With Conditioning Of Transmitter Signal Patents (Class 324/314)
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Patent number: 6965234Abstract: A RF Excitation pulse for MRI applications has built-in saturation sidebands, thereby reducing the time for an excitation sequence. The pulse is created using the Shinnar-Le Roux (SLR) transform and designing beta-polynomials for a desired image slice excitation and for saturation of RF excitation such as by de-phasing in regions adjacent to the desired image slice. The beta-polynomials are combined and an inverse SLR transform creates the RF pulse from the combined beta-polynomial.Type: GrantFiled: October 6, 2004Date of Patent: November 15, 2005Assignee: The Board of Trustees of the Leland Stanford Junior UniversityInventors: Charles H. Cunningham, Juan M. Santos, John M. Pauly, Graham Arnold Wright, Jeffrey Alan Stainsby, John Andrew Derbyshire
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Patent number: 6956374Abstract: A technique is set forth that is designed to reduce RF induced power in high field MR imaging that includes application of an initial contrast preserving phase of RF pulses. These initial RF pulses are designed to have a constant, relatively high flip angle over the initial contrast preserving phase. Following an effective TE, a ramp down phase is applied that has a limited number of RF pulses with a flip angle that is less than the flip angle of those in the initial contrast preserving phase. Further, the RF pulses in the ramp down phase have a flip angle that is decreased over the ramp down phase. This technique provides improved resolution and steady contrast and SNR, while significantly reducing induced RF power.Type: GrantFiled: July 2, 2003Date of Patent: October 18, 2005Assignee: General Electric CompanyInventor: Reed F. Busse
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Patent number: 6944937Abstract: The present invention provides a method of manufacturing a magnetoresistive read head which reduces electrostatic discharge and allows measurement of gap resistances in the head.Type: GrantFiled: June 30, 2003Date of Patent: September 20, 2005Assignee: Hitachi Global Storage Technologies Netherlands B.V.Inventors: Richard Hsiao, James D. Jarratt, Emo Hilbrand Klaassen, Ian Robson McFadyen, Timothy J. Moran
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Patent number: 6937015Abstract: In a method and apparatus for calculating the sampling path of the k-matrix under given boundary conditions for the examination of a subject by means of a magnetic resonance tomography apparatus having a gradient amplifier with appertaining gradient coils, an input-display terminal, a sequence controller and a system computer as well as an analog-to-digital converter, boundary conditions are entered into the sequence controller or into the system computer via the input-display terminal, the sampling path of the k-matrix is calculated taking the boundary conditions into consideration by the sequence controller or the system computer, and the gradient current curves are determined by the sequence controller or the system computer that lead to a sampling along the previously calculated sampling path when applied to the corresponding gradient coils with utilization of the ADC.Type: GrantFiled: April 2, 2003Date of Patent: August 30, 2005Assignee: Siemens AktiengesellschaftInventor: Oliver Heid
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Patent number: 6933720Abstract: An improved magnetic resonance imaging (MRI) methodology uses an abbreviated initial MRI sequence to generate sequence diagnostic parameters. The sequence diagnostic parameters have a fixed relationship to certain sequence-conditioning parameters, and are used for calculating characteristic values of the sequence-conditioning parameters. The read out gradient pulse sequence is modified in accordance with the calculated characteristic values of the sequence-conditioning parameters. The modified read out gradient pulse sequence is then incorporated into a subsequent MRI pulse sequence used for obtaining a diagnostic image. The methodology has particular application in so called ultra fast MRI process which include echo-planar imaging (EPI) and echo-volume imaging (EVI).Type: GrantFiled: December 11, 2001Date of Patent: August 23, 2005Assignee: Toshiba America MRI, Inc.Inventor: Weiguo Zhang
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Patent number: 6900630Abstract: A method and apparatus for performing NMR measurements suppressing contribution to NMR signals from within the borehole. Within the region of examination, the RF magnetic field has a spatially varying intensity. NMR signals (free induction decay or spin echo signals) are inverted to give spin density as a function of field intensity. This inversion is then mapped to spatial positions using the known RF field variation. The effect of signals arising from within the borehole can be suppressed. It is also possible to obtain an azimuthal image of the spin density.Type: GrantFiled: November 19, 2003Date of Patent: May 31, 2005Assignee: Baker Hughes IncorporatedInventor: Carl M. Edwards
