Thomas Järmann widmet sich in seinem Beitrag zwei Fallbeispielen und zeigt auf, wie Komponisten Schweizerisches in ihre Werke einzuarbeiten versuchten. Er stellt dabei auch die Frage, welchen Beitrag die hineinkomponierte »Swissness« bei der Evokation von Heimatgefühlen leisten konnte und welche Bedeutung diese Musikstücke für die nationale Identität hatten. Programminhalte und Musik des Schweizerischen Kurzwellendiensts wurden daher so ausgewählt, dass sie sich von denen der anderen Sender abgrenzten, und die Eigenheiten der Schweiz wurden bewusst betont. So wurde rund die Hälfte der Sendezeit mit Musik gefüllt, und gerade die Schweizerische Volksmusik fungierte dabei als Alleinstellungsmerkmal; aber auch qualitativ hochstehende Unterhaltungsmusik und Ernste Musik von hauptsächlich Schweizer Komponisten interpretiert und von Schweizer Ensembles. Im Fokus des Artikels stehen jedoch nicht die oft gehörten Militärmärsche, sondern zwei Werke aus der Gattung der Sinfonischen Blasmusik.

Recently, pulsed magnetic field therapy (PMFT) systems have become available for private use. Although they may be applied without medical supervision, only a little is known about their field quantities. In this study, the spatial distribution and the temporal characteristics of the magnetic flux densities of three PMFT systems, available in Europe, were analysed. In close proximity to the surface, the maxima of the peak magnetic flux densities were 461 µT, 170 µT and 133 µT, respectively. At a distance of 30 cm above the whole body mat, the peak magnetic flux density was 77 µT. The excitation patterns consisted of repeating bursts with carrier frequencies between 210 and 1667 Hz. In conclusion, magnetic flux densities were far above International Commission on Non-Ionizing Radiation Protection reference levels. Since these systems are supposed to be medical devices as well as wellness devices, risk analysis of PMFT systems and the effectiveness of these devices need to be investigated in future studies.

The potential signal‐to‐noise ratio (SNR) gain at ultrahigh field strengths offers the promise of higher image resolution in single‐shot diffusion‐weighted echo‐planar imaging the challenge being reduced T2 and T2* relaxation times and increased B0 inhomogeneity which lead to geometric distortions and image blurring. These can be addressed using parallel imaging (PI) methods for which a greater range of feasible reduction factors has been predicted at ultrahigh field strengths—the tradeoff being an associated SNR loss. Using comprehensive simulations, the SNR of high‐resolution diffusion‐weighted echo‐planar imaging in combination with spin‐echo and stimulated‐echo acquisition is explored at 7 T and compared to 3 T. To this end, PI performance is simulated for coil arrays with a variable number of circular coil elements. Beyond that, simulations of the point spread function are performed to investigate the actual image resolution. When higher PI reduction factors are applied at 7 T to address increased image distortions, high‐resolution imaging benefits SNR‐wise only at relatively low PI reduction factors. On the contrary, it features generally higher image resolutions than at 3 T due to smaller point spread functions. The SNR simulations are confirmed by phantom experiments. Finally, high‐resolution in vivo images of a healthy volunteer are presented which demonstrate the feasibility of higher PI reduction factors at 7 T in practice. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.

PURPOSE:To construct a temperature-controlled diffusion phantom with known diffusion properties and geometry in order to facilitate the comparison and optimization of diffusion sequences with the objective of increasing the precision of experimentally derived diffusion parameters.MATERIALS AND METHODS:A temperature-stabilized diffusion phantom made up of two crossing strands of hydrophobic polyethylene fibers was constructed. Reproducibility and temperature dependence of several diffusion parameters was investigated and compared with computer simulations. Furthermore, in order to stimulate actual use, the precision of measurement of different diffusion-encoding schemes was compared using bootstrap analysis.RESULTS:The measured values of the diffusion parameters are highly reproducible and feature strong temperature dependence which is reproduced in simulations, underlining the necessity of a temperature-stabilized environment for quality control. The exemplary application presented here demonstrates that the phantom allows comparing and optimizing different diffusion sequences with regard to their measurement precision.CONCLUSION:The present work demonstrates that the diffusion phantom facilitates and improves the comparison and quality control of diffusion sequences and the ensuing parameters. The results show that an accurate temperature control is a vital prerequisite for highly reproducible calibration measurements. As such, the phantom might provide a valuable calibration tool for clinical studies.

