Dieter Leibfritz - Academia.edu (original) (raw)
Papers by Dieter Leibfritz
American Journal of Neuroradiology, Apr 8, 2009
A recent report of detection of neural progenitor cells (NPCs) in living human brain by using in ... more A recent report of detection of neural progenitor cells (NPCs) in living human brain by using in vivo proton MR spectroscopy (1 H-MR spectroscopy) has sparked great excitement in the field of biomedicine because of its potential influence and utility in clinical neuroscience research. On the other hand, the method used and the findings described in the report also caused heated debate and controversy. In this article, we will briefly detail the reasons for the debate and controversy from the point of view of the in vivo 1 H-MR spectroscopy methodology and will propose some technical strategies in both data acquisition and data processing to improve the feasibility of detecting NPCs in future studies by using in vivo 1 H-MR spectroscopy.
Magnetic Resonance Materials in Physics Biology and Medicine, Dec 1, 1994
The development of the Rose Bengal model of cerebral infarction in the rat is monitored using rap... more The development of the Rose Bengal model of cerebral infarction in the rat is monitored using rapid NMR imaging techniques. The lesion volume, T1, Tz, and the apparent diffusion coefficient (ADC) are measured in the time interval between 24 and 168 h postinduction. Volumetric T!-weighted 3D imaging of the lesions produced by this model is shown to have a standard error of about 5% over the first 3 days postinduction, rising to about 15% at i week. Both the T1 and T2 contrasts are found to be more durable than those in ADC and are, hence, more suitable for volumetric monitoring over this time period. An elevation in ADC is also observed in tissue outside the lesion and this is interpreted as being caused by the transport of edema away from the lesion.
Journal of Magnetic Resonance, Series A, Sep 1, 1994
Magnetic Resonance in Chemistry, Nov 1, 1996
Very effective and sensitive HnX selection sequences utilizing the concept of HYSEL and pulsed fi... more Very effective and sensitive HnX selection sequences utilizing the concept of HYSEL and pulsed field gradients are presented. Clean subspectra comprising resonances exclusively from H1C and H2C, using the coherence of the attached natural‐abundance 13C spin, are demonstrated.
Kidney International, Aug 1, 2010
Journal of magnetic resonance, Dec 1, 1990
Inverse NMR spectroscopy leads to increased sensitivity in X, H correlation spectroscopy, since t... more Inverse NMR spectroscopy leads to increased sensitivity in X, H correlation spectroscopy, since the nucleus with the higher gyromagnetic ratio ( ‘H ) is used both for proton polarization to start the pulse sequence and for detection ( 1, 2). Recently a new pulse sequence has been developed: SHIPPED or selective heteronuclear inverse polarization transfer proton editing (3). The pulse sequence is shown in Fig. la. This inverse pulse sequence allows DEPT editing (4-6) of the ‘H NMR spectrum. One possible application of the SHIPPED experiment is the acquisition of oneand two-dimensional spectra, which contain only signals from XH groups. In order to decouple the X nucleus with the GARPl sequence ( 7), it is necessary to extend the original ID SHIPPED sequence by a second delay A’ = A to refocus the direct heteronuclear coupling. In the last two delays A’ two 180” pulses were inserted to refocus the chemical shifts in order to avoid phase problems (Fig. 1 b) . An interesting idea is to combine a 2D SHIPPED sequence with a COSY transfer. A 2D version of the SHIPPED experiment (Fig. la) replaces the 90” excitation pulse in the H,H COSY.90. This would lead to a 3D experiment, but to avoid this, the second evolution time is converted into a fixed delay AZ. This new variant creates an inverse H, X correlation with a H-relayed transfer (Fig. lc). During ti only the chemical shift of the X nucleus evolves, whereas after the SHIPPED part of the experiment XH magnetization is selected. During A2 the transverse magnetization of the methine proton I, evolves under homonuclear JHH coupling to the relayed proton I,, which is not bound to 13C. The 90” mixing pulse at the end of the sequence transfers the magnetization from spin I, to spin I,. During t2 the transverse magnetization of spin I1 evolves under heteronuclear I JXH coupling. The spectrum obtained shows the doublet signals of the methine protons, which are separated in 1L; by ‘JXH. The signals of the relayed protons show up as singlets. Figure 2 shows a section of a H-relayed SHIPPED-COSY spectrum from the olefinic region of strychnine. The second experiment is a combination of the refocused 1 D SHIPPED and COSY experiments (Fig. Id). After the SHIPPED part of the experiment only transverse magnetization of the methine protons, which evolves during tl under homonuclear JHH and heteronuclear ’ Jxn coupling, is selected. Because of the mixing pulse at the end of tl , polarization is transferred from spin 1, to spin I*, which is not directly bound