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Patent number: 6853192Abstract: In a method for designing a selective RF pulse for a magnetic resonance apparatus, based on a determination of a first polynomial (An(z)) and a second polynomial (Bn(z)) that are Shinnar-LeRoux transforms of the RF pulse, a flip angle distribution (?(x)) to be achieved with the RF pulse is prescribed, the first polynomial (An(z)) is determined proceeding from the flip angle distribution (?(x)), the phase distribution of the transverse magnetization to be achieved with the RF pulse is prescribed, and the second polynomial (Bn(z)) is determined such that the magnitude is determined by the flip angle distribution (?(x)) and the phase thereof corresponds to a sum of the prescribed phase distribution and the phase of the, first polynomial (An(z)).Type: GrantFiled: May 16, 2003Date of Patent: February 8, 2005Assignee: Siemens AktiengesellschaftInventor: Oliver Heid
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Patent number: 6850063Abstract: A nuclear magnetic resonance (NMR) spectroscopy or tomography method wherein a sequence of temporally mutually offset radio frequency (RF) pulses is applied onto a spin ensemble like a CPMG multi echo experiment, and wherein the magnetization produced after an initial excitation pulse is transferred to or close to the static pseudo steady state of the initially applied refocussing flip angle ?1 is characterized in that magnetization is transferred through gradual change of the refocussing flip angle in subsequent refocussing intervals to or close to the static pseudo steady state of the respectively used refocussing pulse with refocussing flip angle ?n such that the echo amplitude of the nth echo generated in this fashion approaches the maximum possible value corresponding to the respective refocussing pulse with refocussing flip angle ?n. The RF energy required for excitation of the nuclear spins can thereby be considerably reduced without having to accept signal intensity losses.Type: GrantFiled: November 25, 2002Date of Patent: February 1, 2005Assignee: Universitatsklinikum FreiburgInventor: Jürgen Hennig
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Publication number: 20040263164Abstract: There is disclosed a method of finding a reliable optimum value of a measurement condition in an NMR measurement. This method starts with gaining NMR measurement data while varying the value of the measurement condition to be optimized. Then, a certain property is extracted as a numerical value from the measurement data. A plot is made of the measurement data versus the value of the measurement condition to create a curve. A model equation coincident with the measurement condition, its range, and the certain property extracted as a numerical value is established. Curve fitting is done in which constants of the model equation are varied such that the equation agrees the created curve. The constant values of the model equation and their standard deviation are obtained by curve fitting. An optimum value of the measurement condition is obtained from the results.Type: ApplicationFiled: April 28, 2004Publication date: December 30, 2004Applicant: JEOL Ltd.Inventors: Tomomitsu Kurimoto, Nobuaki Nemoto, Katsuo Asakura, Chiharu Yamasaki
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Patent number: 6836115Abstract: A method of performing a magnetic resonance analysis of a biological object that includes placing the object in a main magnetic field (that has a static field direction) and in a radio frequency field; rotating the object at a frequency of less than about 100 Hz around an axis positioned at an angle of about 54°44′ relative to the main magnetic static field direction; pulsing the radio frequency to provide a sequence that includes a phase-corrected magic angle turning pulse segment; and collecting data generated by the pulsed radio frequency. The object may be reoriented about the magic angle axis between three predetermined positions that are related to each other by 120°. The main magnetic field may be rotated mechanically or electronically. Methods for magnetic resonance imaging of the object are also described.Type: GrantFiled: June 5, 2003Date of Patent: December 28, 2004Assignee: Battelle Memorial InstituteInventors: Robert A. Wind, Jian Zhi Hu
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Patent number: 6809518Abstract: Adiabatic RF pulses are very useful in MRI when precise flip angles are needed. Unfortunately, adiabatic pulses suffer from a long application time and a high SAR. A new concept to modify the usual adiabatic pulse into a “pseudo-adiabatic” pulse having a shorter application time and lower SAR is introduced. For example, a BIR-4 of 32 ms of application time and a relative SAR of 20 will be transformed into a BIR-4-S1 of 1 ms and relative SAR of 1. The new pulse obtained stays insensitive for a large B1 range but loses its slice selectivity to become a 3D pulse. Experimental results are presented to illustrate the sensitivity to B1 and B0.Type: GrantFiled: May 20, 2003Date of Patent: October 26, 2004Inventors: Gilles Beaudoin, Jean-Charles Côte
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Patent number: 6794870Abstract: A method of MRT according to the principle of signal generation in the driven equilibrium (DE) or also steady state free precession (SFP) wherein a periodic sequence of RF pulses with a flip angle &agr; is applied with a time delay TR wherein the phase of these pulses is alternated in subsequent steps, is characterized in that the periodic sequence of RF pulses is preceded by a sequence of (n+1) pulses for which the following conditions are valid: a first excitation pulse with preferred flip angle &agr;0=90° precedes the subsequently equidistant sequence of RF pulses at a preferred separation TR/2, the flip angle &agr;1 of the subsequent pulse is larger than &agr; and identical or approximately identical to 180°, the flip angle &agr;1 of the i-th pulse in the region i=2 . . . n is selected such that &agr;i≦&agr;i-1 and &agr;i≧&agr; and the phases of these pulses alternate.Type: GrantFiled: March 13, 2002Date of Patent: September 21, 2004Assignee: Universitätsklinikum FreiburgInventor: Jurgen Hennig
