WO2001073479A1 - Spectroscopie par resonance magnetique bidimentionnelle correlee localisee du cerveau humain a decalage - Google Patents
Spectroscopie par resonance magnetique bidimentionnelle correlee localisee du cerveau humain a decalage Download PDFInfo
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- WO2001073479A1 WO2001073479A1 PCT/US2001/010227 US0110227W WO0173479A1 WO 2001073479 A1 WO2001073479 A1 WO 2001073479A1 US 0110227 W US0110227 W US 0110227W WO 0173479 A1 WO0173479 A1 WO 0173479A1
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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
- G01R33/483—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
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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]
- G01R33/46—NMR spectroscopy
- G01R33/4633—Sequences for multi-dimensional NMR
Definitions
- the field of the invention is MR Spectroscopy.
- N-acetylaspartate N-acetylaspartate
- Glx glutamate/glutamine
- Choline Choline
- Cr creatine
- ml myo-inositol
- GABA ⁇ - aminobutyrate
- JPRESS J-resolved MR spectroscopic
- McKinnon and Bosiger proposed a conventional COSY sequence with hard rf pulses (90°-t* ⁇ - 90°) followed by three volume selective 180° rf pulses; see McKinnon and Bosiger, supra.
- Haase and co-workers implemented a COSY combined with an outer volume suppressing sequence, namely the Localization of
- a new gradient enhanced COSY in combination with Volume Localized Spectroscopy used the Stimulated Echo Acquisition Mode (STEAM) sequence for volume localization; see Brereton IM, Galloway GJ, Rose SE and Doddrell DM, (1994), "Localized two-dimensional shift correlated and J- resolved NMR spectroscopy", Magn Reson Med, 17:285-303.
- STEAM Stimulated Echo Acquisition Mode
- a human brain 2D COSY spectrum using a 2T MRI scanner was recorded in a gross occipital volume of 5x6x8 cm 3 , which required a total sampling duration of 1 hour and 42 minutes; see Brereton and Galloway et al., supra.
- Non-localized versions of COSY spectra have also been recorded in rat brain and rabbit kidney by other researchers using high field NMR spectrometers; see Peres M, Fedeli O, Barrere B, et al., (1992), "In vivo identification and monitoring of changes in rat brain glucose by two- dimensional shift-correlated 1 H NMR Spectroscopy", Magn Reson Med, 27:356-361 ; Berkowitz BA, Wolff SD and Balaban RS, (1988), "Detection of metabolites in vivo using 2D proton homonuclear correlated spectroscopy", J Magn Reson, 79:547-553.
- the present invention is directed to a localized chemical shift correlated magnetic resonance spectroscopic (L-COSY) sequence, integrated into a new volume localization technique (90°-180°-90 0 ), for use in a method of whole body magnetic resonance (MR) spectroscopy.
- the L-COSY sequence involves applying a pulse train of at least three high frequency (rf) pulses to localize a volume of interest, a first slice selective 90° rf pulse, a second slice selective 180° rf pulse and a last slice selective 90° rf pulse.
- the first and second slice selective pulses generate a first spin echo and the last slice selective 90° pulse generates a second coherence transfer echo.
- An incremental period t-i is inserted after the first spin echo and before the last slice selective 90° pulse. Moreover, a MR signal is detected during interval t 2 after the last slice-selective 90° rf pulse and the MR signal data is stored for further analysis.
- the 1 D analog of the proposed sequence with three slice selective rf pulses (90°, 180°, 90°), CABINET, is a new volume localization sequence next to the most popular PRESS and STEAM sequences commercially available on a MRI scanner. Our new CABINET sequence is as sensitive as STEAM. This will not use the incremental periods and results in a conventional 1 D spectral graph.
- PRESS is based on two spin echoes,
- a preferred version of the L-COSY sequence selects a coherence transfer pathway by: (1) attaching slice-selective B 0 gradient pulses to the first slice selective 90° rf pulse, the second slice selective 180° rf pulse and the last 90° rf pulse; (2) applying slice refocusing B 0 gradient pulses after the first slice selective 90° rf pulse, before the last 90° rf pulse and after the last 90° rf pulse; and (3) applying Bo gradient crusher pulses before and after the second slice selective 180° rf pulse and before and after the last 90° it pulse.