Acute mountain sickness is common amongst not acclimatized persons ascending to high-altitude; the underlying mechanism is unknown, but may be related to cerebral edema. Nine healthy male students were studied before and after 6-hours exposure to isobaric hypoxia. Subjects inhaled room air enriched with N 2 to obtain SaO 2 values of 75-80%. Acute mountain sickness was assessed with the environmental symptom questionnaire, and cerebral edema with 3 Tesla magnetic resonance imaging in 18 regions of interest in the cerebral white matter. The main outcome measures were development of intra-and extracellular cerebral white matter edema assessed by visual inspection and quantitative analysis of apparent diffusion coefficients, derived from diffusion-weighted imaging, and B0 signal intensities, derived from T2-weighted imaging. Seven of nine subjects developed acute mountain sickness. Mean apparent diffusion coefficient increased 2. resonance images failed to reveal cerebral edema. Cerebral acute mountain sickness scores showed a negative correlation with relative changes of apparent diffusion coefficients (r=-0.83, p=0.006); there was no correlation with relative changes of B0 signal intensities. In conclusion, isobaric hypoxia is associated with mild extracellular (vasogenic) cerebral edema irrespective of the presence of acute mountain sickness in most subjects, and severe acute mountain sickness with additional mild intracellular (cytotoxic) cerebral edema.

− ∝⋅ ⋅ ⋅ The first term accounts for a linear increase of the SNR with the main magnetic field strength, the second for signal reduction due to spin relaxation. T2 relaxation times in white matter were set to 69 ms (6) for 3 T and 53 ms for 7 T, respectively. T2 at 7 T was derived from spin-echo experiments with varying echo times. The echo times (TE) and the echo train lengths (TTrain) were computed as a function of the rFOV size and the reduction factor, thereby accounting for the SNR loss per shot caused by the shortening of the readout train when rFOV acquisition or PI were applied. In terms of SNR efficiency the actual SNR loss, however, is smaller since the acquisition time is likewise reduced, so that more signal averages can be acquired in the same timeframe. This was incorporated through the correction factor fcorr. The same gradient performance was assumed on both systems. The last term finally incorporates the g-factor penalty in the case of PI acquisition (7). Mean and maximum g-factor maps at 3 T and 7 T were derived experimentally in a volunteer for various FOV sizes and reduction factors. The 3 T system was equipped with an 8-channel, the 7 T system with a 16-channel receive-only head coil array. Reduction was performed along the AP direction. The relative SNR efficiency at 7 T compared to 3 T was analyzed for a scan with the following parameters: FOV = 200 mm, acquisition matrix = 200, b-factor = 1000 s/mm 2 , partial Fourier encoding of 60 %. An image acquired at 7 T with the same rFOV size and reduction factor as at 3 T features considerably stronger image warping and signal pileup due to the linear increase of B0 inhomogeneity with the magnetic field strength. Thus, to ensure comparable image quality in terms of susceptibility related artefacts, 7/3-times higher reduction factors were used at 7 T. Therefore, to every SNR value at 3 T the corresponding value at 7 T with the same FOV size but a 7/3-times higher PI reduction factor was assigned. The 7 T SNR map is effectively compressed in this step. Results Figure 1 shows the dependence of the mean g-factors on the rFOV size and the reduction factor. As predicted in recent theoretical work, a greater range of PI acceleration factors is feasible at 7 T (8). The introduction of large coil arrays will increase this range further in favor of higher field strengths. Figure 2 shows the relative SNR map of 7 T compared to 3 T. Despite stronger T2 decay SNR at 7 T is always higher than at 3 T. As explained above, two images acquired with the same combination of rFOV size and reduction factor will feature significantly different image quality though. Fig. 3 shows the relative SNR taking increased susceptibility into account. There are two regions where SNR at 7 T is higher than at 3 T. Images acquired in region 1 will feature strong susceptibility artifacts which abate with increasing reduction factor and decreasing rFOV size, however, SNR gain will drop simultaneously. The transition to region 2 occurs for rFOV sizes of 40 mm at a reduction factor of 4.5 and for rFOV sizes of 180 mm at a reduction factor of 9. The corresponding mean g-factors at 7 T are 3.3 and 4.2, respectively. At these g- factors image quality will be deteriorated due to spatially inhomogeneous noise amplification. Discussion and Conclusion The simulations show that due to the linear increase of susceptibility distortions with field strength and the resulting need of higher reduction factors at 7 T it is in practice difficult to achieve the potentially available SNR gain. However, higher reduction factors than in the present study without pronounced noise amplification can be reached, sufficiently large coil arrays provided (8). Moreover, more than a linear increase of SNR with field strength has been reported (9). Some effects have not yet been taken into account in the present work. Firstly, increased B1 inhomogeneity at higher field strengths causes a spatially varying SNR. Moreover, due to an increased SAR level at 7 T, pulse duration is usually prolonged, leading to an increased TE (on our system presently 2.4 ms). This increase strongly depends on the nature of the applied pulse pair and cannot generally be quantified. Finally, enhanced through-plane B0 dephasing has not been incorporated. References