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Patent number: 6781375Abstract: To optimize in advance a desired image quality determining pulse sequence parameter incorporated in an imaging scan, a preparation scan is adopted. The preparation scan is performed with the amount of at least one desired image quality parameter changed for each of plural preparatory images, so that a plurality of preparatory images at the desired same region of the object are acquired. For example, one such image quality parameter is TI (inversion time). The acquired preparatory scan data are processed into a plurality of preparatory images for display. A desired preparatory image is then selected from the plural preparatory images displayed, and the amount of the desired parameter used for that selected preparatory image is then set for use in the pulse sequence for a complete diagnostic imaging scan. Hence the desired image quality determining parameter of the pulse sequence is caused to have an optimum value before an actual complete diagnostic imaging scan.Type: GrantFiled: August 15, 2002Date of Patent: August 24, 2004Assignee: Kabushiki Kaisha ToshibaInventors: Mitsue Miyazaki, Hiroshi Takai
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Publication number: 20040155656Abstract: The invention relates to an arrangement for generating RF fields in the examination volume (100) of an MR apparatus. A plurality of resonator segments are arranged around the examination volume (100) within the gradient tube (103), said resonator segments being connected together so as to form a body coil. Each resonator segment is provided with a conductor element (104) which is constructed as a planar strip and extends parallel to the longitudinal axis of the main field magnet. The resonator segments are electromagnetically decoupled from one another by means of intermediate capacitances, so that a separate transmission channel (1 to 8) can be associated with each resonator segment, the RF feeding into the relevant resonator segment taking place via said channel.Type: ApplicationFiled: November 19, 2003Publication date: August 12, 2004Inventor: Christoph Guenther Leussler
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Publication number: 20040155655Abstract: For the purpose of conducting optimal eddy current correction within a limited output range, a corrective value for eddy current correction for a gradient magnetic field is calculated (501-505), if the calculated value does not exceed a predetermined upper limit value, correction is conducted on the gradient magnetic field using the calculated value (507, 521, 525), and if the calculated value exceeds the predetermined upper limit value, a plurality of gradient magnetic fields affected by eddy current are simulated using a plurality of candidate corrective values not greater than the upper limit value (507-517), and correction is conducted on the gradient magnetic field using a candidate corrective value by which a relatively optimal gradient magnetic field can be obtained (519-525).Type: ApplicationFiled: February 5, 2004Publication date: August 12, 2004Inventor: Nozomu Uetake
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Patent number: 6731112Abstract: MR imaging with gradient oscillations that are essentially at the same frequency to reduce off-resonance effects. Frequencies that are sufficiently close to each other to reduce such effects compared with known approaches are considered essentially the same frequency.Type: GrantFiled: May 22, 2002Date of Patent: May 4, 2004Inventor: Kai Ruppert
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Patent number: 6714807Abstract: A method for performing MRI, including imposing N sets of steady-state free precession (SSFP) sequences on an object to be imaged, the sequences including respective initial radio-frequency (RF) excitation pulses, each initial RF excitation pulse having a predetermined phase shift relative to the other initial RF excitation pulses. N is a whole number larger than one and less than six. The method further includes setting the phase shift of the RF pulse of the sequences so that the phase shift of the RF pulse of an Mth sequence is substantially equal to 2 ⁢ π ⁡ ( M - 1 ) N radians, wherein M is a whole number larger than 0 and less than or equal to N, receiving a respective set of image signals from the object responsive to the N sets of SSFP sequences, and processing the set of received image signals to generate an image of the object.Type: GrantFiled: June 29, 2001Date of Patent: March 30, 2004Assignee: GE Medical Systems Global Technology Co., LLCInventor: Yuval Zur
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Publication number: 20040051528Abstract: A method for decreasing entropy of a quantum system of at least two subsystems, a first subsystem comprising elements with a first relaxation time (hereinafter—computation elements) and a second subsystem comprising elements with a second relaxation time (hereinafter—reset elements). The second relaxation time is shorter than the first relaxation time.Type: ApplicationFiled: June 16, 2003Publication date: March 18, 2004Inventors: Tal Mor, Vwani Roychowdhury, Seth Lloyd, Jose Manuel Fernandez, Yossi Weinstein
