The echoplanar technique in magnetic resonance (MR) imaging allows the acquisition of a series of... more The echoplanar technique in magnetic resonance (MR) imaging allows the acquisition of a series of images from a selected slice with a temporal resolution of 10/s. Simultaneous recording of physiological information on pulse and respiration allows correlation of the MR signal intensity with physiological signals, which can be obtained for each pixel examined. Such correlations can be found within the cerebrospinal fluid (CSF) spaces and within vessels if a flow-sensitive MR measurement technique is used. The use of an MR scanner with a field strength of 3 T improves the signal/noise ratio, but there is a stronger signal decay due to local magnetic inhomogeneities. This study shows that 3-T systems can be used for correlation of MR and physiological signals and that clear differentiation between signals from CSF and from vessels can be obtained due to their strongly different signal decays.
PURPOSE The combination of ASL techniques with imaging sequences insensitive to susceptibility ef... more PURPOSE The combination of ASL techniques with imaging sequences insensitive to susceptibility effects has been shown to provide useful applications on internal organs. Usually averaging of a large number of scans is necessary to achieve a sufficiently high SNR in perfusion images. Doing so, respiratory motion can influence the quality of FAIR images. At higher field strength the sensitivity of the ASL methods is expected to improve. The recently developed FAIR True-FISP technique is suitable for perfusion-weighted imaging of the kidneys at 3 T. The goal of this study was to present a possible strategy for quantitative perfusion measurements of the kidneys at 3 T in breath-hold technique. METHOD AND MATERIALS Examinations of the kidneys of healthy volunteers were performed on a 3 T whole body MR scanner (Siemens Medical Solutions, Erlangen, Germany). The FAIR True-FISP sequences with α=60�-80�, TR/TE=3.6/1.8 ms, TI=1.2 s, BW=890 Hz/pixel, matrix=128�128 and FoV=360�360 mm2 were impl...
Synopsis: In proton MR spectroscopy of the human brain, it is often difficult to select voxels th... more Synopsis: In proton MR spectroscopy of the human brain, it is often difficult to select voxels that contain only one tissue type, such as gray matter (GM) or white matter (WM), due to relatively large voxel sizes. In this study, metabolite concentrations in pure GM and pure WM were calculated from the values obtained from short TE spectra of voxels with mixed tissue components. The tissue composition was determined by image segmentation. Significant differences between GM and WM were found for most of the major metabolites in the parietal region and the cerebellum. Methods: Examinations were performed on a 1.5 T whole-body imager (Magnetom Sonata, Siemens). Short-TE PRESS spectra (TE 30 ms, TR 3,000 ms, 64 acquisitions) were measured in the parietal region and in the cerebellum of nine healthy volunteers. In each of these brain regions, two volumes of interest (VOIs or voxels) of (2 cm) 3 were used, one of them containing mainly gray matter, the other mainly white matter (see Fig. 1...
ABSTRACT MR diffusion tensor imaging (DTI) allows the visualization of location and course of bra... more ABSTRACT MR diffusion tensor imaging (DTI) allows the visualization of location and course of brain fiber bundles. To obtain these results, however, special evaluation techniques are necessary in addition to image acquisition and reconstruction. These include first the calculation of a preferential diffusional direction of water molecules in each voxel, and then the tracking of brain fibers or segmentation of regions with similar fiber directions. In both cases, the procedures available thus far require the interactive definition of seed points. In this paper, we propose a method to segment voxel groups of connected data points without the need of setting seed points. This method is based first on the identification of all voxels of a brain volume with a sufficiently unique preferential diffusional direction and with interconnection. For each selected voxel, neighboring voxels are then identified that have a small deviation from the chosen preferential direction and can therefore be grouped with this point. Finally, the largest partial volumes determined in this way are marked and color-coded to present them as three-dimensional structures. The present method was applied to a DTI data set of a healthy female volunteer, resulting in a largely automatic subdivision of the white matter in the brain in a number of bilateral partial volumes.