- the (90°-180°-90°) pulse train is repeated with different values of t ⁇ ;and the stored MR signal data is subjected to a double Fourier transformation with respect to ti and t 2 to obtain a two dimensional MR spectrum.
- a most preferred version of the L-COSY sequence includes a step for suppressing MR signals of a solvent, such as water, which may obscure the signals of other substances within the volume of interest.
- the present invention may be used as a non-invasive method for identifying brain metabolites, wherein a volume of interest, localized within a region of the brain, is subjected to the 2D L-COSY sequence.
- a combination of different MRI transmit/receive rf coils is used for the 2D L-COSY sequence, e.g., a head MRI coil, and a 3" surface coil receive combined with a body coil transmit.
- Cross peak intensities excited by the proposed 2D L-COSY sequence are asymmetric with respect to the diagonal peaks.
- a characteristic cross peak, corresponding to a brain metabolite, is then identified in the resulting 2D MR spectrum.
- the J cross peaks due to N-acetyl aspartate (NAA), glutamate/glutamine (Glx), myo-inositol (ml), creatine (Cr), choline (Ch), aspartate (Asp), ⁇ -aminobutyrate (GABA), threonine (Thr), glutathione (GSH) and macromolecules (MM) can be identified using the method of the present invention.
- Representative L-COSY spectra of cerebral frontal and occipital gray/white matter regions in fifteen healthy controls are presented in the examples.
- another embodiment of the present invention includes an additional step of extracting a cross-sectional one dimensional (1D) MR spectra of a metabolite from the 2D L-COSY spectrum.
- Spectroscopic sequence (L-COSY);
- Figure 2 b) is an MR image of a 3x3x3 cm 3 voxel localized by the proposed CABINET sequence ;
- Figure 2 c) is a suppression profile recorded in a water phantom using the CABINET sequence combined with CHESS;
- Figure 3 is a localized one-dimensional (1 D) MR spectra of a brain phantom using: a) PRESS, and b) STEAM and c) CABINET sequences;
- Figure 6 is an Axial MR image of a 25 year-old healthy control
- Figure 7a is an in vivo 2D L-COSY spectra recorded in the frontal gray/white matter area using 40 ⁇ t* ⁇ ;
- Figure 7b) is an in vivo 2D L-COSY spectra recorded in the frontal gray/white matter area using 64 ⁇ t ⁇ ;
- Figure 7c is an in vivo 2D L-COSY spectra recorded in the frontal gray/white matter area using 128 ⁇ t* ⁇ ;
- Figure 8 a is an axial MRI of a 25-year old healthy control with the MRS voxel location shown in the occipital gray/white matter area (3x3x3cm 3 );
- Figure 8 b is a 2D L-COSY spectra recorded in the occipital gray/white matter area; DETAILED DESCRIPTION Pulse Sequence
- Figure 1 is a localized two-dimensional Correlated SpectroscopY (L- COSY) sequence with the pertinent coherence transfer pathway diagram.
- the VOI is localized in one shot by a combination of three slice-selective rf pulses (90°-180°-90°). This new MRS volume. localization sequence is called CABINET (coherence transfer based spm-echo spectroscopy). The duration of these rf pulses are 1.8ms, 5.2ms and 1.8ms, respectively.
- the last slice- selective 90° rf pulse also acts as a coherence transfer pulse for the 2D spectrum, after an incremental period for the second dimension is inserted immediately after the formation of the first Hahn spin-echo.
- Bo gradient crusher pulses before and after the slice-selective 180° rf pulse and the last 90° rf pulses, the actions of which are justified below.
- a minimum number of eight averages is acquired for every incremental period in order to improve the signal to noise from a localized volume.
- the proposed sequence can be considered as a single-shot technique in terms of volume localization and coherence transfer.
- Each time point of the pulse sequence is marked, as shown in Figure 1 , to evaluate the time course of magnetization that will take into account the rotation after each rf pulse and the evolution during the B 0 gradient pulses and the incremental period.