Acute mountain sickness is common among not acclimatized persons ascending to high altitude; the underlying mechanism is unknown, but may be related to cerebral edema. Nine healthy male students were studied before and after 6-h exposure to isobaric hypoxia. Subjects inhaled room air enriched with N-2 to obtain arterial O-2 saturation values of 75 to 80%. Acute mountain sickness was assessed with the environmental symptom questionnaire, and cerebral edema with 3 T magnetic resonance imaging in 18 regions of interest in the cerebral white matter. The main outcome measures were development of intra- and extracellular cerebral white matter edema assessed by visual inspection and quantitative analysis of apparent diffusion coefficients derived from diffusion-weighted imaging, and B0 signal intensities derived from T2-weighted imaging. Seven of nine subjects developed acute mountain sickness. Mean apparent diffusion coefficient increased 2.12% (baseline, 0.80 +/- 0.09; 6 h hypoxia, 0.81 +/- 0.09; P = 0.034), and mean B0 signal intensity increased 4.56% (baseline, 432.1 +/- 98.2; 6 h hypoxia, 450.7 +/- 102.5; P < 0.001). Visual inspection of magnetic resonance images failed to reveal cerebral edema. Cerebral acute mountain sickness scores showed a negative correlation with relative changes of apparent diffusion coefficients (r = -0.83, P= 0.006); there was no correlation with relative changes of B0 signal intensities. In conclusion, isobaric hypoxia is associated with mild extracellular (vasogenic) cerebral edema irrespective of the presence of acute mountain sickness in most subjects, and severe acute mountain sickness with additional mild intracellular (cytotoxic) cerebral edema.

A powerful, non-invasive technique for estimating and visualizing white matter tracts in the human brain in vivo is white matter fiber tractography that uses magnetic resonance diffusion tensor imaging. The success of this method depends strongly on the capability of the applied tracking algorithm and the quality of the underlying data set. However, DTI-based fiber tractography still lacks standardized validation. In the present work, a combined fMRI/DTI study was performed, both to develop a setup for verifying fiber tracking results using fMRI-derived functional connections and to explore the limitations of fMRI based DTI fiber tracking. Therefore, a minor fiber bundle that features several fiber crossings and intersections was examined: The striatum and its connections to the primary motor cortex were examined by using two approaches to derive the somatotopic organization of the striatum. First, an fMRI-based somatotopic map of the striatum was reconstructed, based on fMRI activations that were provoked by unilateral motor tasks. Second, fMRI-guided DTI fiber tracking was performed to generate DTI-based somatotopic maps, using a standard line propagation and an advanced fast marching algorithm. The results show that the fiber connections reconstructed by the advanced fast marching algorithm are in good agreement with known anatomy, and that the DTI-revealed somatotopy is similar to the fMRI somatotopy. Furthermore, the study illustrates that the combination of fMRI with DTI can supply additional information in order to choose reasonable seed regions for generating functionally relevant networks and to validate reconstructed fibers.