ABSTRACT Hintergrund: Bei der lokalisierten In-vivo-Protonenspektroskopie des Gehirns ist es oft ... more ABSTRACT Hintergrund: Bei der lokalisierten In-vivo-Protonenspektroskopie des Gehirns ist es oft nicht möglich, die relativ großen Messvolumina (Voxel) so zu platzieren, dass sie nur Anteile der interessierenden Gewebeart enthalten. Bei kleineren, unregelmäßig geformten Läsionen, z. B. Metastasen, Entmarkungsherden oder Ischämien, liegt oft ein erheblicher Anteil des umgebenden Ödems oder Normalgewebes in demselben Voxel (Partialvolumen). Das akquirierte Spektrum stellt somit ein Mischspektrum verschiedener Gewebetypen im Voxel dar, das deutlich vom Spektrum der interessierenden reinen Gewebeart abweichen kann. Material und Methodik: Es wird eine Methode vorgestellt, mit der Spektren interessierender Gewebearten aus gemessenen Mischspektren berechnet werden können. Zur Aufnahme der Spektren wurde eine PRESS-Sequenz verwandt. Um eine Berechnung der Reingewebespektren zu ermöglichen, wurden bei Probanden- und Patientenuntersuchungen Spektren aus verschiedenen Voxeln aufgenommen, die jeweils unterschiedliche Anteile der verschiedenen reinen Gewebearten enthielten, wobei genauso viele Voxel gemessen werden müssen wie insgesamt verschiedene Gewebearten darin enthalten sind. Die Berechnung des Spektrums für die gesuchte reine Gewebeart erfolgte über die Lösung eines linearen Gleichungssystems. Dazu müssen die prozentualen Anteile der verschiedenen Gewebearten in den Voxeln bekannt sein. Um diese zu bestimmen, wurden bei den Probandenuntersuchungen hochaufgelöste native MP-RAGE-Datensätze und bei Patienten in Abhängigkeit von der Signalcharakteristik auch FLAIR- oder kontrastangehobene MP-RAGE-Datensätze aufgenommen, aus denen anschließend durch Bildsegmentierung die Anteile der reinen Gewebearten in den Voxeln bestimmt wurden. Für die Segmentierung wurden sowohl ein automatisches, standardisiertes als auch ein semiautomatisches, histogrammbasiertes Verfahren eingesetzt. Ergebnisse: Es wurden bei Probanden reine Spektren grauer (GS) und weißer Substanz (WS) berechnet. Hierbei zeigten sich bei den Reingewebespektren im Vergleich zu den gemessenen (Misch-)Spektren sehr viel deutlichere Unterschiede in der metabolischen Zusammensetzung von GS und WS sowohl im Kleinhirn als auch supratentoriell. Des Weiteren fanden sich in den Reingewebespektren deutliche Unterschiede der Metaboliten zwischen GS des Klein- und Großhirns, während die Zusammensetzung der WS supra- und infratentoriell identisch war. Auch konnte gezeigt werden, dass bei verschiedenen zerebralen Läsionen erhebliche Unterschiede zwischen den die Läsionen enthaltenden, gemessenen Spektren und den berechneten, reinen Spektren der Läsionen bestanden. Schlussfolgerung: Die Methode zeigt, dass es möglich ist, mit der Einzelvolumenspektroskopie Strukturen aufzulösen, die sehr viel kleiner als die minimal messbaren Voxelgrößen sind. Es gelingt somit, läsionsspezifischere spektrale Muster als mit den herkömmlichen Messungen, die bei kleineren oder unregelmäßig konfigurierten Läsionen immer partialvolumenbehaftet sind, darzustellen.
Hereditary spastic paraplegias (HSP) are a group of clinically and genetically heterogeneous diso... more Hereditary spastic paraplegias (HSP) are a group of clinically and genetically heterogeneous disorders with the hallmark of progressive spastic gait disturbance. We used advanced neuroimaging to identify brain regions involved in SPG4, the most common HSP genotype. Additionally, we analyzed correlations between imaging and clinical findings. We performed 3T MRI scans including isotropic high-resolution 3D T1, T2-FLAIR, and DTI sequences in 15 adult patients with genetically confirmed SPG4 and 15 age- and sex-matched healthy controls. Brain volume loss of gray and white matter was evaluated through voxel-based morphometry (VBM) for supra- and infratentorial regions separately. DTI maps of axial diffusivity (AD), radial diffusivity (RD), mean diffusivity (MD), fractional anisotropy (FA), and measured anisotropy (MA1) were analyzed through tract-based special statistics (TBSS). VBM and TBSS revealed a widespread affection of gray and white matter in SPG4 including the corpus callosum, ...
