WO1995034242A1 - Procede d'imagerie par resonance magnetique a sequences d'images pulsees optimisees, et appareil associe - Google Patents

Procede d'imagerie par resonance magnetique a sequences d'images pulsees optimisees, et appareil associe Download PDF

Info

Publication number
WO1995034242A1
WO1995034242A1 PCT/IB1994/000154 IB9400154W WO9534242A1 WO 1995034242 A1 WO1995034242 A1 WO 1995034242A1 IB 9400154 W IB9400154 W IB 9400154W WO 9534242 A1 WO9534242 A1 WO 9534242A1
Authority
WO
WIPO (PCT)
Prior art keywords
sequence
magnetic resonance
optimisation
magnetic field
pulses
Prior art date
Application number
PCT/IB1994/000154
Other languages
English (en)
Inventor
Peter Van Der Meulen
Jan Bruijns
Original Assignee
Philips Electronics N.V.
Philips Norden Ab
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Philips Electronics N.V., Philips Norden Ab filed Critical Philips Electronics N.V.
Priority to PCT/IB1994/000154 priority Critical patent/WO1995034242A1/fr
Priority to JP8501857A priority patent/JPH09511169A/ja
Priority to EP94916368A priority patent/EP0712292A1/fr
Publication of WO1995034242A1 publication Critical patent/WO1995034242A1/fr

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
    • G01R33/48—NMR imaging systems
    • G01R33/54—Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
    • G01R33/48—NMR imaging systems
    • G01R33/483—NMR imaging systems with selection of signals or spectra from particular regions of the volume, e.g. in vivo spectroscopy
    • G01R33/4833—NMR imaging systems with selection of signals or spectra from particular regions of the volume, e.g. in vivo spectroscopy using spatially selective excitation of the volume of interest, e.g. selecting non-orthogonal or inclined slices
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
    • G01R33/48—NMR imaging systems
    • G01R33/54—Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console
    • G01R33/543—Control of the operation of the MR system, e.g. setting of acquisition parameters prior to or during MR data acquisition, dynamic shimming, use of one or more scout images for scan plane prescription