Pairs of cylindrical knives were used to punch semicircular slices from the left basal, sub-basal, equatorial, and apical ventricular wall of porcine hearts. The sections extended from the epicardium to the endocardium. Their semicircular shape compensated for the depth-related changing orientation of the myocytes relative to the equatorial plane. The slices were analyzed by diffusion tensor magnetic resonance imaging. The primary eigenvector of the diffusion tensor was determined in each pixel to calculate the number and angle of intrusion of the long axis of the aggregated myocytes relative to the epicardial surface. Arrays of axially sectioned aggregates were found in which 53% of the approximately two million segments evaluated intruded up to +/-15 degrees , 40% exhibited an angle of intrusion between +/-15 degrees and +/-45 degrees , and 7% exceeded an angle of +/-45 degrees , the positive sign thereby denoting an epi- to endocardial spiral in clockwise direction seen from the apex, while a negative sign denotes an anticlockwise spiral from the epicardium to the endocardium. In the basal and apical slices, the greater number of segments intruded in positive direction, while in the sub-basal and equatorial slices, negative angles of intrusion prevailed. The sampling of the primary eigenvectors was insensitive to postmortem decomposition of the tissue. In a previous histological study, we also documented the presence of large numbers of myocytes aggregated with their long axis intruding obliquely from the epicardial to the endocardial ventricular surfaces. We used magnetic resonance diffusion tensor imaging in this study to provide a comprehensive statistical analysis.

BACKGROUND AND PURPOSE: The inherent low anisotropy of gray matter and the lack of adequate imaging sensitivity and resolution has, so far, impeded depiction of axonal fibers to their intracortical origin or termination. We tested the hypothesis that an experimental approach with high-resolution diffusion tensor imaging (DTI) provides anisotropic data for fiber tractography with sufficient sensitivity to visualize in vivo the fine distribution of white matter bundles at the intracortical level. MATERIALS AND METHODS: We conducted phantom measurements of signal-to-noise ratio (SNR) and obtained diffusion tensor maps of the occipital lobe in 6 healthy volunteers using a dedicated miniature phased array detector at 3T. We reconstructed virtual fibers using a standard tracking algorithm. RESULTS: The coil array provided a SNR of 8.0 times higher at the head surface compared with a standard quadrature whole head coil. Diffusion tensor maps could be obtained with an in-plane resolution of 0.58 × 0.58 mm2. The axonal trajectories reconstructed from the diffusion data penetrate into the cortical ribbon perpendicular to the pial surface. This is the expected pattern for the terminations of thalamocortical afferent fibers to the middle layers of the occipital cortex and is consistent with the known microstructural organization of the mammalian cerebral cortex. CONCLUSION: High-resolution DTI reveals intracortical anisotropy with a distinct parallel geometrical order, perpendicular to the pial surface, consistent with structures that may be identified as the terminal afferents in cortical gray matter.

The global muscle and collagen fiber orientation in the human uterus has been analyzed hitherto by various standard microscopic techniques. However, no widely accepted model of the fiber architecture of the myometrium could be acquired. The purpose of the present study was to investigate the uterus by magnetic resonance (MR) diffusion tensor imaging (DTI) in a 3D macroscopic approach. Ex vivo MR DTI measurements were performed on five uteri from nonpregnant patients. The main diffusion directions reflecting the orientation of directional structures in the examined tissues were determined from diffusion-weighted spin-echo measurements. A fiber tracking algorithm was used to extrapolate the fiber architecture. The method was validated against histological slides and indirectly through the analysis of leiomyomas, which exhibit less anisotropy than normal myometrium. Significant anisotropy was found in most regions of all examined nonpregnant human uteri. But only two systems of fibers were found running circularly along the intramural part of the uterine tubes. They merged caudally and built a close fitting envelope of circular layers around the uterine cavity. On the cervix, circular fibers were observed in the outer part as well as mostly longitudinal fibers in the inner part. These results confirm the existence of directional structures in the complex fiber architecture of the human uterus. They also indicate that MR DTI is a beneficial and complementary tool to standard microscopic techniques to determine the intrinsic fiber architecture in human organs.