- the superior feature of the proposed L-COSY sequence compared to the previously published sequences is that the volume localization and the coherence transfer for COSY are simultaneously achieved using the last slice-selective rf pulses without adding more rf or gradient pulses.
- TR 2s
- minimal TE of 30ms 40, 64, 128 and 256 increments of ⁇ ti
- 8- 6 number of excitations per ⁇ ti The raw data is acquired using 1024-2048 complex points and the spectral window along the first dimension is 2500Hz. ⁇ ti is incremented to yield a spectral window of 625Hz along the second dimension.
- a 1.5T whole body MRI/MRS scanner (GE Medical Systems, Waukesha, Wl) with 'echo-speed' gradients at a slew rate of 120 ⁇ s is used.
- the crusher gradient pulses for the 180° and the last 90° rf pulses used a maximum amplitude of 2.2G/cm and the duration of each pulse is 6ms long.
- a frequency offset of 20Hz is included for the three slice-selective rf pulses to minimize the voxel shifts.
- a GE brain MRS phantom, MRS-HD sphere (GE Medical Systems, Milwaukee, Wl), is used to optimize the L-COSY sequence; see Schirmer T and Auer DP, (2000), On the reliability of quantitative clinical magnetic resonance spectroscopy of the human brain, NMR Biomed, 13:28-36.
- N-acetyl-L-aspartic acid N-acetyl-L-aspartic acid
- CaAA creatine hydrate
- Cr choline chloride
- myo-inositol ml, 7.5mM
- Glu L-glutamic acid
- Lac DL-lactic acid
- NaOH sodium hydroxide
- the phantom also contains 1ml/l GdDPTA (Magnavist).
- a product operator formalism is used to evaluate the time course of the magnetization; see Ernst and Bodenhausen et al., supra.
- a single spin system (I) is considered first.
- the spin evolution during the first slice selective 90° rf pulse is calculated during three different intervals, (i) the first half, (ii) immediately after the rotation of the 90° rf pulse and (iii) the second half of the slice selective B 0 gradient pulse.
- phase of the signal is scrambled under the influence of a B 0 gradient field.
- a pulsed gradient field modifies the angular precession of the nuclear spin I according to its spatial position. ⁇ i oc -Iycos ⁇ -t + I ⁇ Sin ⁇ [1.3],
- the symmetric gradient crusher pulses also dephase the unwanted magnetization when the refocusing 180° rf pulse is imperfect.
- the 180° rf pulse is supposed to be self-refocusing which means that the transverse magnetization during the first half is dephased and subsequently rephased during the second half.
- the spin state after an evolution during the second Bo gradient crushers is represented by, ⁇ oc I y ⁇ cos ⁇ C ⁇ s ⁇ 2 + sin ⁇ - ⁇ sin ⁇ 2 ⁇ - I x ⁇ cos ⁇ sin ⁇ 2 - cos ⁇ 2 sin ⁇
- Equation [1.8] shows the formation of a Hahn spin echo.
- a second pair of Bo gradient crusher pulses is played around the last slice-selective 90° rf pulse.
- the spin state after an evolution during the first set of crusher gradient pulses can be described by,
- the CABINET sequence retains only 50% net signal from the localized volume due to a selection of only N-type echo after the last pair of B 0 gradient crusher pulses; see Ernst and Bodenhausen et al., supra.
- the second 90° rf pulse along x-direction converts the transverse magnetization into i) longitudinal magnetization contributing to a stimulated echo after the last 90° rf pulse and ii) transverse magnetization which gets dephased by a strong TM-crusher gradient pulse.
- the STEAM sequence retains only 50% signal from the localized voxel due to the selection of N-type echo; see Ernst and Bodenhausen et al., supra.
- Our theoretical calculations as well as phantom spectra show that the volume localization efficiencies of CABINET and STEAM are the same, and both retain only 50% of magnetization compared to a full return in PRESS.
- the proposed sequence uses only a minimal number of rf pulses; see McKinnon and Bosiger, supra; Brereton and Galloway et al., supra.