Definitions

  • Magnetic resonance imaging method with pulse sequence optimisation and device for such method Magnetic resonance imaging method with pulse sequence optimisation and device for such method.
  • the invention relates to 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 invention also relates to a device for performing such a method.
  • MRI pulse sequences are applied to an object (a patient) to generate magnetic resonance signals and obtain information therefrom which is subsequently used to reconstruct images of the object. Since its initial development, the number of clinical relevant fields of application of MRI has grown enormously. MRI can be applied to almost every part of the body and used to obtain information about a number of important functions, such as blood flow, heart functioning, brain activity and many others. For each function a set of MR pulse sequences is necessary. An MR pulse sequence determines completely the characteristics of the reconstructed images, such as location and orientation in a patient, dimensions, resolution, signal-to-noise ratio, contrast, sensitivity for movement, etcetera.
  • EP-A-0 567 794 an MRI device is disclosed in which a basic pulse sequence form is selected from a plurality of stored basic pulse sequence forms.
  • the selected basic pulse sequence form is updated by means of pulse sequence parameters generated corresponding to desired imaging conditions.
  • an appropriate pulse sequence is generated and simulated taking into account system and patient characteristics. From this simulation, which is a calculation starting from a Bloch equation, the effects of the generated pulse sequence are obtained and, subsequently, the pulse sequence is adjusted according to the results of the simulation.
  • EP-A-0 567 794 by performing the known method with the help of a powerful computer to perform the necessary calculations in a short time, the number of measurements and the time needed for pulse sequence adjustment can be minimized.
  • the known method does only adjust the sequence as to obtain the desired imaging conditions but has no effect upon the pulse sequences as such and the quality of the data acquired by measuring the generated magnetic resonance signals.
  • the known method does not relieve the operator from detailed knowledge of the image obtainable by a specific sequence in order to make a proper selection.
  • the known method does not optimise all variable parameters to obtain the best possible sequence.
  • a method according to the invention comprises selecting an elementary sequence type of radio-frequency (RF) and magnetic field gradient pulses for generating magnetic resonance signals in an object; selecting operational parameters which, in combination with the selected elementary sequence, describe desired imaging characteristics; determining an operational sequence of RF and magnetic field gradient pulses by optimisation of said elementary sequence, taking into account machine constraints and said operational parameters; subjecting said portion of a body to said operational sequence thereby generating magnetic resonance signals in said portion, measuring said magnetic resonance signals and obtaining from said measured signals an image of said portion of the body.
  • RF radio-frequency
  • Operational parameters are, for example, field of view, slice thickness, echo or repetition time, location and orientation.
  • Optimisation occurs with respect to a pertinent parameter, for example one that relates to image quality.
  • parameters relating to total imaging time, temporal or spatial resolution, field or view, contrast in the image, short echo time, flow information, SAR (specific absorption rate) or acoustical noise, etcetera can be chosen.
  • the optimisation process can be performed by running a program with a suitable algorithm in a computer, the operator can concentrate on the selection of the characteristics necessary for the desired image. He need not to attend to technicalities related to each of the many variations of an elementary pulse sequence in relation to the desired image conditions and the technical constraints of the MRI device.
  • the selection step is functionally separated from the optimisation step and the optimisation step is implemented in a way that its execution is independent from the determination of the operational sequence.
  • the optimisation step can be implemented in a general way so that the introduction of new pulse sequences is possible without extensive reformulation of the optimisation algorithm.
  • the operational sequence is determined by an optimisation of the elementary sequence by maximising the period for measuring the generated magnetic resonance signals or the signal-to-noise ratio to be expected therein.
  • the signal-to-noise ratio is an important parameter for determining image quality.
  • the signal-to-noise ratio of the data samples acquired from the magnetic resonance signals increases with an increasing time period available for taking each sample.
  • a general description of the operational sequence is determined, said general description comprising the timing of RF-pulses and strength of magnetic field gradients applied simultaneously with the RF-pulses and secondly the optimisation is performed for determining the magnetic field gradient waveform in intervals not provided for in said general description.
  • the occurrence of RF-pulses at certain points in time and of magnetic gradient fields in certain intervals is established.
  • the detailed position, length and strength of the magnetic field gradients is determined in the other intervals of the pulse sequence.
