EP1537431A2 - Procede d'imagerie spectroscopique, dispositif comprenant des moyens pour mettre ce procede en oeuvre et utilisation dudit procede d'imagerie pour caracteriser des materiaux - Google Patents

Procede d'imagerie spectroscopique, dispositif comprenant des moyens pour mettre ce procede en oeuvre et utilisation dudit procede d'imagerie pour caracteriser des materiaux

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Publication number
EP1537431A2
EP1537431A2 EP03757665A EP03757665A EP1537431A2 EP 1537431 A2 EP1537431 A2 EP 1537431A2 EP 03757665 A EP03757665 A EP 03757665A EP 03757665 A EP03757665 A EP 03757665A EP 1537431 A2 EP1537431 A2 EP 1537431A2
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EP
European Patent Office
Prior art keywords
phase coding
imaging method
gradient
switched
ssfp
Prior art date
Legal status (The legal status 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 status listed.)
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Application number
EP03757665A
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German (de)
English (en)
Inventor
Wolfgang Dreher
Christian Geppert
Matthias Althaus
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Universitaet Bremen
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Universitaet Bremen
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Publication of EP1537431A2 publication Critical patent/EP1537431A2/fr
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    • 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
    • G01R33/56—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution
    • G01R33/561—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution by reduction of the scanning time, i.e. fast acquiring systems, e.g. using echo-planar pulse sequences
    • G01R33/5613—Generating steady state signals, e.g. low flip angle sequences [FLASH]
    • 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
    • G01R33/485—NMR imaging systems with selection of signals or spectra from particular regions of the volume, e.g. in vivo spectroscopy based on chemical shift information [CSI] or spectroscopic imaging, e.g. to acquire the spatial distributions of metabolites

Definitions

  • the present invention relates to a spectroscopic imaging method (English “Spectroscopic Imaging”, abbreviated SI) using an SSFP (Steady State Free Precession) RF excitation pulse sequence, a device for carrying out the same, and the use of the imaging method for material characterization.
  • SI Spectroscopic Imaging
  • SSFP Steady State Free Precession
  • the invention is therefore based on the object of providing a spectroscopic imaging method of the type mentioned at the outset and an apparatus for carrying it out, by means of which shorter minimum measuring times are achieved.
  • this object is achieved according to a first aspect by a spectroscopic imaging method using an SSFP-HF excitation pulse sequence, with the following features: with a repetition time (TR), RF excitation pulses with a flip angle ⁇ are radiated onto an examination object, between the HF Excitation pulses are displayed in a first reading window without the presence of a measure.
  • TR repetition time
  • RF excitation pulses with a flip angle ⁇ are radiated onto an examination object, between the HF Excitation pulses are displayed in a first reading window without the presence of a measure.
  • phase coding gradient serve for the spatial coding or spatial resolution.
  • this object is achieved by a spectroscopic imaging method using an SSFP-HF excitation pulse sequence, with the following features: with a repetition time (TR), RF excitation pulses with a flip angle ⁇ are irradiated onto an examination object, between the HF Excitation pulses are read out in a single readout window without the presence of a magnetic field gradient, only an FID-like SSFP signal SI, at least one phase coding gradient for phase coding in at least one spatial direction is switched in front of the readout window, and at least one phase coding gradient is canceled before the next RF excitation pulse the phase coding switched.
  • TR repetition time
  • RF excitation pulses with a flip angle ⁇ are irradiated onto an examination object, between the HF Excitation pulses are read out in a single readout window without the presence of a magnetic field gradient, only an FID-like SSFP signal SI, at least one phase coding gradient for phase coding in at least one spatial direction is switched in front of the readout window, and at
  • this object is achieved by a spectroscopic imaging method using an SSFP-HF excitation pulse sequence with the following features: with a repetition time (TR), RF excitation pulses with a flip angle ⁇ are radiated onto an examination object, between the RF Excitation pulses are read out in a single readout window without the presence of a magnetic field gradient, only an echo-like SSFP signal S2, at least one phase coding gradient for phase coding is switched in at least one spatial direction in front of the readout window, and at least one phase coding gradient is reversed before the next RF excitation pulse Phase coding switched.