- the spin evolution during the first slice selective 90° rf pulse is calculated after three different events, during the first half and the second half of the slice selective B 0 gradient pulse, and after the rotation of the 90° rf pulse.
- the spin state is the same as shown in equation [2.1].
- ⁇ -T oc e i ⁇ 2IX I z e i ⁇ /2Ix oc -l y [2.2]
- the signal is phase scrambled under the influence of B 0 gradient and the J-evolution is neglected.
- ⁇ i oc -I y cos ⁇ i + I x sin ⁇ [2.3], where ⁇ !
- a second set of B 0 gradient crusher pulses are transmitted around the last slice-selective 90° rf pulse.
- the spin state is represented by, ⁇ ' oc AI y cos03 - AI x sin0 3 - CI x cos ⁇ 3 - CI y sin03 - B2I x S z cos ⁇ 3 - B2I y S z sin ⁇ 3 -D2I y S z cos ⁇ 3 + D2I x S z sin ⁇ 3 [2.12]
- phase factors ⁇ 3 and ⁇ , are defined in equations [1.9a] and [1.15a].
- ⁇ 4 ⁇ 3
- ⁇ 8 oc- 0.5 cos( ⁇ Jt ⁇ ) I y cos( ⁇ t ⁇ ) + I x sin( ⁇ t ⁇ )] - 0.5 sin( ⁇ Jt ⁇ ) [2I Z S X cos( ⁇ t ⁇ ) - 21zSy Sin( ⁇ t ⁇ )] [2.17]
- Equation [2.17] clearly indicates that both the diagonal and cross peaks of an L-COSY spectrum have mixed phases along the ⁇ * ⁇ axis.
- the phase modulation in L-COSY is caused by the evolution during the B 0 gradient pulse during the evolution period t
- Pure phase L-COSY spectrum can be recorded using a quadrature detection method along the ⁇ -i axis described by Doddrell and co- workers; see Brereton and Crozier et al., supra.
- Absorption mode spectra can be obtained by recording two separate P- and N- type spectra and recombining the two data sets.
- the voxel image confirmed the correctness of the volume localization part of the CABINET sequence.
- a CHESS sequence of three frequency-selective water suppression pulses with a bandwidth of approximately 75Hz was used, each followed by the dephasing Bo gradient pulses.
- a numerically optimized Shinnar Le-Roux (SLR) waveform is used for each suppression rf pulse; see Michelis et al., supra.
- FIG. 3 Shown in Figure 3 are the localized water suppressed one dimensional (1 D) 1 H MR spectra using the a) PRESS, b) STEAM and c) CABINET sequences.
- TR/TE 3s/30ms
- 2048 complex points and a head MRI coil.
- PRESS double-spin-echo localization sequence
- the time- domain raw signal had 1024 complex points along the t 2 and 64 points along the t-i axes.
- a total of 8 averages is acquired for every ⁇ ti which resulted in a total duration of 17 minutes for signal acquisition.
- the two-dimensional raw data is apodized with sine bell filters and zero filled to a matrix size of
- the methylene and methine protons of NAA and Glu form ABX and ABCDX spin systems, respectively.
- the multiplets due to the methylene protons of NAA (AB) and Glu (ABCD) resonate around 2.5ppm and 2.2 ppm, respectively.
- the multiplets due to the methine protons of NAA and Glu are centered around 4.35ppm and 3.75ppm, respectively.
- the three protons in the lactate methyl and one proton in the methine group lead to an A 3 X spin system.
- the multiplets due to lactate, mainly a doublet and a quartet resonate around 1.25ppm and 4.1 ppm, respectively.
- the six ml ring protons, which are coupled to each other, give rise to multiplets in only three different locations at 3.1 ppm, 3.5ppm and 4ppm due to the symmetry of the ring.
- the 2D cross peaks are predominantly monitored in the following locations:
- NAA (4.35ppm, 2.5ppm); 2) Glu: (3.75ppm, 2.25ppm) and (2.25ppm, 3.75ppm); 3) lactate: (4.1 ppm, 1.25ppm) and (1.25ppm, 4.1 ppm); 4) Cr: (3.9ppm, 3.0ppm) and (3.0ppm, 3.9ppm) and; 5) ml: (4.0ppm, 3.54ppm), (3.54ppm, 3.1 ppm), (3.1 ppm, 3.54ppm) and (3.54ppm, 4.0ppm).