P. Staempfli, C. Reischauer, T. Jaermann, A. Valavanis, S. Kollias, P. Boesiger Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland, Institute of Neuroradiology, University Hospital Zurich, Zurich, Switzerland Introduction Diffusion Tensor Imaging (DTI) [1] is a promising non-invasive method for studying white matter structure of the human brain in vivo. Based on the determined diffusion direction, the fiber network in the brain can be reconstructed by so-called Fiber Tracking (FT) Algorithms [2]. Until now, a variety of different algorithms has been proposed. However, no standard procedure, neither to compare nor to validate the results, has been established. A key obstacle for reconstructing neuronal fibers is the definition of an appropriate seed region. Recently, start regions have been selected in anatomical areas defined by functional MRI (fMRI) activation patterns. With this approach, one attempts to reconstruct the anatomical networks underlying the specific functional systems [3, 4]. In this study, the sensorimotor system has been examined, investigating known cortico-subcortical connections between putamen and primary/sensorimotor cortex (M1/S1). The focus was to combine fMRI with DTI to validate tracking results and to demonstrate the feasibility of fMRI-guided DTI tracking for generating functionally relevant connections. Therefore, the somatotopical organization of the putamen has been derived twice: Firstly, an fMRI based somatotopy was obtained by four motor tasks. Secondly, two tracking algorithms (FACT [2] and advanced Fast Marching (aFM) [5]) were applied to derive somatotopical maps, revealing connection probabilities between fMRI-evoked regions in M1/S1 and putamen. Finally, the somatotopical maps and the fiber connections were compared and analyzed.

BACKGROUND AND PURPOSE:Diffusion tensor and diffusion-weighted spinal cord imaging remain relatively unexplored techniques despite demonstrations that such images can be obtained and may yield clinically relevant findings. In this study, we examined the temporal dynamics of spinal cord motion and their impact on diffusion tensor image quality.METHODS:Four healthy volunteers underwent phase contrast-based velocity mapping and segmented echo-planar diffusion tensor scans of the cervical spinal cord. Regions of interest in the cord were used to identify the temporal patterns of motion. The delay of data acquisition after the cardiac trigger was varied to correspond to either quiescence or motion of the cord.RESULTS:The cervical spinal cord consistently displayed maximal velocities in the range of 0.5 cm/s and accelerations of up to 25 cm/s(2). In both these respects, the cervical cord values were greater than those of the medulla. Despite this pronounced motion, approximately 40% of the cardiac cycle can be described as relatively calm, with absolute velocities and accelerations less than 20% of the maximum values. Confining image acquisition to this window reduced ghosting artifacts and increased the consistency with which the dominant direction of diffusion was along the rostral-caudal axis in both gray and white matter of the spine. Preliminary clinical application and fiber tracking in pathologic cases was feasible, and alterations of the diffusion properties by multiple sclerosis lesions, tumor, and syringomyelia were seen.CONCLUSIONS:Acquiring DTI data during the quiescent phase of spinal cord motion can reduce ghosting artifacts and improve fiber tracking.

Magnetic resonance diffusion tensor tractography is a powerful tool for the non-invasive depiction of the white matter architecture in the human brain. However, due to limitations in the underlying tensor model, the technique is often unable to reconstruct correct trajectories in heterogeneous fiber arrangements, such as axonal crossings. A novel tractography method based on fast marching (FM) is proposed which is capable of resolving fiber crossings and also permits trajectories to branch. It detects heterogeneous fiber arrangements by incorporating information from the entire diffusion tensor. The FM speed function is adapted to the local tensor characteristics, allowing in particular to maintain the front evolution direction in crossing situations. In addition, the FM's discretization error is reduced by increasing the number of considered possible front evolution directions. The performance of the technique is demonstrated in artificial data and in the healthy human brain. Comparisons with standard FM tractography and conventional line propagation algorithms show that, in the presence of interfering structures, the proposed method is more accurate in reconstructing trajectories. The in vivo results illustrate that the elucidated major white matter pathways are consistent with known anatomy and that multiple crossings and tract branching are handled correctly.