  • the optimisation process is performed for determining the timing, length and strength of RF- pulses and magnetic field gradient waveforms.
  • characteristics of the RF- pulses themselves are included in the optimisation process as well. These characteristics can be optimised within certain limits, and optimisation with respect to RF-pulses is advantageous, for example, if the SAR has to be limited.
  • the magnetic field gradient waveforms are piecewise linear functions.
  • a piecewise linear function consists of a number of straight edges. As calculations involving linear functions are relatively fast, the optimisation procedure can be performed with moderate computing power. Piecewise linear waveforms for magnetic field gradient allow a satisfactory approximation of any gradient waveform that would be desirable during imaging.
  • the invention also relates to an MRI device for performing an MRI method.
  • Such an MRI device comprises means for establishing the main magnetic field, means for generating gradient magnetic fields superimposed upon the main magnetic field, means for radiating RF-pulses towards the body, control means for steering the generation of the gradient magnetic fields and the RF-pulses, means for receiving and sampling magnetic resonance signals generated by sequences of RF-pulses and switched gradient magnetic fields, and reconstruction means for forming an image from said signal samples, said control means further comprises - a general description of a limited number of elementary sequences; an operator input section for entering operational parameters (T R , T E , position) describing desired characteristics of images to be obtained and for selecting an elementary sequence; calculation means for determining an operational sequence of RF and magnetic field gradient pulses by optimisation of said elementary sequence, taking into account machine constraints and said operational parameters.
  • the user control means comprises an output for communicating to the operator the result of the optimisation of the sequence and for allowing the operator to apply additional parameters. This allows the operator to some extent to intervene in the optimisation process if not a single solution is found. The operator can either decide which of several possible presented solutions should be used, or add, change or restrict any parameters if no solution can be found that complies with the desired setting.
  • FIG. 1 diagrammatically a magnetic resonance imaging apparatus, suitable for the method according to the invention
  • Figure 2 a spin-echo (SE) sequence having an excitation RF-pulse, a refocusing RF-pulse and slice selection, phase encoding and measurement gradient pulses;
  • Figure 3 magnetic field gradient waveforms with piecewise linear functions and non-coincident nodes.
  • SE spin-echo
  • Figures 4a and 4b a few gradient waveforms obtained for a SE sequence
  • Figures 5a and 5b a functional block diagram displaying the relationships between the different steps in the method according to the invention and a flow diagram illustrating the optimisation procedure.
  • a magnetic resonance imaging apparatus 1 is diagrammatically shown.
  • the apparatus comprises a set of main magnetic coils 2 for generating a stationary and homogeneous main magnetic field and three sets of gradient coils 3, 4 and 5 for superimposing additional magnetic fields with controllable strength and having a gradient in a selected direction.
  • the direction of the main magnetic field is labelled the z direction, the two directions perpendicular thereto the x and y directions.
  • the gradient coils are energised via a power supply 11.
  • the apparatus further comprises radiation emitter 6, an antenna or coil, for emitting radio-frequency pulses (RF-pulses) to a body 7, the radiation emitter being coupled to a modulator 8 for generating and modulating the RF-pulses.
  • RF-pulses radio-frequency pulses
  • a receiver for receiving the NMR-signals can be identical to the emitter 6 or be separate. If the emitter and receiver are physically the same antenna or coil as shown in the Figure, a send-receive switch 9 is arranged to separate the received signals from the pulses to be emitted.
  • the received NMR-signals are input to a demodulator 10.
  • the modulator 8, the emitter 6 and the power supply 11 for the gradient coils 3, 4 and 5 are steered by a control system 12 to generate a predetermined sequence of RF-pulses and magnetic field gradient pulses.
  • the demodulator 10 is coupled to a data processing unit 14, for example a computer, for transformation of the received signals into an image that can be made visible, for example on a visual display unit 15.
  • the magnetic resonance imaging apparatus 1 If the magnetic resonance imaging apparatus 1 is put into operation with a body 7 placed in the magnetic field, a small excess of nuclear dipole moments or nuclear spins in the body will be aligned in the direction of the magnetic field. In equilibrium, this causes a net magnetisation M 0 in the material of the body 7, directed in parallel with the magnetic field.
  • This macroscopic magnetisation M Q is then manipulated by irradiating the body with RF-pulses having a frequency equal to the Larmor frequency of the nuclei, thereby bringing the nuclear dipole moments in an excited state and re-orienting the magnetisation M Q .
  • RF-pulses By applying the proper RF-pulses, a rotation of the macroscopic magnetisation vector is obtained, the angle of rotation is called the flip-angle.
  • NMR-signals are emitted from the body which signals provide information about the density of a certain type of nuclei, for example hydrogen nuclei, and the substance in which they occur.