Background: The brain stem is an anatomic structure of outstanding importance affecting all vital... more Background: The brain stem is an anatomic structure of outstanding importance affecting all vital functions. This is the reason that even smallest lesions may lead to immense clinical symptoms for the patient. In conventional magnetic resonance imaging, the anatomic structures of the brain stem and the localization of the cerebellar peduncles are difficult to visualize. A differentiation of structures within the brain stem is possible by the use of diffusion tensor imaging (DTI). Material and Methods: The analysis of DTI datasets with high spatial resolution allows the calculation of single fiber bundles by fiber-tracking algorithms or the segmentation of regions with similar fiber directions. The segmentation technique can be used to completely separate an acquired complete volume dataset into several subvolumes. In this technique, those voxels are combined to clusters, in which the difference between the preference directions within neighbored voxels does exceed a chosen threshold. Results: In the region of the brain stem, this procedure allows the visualization of the major fiber bundles like the cerebrospinal tract and the cerebellar peduncles, if a multistep procedure with successively increasing threshold angles for the preference direction is used. The technique was successfully performed in datasets of three healthy volunteers.
The purpose of the study was to develop a measuring technique, which allows the investigation of ... more The purpose of the study was to develop a measuring technique, which allows the investigation of brainstem and auditory cortex activation after application of auditory stimuli by functional magnetic resonance imaging (fMRI). In addition to the conventional t-test analysis, a correlation analysis using, the signal in the acoustical cortex was applied. Eight healthy volunteers were examined on 3T scanner (Trio Tim, Siemens, Erlangen, Germany) with pure tones and music stimulation. Cortical and subcortical auditory structures were successfully visualized. Such investigation showed similar behavior comparing the both kind of created maps T and correlation. Maps of correlation demonstrated additional localization of brainstem structures which were not able to obtain after statistical analysis. These results demonstrate a tight functional relation between subcortical and cortical areas in the human brain.
To prospectively compare the image quality and diagnostic performance of orbital MR images obtain... more To prospectively compare the image quality and diagnostic performance of orbital MR images obtained by using a dual-source parallel transmission (pTX) 3D sequence (Sampling Perfection with Application optimized Contrasts using different flip angle Evolution, SPACE) with the image quality of conventional high-resolution standard protocol for clinical use in patients at 3T. After obtaining institutional review board approval and patient consent, 32 patients with clinical indication for orbital MRI were examined using a high-resolution conventional sequences and 3D pTX SPACE sequences. Quantitative measurements, image quality of the healthy orbit, incidence of artifacts, and the subjective diagnostic performance to establish diagnosis was rated. Statistical significance was calculated by using a Student's t-test and nonparametric Wilcoxon signed rank test. Length measurements were comparable in the two techniques, 3D pTX SPACE resulted in significant faster image acquisition with h...
We sought to investigate the dependence of intravoxel incoherent motion (IVIM)-related perfusion ... more We sought to investigate the dependence of intravoxel incoherent motion (IVIM)-related perfusion fraction (f) estimates on the transverse relaxation of brain tissue, blood, and cerebrospinal fluid (CSF), attempting to overcome the influence of CSF on conventional f maps. Eighteen patients with gliomas underwent DWI with 14 b-values (0-1,300 s/mm(2)) and two distinct echo times (TEs). Regions of interest representing tumour and normal brain tissue were analysed by calculating the f values for both TEs. A mask for pixels with relevant CSF partial volume was subsequently created. The f values were tested for significant differences. We found statistically significant differences between the two TEs in the f values for cortical and juxtacortical structures and non-enhancing areas of the tumour /oedema. Normal white matter and gadolinium-enhancing tumour tissue appeared insensitive to TE variation. In all tissue types examined, the masking of voxels with considerable CSF content was able...
Korean journal of radiology : official journal of the Korean Radiological Society
Brain perfusion can be assessed non-invasively by modern arterial spin labeling MRI. The FAIR (fl... more Brain perfusion can be assessed non-invasively by modern arterial spin labeling MRI. The FAIR (flow-sensitive alternating inversion recovery)-TrueFISP (true fast imaging in steady precession) technique was applied for regional assessment of cerebral blood flow in brain areas close to the skull base, since this approach provides low sensitivity to magnetic susceptibility effects. The investigation of the rhinal cortex and the amygdala is a potentially important feature for the diagnosis and research on dementia in its early stages. Twenty-three subjects with no structural or psychological impairment were investigated. FAIR-True-FISP quantitative perfusion data were evaluated in the amygdala on both sides and in the pons. A preparation of the radiofrequency FOCI (frequency offset corrected inversion) pulse was used for slice selective inversion. After a time delay of 1.2 sec, data acquisition began. Imaging slice thickness was 5 mm and inversion slab thickness for slice selective inve...