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Publication number: 20040046554Abstract: A method of compensating for eddy currents induced by the switching on and off magnetic fields in gradient coils in NMR imaging apparatuses, which method includes at least one compensation cycle including the steps of performing at least one detection of the magnetic field generated by the current flowing in a gradient coil, i.e., a gradient field; extrapolating the course of the effectively generated gradient field from the data of said at least one detection; generating a gradient fields excitation current compensating the eddy current effects on the gradient fields on the basis of the comparison of the effectively generated gradient fields and of the target gradient field.Type: ApplicationFiled: July 1, 2003Publication date: March 11, 2004Inventor: Davide Carlini
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Patent number: 6700375Abstract: In fast imaging of a multi-echo method represented by a fast spin echo (FSE) method, a pulse sequence is arranged such that a basic condition relating to a CPMG method is satisfied and a spoiler gradient magnetic field pulse is independently applied immediately after a flop pulse. The spoiler gradient magnetic field pulse for suppressing an undesired signal is applied by a predetermined amount or more so as to prevent superimposition of other gradient magnetic field components such as a phase encoding component, a rewind component, etc., and to prevent a residual component of an FID signal caused by a certain RF pulse from being refocused by a subsequent RF pulse.Type: GrantFiled: December 13, 2000Date of Patent: March 2, 2004Assignee: Kabushiki Kaisha ToshibaInventors: Yoshio Machida, Satoshi Sugiura, Yoshimori Kassai
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Patent number: 6693428Abstract: For the purpose of providing an RF coil that prevents a troublesome force from arising when a hanging portion is lifted up, a pair of handhold members 308 is provided along a side that corresponds to an inner side of a cylinder 110, each member extending from one end to the other end of one of a pair of flexible substrates 304 so that an operator can lift the hanging portion up using such handhold member.Type: GrantFiled: October 15, 2002Date of Patent: February 17, 2004Assignee: GE Medical Systems Global Technology Company, LLCInventors: Yoshiro Udo, Akira Izuhara
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Patent number: 6690167Abstract: A method for acquiring nuclear magnetic resonance measurements of a material uses a modified CPMG sequence with a refocusing pulse having a tipping angle less than 180 °. The results of using the shortened refocusing pulse with reduced power requirements are comparable to those obtained with a conventional CPMG sequence.Type: GrantFiled: October 12, 2001Date of Patent: February 10, 2004Assignee: Baker Hughes IncorporatedInventors: Arcady Reiderman, Carl M. Edwards
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Publication number: 20040021464Abstract: Perturbations in a static magnetic field of magnetic resonance imaging apparatus are compensated by creating magnetic fields near an object creating the perturbations with the magnetic fields adjusted to offset the perturbations in the static magnetic field. In an embodiment where the perturbations are caused by an x-ray detector in a combined modality imaging apparatus, the coils are positioned to surround the x-ray detector and create magnetic fields in the static magnetic field outside of the detector which compensate for the perturbations caused by the x-ray detector.Type: ApplicationFiled: August 5, 2002Publication date: February 5, 2004Applicant: THE BOARD OF TRUSTEES OF THE LELAND STANFORD JUNIOR UNIVERSITYInventors: Rebecca Fahrig, Norbert J. Pelc, Steven Conolly
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Patent number: 6680610Abstract: An apparatus and method for decreasing image acquisition and reconstruction times in magnetic resonance imaging are provided. Magnetic resonance data is acquired in parallel by an array of separate RF receiver coils disposed at generally circumferentially-spaced locations relative to one another around the imaging volume defined by the body coil of a magnetic resonance imaging apparatus. Further, the image reconstruction also is performed in parallel, thereby shortening up image display times. The apparatus and method operate on the basis of determining an estimate of the sensitivity profile of each RF coil in the array, and thereafter, utilizing those profiles in the creation of a desired image by encoding later acquired magnetic resonance data from a body of interest disposed in the imaging volume of the magnetic resonance imaging apparatus.Type: GrantFiled: May 23, 2000Date of Patent: January 20, 2004Inventors: Walid E. Kyriakos, Daniel F. Kacher
