TY - JOUR A1 - Kobus, Thiele A1 - Bitz, Andreas A1 - Uden, Mark J. van A1 - Lagemaat, Miram W. A1 - Rothgang, Eva A1 - Orzada, Stephan A1 - Heerschap, Arend A1 - Scheenen, Tom W. J. T1 - In vivo 31P MR spectroscopic imaging of the human prostate at 7 T: safety and feasibility JF - Magnetic Resonance in Medicine N2 - 31P MR spectroscopic imaging of the human prostate provides information about phosphorylated metabolites that could be used for prostate cancer characterization. The sensitivity of a magnetic field strength of 7 T might enable 3D 31P MR spectroscopic imaging with relevant spatial resolution in a clinically acceptable measurement time. To this end, a 31P endorectal coil was developed and combined with an eight-channel 1H body-array coil to relate metabolic information to anatomical location. An extensive safety validation was performed to evaluate the specific absorption rate, the radiofrequency field distribution, and the temperature distribution of both coils. This validation consisted of detailed Finite Integration Technique simulations, confirmed by MR thermometry and Burn:x-wiley:07403194:media:MRM24175:tex2gif-stack-1 measurements in a phantom and in vivo temperature measurements. The safety studies demonstrated that the presence of the 31P endorectal coil had no influence on the specific absorption rate levels and temperature distribution of the external eight-channel 1H array coil. To stay within a 10 g averaged local specific absorption rate of 10 W/kg, a maximum time-averaged input power of 33 W for the 1H array coil was allowed. For transmitting with the 31P endorectal coil, our safety limit of less than 1°C temperature increase in vivo during a 15-min MR spectroscopic imaging experiment was reached at a time-averaged input power of 1.9 W. With this power setting, a second in vivo measurement was performed on a healthy volunteer. Using adiabatic excitation, 3D 31P MR spectroscopic imaging produced spectra from the entire prostate in 18 min with a spatial resolution of 4 cm3. The spectral resolution enabled the separate detection of phosphocholine, phosphoethanolamine, inorganic phosphate, and other metabolites that could play an important role in the characterization of prostate cancer. Y1 - 2012 U6 - https://doi.org/10.1002/mrm.24175 SN - 1522-2594 VL - 68 IS - 6 SP - 1683 EP - 1695 PB - Wiley-Liss CY - New York ER - TY - JOUR A1 - Orzada, Stephan A1 - Maderwald, Stefan A1 - Poser, Benedikt Andreas A1 - Bitz, Andreas A1 - Quick, Harald H. A1 - Ladd, Mark E. T1 - RF excitation using time interleaved acquisition of modes (TIAMO) to address B1 inhomogeneity in high-field MRI JF - Magnetic Resonance in Medicine N2 - As the field strength and, therefore, the operational frequency in MRI is increased, the wavelength approaches the size of the human head/body, resulting in wave effects, which cause signal decreases and dropouts. Several multichannel approaches have been proposed to try to tackle these problems, including RF shimming, where each element in an array is driven by its own amplifier and modulated with a certain (constant) amplitude and phase relative to the other elements, and Transmit SENSE, where spatially tailored RF pulses are used. In this article, a relatively inexpensive and easy to use imaging scheme for 7 Tesla imaging is proposed to mitigate signal voids due to B1 field inhomogeneity. Two time-interleaved images are acquired using a different excitation mode for each. By forming virtual receive elements, both images are reconstructed together using GRAPPA to achieve a more homogeneous image, with only small SNR and SAR penalty in head and body imaging at 7 Tesla. Y1 - 2010 U6 - https://doi.org/10.1002/mrm.22527 SN - 1522-2594 VL - 64 IS - 2 SP - 327 EP - 333 PB - Wiley-Liss CY - New York ER - TY - JOUR A1 - Umutlu, Lale A1 - Bitz, Andreas A1 - Maderwald, Stefan A1 - Orzada, Stephan A1 - Kinner, Sonja A1 - Kraff, Oliver A1 - Brote, Irina A1 - Ladd, Susanne C. A1 - Schroeder, Tobias A1 - Forsting, Michael T1 - Contrast-enhanced ultra-high-field liver MRI: a feasibility trial JF - European Journal of Radiology Y1 - 2013 U6 - https://doi.org/10.1016/j.ejrad.2011.07.004 SN - 0720-048X VL - 82 IS - 5 SP - 760 EP - 767 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Yazdanbakhsh, Pedram A1 - Solbach, Klaus A1 - Bitz, Andreas T1 - Variable power combiner for RF mode shimming in 7-T MR imaging JF - IEEE Transaction on Biomedical Engineering N2 - This contribution discusses the utilization of RF power in an MRI system with RF mode shimming which enables the superposition of circularly polarized modes of a transmit RF coil array driven by a Butler matrix. Since the required power for the individual modes can vary widely, mode-shimming can result in a significant underutilization of the total available RF power. A variable power combiner (VPC) is proposed to improve the power utilization: it can be realized as a reconfiguration of the MRI transmit system by the inclusion of one additional matrix network which receives the power from all transmit amplifiers at its input ports and provides any desired (combined) power distribution at its output ports by controlling the phase and amplitude of the amplifiers’ input signals. The power distribution at the output ports of the VPC is