Journal of magnetic resonance, Dec 1, 1990
Journal of magnetic resonance, Jun 1, 1988
Tetrahedron Letters, 1969
Journal of magnetic resonance, Jun 1, 1990
Tetrahedron Letters, 1970
Tetrahedron Letters, 1970
Botanica acta, Apr 1, 1992
Photoautotrophic cell supension cultures of C. rubrum exhibit a C3-type of photosynthesis. Yet, u... more Photoautotrophic cell supension cultures of C. rubrum exhibit a C3-type of photosynthesis. Yet, up to 20% of total CO2-fixation is directly incorporated into malate and aspartate during short-term photosynthesis. The rate of 14C-labeling of malate and aspartate was doubled if the pH of the medium of the cells was increased from the normal value of 4.5 to 6.0 or 7.0. In vivo 31P-NMR spectroscopy demonstrated that an increase in the external pH from 4.5 to 6.3 increased the cytosolic pH by 0.3 units and the vacuolar pH by about 1.3 units. Possible mechanisms for the effect of extracellular pH on intracellular pH and PEP-carboxylase-dependent carboxylation reactions are discussed.
Angewandte Chemie, May 1, 1980
Magnetic Resonance in Medicine, 1990
With a semiselective ID COSY, related to the soft COSY sequence, metabolites with concentrations ... more With a semiselective ID COSY, related to the soft COSY sequence, metabolites with concentrations of a few millimolar can be detected, while highly abundant molecules as water or lipids are efficiently suppressed.
Tetrahedron Letters, 1969
Magnetic Resonance in Medicine, Apr 15, 2003
A new fast correlation-peak imaging technique is presented that combines 2D correlation spectrosc... more A new fast correlation-peak imaging technique is presented that combines 2D correlation spectroscopy with an ultrafast low-angle rapid acquisition with relaxation enhancement (U-FLARE) imaging module. Constant time chemical shift (CS) encoding is used in both time dimensions to achieve effective homonuclear decoupling in both frequency dimensions. The intervals between excitation and mixing (t c1) and between mixing and start of the MRI module (t c2) can be optimized to maximize the coherence transfer for a particular metabolite. Experiments were performed with evolution times t c1 and t c2 of 100 ms and 50 ms, respectively, which were determined by simulation of the spectroscopic part of the sequence for the spin systems of myo-inositol (Ins) and taurine (Tau). The use of a circularly reduced CS-encoding scheme shortened the minimum total measurement time to 35 min. The sequence was implemented on a 4.7 T imaging system and tested on a spherical phantom filled with a solution of Ins. The in vivo application of this method on healthy rat brain demonstrates its improved spectral resolution, as cross-peak signals from both Ins and Tau can be separated clearly. Magn Reson Med 49: 810-816, 2003.
Journal of Magnetic Resonance, May 1, 1998
The standard model of magnetization transfer consists of six The general solution of the standard... more The standard model of magnetization transfer consists of six The general solution of the standard model extends its coupled, first-order differential equations which describe a lossless applicability to any experimental procedure. In addition to exchange of magnetization between two sites. The system of differthe cases considered in (12, 13) it allows one to investigate, ential equations is solved semi-analytically in full generality. The e.g., the case of continuous off-resonance irradiation apsolution allows one to model any experiment generating magnetiproaching resonance, or off-resonance effects arising in zation transfer. It is especially useful in investigation spin systems pulsed MT experiments. The extended applicability is particsubjected to pulsed magnetization transfer experiments. ᭧ 1998 ularly useful for designing MT pulse sequences and for ob-Academic Press serving MT of off-resonance spins by MR spectroscopy (see,
American Journal of Neuroradiology, Apr 8, 2009
A recent report of detection of neural progenitor cells (NPCs) in living human brain by using in ... more A recent report of detection of neural progenitor cells (NPCs) in living human brain by using in vivo proton MR spectroscopy (1 H-MR spectroscopy) has sparked great excitement in the field of biomedicine because of its potential influence and utility in clinical neuroscience research. On the other hand, the method used and the findings described in the report also caused heated debate and controversy. In this article, we will briefly detail the reasons for the debate and controversy from the point of view of the in vivo 1 H-MR spectroscopy methodology and will propose some technical strategies in both data acquisition and data processing to improve the feasibility of detecting NPCs in future studies by using in vivo 1 H-MR spectroscopy.