MR diffusion tensor imaging (DTI) allows the visualization of location and course of brain fiber ... more MR diffusion tensor imaging (DTI) allows the visualization of location and course of brain fiber bundles. To obtain these results, however, special evaluation techniques are necessary in addition to image acquisition and reconstruction. These include first the calculation of a preferential diffusional direction of water molecules in each voxel and then the tracking of brain fibers or segmentation of regions with similar fiber directions. In both cases, the procedures available thus far require the interactive definition of seed points. In this paper, we propose a method to segment voxel groups of connected data points without the need of setting seed points. This method is based first on the identification of all voxels of a brain volume with a sufficiently unique preferential diffusional direction and with interconnection. For each selected voxel, neighboring voxels are then identified that have a small deviation from the chosen preferential direction and can therefore be grouped w...
RöFo : Fortschritte auf dem Gebiete der Röntgenstrahlen und der Nuklearmedizin, 1999
In chronic liver dysfunction with portal hypertension the risk of variceal bleeding can be lowere... more In chronic liver dysfunction with portal hypertension the risk of variceal bleeding can be lowered by intrahepatic portosystemic shunting (TIPS). Although less pronounced than in surgical shunting, hepatic encephalopathy (HE) is a well-known undesired side effect. In cerebral proton MR spectroscopy (MRS), HE can be detected by a specific pattern of brain metabolite changes (increase of glutamine/glutamate (Glx) and decrease of myo-inositol (ml) and choline (Cho)). The aim of this study was to examine whether, after TIPS implantation, there is a correlation of the reduction of the portosystemic pressure gradient (PSPG) and the cerebral metabolite changes and their correspondence to the clinical status. We examined 10 cirrhotic patients (Child B, C) before and 3-20 days after TIPS implantation. Clinical examination was performed by a senior hepatologist. Localized MR spectra were acquired in parieto-occipital gray/white matter using a short echo time (TE = 5 ms) STEAM sequence. After ...
The echoplanar technique in magnetic resonance (MR) imaging allows the acquisition of a series of... more The echoplanar technique in magnetic resonance (MR) imaging allows the acquisition of a series of images from a selected slice with a temporal resolution of 10/s. Simultaneous recording of physiological information on pulse and respiration allows correlation of the MR signal intensity with physiological signals, which can be obtained for each pixel examined. Such correlations can be found within the cerebrospinal fluid (CSF) spaces and within vessels if a flow-sensitive MR measurement technique is used. The use of an MR scanner with a field strength of 3 T improves the signal/noise ratio, but there is a stronger signal decay due to local magnetic inhomogeneities. This study shows that 3-T systems can be used for correlation of MR and physiological signals and that clear differentiation between signals from CSF and from vessels can be obtained due to their strongly different signal decays.
PURPOSE The combination of ASL techniques with imaging sequences insensitive to susceptibility ef... more PURPOSE The combination of ASL techniques with imaging sequences insensitive to susceptibility effects has been shown to provide useful applications on internal organs. Usually averaging of a large number of scans is necessary to achieve a sufficiently high SNR in perfusion images. Doing so, respiratory motion can influence the quality of FAIR images. At higher field strength the sensitivity of the ASL methods is expected to improve. The recently developed FAIR True-FISP technique is suitable for perfusion-weighted imaging of the kidneys at 3 T. The goal of this study was to present a possible strategy for quantitative perfusion measurements of the kidneys at 3 T in breath-hold technique. METHOD AND MATERIALS Examinations of the kidneys of healthy volunteers were performed on a 3 T whole body MR scanner (Siemens Medical Solutions, Erlangen, Germany). The FAIR True-FISP sequences with α=60�-80�, TR/TE=3.6/1.8 ms, TI=1.2 s, BW=890 Hz/pixel, matrix=128�128 and FoV=360�360 mm2 were impl...