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Patent number: 6670811Abstract: A method of performing a magnetic resonance analysis of a biological object that includes placing the object in a main magnetic field (that has a static field direction) and in a radio frequency field; rotating the object at a frequency of less than about 100 Hz around an axis positioned at an angle of about 54°44′ relative to the main magnetic static field direction; pulsing the radio frequency to provide a sequence that includes a phase-corrected magic angle turning pulse segment; and collecting data generated by the pulsed radio frequency. The object may be reoriented about the magic angle axis between three predetermined positions that are related to each other by 120°. The main magnetic field may be rotated mechanically or electronically. Methods for magnetic resonance imaging of the object are also described.Type: GrantFiled: March 7, 2002Date of Patent: December 30, 2003Assignee: Battelle Memorial InstituteInventors: Robert A. Wind, Jian Zhi Hu
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Publication number: 20030227289Abstract: In a communication method for a magnetic resonance signal and a reception arrangement and magnetic resonance system corresponding therewith, a non-linear reactance is supplied with a magnetic resonance signal by a magnetic resonance reception antenna and with auxiliary energy by an auxiliary reception antenna. The auxiliary energy is emitted by an auxiliary transmission antenna. The non-linear reactance mixes the auxiliary energy and the magnetic resonance signal to form a mixed signal with a sum frequency and supplies it to a mixed signal transmission antenna. The latter emits at the mixed frequency. A mixed signal reception antenna receives the mixed signal and supplies it to an evaluation device.Type: ApplicationFiled: May 2, 2003Publication date: December 11, 2003Inventors: Oliver Heid, Markus Vester
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Publication number: 20030218459Abstract: Provided are pulse imaging sequences and methods for 2D multi-slice T1&rgr;-weighted and 3D T1&rgr;-weighted magnetic resonance imaging (MRI). Further provided is a self-compensating spin-locking sequence for correcting and reducing artifacts in T1&rgr;-weighted imaging. Also provided is a sequence combining 3D T1&rgr;-weighted MRI with a self-compensating spin-locking pulse for facilitating T1&rgr;-weighted imaging with surface coils.Type: ApplicationFiled: March 14, 2003Publication date: November 27, 2003Inventors: Ravinder Reddy, Sridhar R. Charagundla, Ari Borthakur, Erik M. Shapiro
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Patent number: 6653832Abstract: A method of performing a magnetic resonance analysis of a biological object that includes placing the biological object in a main magnetic field and in a radio frequency field, the main magnetic field having a static field direction; rotating the biological object at a rotational frequency of less than about 100 Hz around an axis positioned at an angle of about 54°44′ relative to the main magnetic static field direction; pulsing the radio frequency to provide a sequence that includes a magic angle turning pulse segment; and collecting data generated by the pulsed radio frequency. According to another embodiment, the radio frequency is pulsed to provide a sequence capable of producing a spectrum that is substantially free of spinning sideband peaks.Type: GrantFiled: March 9, 2001Date of Patent: November 25, 2003Assignee: Battelle Memorial InstituteInventors: Robert A. Wind, Jian Zhi Hu
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Publication number: 20030206014Abstract: In a method for designing a selective RF pulse for a magnetic resonance apparatus, a desired excitation spectrum of the RF pulse is prescribed, a time function is formed by Fourier transformation of the excitation spectrum, a part is selected from the time function that, proceeding from a region around the zero point of the Fourier transformation, extends in a direction, and the selected part is designed to substantially convert to zero at least in the aforementioned region.Type: ApplicationFiled: May 2, 2003Publication date: November 6, 2003Applicant: Siemens AktiengesellschaftInventor: Oliver Heid
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Patent number: 6636038Abstract: In a method for the control of the pulse sequence for a nuclear magnetic resonance tomography system and apparatus for the implementation of the method, the calculation of a control dataset is undertaken during the running time of the sequence, so that the sequence execution can be non-deterministically controlled with minimum dwell time with optimum utilization of the gradient system.Type: GrantFiled: August 28, 2000Date of Patent: October 21, 2003Assignee: Siemens AktiengesellschaftInventor: Oliver Heid
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Patent number: 6608479Abstract: A method and system are provided for acquiring images with water and lipid separation using a magnetic resonance imaging (MRI) system comprising applying a plurality of steady-state free precession (SSFP) radio-frequency (RF) excitation pulses to discriminate lipids from water, the pulses having respective inter-pulse gaps between the pulses, the inter-pulse gaps varying among different widths.Type: GrantFiled: May 15, 2002Date of Patent: August 19, 2003Assignee: General Electric CompanyInventors: William Thomas Dixon, Christopher Judson Hardy
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Patent number: 6591149Abstract: 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.Type: GrantFiled: September 20, 2000Date of Patent: July 8, 2003Assignee: Siemens AktiengesellschaftInventor: Oliver Heid