then fed into the “mode” ports of the coil array Butler matrix in order to superimpose the spatial modes at the highest achievable power utilization. The VPC configuration is compared to the standard configuration of the transmit chain of our MRI system with 8 transmit channels and 16 coils. In realistic scenarios, improved power utilization was achieved from 17% to 60% and from 14% to 55% for an elliptical phantom and a region of interest in the abdomen, respectively, and an increase of the power utilization of 1 dB for a region of interest in the upper leg. In general, it is found that the VPC allows significant improvement in power utilization when the shimming solution demands only a few modes to be energized, while the technique can yield loss in power utilization in cases with many modes required at high power level. Y1 - 2012 U6 - https://doi.org/10.1109/TBME.2012.2205926 SN - 1558-2531 VL - 59 IS - 9 SP - 2549 EP - 2557 PB - IEEE CY - New York ER - TY - JOUR A1 - Prochnow, Nora A1 - Gebing, Tina A1 - Ladage, Kerstin A1 - Krause-Finkeldey, Dorothee A1 - Ourdi, Abessamad El A1 - Bitz, Andreas A1 - Streckert, Joachim A1 - Hansen, Volkert A1 - Dermietzel, Rolf T1 - Electromagnetic field effect or simply stress? Effects of UMTS exposure on hippocampal longterm plasticity in the context of procedure related hormone release JF - PLoS one N2 - Harmful effects of electromagnetic fields (EMF) on cognitive and behavioural features of humans and rodents have been controversially discussed and raised persistent concern about adverse effects of EMF on general brain functions. In the present study we applied radio-frequency (RF) signals of the Universal Mobile Telecommunications System (UMTS) to full brain exposed male Wistar rats in order to elaborate putative influences on stress hormone release (corticosteron; CORT and adrenocorticotropic hormone; ACTH) and on hippocampal derived synaptic long-term plasticity (LTP) and depression (LTD) as electrophysiological hallmarks for memory storage and memory consolidation. Exposure was computer controlled providing blind conditions. Nominal brain-averaged specific absorption rates (SAR) as a measure of applied mass-related dissipated RF power were 0, 2, and 10 W/kg over a period of 120 min. Comparison of cage exposed animals revealed, regardless of EMF exposure, significantly increased CORT and ACTH levels which corresponded with generally decreased field potential slopes and amplitudes in hippocampal LTP and LTD. Animals following SAR exposure of 2 W/kg (averaged over the whole brain of 2.3 g tissue mass) did not differ from the sham-exposed group in LTP and LTD experiments. In contrast, a significant reduction in LTP and LTD was observed at the high power rate of SAR (10 W/kg). The results demonstrate that a rate of 2 W/kg displays no adverse impact on LTP and LTD, while 10 W/kg leads to significant effects on the electrophysiological parameters, which can be clearly distinguished from the stress derived background. Our findings suggest that UMTS exposure with SAR in the range of 2 W/kg is not harmful to critical markers for memory storage and memory consolidation, however, an influence of UMTS at high energy absorption rates (10 W/kg) cannot be excluded. Y1 - 2011 U6 - https://doi.org/10.1371/journal.pone.0019437 VL - 6 IS - 5 PB - PLOS CY - San Francisco ER - TY - JOUR A1 - Orzada, Stephan A1 - Bitz, Andreas A1 - Schäfer, Lena C. A1 - Ladd, Susanne C. A1 - Ladd, Mark E. A1 - Maderwald, Stefan T1 - Open design eight-channel transmit/receive coil for high-resolution and real-time ankle imaging at 7 T JF - Medical Physics N2 - Purpose: At 1.5 T, real-time MRI of joint movement has been shown to be feasible. However, 7 T, provides higher SNR and thus an improved potential for parallel imaging acceleration. The purpose of this work was to build an open, U-shaped eight-channel transmit/receive microstrip coil for 7 T MRI to enable high-resolution and real-time imaging of the moving ankle joint. Methods: A U-shaped eight-channel transmit/receive array for the human ankle was built.urn:x-wiley:00942405:mp3399:equation:mp3399-math-0001-parameters and urn:x-wiley:00942405:mp3399:equation:mp3399-math-0002-factor were measured. SAR calculations of different ankle postures were performed to ensure patient safety. Inhomogeneities in the transmit field consequent to the open design were compensated for by the use of static RF shimming. High-resolution and real-time imaging was performed in human volunteers. Results: The presented array showed good performance with regard to patient comfort and image quality. High acceleration factors of up to 4 are feasible without visible acceleration artifacts. Reasonable image homogeneity was achieved with RF shimming. Conclusions: Open, noncylindrical designs for transmit/receive coils are practical at 7 T and real-time imaging of the moving joint is feasible with the presented coil design. Y1 - 2011 U6 - https://doi.org/10.1118/1.3553399 SN - 2473-4209 VL - 38 IS - 3 SP - 1162 EP - 1167 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Kraff, Oliver A1 - Bitz, Andreas A1 - Dammann, Philipp A1 - Ladd, Susanne C. A1 - Ladd, Mark E. A1 - Quick, Harald H. T1 - An eight-channel transmit/receive multipurpose coil for musculoskeletal MR imaging at 7 T JF - Medical Physics N2 - Purpose: MRI plays a leading diagnostic role in assessing the musculoskeletal (MSK) system and is well established for most questions at clinically used field strengths (up to 3 T). However, there are still limitations in imaging early stages of cartilage degeneration, very fine tendons and ligaments, or in locating nerve lesions, for example. 