.

In a method and magnetic resonance system for homogenization of the B1 field for a magnetic resonance data acquisition with a number of iteration steps. An iteration step includes the following sub-steps: Measurement data are acquired that represent a B1 field distribution in at least one part of the examination volume of the magnetic resonance system. A B1 homogeneity analysis based on the acquired measurement data is automatically implemented. A specific homogenization action is automatically selected from among a number of possible homogenization actions based on the B1 homogeneity analysis, or the iterative homogenization method is ended if the diagnosed homogeneity is sufficient for an intended magnetic resonance measurement. The selected homogenization action is implemented.

In a method for determination of flip angle distributions for various antenna transmission configurations in a magnetic resonance system, magnetic resonance measurements are implemented with the various transmission configurations, with the reception configuration being identical for all implemented magnetic resonance measurements, and all magnetic resonance measurements for the various transmission configurations are implemented with a specific pulse sequence. This pulse sequence is selected such that the total function that describes the dependency of the image signal at a specific location on the flip angle achieved at this location with the radiated radio-frequency field, as well as on further MR-relevant parameters, can be factored into a first sub-function that describes the dependency of the image signal on the achieved flip angle and a second sub-function (Tb) that describes the dependency of the image signal on the further MR-relevant parameters, and such that the functional dependency of the image signal on the achieved flip angle is known. The absolute flip angle distribution is measured for a reference transmission configuration, and the flip angle distributions of the other transmission configurations are then respectively determined on the basis of the absolute flip angle distribution of the reference transmission configuration and on the basis of the ratio of the spatially-dependent image signals of the magnetic resonance measurements of the respective transmission configuration to the corresponding spatially-dependent image signals of the magnetic resonance measurement of the reference transmission configuration.