  • signals provide information about the density of a certain type of nuclei, for example hydrogen nuclei, and the substance in which they occur.
  • information about the internal structure of th body 7 is accessible.
  • Figure 2 shows, as an example, a so-called spin-echo (SE) sequence, consisting o an excitation RF-pulse and a refocusing RF-pulse.
  • SE spin-echo
  • Other sequences such as FLASH, RARE, GRASE or EPI-spiral can be used as well.
  • the Figure shows five rows, labelled RF, indicating the occurrence of RF-pulses as a function of time, G x , G y and G z , indicating the occurrence of magnetic gradient fields in the x-, y- and z-directions, respectively, and MR, indicating the occurrence of the magnetic resonance signals in the body 7 caused by the RF and gradient pulses.
  • a free induction decay (FID) nuclear magnetic resonance signal 61 is generated which vanishes rapidly when the individual precessing nuclear magnetic dipole moments loose phase coherence (dephase) due to local variations in the magnetic field.
  • the refocusing RF-pulse 22 reverses the direction o these individual magnetic dipole moments without affecting the local magnetic field.
  • a compensating field 51' with the gradient in the opposite direction is applied.
  • a magnetic field 31 with a gradient in thex- direction is applied prior to the refocusing RF-pulse 22, this gradient field causes an initial dephasing of the nuclear spins.
  • a magnetic field measurement gradient 32 is applied, such that a magnetic resonance signal 62 is generated with a space dependent frequency.
  • the two mentioned x-gradients 31 and 32 are chosen such that the time integrated strength thereof between to and t j equals the time integrated strength between t x and t 2 , there is no nett effect of the j -gradient at time t ⁇ and a maximum spin echo signal is obtained.
  • a gradient 42 is applied prior to the measurement of the NMR signal, before or after the refocusing RF-pulse, resulting in a relation between the phase of the NMR signal and the position in y direction of the source of the NMR signal.
  • a two-dimensional Fourier transform is used for the conversion of the measurements acquired with different time- integrated x- and y-gradients in a spatial image.
  • the quality of the acquired data increases with the amount of time available for each signal sample measured. This is because the signal-to-noise ratio is proportional to the square root of the length of the total measurement period. So it is desirable that the available measurement period is as long as possible while obeying the physical and technical constraints of the gradients.
  • the main physical constraints are the need of avoiding any nett dephasing effect of the gradient in the z-direction, the need to have a zero nett dephasing effect between to and t E of the gradient in the ⁇ -direction and the application of a fixed strength gradient in the z-direction as well as the absence of other gradients during the RF- pulses.
  • the technical or machine constrains are the maximum gradient strengths and slopes that can be provided by the machine hardware. The present invention aims at providing a method to obtain the best signal within these constraints.
  • Flow compensation can be obtained without sacrificing the parameter to be optimised, or, if desired, flow compensation can be improved at the expense of the optimum solution with respect to the parameter to be optimised. Further, in a sequence the relative times for the RF-pulses and the gradient fields are highly interlinked, allowing a reduction of the number of parameters involved in the optimisation procedure.
  • a first possible additional constraint prescribes trapezium shaped magnetic field gradients with fixed rising and falling times. The amount of parameters is now limited, the relations between the parameters is linear and there are one or two nonlinear inequality constraints, following from the gradient slopes and strengths which should not exceed their maximum possible values. In a first method to search for an optimum solution the duration of the measurement gradient is set to its maximum value, i.e.
  • sequences in which echoes are generated by a gradient field TSE (turbo spin echo) or RARE (rapid acquisition by repeated echoes) comprising a plurality of refocusing RF-pulses causing a repetition of magnetic resonance signals
  • EPI echo planar imaging
  • GRASE gradient and spin echo
  • This solution method has some disadvantages. Firstly, as new imaging techniques in MRI with improved image quality and acquisition time reduction are constantly being developed, new physical constraints are likely to be implemented. For each new constraint introduced, the method has to be adapted. Due to the probable non-linearity of such constraints any significant adjustment of the method will be difficult to make. Secondly, as only a limited number of parameters is varied and only a single possible solution is searched, this solution need not be the optimum solution that could be obtained with the use of more parameters. Finally, because of the discrete step ⁇ , the optimum value is bound to be inaccurate. Any increase in accuracy by choosing a smaller value for ⁇ increases the calculation time.
  • a more flexible formulation of the set of constraints in particular allowing for a larger number of parameters and for non-linear constraints is proposed.
  • the gradient magnetic fields are given as piecewise linear waveforms, i.e. continuous functions composed of linear segments.
  • the nodes where the linear segments join are imposed to coincide in time in the gradient waveforms in each of the x-, y- and z-directions.