Limited spatial resolution is a key obstacle to the study of brain white matter structure with diffusion tensor imaging (DTI). In its frequent implementation with single‐excitation spin‐echo echo‐planar sequences, DTI's ability to resolve small structures is strongly restricted by T2 and T  2* decay, B0 inhomogeneity, and limited signal‐to‐noise ratio (SNR). In this work the influence of sensitivity encoding (SENSE) on diffusion‐weighted (DW) image properties is investigated. Computer simulations showed that the PSF becomes narrower with increasing SENSE reduction factors, R, enhancing the intrinsic resolution. After a brief theoretical discussion, we describe the estimation of SNR on a pixel‐by‐pixel basis as a function of R. The mean image SNR behavior is manifold: SENSE is capable of increasing SNR efficiency by reducing the echo time (TE). Each SNR(R) curve reveals a maximum that depends on the amount of partial Fourier encoding used. The overall best SNR efficiency for an eight‐element head coil array and a b‐factor of 1000 s/mm2 is achieved at R = 2.1 and partial Fourier encoding of 60%. In vivo tensor maps of volunteers and a patient, with an in‐plane resolution of 0.78 × 0.78 mm2, are also presented to demonstrate the practical implementation of the parallel approach. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.

Objective: The three-dimensional arrangement of the ventricular myocardial architecture remains controversial, in part because histological assessment is difficult to achieve, white anatomic dissections are, of necessity, destructive. In this study, we describe how the use of magnetic resonance diffusion tensor imaging has permitted us to reconstruct with precision the architecture of the ventricular myocardial fibres in the post-mortem swine heart. Methods and Results: We obtained diffusion-weighted spin-echo measurements of autopsied porcine hearts using a whole body MR system. We calculated the diffusion tensor and the corresponding eigenvectors on a voxel-by-voxel basis. This permitted us to colour code the fibres, and reconstruct them by connecting voxels in direction of the largest eigenvector. Such reconstructions show that, in the middle Layer of the left ventricle, most of the fibres have a circular orientation, albit that a far from negligible component runs in a transverse direction. With increasing distance from the epicardium, the orientation of the fibres shows a continuous change in angulation with respect to an axis normal to the epicardium. Conclusion: Our data presented here supports the concept that the ventricular mass is arranged as a complex three-dimensional mesh of tangential and intruding fibres. The data offers no support for the concept of a 'unique myocardial band'. The method has the potential to detecting deviations from this basic normal architecture, being capable of reconstructing the ventricular mass so as to assess the spatial coordinates of any single fibre strand. The technique, therefore, has major potential clinical applications in the setting of the failing or malformed heart, potentially being able to identify either systematic or regional disarray of the myocardial fibres. (c) 2005 Elsevier B.V. All rights reserved.

When both detections and responses to visual stimuli are performed within one and the same hemisphere, manual reaction times (RTs) are faster than when the two operations are carried out in different hemispheres. A widely accepted explanation for this difference is that it reflects the time lost in callosal transmission. Interhemispheric transfer time can be estimated by subtracting RTs for uncrossed from RTs for crossed responses (crossed-uncrossed difference, or CUD). In the present study, we wanted to ascertain the role of spatial attention in affecting the CUD and to chart the brain areas whose activity is related to these attentional effects on interhemispheric transfer. To accomplish this, we varied the proportion of crossed and uncrossed trials in different blocks. With this paradigm subjects are likely to focus attention either on the hemifield contralateral to the responding hand (blocks with 80% crossed trials) or on the ipsilateral hemifield (blocks with 80% uncrossed trials). We found an inverse correlation between the proportion of crossed trials in a block and the CUD and this effect can be attributed to spatial attention. As to the imaging results, we found that in the crossed minus uncrossed subtraction, an operation that highlights the neural processes underlying interhemispheric transfer, there was an activation of the genu of the corpus callosum as well as of a series of cortical areas. In a further commonality analysis, we assessed those areas which were activated specifically during focusing of attention onto one hemifield either contra- or ipsilateral to the responding hand. We found an activation of a number of cortical and subcortical areas, notably, parietal area BA 7 and the superior colliculi. We believe that the main thrust of the present study is to have teased apart areas important in interhemispheric transmission from those involved in spatial attention.