7 T MRI of the knee has already received increasing attention in the current published literature, but there is a strong need to develop new radiofrequency (RF) coils to assess more regions of the MSK system. In this work, an eight-channel transmit/receive RF array was built as a multipurpose coil for imaging some of the thus far neglected regions. An extensive coil characterization protocol and first in vivo results of the human wrist, shoulder, elbow, knee, and ankle imaged at 7 T will be presented. Methods: Eight surface loop coils with a dimension ofurn:x-wiley:00942405:media:mp7176:mp7176-math-0001 were machined from FR4 circuit board material. To facilitate easy positioning, two coil clusters, each with four loop elements, were combined to one RF transmit/receive array. An overlapped and shifted arrangement of the coil elements was chosen to reduce the mutual inductance between neighboring coils. A phantom made of body-simulating liquid was used for tuning and matching on the bench. Afterward, the S-parameters were verified on a human wrist, elbow, and shoulder. For safety validation, a detailed compliance test was performed including full wave simulations of the RF field distribution and the corresponding specific absorption rate (SAR) for all joints. In vivo images of four volunteers were assessed with gradient echo and spin echo sequences modified to obtain optimal image contrast, full anatomic coverage, and the highest spatial resolution within a reasonable acquisition time. The performance of the RF coil was additionally evaluated by in vivo B1 mapping. Results: A comparison of B1 per unit power, flip angle distribution, and anatomic images showed a fairly homogeneous excitation for the smaller joints (elbow, wrist, and ankle), while for the larger joints, the shoulder and especially the knee, B1 inhomogeneities and limited penetration depth were more pronounced. However, the greater part of the shoulder joint could be imaged.In vivo images rendered very fine anatomic details such as fascicles of the median nerve and the branching of the nerve bundles. High-resolution images of cartilage, labrum, and tendons could be acquired. Additionally, turbo spin echo (TSE) and inversion recovery sequences performed very well. Conclusions: This study demonstrates that the concept of two four-channel transmit/receive RF arrays can be used as a multipurpose coil for high-resolutionin vivo MR imaging of the musculoskeletal system at 7 T. Not only gradient echo but also typical clinical and SAR-intensive sequences such as STIR and TSE performed well. Imaging of small structures and peripheral nerves could in particular benefit from this technique. Y1 - 2010 U6 - https://doi.org/10.1118/1.3517176 SN - 2473-4209 VL - 37 IS - 12 SP - 6368 EP - 6376 PB - Wiley CY - Hoboken, NJ ER - TY - JOUR A1 - Orzada, Stephan A1 - Ladd, Mark E. A1 - Bitz, Andreas T1 - A method to approximate maximum local SAR in multichannel transmit MR systems without transmit phase information JF - Magnetic Resonance in Medicine N2 - Purpose To calculate local specific absorption rate (SAR) correctly, both the amplitude and phase of the signal in each transmit channel have to be known. In this work, we propose a method to derive a conservative upper bound for the local SAR, with a reasonable safety margin without knowledge of the transmit phases of the channels. Methods The proposed method uses virtual observation points (VOPs). Correction factors are calculated for each set of VOPs that prevent underestimation of local SAR when the VOPs are applied with the correct amplitudes but fixed phases. Results The proposed method proved to be superior to the worst-case calculation based on the maximum eigenvalue of the VOPs. The mean overestimation for six coil setups could be reduced, whereas no underestimation of the maximum local SAR occurred. In the best investigated case, the overestimation could be reduced from a factor of 3.3 to a factor of 1.7. Conclusion The upper bound for the local SAR calculated with the proposed method allows a fast estimation of the local SAR based on power measurements in the transmit channels and facilitates SAR monitoring in systems that do not have the capability to monitor transmit phases Y1 - 2016 U6 - https://doi.org/10.1002/mrm.26398 SN - 1522-2594 VL - 78 IS - 2 SP - 805 EP - 811 PB - International Society for Magnetic Resonance in Medicine ER - TY - JOUR A1 - Chen, Bixia A1 - Schoemberg, Tobias A1 - Kraff, Oliver A1 - Dammann, Philipp A1 - Bitz, Andreas A1 - Schlamann, Marc A1 - Quick, Harald H. A1 - Ladd, Mark E. A1 - Sure, Ulrich A1 - Wrede, Karsten H. T1 - Cranial fixation plates in cerebral magnetic resonance imaging: a 3 and 7 Tesla in vivo image quality study JF - Magnetic Resonance Materials in Physics, Biology and Medicine N2 - Objective This study assesses and quantifies impairment of postoperative magnetic resonance imaging (MRI) at 7 