Magnetic Resonance Materials in Physics Biology and Medicine, Dec 1, 1994
The development of the Rose Bengal model of cerebral infarction in the rat is monitored using rap... more The development of the Rose Bengal model of cerebral infarction in the rat is monitored using rapid NMR imaging techniques. The lesion volume, T1, Tz, and the apparent diffusion coefficient (ADC) are measured in the time interval between 24 and 168 h postinduction. Volumetric T!-weighted 3D imaging of the lesions produced by this model is shown to have a standard error of about 5% over the first 3 days postinduction, rising to about 15% at i week. Both the T1 and T2 contrasts are found to be more durable than those in ADC and are, hence, more suitable for volumetric monitoring over this time period. An elevation in ADC is also observed in tissue outside the lesion and this is interpreted as being caused by the transport of edema away from the lesion.
Journal of Magnetic Resonance, Series A, Sep 1, 1994
Magnetic Resonance in Chemistry, Nov 1, 1996
Very effective and sensitive HnX selection sequences utilizing the concept of HYSEL and pulsed fi... more Very effective and sensitive HnX selection sequences utilizing the concept of HYSEL and pulsed field gradients are presented. Clean subspectra comprising resonances exclusively from H1C and H2C, using the coherence of the attached natural‐abundance 13C spin, are demonstrated.
Kidney International, Aug 1, 2010
Journal of magnetic resonance, Dec 1, 1990
Inverse NMR spectroscopy leads to increased sensitivity in X, H correlation spectroscopy, since t... more Inverse NMR spectroscopy leads to increased sensitivity in X, H correlation spectroscopy, since the nucleus with the higher gyromagnetic ratio ( ‘H ) is used both for proton polarization to start the pulse sequence and for detection ( 1, 2). Recently a new pulse sequence has been developed: SHIPPED or selective heteronuclear inverse polarization transfer proton editing (3). The pulse sequence is shown in Fig. la. This inverse pulse sequence allows DEPT editing (4-6) of the ‘H NMR spectrum. One possible application of the SHIPPED experiment is the acquisition of oneand two-dimensional spectra, which contain only signals from XH groups. In order to decouple the X nucleus with the GARPl sequence ( 7), it is necessary to extend the original ID SHIPPED sequence by a second delay A’ = A to refocus the direct heteronuclear coupling. In the last two delays A’ two 180” pulses were inserted to refocus the chemical shifts in order to avoid phase problems (Fig. 1 b) . An interesting idea is to combine a 2D SHIPPED sequence with a COSY transfer. A 2D version of the SHIPPED experiment (Fig. la) replaces the 90” excitation pulse in the H,H COSY.90. This would lead to a 3D experiment, but to avoid this, the second evolution time is converted into a fixed delay AZ. This new variant creates an inverse H, X correlation with a H-relayed transfer (Fig. lc). During ti only the chemical shift of the X nucleus evolves, whereas after the SHIPPED part of the experiment XH magnetization is selected. During A2 the transverse magnetization of the methine proton I, evolves under homonuclear JHH coupling to the relayed proton I,, which is not bound to 13C. The 90” mixing pulse at the end of the sequence transfers the magnetization from spin I, to spin I,. During t2 the transverse magnetization of spin I1 evolves under heteronuclear I JXH coupling. The spectrum obtained shows the doublet signals of the methine protons, which are separated in 1L; by ‘JXH. The signals of the relayed protons show up as singlets. Figure 2 shows a section of a H-relayed SHIPPED-COSY spectrum from the olefinic region of strychnine. The second experiment is a combination of the refocused 1 D SHIPPED and COSY experiments (Fig. Id). After the SHIPPED part of the experiment only transverse magnetization of the methine protons, which evolves during tl under homonuclear JHH and heteronuclear ’ Jxn coupling, is selected. Because of the mixing pulse at the end of tl , polarization is transferred from spin 1, to spin I*, which is not directly bound