  • TR repetition time
  • RF excitation pulses with a flip angle ⁇ are radiated onto an examination object, between the RF Excitation pulses are read out in a single readout window without the presence of a magnetic field gradient, only an echo-like SSFP signal S2, at least one phase coding gradient for phase coding is switched in at least one spatial direction in front of the readout window, and at least one phase coding gradient is reverse
  • this object is achieved by a spectroscopic imaging method using an SSFP-HF excitation pulse sequence, with the following features: with a repetition time (TR), RF excitation pulses with a flip angle ⁇ are radiated onto an examination object, and between the RF excitation pulses are read out in a first readout window under at least one readout gradient oscillating in one spatial direction and an FID-like SSFP signal SI in a second readout window separate from the first readout window under at least one readout gradient oscillating in one spatial direction ,
  • the oscillating readout gradient (s) serves for the purpose of spatial coding or spatial resolution.
  • this object is also achieved according to a fifth aspect of the invention by a spectroscopic imaging method using an SSFP-HF excitation pulse sequence, with the following features: with a repetition time (TR), RF excitation pulses with a flip angle ⁇ are radiated onto an examination object, and between the RF excitation pulses, only one FID-like SSFP signal SI is read out in a single readout window under at least one readout gradient oscillating in one spatial direction.
  • TR repetition time
  • RF excitation pulses with a flip angle ⁇ are radiated onto an examination object, and between the RF excitation pulses, only one FID-like SSFP signal SI is read out in a single readout window under at least one readout gradient oscillating in one spatial direction.
  • a further solution consists in a spectroscopic imaging method using an SSFP-HF excitation pulse sequence, with the following features: with a repetition time (TR), RF excitation pulses with a flip angle ⁇ are radiated onto an examination object, and between the HF Excitation pulses, only one echo-like SSFP signal S2 is read out in a single readout window under at least one readout gradient oscillating in one direction.
  • TR repetition time
  • the separation of the first and second readout windows advantageously takes place by switching a first spoiler gradient between the FID-like SSFP signal SI and the echo-like SSFP signal S2.
  • the RF excitation pulses are irradiated in a layer-selective manner. This is e.g. B. possible by irradiation of the RF excitation pulses with simultaneously switched slice selection gradient.
  • the spatially layer-selective irradiation of the RF excitation pulses is used for spatial coding or spatial resolution.
  • a second spoiler gradient is advantageously connected between the FID-like SSFP signal SI and the echo-like SSFP signal S2 and a frequency-selective saturation pulse is radiated in between the first and second spoiler gradients to suppress an interfering signal.
  • the interfering signal can generally be the signal of a dominant solvent, e.g. B. water act.
  • At least one phase coding gradient for reversing the phase coding in at least one spatial direction and at least one phase coding gradient for phase coding in at least one spatial direction are switched in succession after the first read window and before the second read window.
  • the RF excitation pulses are frequency selective.
  • the RF excitation pulses are so f selective that generally a disturbing dominant signal, such as. B. a water signal, not or only slightly excited and / or not or only slightly refocused.
  • a frequency-selective excitation and or refocusing can take place in particular by means of amplitude and / or frequency-modulated RF pulses or by groups of rectangular RF excitation pulses (“hard pulses”).
  • a first spoiler gradient is advantageously switched after the readout window.
  • the RF excitation pulses are irradiated in a layer-selective manner.
  • a second spoiler gradient is switched after the readout window and a frequency-selective saturation pulse is radiated in between the first and second spoiler gradients to suppress an interfering signal.
  • the RF excitation pulses are frequency selective.
  • a first spoiler gradient is switched in front of the readout window.
  • the RF excitation pulses are irradiated in a layer-selective manner.
  • a second spoiler gradient is expediently switched in front of the readout window and an equivalence-selective saturation pulse is radiated in between the first and second spoiler gradients to suppress an interfering signal.
  • the RF excitation pulses are frequency selective.
  • exactly two phase coding gradients for phase coding are switched in two spatial directions in front of the first readout window and exactly two phase coding gradients for reversing phase coding in the two spatial directions are switched in front of the next RF excitation pulse.
  • This provides a two-dimensional resolution within a selected layer.
  • exactly three phase coding gradients for phase coding in three spatial directions are switched in front of the first readout window and exactly three phase coding gradients for reversing phase coding in the three spatial directions are switched before the next RF excitation pulse. This provides a three-dimensional resolution in the selected layer.
  • phase coding gradients for phase coding in three spatial directions are switched in front of the readout window and exactly three phase coding gradients for reversing phase coding in the three spatial directions are switched before the next RF excitation pulse.