Synopsis: In proton MR spectroscopy of the human brain, it is often difficult to select voxels th... more Synopsis: In proton MR spectroscopy of the human brain, it is often difficult to select voxels that contain only one tissue type, such as gray matter (GM) or white matter (WM), due to relatively large voxel sizes. In this study, metabolite concentrations in pure GM and pure WM were calculated from the values obtained from short TE spectra of voxels with mixed tissue components. The tissue composition was determined by image segmentation. Significant differences between GM and WM were found for most of the major metabolites in the parietal region and the cerebellum. Methods: Examinations were performed on a 1.5 T whole-body imager (Magnetom Sonata, Siemens). Short-TE PRESS spectra (TE 30 ms, TR 3,000 ms, 64 acquisitions) were measured in the parietal region and in the cerebellum of nine healthy volunteers. In each of these brain regions, two volumes of interest (VOIs or voxels) of (2 cm) 3 were used, one of them containing mainly gray matter, the other mainly white matter (see Fig. 1...
ABSTRACT MR diffusion tensor imaging (DTI) allows the visualization of location and course of bra... more ABSTRACT MR diffusion tensor imaging (DTI) allows the visualization of location and course of brain fiber bundles. To obtain these results, however, special evaluation techniques are necessary in addition to image acquisition and reconstruction. These include first the calculation of a preferential diffusional direction of water molecules in each voxel, and then the tracking of brain fibers or segmentation of regions with similar fiber directions. In both cases, the procedures available thus far require the interactive definition of seed points. In this paper, we propose a method to segment voxel groups of connected data points without the need of setting seed points. This method is based first on the identification of all voxels of a brain volume with a sufficiently unique preferential diffusional direction and with interconnection. For each selected voxel, neighboring voxels are then identified that have a small deviation from the chosen preferential direction and can therefore be grouped with this point. Finally, the largest partial volumes determined in this way are marked and color-coded to present them as three-dimensional structures. The present method was applied to a DTI data set of a healthy female volunteer, resulting in a largely automatic subdivision of the white matter in the brain in a number of bilateral partial volumes.
ABSTRACT Hintergrund: Bei der lokalisierten In-vivo-Protonenspektroskopie des Gehirns ist es oft ... more ABSTRACT Hintergrund: Bei der lokalisierten In-vivo-Protonenspektroskopie des Gehirns ist es oft nicht möglich, die relativ großen Messvolumina (Voxel) so zu platzieren, dass sie nur Anteile der interessierenden Gewebeart enthalten. Bei kleineren, unregelmäßig geformten Läsionen, z. B. Metastasen, Entmarkungsherden oder Ischämien, liegt oft ein erheblicher Anteil des umgebenden Ödems oder Normalgewebes in demselben Voxel (Partialvolumen). Das akquirierte Spektrum stellt somit ein Mischspektrum verschiedener Gewebetypen im Voxel dar, das deutlich vom Spektrum der interessierenden reinen Gewebeart abweichen kann. Material und Methodik: Es wird eine Methode vorgestellt, mit der Spektren interessierender Gewebearten aus gemessenen Mischspektren berechnet werden können. Zur Aufnahme der Spektren wurde eine PRESS-Sequenz verwandt. Um eine Berechnung der Reingewebespektren zu ermöglichen, wurden bei Probanden- und Patientenuntersuchungen Spektren aus verschiedenen Voxeln aufgenommen, die jeweils unterschiedliche Anteile der verschiedenen reinen Gewebearten enthielten, wobei genauso viele Voxel gemessen werden müssen wie insgesamt verschiedene Gewebearten darin enthalten sind. Die Berechnung des Spektrums für die gesuchte reine Gewebeart erfolgte über die Lösung eines linearen Gleichungssystems. Dazu müssen die prozentualen Anteile der verschiedenen Gewebearten in den Voxeln bekannt sein. Um diese zu bestimmen, wurden bei den Probandenuntersuchungen hochaufgelöste native MP-RAGE-Datensätze und bei Patienten in Abhängigkeit von der Signalcharakteristik auch FLAIR- oder kontrastangehobene MP-RAGE-Datensätze aufgenommen, aus denen anschließend durch Bildsegmentierung die Anteile der reinen Gewebearten in den Voxeln bestimmt wurden. Für die Segmentierung wurden sowohl ein automatisches, standardisiertes als auch ein semiautomatisches, histogrammbasiertes Verfahren eingesetzt. Ergebnisse: Es wurden bei Probanden reine Spektren grauer (GS) und weißer Substanz (WS) berechnet. Hierbei zeigten sich bei den Reingewebespektren im Vergleich zu den gemessenen (Misch-)Spektren sehr viel deutlichere Unterschiede in der metabolischen Zusammensetzung von GS und WS sowohl im Kleinhirn als auch supratentoriell. Des Weiteren fanden sich in den Reingewebespektren deutliche Unterschiede der Metaboliten zwischen GS des Klein- und Großhirns, während die Zusammensetzung der WS supra- und infratentoriell identisch war. Auch konnte gezeigt werden, dass bei verschiedenen zerebralen Läsionen erhebliche Unterschiede zwischen den die Läsionen enthaltenden, gemessenen Spektren und den berechneten, reinen Spektren der Läsionen bestanden. Schlussfolgerung: Die Methode zeigt, dass es möglich ist, mit der Einzelvolumenspektroskopie Strukturen aufzulösen, die sehr viel kleiner als die minimal messbaren Voxelgrößen sind. Es gelingt somit, läsionsspezifischere spektrale Muster als mit den herkömmlichen Messungen, die bei kleineren oder unregelmäßig konfigurierten Läsionen immer partialvolumenbehaftet sind, darzustellen.