- the 1 D spectra have also been extracted at various cross-sections of the L-COSY spectrum; see Ernst and Bodenhausen et al., supra.
- the peaks denoted by * are due to the contamination originating from the F-i ridges and the nearest 2D cross peaks.
- a concentration of 4mM has been reported for ml in the frontal gray matter.
- the reported concentration of choline in the frontal gray matter is around 1.3mM.
- the three N-methyl protons resonate at 3.15ppm as a singlet due to the magnetic equivalence of the nine protons.
- the glutamate of GSH severely overlap with free glutamate peaks centered at 2,2ppm and 3.7 ppm in a conventional 1 D spectrum.
- the ABX spin system formed by the methylene and methine protons of cysteine appear around 2.95 PPM and 4.5ppm.
- the cross peaks between the cysteine resonances at 4.5ppm and 2.95ppm are indistinguishable from the dominant t-i ridge of water in the L-COSY spectrum, but the presence of cross peaks is confirmed whenever the water suppression is excellent.
- GABA Gamma-aminobutyric acid
- NAAG N-acetyl aspartyl glutamate
- CNS central nervous system
- NAA N-acetyl aspartyl glutamate
- Taurine is an AA'BB' spin system at 1.5T magnetic field strength and two triplets centered around 3.25ppm and 3.43ppm have been reported in a 1 D spectrum; see Gruetter et al., supra. Due to the proximity to the diagonal peaks, the 2D L- COSY cross peaks are not clearly visible and a high field spectrum may show these peaks. There are only diagonal peaks between 7-7.5 PPM and at 6 PPM, and at 8 PPM which probably represent exchangeable protons of cytosolic proteins (NAA, Glx, etc.) and also, aromatic protons of adenosine nucleotides, respectively.
- the L-COSY spectra are also recorded in the occipital gray/white regions. Shown in Figure ⁇ b is recorded in the occipital gray matter region in a 25-year old healthy volunteer with the MRS voxel location shown in Figure 8a.
- Doddrell and co-workers proposed a sequence in which the localization and coherence transfer parts of the localized 2D COSY sequence are separated.
- a VOSY sequence same as STEAM, is used first for voxel localization, followed by a coherence transfer hard 90° rf pulse; see Brereton and Galloway et al., supra.
- a problem with this sequence is due to the inferior signal compared to our L-COSY, since there is a signal loss by a factor of four, two from the localization and remaining two from the coherence transfer. Due to the severe loss of signal, they had to use a voxel size of 240ml (5x6x8 cm 3 ) and a long acquisition time of 1hr and 42 minutes.
- the twisted line-shape of the L-COSY spectrum is advantageous for human MR spectroscopy, since a poor resolution along the t-i dimension does not lead to cancellation of the cross peaks as demonstrated in Figure 7a for NAA and Glx.
- one major problem with the mixed phase of diagonal peaks is that the auto- and cross- peaks close to the diagonal are not resolved.
- the cross peaks due to ml are resolved only with a better resolution where 64 and 128 ⁇ ti increments are used.
- this can be overcome by recording the P-and N-type L-COSY spectra separately; see Brereton and Crozier et al., supra.
- a new volume localization sequence CABINET
- the 1 D analogue of the L-COSY has been implemented on a whole body 1.5T MRI/MRS scanner.
- the proposed sequence is also double spin-echo based, where the first spin echo originates from the first two slice-selective 90° and 180° rf pulses and the second coherence transfer echo originates from the last slice-selective 90° rf pulse.
- the volume localization efficiency of the proposed sequence is only 50% the same as that of STEAM.
- the L-COSY spectra of a brain phantom as well as human brain in vivo showed asymmetric cross peaks for J-coupled metabolites.
- Localized 2D COSY spectra have been recorded in the human frontal and occipital gray/white matter regions using a minimal number of rf pulses for both volume localization and coherence transfer.