  • the ' FID-like SSFP signal SI and the echo-like SSFP signal S2 are each read out under exactly one oscillating readout gradient, one or in front of the first readout window two phase gradient (s) for phase coding are switched in one or two spatial directions and one or two phase coding gradient (s) for reversing a phase coding in one or two spatial directions are switched before the next RF excitation pulse. Since the oscillating readout gradient already provides a resolution in one dimension within a selected layer, one phase gradient contributes to the resolution in the second dimension and another phase gradient contributes to the resolution in the third dimension.
  • the FID-like SSFP signal SI and the echo-like SSFP signal S2 are each read out from exactly two read gradients oscillating in different spatial directions and exactly one phase coding gradient for phase coding in one in front of the first read window The spatial direction is switched and exactly one phase coding gradient is switched before the next RF excitation pulse to undo a phase coding in the spatial direction.
  • the FID-like SSFP signal SI and echo-like SSFP signal S2 are each read out using exactly three read-out gradients oscillating in different spatial directions.
  • the first and second read-out windows are advantageously separated by switching a first spoiler gradient between the FID-like SSFP signal SI and the echo-like SSFP signal S2.
  • the RF excitation pulses are irradiated in a layer-selective manner.
  • a second spoiler gradient is favorably switched between the FID-like SSFP signal SI and echo-like SSFP signal S2 and an equivalence-selective saturation pulse is radiated between the first and second spoiler gradients to suppress an interfering signal.
  • at least one phase coding gradient for reversing the phase coding in at least one spatial direction and at least one phase coding gradient for phase coding in at least one spatial direction are advantageously switched.
  • the RF excitation pulses are frequency selective.
  • the FID-like SSFP signal SI is advantageously read out under exactly one readout gradient oscillating in one spatial direction, one or two phase gradient (s) for phase coding in one or two spatial direction (s) and one or two phase coding gradients are switched in front of the next RF excitation pulse in order to undo a phase coding in one or two spatial directions.
  • the FID-like SSFP signal SI is read out under exactly two read gradients oscillating in different spatial directions and exactly one phase coding gradient for phase coding in one spatial direction is switched in front of the readout window and exactly one phase coding gradient for reversing before the next RF excitation pulse a phase coding can be switched in the spatial direction.
  • the FID-like SSFP signal SI is read out under exactly three read-out gradients oscillating in different spatial directions.
  • a first spoiler gradient is favorably switched after the readout window.
  • the RF excitation pulses are irradiated in a layer-selective manner.
  • a second spoiler gradient is advantageously switched after the reading window and a frequency-selective saturation pulse is radiated in between the first and second spoiler gradients to suppress an interfering signal.
  • the RF excitation pulses are frequency-selective.
  • the echo-like SSFP signal S2 is read out under exactly one readout gradient oscillating in one spatial direction, in front of the readout window one or two phase grades (s) are used for phase coding in one or switched in two spatial directions and one or two phase encoding gradient (s) is switched in front of the next RF excitation pulse in order to undo a phase encoding in one or two spatial directions.
  • the echo-like SSFP signal S2 is read out under exactly two read gradients oscillating in different spatial directions, and exactly one phase coding gradient for phase coding is switched in one spatial direction in front of the read window and before the next RF excitation pulse exactly one phase coding gradient can be switched in order to undo a phase coding in the spatial direction.
  • the echo-like SSFP signal S2 is read out under exactly three read gradients oscillating in different spatial directions.
  • a first spoiler gradient is advantageously switched after the readout window.
  • the RF excitation pulses are irradiated in a layer-selective manner.
  • a second spoiler gradient is expediently switched after the readout window and a frequency-selective saturation pulse is radiated in between the first and second spoiler gradients to suppress an interfering signal.
  • the RF excitation pulses are frequency selective.
  • the signals SI and / or S2 are detected with a single RF coil.
  • the signals SI and / or S2 are detected with at least two RF coils with spatially different sensitivity profiles. Signals are recorded in parallel in each RF coil. In this way, the number of necessary phase coding steps can be reduced for a defined voxel size and voxel number ("parallel imaging").
  • parallel imaging For details on this, see K. Pruessmann, M. Weiger, MB Scheidegger, P. Boesiger: "SENSE: Sensitivity encoding for fast MRI ", Magn. Reson. Med. 42, 952-962 (1999), the content of which is hereby incorporated by reference.
  • the device can be provided that it is a magnetic resonance device, in particular a magnetic resonance tomography device or magnetic resonance spectroscopy device or a combination thereof.