Hereditary spastic paraplegias (HSP) are a group of clinically and genetically heterogeneous diso... more Hereditary spastic paraplegias (HSP) are a group of clinically and genetically heterogeneous disorders with the hallmark of progressive spastic gait disturbance. We used advanced neuroimaging to identify brain regions involved in SPG4, the most common HSP genotype. Additionally, we analyzed correlations between imaging and clinical findings. We performed 3T MRI scans including isotropic high-resolution 3D T1, T2-FLAIR, and DTI sequences in 15 adult patients with genetically confirmed SPG4 and 15 age- and sex-matched healthy controls. Brain volume loss of gray and white matter was evaluated through voxel-based morphometry (VBM) for supra- and infratentorial regions separately. DTI maps of axial diffusivity (AD), radial diffusivity (RD), mean diffusivity (MD), fractional anisotropy (FA), and measured anisotropy (MA1) were analyzed through tract-based special statistics (TBSS). VBM and TBSS revealed a widespread affection of gray and white matter in SPG4 including the corpus callosum, ...
Background: The brain stem is an anatomic structure of outstanding importance affecting all vital... more Background: The brain stem is an anatomic structure of outstanding importance affecting all vital functions. This is the reason that even smallest lesions may lead to immense clinical symptoms for the patient. In conventional magnetic resonance imaging, the anatomic structures of the brain stem and the localization of the cerebellar peduncles are difficult to visualize. A differentiation of structures within the brain stem is possible by the use of diffusion tensor imaging (DTI). Material and Methods: The analysis of DTI datasets with high spatial resolution allows the calculation of single fiber bundles by fiber-tracking algorithms or the segmentation of regions with similar fiber directions. The segmentation technique can be used to completely separate an acquired complete volume dataset into several subvolumes. In this technique, those voxels are combined to clusters, in which the difference between the preference directions within neighbored voxels does exceed a chosen threshold. Results: In the region of the brain stem, this procedure allows the visualization of the major fiber bundles like the cerebrospinal tract and the cerebellar peduncles, if a multistep procedure with successively increasing threshold angles for the preference direction is used. The technique was successfully performed in datasets of three healthy volunteers.
The purpose of the study was to develop a measuring technique, which allows the investigation of ... more The purpose of the study was to develop a measuring technique, which allows the investigation of brainstem and auditory cortex activation after application of auditory stimuli by functional magnetic resonance imaging (fMRI). In addition to the conventional t-test analysis, a correlation analysis using, the signal in the acoustical cortex was applied. Eight healthy volunteers were examined on 3T scanner (Trio Tim, Siemens, Erlangen, Germany) with pure tones and music stimulation. Cortical and subcortical auditory structures were successfully visualized. Such investigation showed similar behavior comparing the both kind of created maps T and correlation. Maps of correlation demonstrated additional localization of brainstem structures which were not able to obtain after statistical analysis. These results demonstrate a tight functional relation between subcortical and cortical areas in the human brain.
To prospectively compare the image quality and diagnostic performance of orbital MR images obtain... more To prospectively compare the image quality and diagnostic performance of orbital MR images obtained by using a dual-source parallel transmission (pTX) 3D sequence (Sampling Perfection with Application optimized Contrasts using different flip angle Evolution, SPACE) with the image quality of conventional high-resolution standard protocol for clinical use in patients at 3T. After obtaining institutional review board approval and patient consent, 32 patients with clinical indication for orbital MRI were examined using a high-resolution conventional sequences and 3D pTX SPACE sequences. Quantitative measurements, image quality of the healthy orbit, incidence of artifacts, and the subjective diagnostic performance to establish diagnosis was rated. Statistical significance was calculated by using a Student's t-test and nonparametric Wilcoxon signed rank test. Length measurements were comparable in the two techniques, 3D pTX SPACE resulted in significant faster image acquisition with h...