Tesla (T) after implantation of titanium cranial fixation plates (CFPs) for neurosurgical bone flap fixation. Materials and methods The study group comprised five patients who were intra-individually examined with 3 and 7 T MRI preoperatively and postoperatively (within 72 h/3 months) after implantation of CFPs. Acquired sequences included T₁-weighted magnetization-prepared rapid-acquisition gradient-echo (MPRAGE), T₂-weighted turbo-spin-echo (TSE) imaging, and susceptibility-weighted imaging (SWI). Two experienced neurosurgeons and a neuroradiologist rated image quality and the presence of artifacts in consensus reading. Results Minor artifacts occurred around the CFPs in MPRAGE and T2 TSE at both field strengths, with no significant differences between 3 and 7 T. In SWI, artifacts were accentuated in the early postoperative scans at both field strengths due to intracranial air and hemorrhagic remnants. After resorption, the brain tissue directly adjacent to skull bone could still be assessed. Image quality after 3 months was equal to the preoperative examinations at 3 and 7 T. Conclusion Image quality after CFP implantation was not significantly impaired in 7 T MRI, and artifacts were comparable to those in 3 T MRI. Y1 - 2016 U6 - https://doi.org/10.1007/s10334-016-0548-1 SN - 1352-8661 VL - 29 IS - 3 SP - 389 EP - 398 PB - Springer CY - Berlin ER - TY - JOUR A1 - Schmidt, K. A1 - Forkmann, K. A1 - Sinke, C. A1 - Gratz, M. A1 - Bitz, Andreas A1 - Bingel, U. T1 - The differential effect of trigeminal vs. peripheral pain stimulation on visual processing and memory encoding is influenced by pain-related fear JF - NeuroImage N2 - Compared to peripheral pain, trigeminal pain elicits higher levels of fear, which is assumed to enhance the interruptive effects of pain on concomitant cognitive processes. In this fMRI study we examined the behavioral and neural effects of trigeminal (forehead) and peripheral (hand) pain on visual processing and memory encoding. Cerebral activity was measured in 23 healthy subjects performing a visual categorization task that was immediately followed by a surprise recognition task. During the categorization task subjects received concomitant noxious electrical stimulation on the forehead or hand. Our data show that fear ratings were significantly higher for trigeminal pain. Categorization and recognition performance did not differ between pictures that were presented with trigeminal and peripheral pain. However, object categorization in the presence of trigeminal pain was associated with stronger activity in task-relevant visual areas (lateral occipital complex, LOC), memory encoding areas (hippocampus and parahippocampus) and areas implicated in emotional processing (amygdala) compared to peripheral pain. Further, individual differences in neural activation between the trigeminal and the peripheral condition were positively related to differences in fear ratings between both conditions. Functional connectivity between amygdala and LOC was increased during trigeminal compared to peripheral painful stimulation. Fear-driven compensatory resource activation seems to be enhanced for trigeminal stimuli, presumably due to their exceptional biological relevance. Y1 - 2016 U6 - https://doi.org/10.1016/j.neuroimage.2016.03.026 SN - 1053-8119 VL - 134 SP - 386 EP - 395 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Bank, Bart L. van de A1 - Orzada, Stephan A1 - Smits, Frits A1 - Lagemaat, Miriam W. A1 - Rodgers, Christopher T. A1 - Bitz, Andreas A1 - Scheenen, Tom W. J. T1 - Optimized (31) P MRS in the human brain at 7 T with a dedicated RF coil setup JF - NMR in Biomedicine Y1 - 2015 U6 - https://doi.org/10.1002/nbm.3422 SN - 1099-1492 VL - 28 IS - 11 SP - 1570 EP - 1578 PB - Wiley CY - Weinheim ER - TY - JOUR A1 - Noureddine, Yacine A1 - Bitz, Andreas A1 - Ladd, Mark E. A1 - Thürling, Markus A1 - Ladd, Susanne C. A1 - Schaefers, Gregor A1 - Kraff, Oliver T1 - Experience with magnetic resonance imaging of human subjects with passive implants and tattoos at 7 T: a retrospective study JF - Magnetic Resonance Materials in Physics, Biology and Medicine Y1 - 2015 U6 - https://doi.org/10.1007/s10334-015-0499-y SN - 1352-8661 VL - 28 IS - 6 SP - 577 EP - 590 PB - Springer CY - Berlin ER - TY - JOUR A1 - Lagemaat, Miriam W. A1 - Breukels, Vincent A1 - Vos, Eline K. A1 - B., Adam A1 - Uden, Mark J. van A1 - Orzada, Stephan A1 - Bitz, Andreas A1 - Maas, Marnix C. A1 - Scheenen, Tom W. J. T1 - ¹H MR spectroscopic imaging of the prostate at 7T using spectral-spatial pulses JF - Magnetic Resonance in Medicine N2 - Purpose To assess the feasibility of prostate ¹H MR spectroscopic imaging (MRSI) using low-power spectral-spatial (SPSP) pulses at 7T, exploiting accurate spectral selection and spatial selectivity simultaneously. Methods A double spin-echo sequence was equipped with SPSP refocusing pulses with a spectral selectivity of 1 ppm. Three-dimensional prostate ¹H-MRSI at 7T was performed with the SPSP-MRSI sequence using an 8-channel transmit array coil and an endorectal receive coil in three patients with prostate cancer and in one healthy subject. No additional water or lipid suppression pulses were used. Results Prostate ¹H-MRSI could be obtained well within specific absorption rate (SAR) limits