  • the waveform of the magnetic field gradients can have an arbitrary shape in those intervals were no preset value is required, i.e. when no RF-pulses are emitted or data acquisition takes place. Only the physical and technical constraints have to be obeyed.
  • the fixed portions of the gradient waveforms are indicated by solid lines, the positions that may be varied during the optimisation by dashed lines with nodes points.
  • the time-integrated gradient strengths are expressed in terms of the piecewise linear functions, and the physical constraints are expressed in relations between the integrated gradient strengths in different intervals. These time-integrated gradient strengths are composed of the sum over the contribution of each linear piece. For example, the time integrated strength of the -direction gradient, the measurement gradient, in the interval between the excitation and refocusing pulse of a spin echo sequence can be expressed as:
  • the device constraints can be expressed by: -M n ⁇ x ⁇ Gx x ⁇ M ⁇ and
  • Figures 4a and 4b show possible solutions for gradient waveforms for the slice selection and measurement gradients.
  • the waveform shown in Figure 4a has two variable nodes at both sides of the refocusing RF-pulse and the waveform shown in Figure 4b has six variable nodes at both sides.
  • substantially the same waveform results from the optimisation process. A larger number of variable nodes does result in a better solution but only consumes more computer time. So, a limited number of nodes seems to be sufficient.
  • penalty function In order to avoid magnetic field gradient waveforms which are undesirable from a technical point of view, a penalty function can be introduced. Such penalty function gives a slight preference to a solution with desirable features. So, it selects from a set of substantially equivalent solutions the one with the most desirable features, for example the one with equal gradient strengths at adjacent nodes or the one with a limited change in slope at each node.
  • variable nodes have a fixed time relationship imposed upon them, leaving the magnetic field gradient strength as the only independent variable.
  • This has the advantage that all constraints are linear and, consequently, that the optimisation process is very fast.
  • the other variable nodes are distributed in the relevant interval ate equal distances.
  • the existence of a solution is determined with help of the routine "E04MBF" of the NAG Fortran Library.
  • This method has as a disadvantage that the optimum solution, for example the one with the longest measurement period, if not found directly. If no solution can be reached with the maximum measurement time, but one can be reached with the minimum acceptable measurement time, in this embodiment a binary search is performed to determine the maximum measurement time for which a solution exists. It appears that also in this case, a limited number of variable nodes is sufficient for an acceptable solution. Using a large number of node points can be advantageous as smooth gradient waveforms can be imposed, i.e. the difference in slope between adjacent edges is limited.
  • Figure 5a shows a block diagram representing the functional relationship between the different steps in the method according to the invention is shown and Figure 5b shows a flow diagram of the method.
  • the functions will be accommodated in the control unit 12 as shown in Figure 1.
  • a user interface unit 90 instructions from an operator are accepted (box 110) to select an elementary pulse sequence and physical relevant parameters such as frame rate and related parameters echo time T E and repetition time T R , slice thickness and orientation and field-of-view. Also selected are the optimisation criteria.
  • box 120 a global description, retrieved from a storage 92 or already contained in the code of a stored computer program, is combined with the specified parameters in pulse generation unit 94 to a global physical description of the pulse sequence, comprising also the constraints that have to be applied.
  • This global physical description contains the areas and relative timing of the various gradient fields. If the RF-pulses themselves are to be included in the optimisation process the global physical description also contains the timing and time- integrated strength thereof. Box 130 indicates the technical constraints that have to be applied.
  • the details of the sequence are determined according to an optimisation procedure (box 140).
  • the results are then transmitted to the operator via user interface 90 (box 170).
  • the operator can than amend the constraints or impose additional constraints after which the optimisation procedure is repeated. If the operator accepts the results of the optimisation procedure, these are then used to control the MRI device via a control interface 98 for imaging (box 160).
  • Initialisation 110 Enter imaging sequence type, imaging parameters and optimisation criteria
  • the invented method allows a separation between the physical requirements of the MRI-sequence and the detailed description thereof, the latter being determined in the optimisation procedure.
  • the optimisation procedure can be implemented in a general way, a sequence with new or different constraints can be easily implemented.
  • the amount of time necessary to perform the optimisation procedure is quite acceptable.
  • the optimisation process took in general less than 10 seconds on a HP9000/735 computer and was only exceptionally not completed within 20 seconds.
  • the results strongly varied with the initial values of the parameters.
  • a set of initial values did not lead to a result, but always there were other sets of initial values for the same sequence and constraints that provided a result.