Journal of magnetic resonance, Dec 1, 1990
Journal of magnetic resonance, Jun 1, 1988
Tetrahedron Letters, 1969
Journal of magnetic resonance, Jun 1, 1990
Tetrahedron Letters, 1970
Tetrahedron Letters, 1970
Botanica acta, Apr 1, 1992
Photoautotrophic cell supension cultures of C. rubrum exhibit a C3-type of photosynthesis. Yet, u... more Photoautotrophic cell supension cultures of C. rubrum exhibit a C3-type of photosynthesis. Yet, up to 20% of total CO2-fixation is directly incorporated into malate and aspartate during short-term photosynthesis. The rate of 14C-labeling of malate and aspartate was doubled if the pH of the medium of the cells was increased from the normal value of 4.5 to 6.0 or 7.0. In vivo 31P-NMR spectroscopy demonstrated that an increase in the external pH from 4.5 to 6.3 increased the cytosolic pH by 0.3 units and the vacuolar pH by about 1.3 units. Possible mechanisms for the effect of extracellular pH on intracellular pH and PEP-carboxylase-dependent carboxylation reactions are discussed.
Angewandte Chemie, May 1, 1980
Magnetic Resonance in Medicine, 1990
With a semiselective ID COSY, related to the soft COSY sequence, metabolites with concentrations ... more With a semiselective ID COSY, related to the soft COSY sequence, metabolites with concentrations of a few millimolar can be detected, while highly abundant molecules as water or lipids are efficiently suppressed.
Tetrahedron Letters, 1969
Magnetic Resonance in Medicine, Apr 15, 2003
A new fast correlation-peak imaging technique is presented that combines 2D correlation spectrosc... more A new fast correlation-peak imaging technique is presented that combines 2D correlation spectroscopy with an ultrafast low-angle rapid acquisition with relaxation enhancement (U-FLARE) imaging module. Constant time chemical shift (CS) encoding is used in both time dimensions to achieve effective homonuclear decoupling in both frequency dimensions. The intervals between excitation and mixing (t c1) and between mixing and start of the MRI module (t c2) can be optimized to maximize the coherence transfer for a particular metabolite. Experiments were performed with evolution times t c1 and t c2 of 100 ms and 50 ms, respectively, which were determined by simulation of the spectroscopic part of the sequence for the spin systems of myo-inositol (Ins) and taurine (Tau). The use of a circularly reduced CS-encoding scheme shortened the minimum total measurement time to 35 min. The sequence was implemented on a 4.7 T imaging system and tested on a spherical phantom filled with a solution of Ins. The in vivo application of this method on healthy rat brain demonstrates its improved spectral resolution, as cross-peak signals from both Ins and Tau can be separated clearly. Magn Reson Med 49: 810-816, 2003.
Journal of Magnetic Resonance, May 1, 1998
The standard model of magnetization transfer consists of six The general solution of the standard... more The standard model of magnetization transfer consists of six The general solution of the standard model extends its coupled, first-order differential equations which describe a lossless applicability to any experimental procedure. In addition to exchange of magnetization between two sites. The system of differthe cases considered in (12, 13) it allows one to investigate, ential equations is solved semi-analytically in full generality. The e.g., the case of continuous off-resonance irradiation apsolution allows one to model any experiment generating magnetiproaching resonance, or off-resonance effects arising in zation transfer. It is especially useful in investigation spin systems pulsed MT experiments. The extended applicability is particsubjected to pulsed magnetization transfer experiments. ᭧ 1998 ularly useful for designing MT pulse sequences and for ob-Academic Press serving MT of off-resonance spins by MR spectroscopy (see,