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Publication number: 20030112008Abstract: A nuclear magnetic resonance (NMR) spectroscopy or tomography method wherein a sequence of temporally mutually offset radio frequency (RF) pulses is applied onto a spin ensemble like a CPMG multi echo experiment, and wherein the magnetization produced after an initial excitation pulse is transferred to or close to the static pseudo steady state of the initially applied refocussing flip angle &agr;1 is characterized in that magnetization is transferred through gradual change of the refocussing flip angle in subsequent refocussing intervals to or close to the static pseudo steady state of the respectively used refocussing pulse with refocussing flip angle &agr;n such that the echo amplitude of the nth echo generated in this fashion approaches the maximum possible value corresponding to the respective refocussing pulse with refocussing flip angle &agr;n. The RF energy required for excitation of the nuclear spins can thereby be considerably reduced without having to accept signal intensity losses.Type: ApplicationFiled: November 25, 2002Publication date: June 19, 2003Inventor: Jurgen Hennig
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Patent number: 6573716Abstract: A downhole controller is used to tune the resonance frequency of an antenna after each NMR measurement sequence. At the end of the sequence, the downhole controller causes a pulse sequencer to generate a calibration pulse. The downhole controller then observes a voltage decay across the antenna after the calibration pulse. The downhole controller performs a Fast Fourier Transform (FFT) of the voltage decay to derive the resonant frequency of the antenna. The downhole controller determines a difference between the determined resonance frequency and the Larmor frequency and makes corresponding corrections by activating switches of the resonance tuning circuit. After each NMR measurement sequence, the downhole controller repeats the calibration to keep the antenna tuned to a frequency near the Larmor frequency.Type: GrantFiled: November 28, 2001Date of Patent: June 3, 2003Assignee: Schlumberger Technology CorporationInventors: Ali K. Toufaily, Abdurrahman Sezginer, Bruno Jorion, Luis E. DePavia
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Patent number: 6570383Abstract: A method and system for imaging using an inhomogeneous static magnetic field is disclosed herein. The imaging includes providing the inhomogeneous static magnetic field to an object of interest located within an imaging volume. The imaging further includes providing a pulse sequence including a readout gradient pulse and a slice selection gradient pulse, both gradient pulses comprising a part of the inhomogeneous static magnetic field. The pulse sequence is configured to acquire a plurality of lines of k-space data per excitation.Type: GrantFiled: December 27, 2000Date of Patent: May 27, 2003Assignee: GE Medical Systems Global Technology Company, LLCInventors: Graeme C. McKinnon, Jean H. Brittain
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Patent number: 6566877Abstract: A subject is disposed in an imaging region (10) of a magnetic resonance imaging apparatus. An operator submits a series of user preferences to the apparatus. A gradient optimizer (82) generates a gradient waveform that is optimal for the imaging procedure based on the user submitted specifications and the apparatus hardware specifications. The optimizer (82) accesses a memory that stores ideal gradient waveform models. The model that best fits the user specifications is selected and digitized (84). The digitized waveform is then convolved (86) with a band-limited kernel (88) that represents a frequency spectrum (89) of a gradient amplifier (28), producing a gradient waveform (90) that is smooth and does not exceed the capabilities of the amplifier. This optimized waveform is used in an imaging process including a collected data reconstruction portion of the process.Type: GrantFiled: December 26, 2000Date of Patent: May 20, 2003Assignee: Koninklijke Philips Electronics, N.V.Inventors: Christopher K. Anand, Michael R. Thompson
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Patent number: 6566873Abstract: A method of nuclear quadrupole resonance testing a sample is disclosed in which the excitation applied to the sample is arranged so that phase and amplitude information may be obtained from the response signal, and in which the signal is resolved into two components. Particularly if a parameter such as radio-frequency field strength varies with position, this may give an indication of the distribution of nuclei in the sample, preferably from the phase of the response signal. Positional information can also be obtained by measuring from two or more reference points. This may be employed in imaging. The phase information may be employed to improve the signal to noise ratio obtainable in other methods where only amplitude information was previously available, for example in distinguishing genuine NQR response signals from spurious signals.Type: GrantFiled: February 26, 1999Date of Patent: May 20, 2003Assignee: BTG International LimitedInventors: John Alec Sydney Smith, Neil Francis Peirson
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Publication number: 20030071620Abstract: A method for acquiring nuclear magnetic resonance measurements of a material uses a gradient tool. A modified CPMG sequence is used wherein the duration of the refocusing pulse is selected to maximize the SNR of the pulse echoes relative to a standard CPMG sequence in which the refocusing pulse has twice the duration of the tipping pulse. The results of using the shortened refocusing pulse with reduced power requirements are comparable to those obtained with a conventional CPMG sequence.Type: ApplicationFiled: October 12, 2001Publication date: April 17, 2003Inventors: Arcady Reiderman, Carl M. Edwards