We sought to investigate the dependence of intravoxel incoherent motion (IVIM)-related perfusion ... more We sought to investigate the dependence of intravoxel incoherent motion (IVIM)-related perfusion fraction (f) estimates on the transverse relaxation of brain tissue, blood, and cerebrospinal fluid (CSF), attempting to overcome the influence of CSF on conventional f maps. Eighteen patients with gliomas underwent DWI with 14 b-values (0-1,300 s/mm(2)) and two distinct echo times (TEs). Regions of interest representing tumour and normal brain tissue were analysed by calculating the f values for both TEs. A mask for pixels with relevant CSF partial volume was subsequently created. The f values were tested for significant differences. We found statistically significant differences between the two TEs in the f values for cortical and juxtacortical structures and non-enhancing areas of the tumour /oedema. Normal white matter and gadolinium-enhancing tumour tissue appeared insensitive to TE variation. In all tissue types examined, the masking of voxels with considerable CSF content was able...
Korean journal of radiology : official journal of the Korean Radiological Society
Brain perfusion can be assessed non-invasively by modern arterial spin labeling MRI. The FAIR (fl... more Brain perfusion can be assessed non-invasively by modern arterial spin labeling MRI. The FAIR (flow-sensitive alternating inversion recovery)-TrueFISP (true fast imaging in steady precession) technique was applied for regional assessment of cerebral blood flow in brain areas close to the skull base, since this approach provides low sensitivity to magnetic susceptibility effects. The investigation of the rhinal cortex and the amygdala is a potentially important feature for the diagnosis and research on dementia in its early stages. Twenty-three subjects with no structural or psychological impairment were investigated. FAIR-True-FISP quantitative perfusion data were evaluated in the amygdala on both sides and in the pons. A preparation of the radiofrequency FOCI (frequency offset corrected inversion) pulse was used for slice selective inversion. After a time delay of 1.2 sec, data acquisition began. Imaging slice thickness was 5 mm and inversion slab thickness for slice selective inve...
MR diffusion tensor imaging (DTI) allows the visualization of location and course of brain fiber ... more MR diffusion tensor imaging (DTI) allows the visualization of location and course of brain fiber bundles. To obtain these results, however, special evaluation techniques are necessary in addition to image acquisition and reconstruction. These include first the calculation of a preferential diffusional direction of water molecules in each voxel and then the tracking of brain fibers or segmentation of regions with similar fiber directions. In both cases, the procedures available thus far require the interactive definition of seed points. In this paper, we propose a method to segment voxel groups of connected data points without the need of setting seed points. This method is based first on the identification of all voxels of a brain volume with a sufficiently unique preferential diffusional direction and with interconnection. For each selected voxel, neighboring voxels are then identified that have a small deviation from the chosen preferential direction and can therefore be grouped w...
RöFo : Fortschritte auf dem Gebiete der Röntgenstrahlen und der Nuklearmedizin, 1999
In chronic liver dysfunction with portal hypertension the risk of variceal bleeding can be lowere... more In chronic liver dysfunction with portal hypertension the risk of variceal bleeding can be lowered by intrahepatic portosystemic shunting (TIPS). Although less pronounced than in surgical shunting, hepatic encephalopathy (HE) is a well-known undesired side effect. In cerebral proton MR spectroscopy (MRS), HE can be detected by a specific pattern of brain metabolite changes (increase of glutamine/glutamate (Glx) and decrease of myo-inositol (ml) and choline (Cho)). The aim of this study was to examine whether, after TIPS implantation, there is a correlation of the reduction of the portosystemic pressure gradient (PSPG) and the cerebral metabolite changes and their correspondence to the clinical status. We examined 10 cirrhotic patients (Child B, C) before and 3-20 days after TIPS implantation. Clinical examination was performed by a senior hepatologist. Localized MR spectra were acquired in parieto-occipital gray/white matter using a short echo time (TE = 5 ms) STEAM sequence. After ...
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Papers by Uwe Klose