  • the invention is based on the surprising finding that with the spectroscopic imaging method according to the invention that when using SSFP sequences in the Advantages that can be achieved with MRI (Magnetic Resonance Imaging), such as in particular short minimum measurement times (ie the time required to record a complete data set) and high SNR can also be achieved.
  • the minimum measuring times are particularly short if the signals are read out under an oscillating readout gradient.
  • the spectroscopic imaging methods according to the invention place only small demands on the hardware (magnetic field (Bo) gradient, RF power, etc.) and can be scaled favorably if the measurements are carried out at higher magnetic field strengths.
  • the use of higher magnetic fields is a main trend for the clinical or other areas of application of magnetic resonance imaging / spectroscopy.
  • the SNR t can be higher, especially for uncoupled signals, than in other previously known spectroscopic imaging methods. Optimization is also possible for J-coupled signals (repetition time TR depending on T (spin-spin relaxation time) and J-coupling).
  • phase encoding gradients are used for phase encoding the spatial information, losses in spatial resolution are avoided which are caused by the signal drop with T 2 or T (effective transverse relaxation time), how he z.
  • T 2 or T effective transverse relaxation time
  • the exclusive reading of the FFD signal SI in particular also enables detection of signals which have a short T 2 and therefore do not contribute to the echo-like SSFP signal S2 or only with a low intensity. Due to the low T 2, the SNR is higher than for the echo-like SSFP signal S2. In addition, the detection of SI begins only shortly after signal excitation (typically a few ms), since the phase modulation of J-coupled signals, which in particular lead to signal losses from multiplet signals, is very low.
  • the exclusive reading of the SSFP signal S2 enables in particular the detection of signals with a longer T, but not of signals with a short T 2 .
  • Singlet signals (without J-coupling) can be detected, but also J-coupled signals, the distance between the RF excitation pulses strongly influencing their intensity.
  • J-coupled signals with good SNR can be detected as well as deliberately suppressed (e.g. to avoid being overlaid with another signal).
  • the simpler (and stronger) suppression of interfering signals e.g. water and lipid signals in the ⁇ -NMR is particularly advantageous.
  • the advantages of the spectroscopic imaging methods can be used with only reading out the respective SI and S2, but with the disadvantage that, of course, given the repetition time of the RF excitation pulses for reading out each individual SI and S2 less reading time compared to the exclusive reading is available. Otherwise, the repetition time . TR can be optimized in such a way that the measurement times are evaluated either in the frequency domain (reconstruction e.g. by Fourier transformation) after using special apodization extinctions (data preprocessing) and / or with the aid of data extrapolation methods for the measured time signal or by analysis in the time domain ( Adapting model functions) can be done. Adequate spectral resolution and an adequate SNR are achieved.
  • the optimal repetition time TR depends on Ti (spin-lattice relaxation time), T 2 , T 2 * and the necessary or desired width and resolution of the spectrum.
  • the detection of the signals of J-coupled spins can be optimized in that the repetition time TR is also selected as a function of the multiplet structure and the J-coupling constants.
  • a disturbing dominant signal such as. B. a water signal is suppressed
  • this enables use in particular in proton spectroscopy ( 1 H) -SI, which, for.
  • 1 H proton spectroscopy
  • FIG. 8 examples of measurement results obtained with a spectroscopic imaging method according to a particular embodiment of the present invention
  • FIG. 9 results of computer simulations of signal-to-noise ratios (SNR t ) achievable by means of SSFP-based spectroscopic imaging and spectroscopic imaging in the prior art per unit measuring time.
  • SNR t signal-to-noise ratios
  • a third phase coding gradient is optional, particularly for the use of a slice-selective RF excitation pulse.
  • the spatial directions for the phase coding, slice selection and readout gradients should preferably be orthogonal in pairs, even if this is not mandatory.
  • the spoiler gradients can be at a different angle to this, since they can (arise) by summing several gradients (x, y, z).
  • the excitation pulse and gradient diagram shown in FIG. 1 shows a spectroscopic imaging method according to a particular embodiment of the present invention, which is based on a FADE (Fast Acquisition Double Echo (for details, see “FADE - A New Fast Imaging Sequence", TW Redpath, RA Jones, Magnetic Reso- nace in Medicine 6, 224 to 234 (1988)) -SSFP sequence.