in a clinically feasible time (10 min). Next to the common citrate signals, the prostate spectra exhibited high spermine signals concealing creatine and sometimes also choline. Residual lipid signals were observed at the edges of the prostate because of limitations in spectral and spatial selectivity. Conclusion It is possible to perform prostate ¹H-MRSI at 7T with a SPSP-MRSI sequence while using separate transmit and receive coils. This low-SAR MRSI concept provides the opportunity to increase spatial resolution of MRSI within reasonable scan times. Y1 - 2016 U6 - https://doi.org/10.1002/mrm.25569 SN - 1522-2594 VL - 75 IS - 3 SP - 933 EP - 945 PB - International Society for Magnetic Resonance in Medicine ER - TY - JOUR A1 - Vos, E. K. A1 - Lagemaat, M. W. A1 - Barentsz, J. O. A1 - Fütterer, J. J. A1 - Zamecnik, P. A1 - Roozen, H. A1 - Orzada, S. A1 - Bitz, Andreas A1 - Maas, M. C. A1 - Scheenen, T. W. J. T1 - Image quality and cancer visibility of T2-weighted Magnetic Resonance Imaging of the prostate at 7 Tesla JF - European Radiology N2 - Objectives To assess the image quality of T2-weighted (T2w) magnetic resonance imaging of the prostate and the visibility of prostate cancer at 7 Tesla (T). Materials & methods Seventeen prostate cancer patients underwent T2w imaging at 7T with only an external transmit/receive array coil. Three radiologists independently scored images for image quality, visibility of anatomical structures, and presence of artefacts. Krippendorff’s alpha and weighted kappa statistics were used to assess inter-observer agreement. Visibility of prostate cancer lesions was assessed by directly linking the T2w images to the confirmed location of prostate cancer on histopathology. Results T2w imaging at 7T was achievable with ‘satisfactory’ (3/5) to ‘good’ (4/5) quality. Visibility of anatomical structures was predominantly scored as ‘satisfactory’ (3/5) and ‘good’ (4/5). If artefacts were present, they were mostly motion artefacts and, to a lesser extent, aliasing artefacts and noise. Krippendorff’s analysis revealed an α = 0.44 between three readers for the overall image quality scores. Clinically significant cancer lesions in both peripheral zone and transition zone were visible at 7T. Conclusion T2w imaging with satisfactory to good quality can be routinely acquired, and cancer lesions were visible in patients with prostate cancer at 7T using only an external transmit/receive body array coil. Y1 - 2014 U6 - https://doi.org/10.1007/s00330-014-3234-6 SN - 1432-1084 VL - 24 IS - 8 SP - 1950 EP - 1958 PB - Springer CY - Cham ER - TY - JOUR A1 - Lagemaat, Miriam W. A1 - Maas, Marnix C. A1 - Vos, Eline K. A1 - Bitz, Andreas A1 - Orzada, Stephan A1 - Weiland, Elisabeth A1 - Uden, Mark J. van A1 - Kobus, Thiele A1 - Heerschap, Arend A1 - Scheenen, Tom W. J. T1 - (31) P MR spectroscopic imaging of the human prostate at 7 T: T1 relaxation times, Nuclear Overhauser Effect, and spectral characterization JF - Magnetic Resonance in Medicine Y1 - 2015 U6 - https://doi.org/10.1002/mrm.25209 SN - 1522-2594 VL - 73 IS - 3 SP - 909 EP - 920 PB - Wiley CY - Weinheim ER - TY - JOUR A1 - Theysohn, Jens M. A1 - Kraff, Oliver A1 - Eilers, Kristina A1 - Andrade, Dorian A1 - Gerwig, Marcus A1 - Timmann, Dagmar A1 - Schmitt, Franz A1 - Ladd, Mark E. A1 - Ladd, Susanne C. A1 - Bitz, Andreas T1 - Vestibular effects of a 7 Tesla MRI examination compared to 1.5 T and 0 T in healthy volunteers JF - PLoS one N2 - Ultra-high-field MRI (7 Tesla (T) and above) elicits more temporary side-effects compared to 1.5 T and 3 T, e.g. dizziness or “postural instability” even after exiting the scanner. The current study aims to assess quantitatively vestibular performance before and after exposure to different MRI scenarios at 7 T, 1.5 T and 0 T. Sway path and body axis rotation (Unterberger's stepping test) were quantitatively recorded in a total of 46 volunteers before, 2 minutes after, and 15 minutes after different exposure scenarios: 7 T head MRI (n = 27), 7 T no RF (n = 22), 7 T only B₀ (n = 20), 7 T in & out B₀ (n = 20), 1.5 T no RF (n = 20), 0 T (n = 15). All exposure scenarios lasted 30 minutes except for brief one minute exposure in 7 T in & out B₀. Both measures were documented utilizing a 3D ultrasound system. During sway path evaluation, the experiment was repeated with eyes both open and closed. Sway paths for all long-lasting 7 T scenarios (normal, no RF, only B₀) with eyes closed were significantly prolonged 2 minutes after exiting the scanner, normalizing after 15 minutes. Brief exposure to 7 T B₀ or 30 minutes exposure to 1.5 T or 0 T did not show significant changes. End positions after Unterberger's stepping test were significantly changed counter-clockwise after all 7 T scenarios, including the brief in & out B₀ exposure. Shorter exposure resulted in a smaller alteration angle. In contrast to sway path, reversal of changes in body axis rotation was incomplete after 15 minutes. 