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Patent number: 6546274Abstract: A nuclear magnetic resonance imaging apparatus in which a synchronizing signal is generated from a periodic physiological signal generated by a subject to be inspected, and a radiofrequency burst pulse is applied to the subject to be inspected in synchronism with the synchronizing signal while a gradient magnetic field in one direction is being applied to the subject to be inspected to modulate nuclear magnetizations of the subject to be inspected in the one direction. The radiofrequency burst pulse includes plural sub-pulses which are formed at equidistant intervals on a time axis and which have amplitudes modulated by a sinc function.Type: GrantFiled: February 21, 2001Date of Patent: April 8, 2003Assignee: Hitachi Medical CorporationInventors: Hiroyuki Itagaki, Hisaaki Ochi
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Publication number: 20030042905Abstract: To optimize in advance an amount of a desired parameter incorporated in a pulse sequence performed by an imaging scan, a preparation scan is adopted. The preparation scan is performed with the amount of the desired parameter changed every preparatory image, so that data of a plurality of preparatory images at a desired region of the object can be acquired. For example, such parameter is a TI (inversion time) and its amount is a period of TI. The acquired data are produced into a plurality of preparatory images for display. A desired preparatory image is then selected from the plural preparatory images displayed, and the amount of the desired parameter given from the selected preparatory image is set to the pulse sequence. Hence the desired parameter of the pulse sequence is able to have an optimum amount before actual imaging.Type: ApplicationFiled: August 15, 2002Publication date: March 6, 2003Inventors: Mitsue Miyazaki, Hiroshi Takai
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Publication number: 20030006770Abstract: An MRI apparatus and method useful for both industrial applications and medical applications is provided. The apparatus and procedures are capable of estimating the value of a continuous property, such as concentration, viscosity or the like by interpolating or extrapolating from a model derived from training sets of data representing measurements of samples with known properties. A number of techniques are provided for objectifying the analysis. Cluster analysis techniques can be used to supplement, assist or replace subjective judgments by trained operators. Calculations or judgments regarding similarity can be made with respect to stored libraries of signatures, particularly where the library of stored signatures is obtained objectively, e.g., using cluster analysis, standardization and calibration. The signatures can be expanded signatures which include non-MR as well as MR data.Type: ApplicationFiled: March 19, 2002Publication date: January 9, 2003Applicant: Board of Regents of the University of WashingtonInventor: Justin P. Smith
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Patent number: 6498484Abstract: 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.Type: GrantFiled: June 15, 2000Date of Patent: December 24, 2002Assignee: Schlumberger Technology CorporationInventors: Boqin Sun, Reza Taherian
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Publication number: 20020180437Abstract: An electrostatic relay is employed for switching in an electrical line system of a magnetic resonance tomography apparatus. The relay is employed for detuning a radio-frequency reception coil during a radio-frequency transmission phase of the nuclear magnetic resonance tomography apparatus.Type: ApplicationFiled: April 10, 2002Publication date: December 5, 2002Applicant: Siemens AktiengesellschaftInventors: Arne Reykowski, Jianmin Wang
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Publication number: 20020175683Abstract: In a method for the fast acquisition of a magnetic resonance image, magnetic resonance signals from an imaging region are conditioned with magnetic gradient fields that define a spatial frequency space so that the spatial frequency domain is occupied with magnetic resonance signals having trajectories that are radially directed and proceed through a projection center, and the imaging region is divided into subregions with an antenna of an antenna array respectively allocated to each sub-region. The antennas have respective positions relative to the projection center such that the antennas simultaneously receive the magnetic resonance signals and form reception signals from the magnetic resonance signals according to their sensitivity. The number of radially directed trajectories is of only such a size so that the sub-zones regardless of their spatial position in the imaging zone from the respective reception signals can be unambiguously reconstructed.Type: ApplicationFiled: April 19, 2002Publication date: November 28, 2002Inventors: Thomas Mertelmeier, Arnulf Oppelt