  • FADE Full Acquisition Double Echo
  • phase coding gradients GP1, GP21 and G31 are switched in front of a first readout window 10, the phase coding being reversed after a second readout window 20 by means of the phase coding gradients GP14, GP24 and GP34.
  • the information of the chemical shift is also recorded in addition to the spatial signal distribution.
  • the first and second readout windows 10 and 20 are separated by switching a first spoiler gradient GS1 between the FID-like SSFP signal SI and echo-like SSFP signal S2. Furthermore, a second spoiler gradient GS2 is connected between the FID-like SSFP signal SI and the SSFP echo S2, and a frequency-selective saturation pulse Sat is suppressed between the first and second spoiler gradients GS1 and GS2 to suppress an interference signal, here a water signal.
  • phase encodings by GP1, GP21 and GP31 are reversed by switching the phase encoding gradients GP12, GP22 and GP32 and before the second readout window, new phase encodings are carried out by switching the phase encoding gradients GP13, GP23 and GP33.
  • the saturation pulse Sat has a length in the range from 10 to 15 ms.
  • a number of dummy measurement cycles are carried out in order to achieve the dynamic equilibrium state (SSFP state).
  • the number of dummy Measuring cycles are typically 64th to 128 cycles.
  • the FOV Field-Of-View
  • the number of coding steps per spatial direction is 8, 16 or 32 (a multiple of 2 is not necessary, can also be different in the spatial directions, whereby the number in one direction can depend on the index in one or the other direction).
  • the excitation pulse and gradient scheme shown in FIG. 2 belongs to a spectroscopic imaging method according to a further special embodiment of the invention, which is based on a FAST (Fourier Acquired Steady State) (also FISP (Fast Imaging with Study Precession) or GRASS (GRAdient-Recalled Steady State), with regard to details on "Fast Field Echo Imaging: In Overview and Contrast Calculations", P. von der Meulen, JP Groen, AMC Tinus, G. Bruntink, Magnetic Resonance Imaging, Volume 6, pages 355 to 368, 1988
  • a slice-selective RF excitation pulse with a flip angle ⁇ is irradiated onto an examination object, just like in the embodiment of Figure 1.
  • phase coding gradients GP1, GP21 and GP31 are switched for three-dimensional phase coding.
  • the phase encoding before the next RF excitation pulse (not shown) by phase encoding gradients GP14, GP24 and GP34 can be undone.
  • the echo-like SSFP signal S2 is suppressed by switching a first spoiler gradient GS1 after the readout window 15.
  • a second spoiler gradient GS2 is switched after the readout window 15 and a frequency-selective saturation pulse Sat between the first and second spoiler gradients GS1 and GS2 for suppressing one Water signal radiated.
  • the saturation pulse Sat is optional. If it is not provided, the spoiler gradients GS1 and GS2 can also be combined to suppress the SSFP echo S2.
  • the FID-like SSFP signal SI is read out in the single readout window 15 without a magnetic field gradient.
  • FIG. 3 shows an excitation pulse and gradient diagram of a spectroscopic imaging method according to a further particular embodiment of the invention, which is based on a CE-FAST (Contrast Enhanced FAST) (also called PSTF (Time Reversed FISP))) SSFP sequence.
  • CE-FAST Contrast Enhanced FAST
  • PSTF Time Reversed FISP
  • a slice-selective RF excitation pulse with a flip angle ⁇ is irradiated onto an examination object.
  • a three-dimensional phase coding is carried out as in the embodiments according to FIGS. 1 and 2, which is reversed after the readout window 25 by switching the phase coding gradients GP14, GP24 and GP34.
  • a first spoiler gradient GS1 is switched in front of the readout window 25.
  • a second spoiler gradient GS2 is switched in front of the readout window 25 and a frequency-selective saturation pulse Sat is radiated in between the first and second spoiler gradients GS1 and GS2 to suppress a water signal.
  • the echo-like SSFP signal S2 is read out in the single readout window 25 without a magnetic field gradient.
  • FIG. 4 shows an excitation pulse and gradient diagram of a spectroscopic imaging method according to a further special embodiment of the invention, which differs from that shown in FIG. 1 in that instead of a slice-selective RF excitation pulse, a frequency-selective RF excitation pulse in the form of rectangular pulses ("Hard Pulses") is present, which means that suppression of the water signal by means of a saturation pulse can also be dispensed with for the ⁇ - IVIR.