1.5 T caused no rotational changes. The results show that exposure to the 7 Tesla static magnetic field causes only a temporary dysfunction or “over-compensation” of the vestibular system not measurable at 1.5 or 0 Tesla. Radiofrequency fields, gradient switching, and orthostatic dysregulation do not seem to play a role. Y1 - 2014 U6 - https://doi.org/10.1371/journal.pone.0092104 SN - 1932-6203 VL - 9 IS - 3 PB - PLOS CY - San Francisco ER - TY - JOUR A1 - Kraff, Oliver A1 - Bitz, Andreas A1 - Breyer, Tobias A1 - Kruszona, Stefan A1 - Maderwald, Stefan A1 - Brote, Irina A1 - Gizewski, Elke R. A1 - Ladd, Mark E. A1 - Quick, Harald H. T1 - A transmit/receive radiofrequency array for imaging the carotid arteries at 7 Tesla: coil design and first in vivo results JF - Investigative Radiology N2 - Objective: To develop a transmit/receive radiofrequency (RF) array for magnetic resonance imaging (MRI) of the carotid arteries at 7 T. The prototype is characterized in numerical simulations and bench measurements, and the feasibility of plaque imaging at 7 T is demonstrated in first in vivo images. Materials and Methods: The RF phased array coil consists of 8 surface loop coils. To allow imaging of both sides of the neck, the RF array is divided into 2 coil clusters, each with 4 overlapping loop elements. For safety validation, numerical computations of the RF field distribution and the corresponding specific absorption rate were performed on the basis of a heterogeneous human body model. To validate the coil model, maps of the transmit B1+ field were compared between simulation and measurement. In vivo images of a healthy volunteer and a patient (ulcerating plaque and a 50% stenosis of the right internal carotid artery) were acquired using a 3-dimensional FLASH sequence with a high isotropic spatial resolution of 0.54 mm as well as using pulse-triggered proton density (PD)/T2-weighted turbo spin echo sequences. Results: Measurements of the S-parameters yielded a reflection and isolation of the coil elements of better than −18 and −13 dB, respectively. Measurements of the g-factor indicated good image quality for parallel imaging acceleration factors up to 2.4. A similar distribution and a very good match of the absolute values were found between the measured and simulated B1+ transmit RF field for the validation of the coil model. In vivo images revealed good signal excitation of both sides of the neck and a high vessel-to-background image contrast for the noncontrast-enhanced 3-dimensional FLASH sequence. Imaging at 7 T could depict the extent of stenosis, and revealed the disruption and ulcer of the plaque. Conclusions: This study demonstrates that 2 four-channel transmit/receive RF arrays for each side of the neck is a suitable concept for in vivo MRI of the carotid arteries at 7 Tesla. Further studies are needed to explore and exploit the full potential of 7 T high-field MRI for carotid atherosclerotic plaque imaging. Y1 - 2011 U6 - https://doi.org/10.1097/RLI.0b013e318206cee4 SN - 1536-0210 VL - 46 IS - 4 SP - 246 EP - 254 PB - Wolters Kluwer CY - Köln ER - TY - JOUR A1 - El Quardi, A. A1 - Streckert, J. A1 - Bitz, Andreas A1 - Münkner, S. A1 - Engel, J. A1 - Hansen, V. T1 - New fin-line devices for radiofrequency exposure of small biological samples in vitro allowing whole-cell patch clamp recordings JF - Bioelectromagnetics N2 - The development and analysis of three waveguides for the exposure of small biological in vitro samples to mobile communication signals at 900 MHz (GSM, Global System for Mobile Communications), 1.8 GHz (GSM), and 2 GHz (UMTS, Universal Mobile Telecommunications System) is presented. The waveguides were based on a fin-line concept and the chamber containing the samples bathed in extracellular solution was placed onto two fins with a slot in between, where the exposure field concentrates. Measures were taken to allow for patch clamp recordings during radiofrequency (RF) exposure. The necessary power for the achievement of the maximum desired specific absorption rate (SAR) of 20 W/kg (average over the mass of the solution) was approximately Pin = 50 mW, Pin = 19 mW, and Pin = 18 mW for the 900 MHz, 1800 MHz, and 2 GHz devices, respectively. At 20 W/kg, a slight RF-induced temperature elevation in the solution of no more than 0.3 °C was detected, while no thermal offsets due to the electromagnetic exposure could be detected at the lower SAR settings (2, 0.2, and 0.02 W/kg). A deviation of 10% from the intended solution volume yielded a calculated SAR deviation of 8% from the desired value. A maximum ±10% variation in the local SAR could occur when the position of the patch clamp electrode was altered within the area where the cells to be investigated were located. Y1 - 2011 U6 - https://doi.org/10.1002/bem.20621 SN - 1521-186X VL - 32 IS - 2 SP - 102 EP - 112 PB - Wiley CY - Weinheim ER - TY - JOUR A1 - Schlamann, Marc A1 - Voigt, Melanie A. A1 - Maderwald, Stefan A1 - Bitz, Andreas A1 - Kraff, Oliver A1 - Ladd, Susanne C. A1 - Ladd, Mark E. A1 - Forsting, Michael A1 - Wilhelm, Hans T1 - Exposure to high-field MRI does not affect cognitive function JF - Journal of Magnetic Resonance Imaging N2 - Purpose To assess potential cognitive deficits under the influence of static magnetic fields at various field strengths some studies already exist. These studies were not focused on attention as the most vulnerable cognitive function. Additionally, mostly no magnetic resonance imaging (MRI) sequences were performed. Materials and Methods In all, 25 right-handed men were enrolled in this study. All subjects underwent one MRI examination