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Patent number: 6486838Abstract: An apparatus for and a method of Nuclear Quadrupole Resonance testing a sample in the presence of interference are disclosed. The apparatus comprises excitation applying means for applying excitation, a first antenna for detecting a response to the excitation together with the interference, and a second antenna for detecting the interference, the first and second antennas being arranged such that a signal commonly detected in the two antennas is attenuated relative to a signal that is detected by only one of the antennas. The apparatus may provide suppression of interference.Type: GrantFiled: September 6, 2000Date of Patent: November 26, 2002Assignee: BTG International LimitedInventors: John Alec Sydney Smith, Michael David Rowe
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Patent number: 6472870Abstract: For an NMR (nuclear magnetic resonance) experiment exact quantum-mechanical solutions have been obtained for the effect of RF (radiofrequency) pulses of constant amplitude, phase, and frequency, on any initial configuration of an ImSn J-coupled system. Subsets of these equations (rotation matrices) can be used to calculate the exact result of shaped RF pulses (modulated amplitude and phase). The rotation matrices remain valid when no RF is applied, so the result of a pulse sequence can be calculated continuosly throughout an NMR pulse sequence, yielding a method useful for specifying steps throughout sequences, the design of new sequences, or the display or debugging of sequences. During continuous wave (CW) decoupling applied to the I spins, the S-spin signal yields sidebands whose frequency depends on RF field strength and homogeneity, and these sidebands are further enhanced starting with antiparallel spinstates instead of in-phase magnetization.Type: GrantFiled: February 28, 2000Date of Patent: October 29, 2002Inventors: M. Robin Bendall, Thomas E. Skinner
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Patent number: 6466015Abstract: The invention relates to an MR imaging method, notably for real-time imaging, in which the phase errors that occur in the MR signals because of inter alia eddy currents, are continuously monitored on the basis of the MR data sets acquired for imaging. To this end, MR signals that are successively acquired with different read-out gradients are related to one another in order to detect changes in the eddy current behavior on the basis of the phase differences. If necessary, calibration measurements are initiated so as to determine phase correction profiles whereby the phase errors of the MR data sets are compensated. For the imaging in accordance with the invention use can be made of Echo Planar Imaging (EPI) sequences for which individual, successively acquired echo signals are related to one another in order to monitor the phase errors. These echo signals are measured with the same phase encoding and with each time opposed read-out gradients for this purpose.Type: GrantFiled: October 17, 2001Date of Patent: October 15, 2002Assignee: Koninklijke Philips Electronics N.V.Inventors: Tobias Schaeffter, Peter Koken
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Publication number: 20020145424Abstract: A method of correcting a resonance frequency variation and an MRI apparatus both capable of handling all frequency drifts including a frequency drift whose time change is slow, a frequency drift in a slice direction and a frequency drift whose time change is fast. An amount of a resonance frequency variation is measured, the frequency variation is corrected when an amount of the resonance frequency variation is smaller than a threshold value, and the amount of the resonance frequency variation is not stored. On the other hand, when the amount of the resonance frequency variation is not smaller than the threshold value, the amount of the resonance frequency variation is stored and correction operation is made based thereon later.Type: ApplicationFiled: April 3, 2002Publication date: October 10, 2002Inventor: Nozomu Uetake
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Publication number: 20020145427Abstract: A detunable coil assembly includes a main coil which resonates at a specified resonance frequency and a switchable detuning coil which, when switched on, becomes inductively coupled to the main coil and serves to detune it from its resonance frequency. The detuning coil and the main coil are electrically insulated from each other. The main coil may be of a multiply tuned kind and it may be detuned from more than one of its specified resonance frequencies at the same time by switching on the detuning coil.Type: ApplicationFiled: April 5, 2001Publication date: October 10, 2002Inventors: Wai Ha Wong, Alan R. Rath
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Publication number: 20020135365Abstract: A method of performing a magnetic resonance analysis of a biological object that includes placing the biological object in a main magnetic field and in a radio frequency field, the main magnetic field having a static field direction; rotating the biological object at a rotational frequency of less than about 100 Hz around an axis positioned at an angle of about 54°44′ relative to the main magnetic static field direction; pulsing the radio frequency to provide a sequence that includes a magic angle turning pulse segment; and collecting data generated by the pulsed radio frequency. According to another embodiment, the radio frequency is pulsed to provide a sequence capable of producing a spectrum that is substantially free of spinning sideband peaks.Type: ApplicationFiled: March 9, 2001Publication date: September 26, 2002Inventors: Robert A. Wind, Jian Zhi Hu