- the 2D J-cross peaks between the methine and methylene protons of NAA, glutamate/glutamine, myo- inositol, creatine, aspartate, threonine/lactate, GABA and macromolecules have been recorded.
- the cerebral metabolites recorded in the frontal as well as the occipital gray/white matter regions using 2D L-COSY reveal the reliability of the technique in different regions of human brain. Due to the increased signal to noise compared to a head MRI coil, a 3" surface coil is used for reception in combination with the body coil transmission.
- the 2D L-COSY spectra recorded at smaller volumes (8ml or 18ml) showed the 2D cross peaks only due to the most abundant cerebral metabolites, namely NAA, Glx and ml.
- the 2D cross peaks of glutamate are not distinguishable from that of glutamine at the 1.5T magnetic field strength, however high field strengths (>3T) will facilitate such differentiation.
- Thomas MA Ke Y, Levitt J, et al., (1998), Preliminary Study of Frontal Lobe 1 H MR Spectroscopy in Childhood-Onset Schizophrenia. J Magn Reson Ima, 8:841-846. Thomas MA, Ryner LN, Mehta M, Turski P and Sorenson JA, (1996), J.
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US10/221,385 US7200430B2 (en) | 2001-03-29 | 2001-03-29 | Localized two-dimensional shift correlated MR spectroscopy of human brain |
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Cited By (3)
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WO2009031716A1 (fr) * | 2007-09-07 | 2009-03-12 | Kyoto University | Procédé de mesure de résonance magnétique nucléaire |
CN109001242A (zh) * | 2018-04-19 | 2018-12-14 | 厦门大学 | 一种实现可视化解码化学位移偏移率的高分辨二维谱方法 |
CN110632482A (zh) * | 2019-11-03 | 2019-12-31 | 西南交通大学 | 基于高斯金字塔的epr电缆绝缘老化状态测评方法 |
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US5172060A (en) * | 1989-04-29 | 1992-12-15 | Bruker Medizintechnik Gmbh | Method for recording spin resonance spectra |
US5617861A (en) * | 1994-02-16 | 1997-04-08 | Huntington Medical Research Institutes | Magnetic resonance spectral analysis of the brain for diagnosis of clinical conditions |
US5677628A (en) * | 1995-03-15 | 1997-10-14 | Kabushiki Kaisha Toshiba | Magnetic resonance diagnostic apparatus |
US6005390A (en) * | 1995-03-15 | 1999-12-21 | Kabushiki Kaisha Toshiba | Magnetic resonance diagnostic apparatus |
-
2001
- 2001-03-29 AU AU2001251131A patent/AU2001251131A1/en not_active Abandoned
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US5172060A (en) * | 1989-04-29 | 1992-12-15 | Bruker Medizintechnik Gmbh | Method for recording spin resonance spectra |
US5617861A (en) * | 1994-02-16 | 1997-04-08 | Huntington Medical Research Institutes | Magnetic resonance spectral analysis of the brain for diagnosis of clinical conditions |
US5677628A (en) * | 1995-03-15 | 1997-10-14 | Kabushiki Kaisha Toshiba | Magnetic resonance diagnostic apparatus |
US6005390A (en) * | 1995-03-15 | 1999-12-21 | Kabushiki Kaisha Toshiba | Magnetic resonance diagnostic apparatus |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
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WO2009031716A1 (fr) * | 2007-09-07 | 2009-03-12 | Kyoto University | Procédé de mesure de résonance magnétique nucléaire |
US8773126B2 (en) | 2007-09-07 | 2014-07-08 | Canon Kabushiki Kaisha | Nuclear magnetic resonance measuring method using an isotope-labeled compound |
CN109001242A (zh) * | 2018-04-19 | 2018-12-14 | 厦门大学 | 一种实现可视化解码化学位移偏移率的高分辨二维谱方法 |
CN110632482A (zh) * | 2019-11-03 | 2019-12-31 | 西南交通大学 | 基于高斯金字塔的epr电缆绝缘老化状态测评方法 |
CN110632482B (zh) * | 2019-11-03 | 2021-04-13 | 西南交通大学 | 基于高斯金字塔的epr电缆绝缘老化状态测评方法 |
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