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Magnetic Resonance Imaging Apparatus (AREA)

Abstract

Procédé d'imagerie par résonance magnétique où des séquences d'images consistant en impulsions HF et de gradient de champ magnétique (RF, Gx, Gy, Gz) sont optimisées par rapport à un paramètre significatif (signal/bruit, etc.) avant d'être appliquées à l'objet ou au patient (7) à examiner. On peut ainsi réduire le nombre des séquences à un nombre limité de séquences de base parmi lesquelles l'opérateur peut choisir celles le mieux adaptées au type d'image recherché.
PCT/IB1994/000154 1994-06-14 1994-06-14 Procede d'imagerie par resonance magnetique a sequences d'images pulsees optimisees, et appareil associe WO1995034242A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
PCT/IB1994/000154 WO1995034242A1 (fr) 1994-06-14 1994-06-14 Procede d'imagerie par resonance magnetique a sequences d'images pulsees optimisees, et appareil associe
JP8501857A JPH09511169A (ja) 1994-06-14 1994-06-14 パルスシーケンスの最適化された磁気共鳴画像化方法及び装置
EP94916368A EP0712292A1 (fr) 1994-06-14 1994-06-14 Procede d'imagerie par resonance magnetique a sequences d'images pulsees optimisees, et appareil associe

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/IB1994/000154 WO1995034242A1 (fr) 1994-06-14 1994-06-14 Procede d'imagerie par resonance magnetique a sequences d'images pulsees optimisees, et appareil associe

Publications (1)

Publication Number Publication Date
WO1995034242A1 true WO1995034242A1 (fr) 1995-12-21

Family

ID=11004301

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IB1994/000154 WO1995034242A1 (fr) 1994-06-14 1994-06-14 Procede d'imagerie par resonance magnetique a sequences d'images pulsees optimisees, et appareil associe

Country Status (3)

Country Link
EP (1) EP0712292A1 (fr)
JP (1) JPH09511169A (fr)
WO (1) WO1995034242A1 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1004891A2 (fr) * 1998-11-25 2000-05-31 General Electric Company Système d'imagerie RM avec contrôle interactif du contraste de l'image
CN104049545A (zh) * 2013-03-13 2014-09-17 西门子公司 用于确定成像医学设备的优化测量序列的计算机运行方法
US9684048B2 (en) 2013-02-18 2017-06-20 Siemens Aktiengesellschaft Optimization of a pulse sequence for a magnetic resonance system
US9846213B2 (en) 2013-09-30 2017-12-19 Siemens Aktiengesellschaft Optimization of the noise development of a 3D gradient echo sequence in a magnetic resonance system

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5518403B2 (ja) * 2008-09-09 2014-06-11 株式会社東芝 磁気共鳴イメージング装置及び磁気共鳴イメージング方法
CN103106647B (zh) * 2013-03-06 2015-08-19 哈尔滨工业大学 基于四元数小波和区域分割的多焦点图像融合方法

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4728890A (en) * 1985-08-16 1988-03-01 Picker International, Inc. Motion artifact suppression technique of magnetic resonance imaging
US4835690A (en) * 1985-11-19 1989-05-30 Picker International, Inc. Integrated expert system for medical imaging scan, set-up, and scheduling
EP0567794A2 (fr) * 1992-03-31 1993-11-03 Kabushiki Kaisha Toshiba Imagerie par RMN à haute vitesse et commande interactive de séquence d'impulsions
US5317260A (en) * 1989-06-27 1994-05-31 Bruker Analytische Messtechnik Gmbh Process for generating a pulse sequence

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4728890A (en) * 1985-08-16 1988-03-01 Picker International, Inc. Motion artifact suppression technique of magnetic resonance imaging
US4835690A (en) * 1985-11-19 1989-05-30 Picker International, Inc. Integrated expert system for medical imaging scan, set-up, and scheduling
US5317260A (en) * 1989-06-27 1994-05-31 Bruker Analytische Messtechnik Gmbh Process for generating a pulse sequence
EP0567794A2 (fr) * 1992-03-31 1993-11-03 Kabushiki Kaisha Toshiba Imagerie par RMN à haute vitesse et commande interactive de séquence d'impulsions

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
J. NUCL. MED., Volume 27, No. 2, February 1986, CORNELIS N. DE GRAAF et al.: "Simulation Procedure to Determine Nuclear Magnetic Resonance Imaging Pulse Sequence Parameters for Optimal Tissue Contrast", page 281 - page 286, see the whole document. *