  • a single spoiler gradient GS1 is therefore sufficient to separate the two readout windows 10 and 20. Also the switching of the phase coding gradients is also sufficient GP12, GP22 and GP32 as well as GP31, GP23 and GP33 are no longer available.
  • the metabolite signals are excited or refocused, but not (or only slightly) the water signal.
  • Typical repetition time TR is in the range from 30 to 120 ms.
  • a number of dummy measurement cycles are carried out in order to achieve the dynamic equilibrium state. The number of dummy measurement cycles is typically 64 to 128.
  • the FOV has the dimensions 48 mm ⁇ 48 mm ⁇ 48 mm or 32 mm ⁇ 32 mm ⁇ 32 mm, although it does not necessarily have to be the same size in x, y and z.
  • the number of coding steps per spatial direction is 8, 16 or 32 (not necessarily a multiple of 2, can vary in the spatial directions, whereby the number of directions can depend on the index in one or the other direction).
  • FIG. 5 shows an excitation pulse and gradient diagram of a spectrocopical imaging method according to a further particular embodiment of the invention, which differs from the embodiment according to FIG. 2 in that a frequency-selective RF excitation pulse is used instead of a slice-selective RF excitation pulse, which also means the radiation of a saturation pulse and the spoiler gradient GS2 can be dispensed with.
  • the echo-like SSFP signal S2 is suppressed by switching the spoiler gradient GS1.
  • FIG. 6 shows an excitation pulse and gradient diagram of a spectroscopic imaging method according to a further special embodiment of the invention, which differs from the embodiment according to FIG. 3 in that instead of a slice-selective RF excitation pulse, a frequency-selective RF excitation pulse in the form of rectangular Pulses ("hard pulses") is used, which means that a saturation pulse Sat for suppressing a water signal and a spoiler gradient GS2 can also be dispensed with.
  • the FID-like SSFP signal SI is suppressed by switching the spoiler gradient GS1.
  • FIG. 7 shows an excitation pulse and gradient diagram of a spectroscopic imaging method according to a further particular embodiment of the invention, which differs from the embodiment according to FIG. 2 in that only two phase coding gradients GP1 and GP21 are switched in front of the readout window 15 and after the readout window 15 the phase coding gradients GP14 and GP24 are switched in order to undo the phase coding.
  • the embodiment shown in Figure 7 differs from that shown in the Figure 2 embodiment in that the FID-like SSFP signal SI in the measuring window 15 at an oscillating read-out gradient G is read rea d. Together with the two-dimensional phase coding, this provides a three-dimensional resolution in a selected layer.
  • FIG. 8 shows the measurement results of the spectroscopic imaging method according to FIG. 1 on a spherical phantom which is filled with 100 mm NAA.
  • FIG. 8 a shows the spectrum obtained on the basis of the evaluation of the FID-like SSFP signal SI
  • the inherently short repetition time TR of SSFP-based sequences achieves a short minimum measurement time and nevertheless, due to the properties of SSFP sequences, a high signal-to-noise ratio is achieved.

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Abstract

L'invention se rapporte à un procédé rapide d'imagerie spectroscopique utilisant des séquences SSFP modifiées, à un dispositif permettant de mettre ce procédé en oeuvre ainsi qu'à l'utilisation dudit procédé pour caractériser des matériaux.
EP03757665A 2002-09-13 2003-09-10 Procede d'imagerie spectroscopique, dispositif comprenant des moyens pour mettre ce procede en oeuvre et utilisation dudit procede d'imagerie pour caracteriser des materiaux Withdrawn EP1537431A2 (fr)

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DE10243830 2002-09-13
DE10243830A DE10243830B4 (de) 2002-09-13 2002-09-13 Spektroskopisches Bildgebungsverfahren sowie Verwendung desselben zur Materialcharakterisierung
PCT/DE2003/002997 WO2004027441A2 (fr) 2002-09-13 2003-09-10 Procede d'imagerie spectroscopique, dispositif comprenant des moyens pour mettre ce procede en oeuvre et utilisation dudit procede d'imagerie pour caracteriser des materiaux

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AU2003273732A1 (en) 2004-04-08
WO2004027441A3 (fr) 2004-08-05
US20060139027A1 (en) 2006-06-29
AU2003273732A8 (en) 2004-04-08
DE10243830B4 (de) 2006-11-16
WO2004027441A2 (fr) 2004-04-01
DE10243830A1 (de) 2004-03-25
JP2005537896A (ja) 2005-12-15

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