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1004891A2 (fr) * 1998-11-25 2000-05-31 General Electric Company Système d'imagerie RM avec contrôle interactif du contraste de l'image
EP1004891A3 (fr) * 1998-11-25 2000-07-05 General Electric Company Système d'imagerie RM avec contrôle interactif du contraste de l'image
US6166544A (en) * 1998-11-25 2000-12-26 General Electric Company MR imaging system with interactive image contrast control
US6362620B1 (en) 1998-11-25 2002-03-26 Ge Medical Systems Global Technology Company, Llc MR imaging system with interactive image contrast control over a network
US6377046B1 (en) 1998-11-25 2002-04-23 Ge Medical Systems Global Technology Company, Llc System and method for interactive image contrast control in a magnetic resonance imaging system
US9684048B2 (en) 2013-02-18 2017-06-20 Siemens Aktiengesellschaft Optimization of a pulse sequence for a magnetic resonance system
CN104049545A (zh) * 2013-03-13 2014-09-17 西门子公司 用于确定成像医学设备的优化测量序列的计算机运行方法
US9557248B2 (en) 2013-03-13 2017-01-31 Siemens Aktiengesellschaft Operating method for a computer to determine an optimized measurement sequence for a medical imaging system
CN104049545B (zh) * 2013-03-13 2017-08-18 西门子公司 用于确定成像医学设备的优化测量序列的计算机运行方法
US9846213B2 (en) 2013-09-30 2017-12-19 Siemens Aktiengesellschaft Optimization of the noise development of a 3D gradient echo sequence in a magnetic resonance system

Also Published As

Publication number Publication date
JPH09511169A (ja) 1997-11-11
EP0712292A1 (fr) 1996-05-22

Similar Documents

Publication Publication Date Title
US5758646A (en) Magnetic resonance imaging method with pulse sequence optimization and device for such method
US5561370A (en) Artefact suppression in GRASE Mr imaging
US5168226A (en) Acquisition of multiple images in fast spin echo nmr scans
US4734646A (en) Method for obtaining T1-weighted and T2-weighted NMR images for a plurality of selected planes in the course of a single scan
EP0366232B1 (fr) Procédé pour la production d'images en tranches multiples par RMN
EP0529527B1 (fr) Procédé et appareil d'imagerie rapide par résonance magnétique à qualité d'image améliorée
US4549140A (en) Method utilizing combined, interleaved pulse sequences for reducing motion artifacts in computed T1,T2 and M0 NMR imaging
EP2615470A1 (fr) Imagerie par RM avec cartographie B1
US5347216A (en) Fast NMR image acquisition with spectrally selective inversion pulse
US20140070805A1 (en) Mr imaging with b1 mapping
US20090292197A1 (en) Magnetic resonance device and method
Talagala et al. Introduction to magnetic resonance imaging
EP2648014A1 (fr) Imagerie par RM utilisant une amélioration de contraste APT
US8076939B2 (en) Method for fast magnetic resonance radiofrequency coil transmission profile mapping
EP0322968B1 (fr) Procédé et dispositif pour engendrer des suites d'impulsions multitranches et multiéchos entrelacées pour imagerie par résonance magnétique
EP0414318B1 (fr) Méthode multimode rapide d'imagerie par résonance magnétique
EP0526065A1 (fr) Imagerie par RMN utilisant des séquences d'impulsions SSFP compensées en flux
US6828790B2 (en) Magnetic resonance apparatus with excitation antennae system
US5101156A (en) Rapid flow measurement using an nmr imaging system
EP0165610B2 (fr) Procédé pour la formation à grande vitesse d'images à trois dimensions par résonance magnétique nucléaire
JP7023954B2 (ja) プロペラｍｒイメージング
JP3173612B2 (ja) 磁気共鳴分光法および映像法における、またはそれに関連する改良
US4855679A (en) Magnetic resonance studies of restricted volumes
EP0712292A1 (fr) Procede d'imagerie par resonance magnetique a sequences d'images pulsees optimisees, et appareil associe
EP3640662A1 (fr) Imagerie par résonance magnétique utilisant une reconstruction d'images compensées en mouvement

Legal Events

Date Code Title Description
WWE Wipo information: entry into national phase

Ref document number: 94193489.6

Country of ref document: CN

AK Designated states

Kind code of ref document: A1

Designated state(s): CN JP

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): AT BE CH DE DK ES FR GB GR IE IT LU MC NL PT SE

WWE Wipo information: entry into national phase

Ref document number: 1994916368

Country of ref document: EP

121 Ep: the epo has been informed by wipo that ep was designated in this application
WWP Wipo information: published in national office

Ref document number: 1994916368

Country of ref document: EP

WWW Wipo information: withdrawn in national office

Ref document number: 1994916368

Country of ref document: EP