of 63 minutes at 1.5 T and one at 7 T within an interval of 10 to 30 days. The order of the examinations was randomized. Subjects were referred to six standardized neuropsychological tests strictly focused on attention immediately before and after each MRI examination. Differences in neuropsychological variables between the timepoints before and after each MRI examination were assessed and P-values were calculated Results Only six subtests revealed significant differences between pre- and post-MRI. In these tests the subjects achieved better results in post-MRI testing than in pre-MRI testing (P = 0.013–0.032). The other tests revealed no significant results. Conclusion The improvement in post-MRI testing is only explicable as a result of learning effects. MRI examinations, even in ultrahigh-field scanners, do not seem to have any persisting influence on the attention networks of human cognition immediately after exposure. Y1 - 2010 U6 - https://doi.org/10.1002/jmri.22065 SN - 1522-2586 VL - 31 IS - 5 SP - 1061 EP - 1066 PB - Wiley-Liss CY - New York ER - TY - JOUR A1 - Bitz, Andreas A1 - Zhou, Yi A1 - El Quardi, Abdessamad A1 - Streckert, Joachim T1 - Occupational Exposure at Mobile Communication Base Station Antenna Sites JF - Frequenz Y1 - 2009 U6 - https://doi.org/10.1515/FREQ.2009.63.7-8.123 SN - 2191-6349 VL - 63 IS - 7-8 SP - 123 EP - 128 ER - TY - JOUR A1 - Schlamann, Marc A1 - Yoon, Min-Suk A1 - Maderwald, Stefan A1 - Pietrzyk, Thomas A1 - Bitz, Andreas A1 - Gerwig, Marcus A1 - Forsting, Michael A1 - Ladd, Susanne C. A1 - Ladd, Mark E. A1 - Kastrup, Oliver T1 - Short term effects of magnetic resonance imaging on excitability of the motor cortex at 1.5T and 7T JF - Academic Radiology N2 - Rationale and Objectives The increasing spread of high-field and ultra-high-field magnetic resonance imaging (MRI) scanners has encouraged new discussion of the safety aspects of MRI. Few studies have been published on possible cognitive effects of MRI examinations. The aim of this study was to examine whether changes are measurable after MRI examinations at 1.5 and 7 T by means of transcranial magnetic stimulation (TMS). Materials and Methods TMS was performed in 12 healthy, right-handed male volunteers. First the individual motor threshold was specified, and then the cortical silent period (SP) was measured. Subsequently, the volunteers were exposed to the 1.5-T MRI scanner for 63 minutes using standard sequences. The MRI examination was immediately followed by another TMS session. Fifteen minutes later, TMS was repeated. Four weeks later, the complete setting was repeated using a 7-T scanner. Control conditions included lying in the 1.5-T scanner for 63 minutes without scanning and lying in a separate room for 63 minutes. TMS was performed in the same way in each case. For statistical analysis, Wilcoxon's rank test was performed. Results Immediately after MRI exposure, the SP was highly significantly prolonged in all 12 subjects at 1.5 and 7 T. The motor threshold was significantly increased. Fifteen minutes after the examination, the measured value tended toward normal again. Control conditions revealed no significant differences. Conclusion MRI examinations lead to a transient and highly significant alteration in cortical excitability. This effect does not seem to depend on the strength of the static magnetic field. Y1 - 2010 U6 - https://doi.org/10.1016/j.acra.2009.10.004 SN - 1076-6332 VL - 17 IS - 3 SP - 277 EP - 281 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Kraff, Oliver A1 - Bitz, Andreas A1 - Kruszona, Stefan A1 - Orzada, Stephan A1 - Schaefer, Lena C. A1 - Theysohn, Jens M. A1 - Maderwald, Stefan A1 - Ladd, Mark E. A1 - Quick, Harald H. T1 - An eight-channel phased array RF coil for spine MR imaging at 7 T JF - Investigative Radiology Y1 - 2009 U6 - https://doi.org/10.1097/RLI.0b013e3181b24ab7 SN - 1536-0210 VL - 44 IS - 11 SP - 734 EP - 740 PB - Lippincott Williams & Wilkins ER - TY - JOUR A1 - Schlamann, M. A1 - Yoon, M.-S. A1 - Maderwald, S. A1 - Pietrzyk, T. A1 - Bitz, Andreas A1 - Gerwig, M. A1 - Forsting, M. A1 - Ladd, S. C. A1 - Ladd, M. E. A1 - Kastrup, O. T1 - Auswirkungen der Magnetresonanztomografie auf die Elektrophysiologie des motorischen Kortex: eine Studie mit transkranieller Magnetstimulation T1 - Effects of MRI on the electrophysiology of the motor cortex: a TMS study JF - RöFo - Fortschritte auf dem Giebiet der Röntgenstrahlen und der bildgebenden Verfahren Y1 - 2009 U6 - https://doi.org/10.1055/s-0028-1109038 SN - 1438-9029 VL - 181 IS - 3 SP - 215 EP - 219 PB - Thieme CY - Stuttgart ER - TY - JOUR A1 - Klomp, D. W. J. A1 - Bitz, Andreas A1 - Heerschap, A. A1 - Scheenen, T. W. J. T1 - Proton spectroscopic imaging of the human prostate at 7 T JF - NMR in Biomedicine Y1 - 2009 U6 - https://doi.org/10.1002/nbm.1360 SN - 1099-1492 VL - 22 IS - 5 SP - 495 EP - 501 ER - TY - JOUR A1 - Lerchl, Alexander A1 - Krüger, Heike A1 - Niehaus, Michael A1 - Streckert, Joachim R. A1 - Bitz, Andreas A1 - Hansen, Volkert T1 - Effects of mobile phone electromagnetic fields at nonthermal SAR values on melatonin and body weight of Djungarian hamsters (Phodopus sungorus) JF - Journal of Pineal Research Y1 - 2008 U6 - https://doi.org/10.1111/j.1600-079X.2007.00522.x SN - 1600-079X VL - 44 IS - 3 SP - 267 EP - 272 ER - TY - JOUR A1 - Fiedler, Thomas M. A1 - Ladd, Mark E. A1 - Bitz, Andreas T1 - SAR Simulations & Safety JF - NeuroImage Y1 - 2017 U6 - https://doi.org/10.1016/j.neuroimage.2017.03.035 SN - 1053-8119 IS - Epub ahead of print PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Noureddine, Yacine A1 - Kraff, Oliver A1 - Ladd, Mark E. A1 - Wrede, Karsten H. A1 - Chen, Bixia A1 - Quick, Harald H. A1 - Schaefers, Gregor A1 - Bitz, Andreas T1 - In vitro and in silico assessment of RF-induced heating around intracranial aneurysm clips at 7 Tesla JF - Magnetic Resonance in Medicine Y1 - 2017 U6 - https://doi.org/10.1002/mrm.26650 SN - 1522-2594 IS - Early view PB - Wiley CY - Weinheim ER - TY - JOUR A1 - Fiedler, Thomas M. A1 - Ladd, Mark E. A1 - Bitz, Andreas T1 - RF safety assessment of a bilateral four-channel transmit/receive 7 Tesla breast coil: SAR versus temperature limits JF - Medical Physics Y1 - 2017 U6 - https://doi.org/10.1002/mp.12034 N1 - This article is corrected by: Errata: Erratum: “RF safety assessment of a bilateral four-channel transmit/receive 7 Tesla breast coil: SAR versus tissue temperature limits” [Med. Phys. 44(1), 143–157 (2017)] Volume 44, Issue 2, 772 VL - 44 IS - 1 SP - 143 EP - 157 ER - TY - JOUR A1 - Lagemaat, Miriam W. A1 - Vos, Eline K. A1 - Maas, Marnix C. A1 - Bitz, Andreas A1 - Orzada, Stephan A1 - Uden, Mark J. van A1 - Kobus, Thiele A1 - Heerschap, Arend A1 - Scheenen, Tom W. J. T1 - Phosphorus magnetic resonance spectroscopic imaging at 7 T in patients with prostate cancer JF - Investigative Radiology N2 - Objectives The aim of this study was to identify characteristics of phosphorus (³¹P) spectra of the human prostate and to investigate changes of individual phospholipid metabolites in prostate cancer through in vivo ³¹P magnetic resonance spectroscopic imaging (MRSI) at 7 T. Materials and Methods In this institutional review board–approved study, 15 patients with biopsy-proven prostate cancer underwent T₂-weighted magnetic resonance imaging and 3-dimensional ³¹P MRSI at 7 T. Voxels were selected at the tumor location, in normal-appearing peripheral zone tissue, normal-appearing transition zone tissue, and in the base of the prostate close to the seminal vesicles. Phosphorus metabolite ratios were determined and compared between tissue types. Results Signals of phosphoethanolamine (PE) and phosphocholine (PC) were present and well resolved in most ³¹P spectra in the prostate. Glycerophosphocholine signals were observable in 43% of the voxels in malignant tissue, but in only 10% of the voxels in normal-appearing tissue away from the seminal vesicles. In many spectra, independent of tissue type, 2 peaks resonated in the chemical shift range of inorganic phosphate, possibly representing 2 separate pH compartments. The PC/PE ratio in the seminal vesicles was highly elevated compared with the prostate in 5 patients. A considerable overlap of ³¹P metabolite ratios was found between prostate cancer and normal-appearing prostate tissue, preventing direct discrimination of these tissues. The only 2 patients with high Gleason scores tumors (≥4+5) presented with high PC and glycerophosphocholine levels in their cancer lesions. Conclusions Phosphorus MRSI at 7 T shows distinct features of phospholipid metabolites in the prostate gland and its surrounding structures. In this exploratory study, no differences in ³¹P metabolite ratios were observed between prostate cancer and normal-appearing prostate tissue possibly because of the partial volume effects of small tumor foci in large MRSI voxels. Y1 - 2014 U6 - https://doi.org/10.1097/RLI.0000000000000012 SN - 1536-0210 VL - 49 IS - 5 SP - 363 EP - 372 PB - Lippincott Williams & Wilkins CY - Philadelphia, Pa. ER - TY - JOUR A1 - Maas, Marnix C. A1 - Vos, Eline K. A1 - Lagemaat, Miriam W. A1 - Bitz, Andreas A1 - Orzada, Stephan A1 - Kobus, Thiele A1 - Kraff, Oliver A1 - Maderwald, Stefan A1 - Ladd, Mark E. A1 - Scheenen, Tom W. J. T1 - Feasibility of T₂-weighted turbo spin echo imaging of the human prostate at 7 tesla JF - Magnetic Resonance in Medicine N2 - Purpose To demonstrate that high quality T₂-weighted (T2w) turbo spin-echo (TSE) imaging of the complete prostate can be achieved routinely and within safety limits at 7 T, using an external transceive body array coil only. Methods Nine healthy volunteers and 12 prostate cancer patients were scanned on a 7 T whole-body system. Preparation consisted of B₀ and radiofrequency shimming and localized flip angle calibration. T₁ and T₂ relaxation times were measured and used to define the T2w-TSE protocol. T2w imaging was performed using a TSE sequence (pulse repetition time/echo time 3000–3640/71 ms) with prolonged excitation and refocusing pulses to reduce specific absorption rate. Results High quality T2w TSE imaging was performed in less than 2 min in all subjects. Tumors of patients with gold-standard tumor localization (MR-guided biopsy or prostatectomy) were well visualized on 7 T imaging (n = 3). The number of consecutive slices achievable within a 10-g averaged specific absorption rate limit of 10 W/kg was ≥28 in all subjects, sufficient for full prostate coverage with 3-mm slices in at least one direction. Conclusion High quality T2w TSE prostate imaging can be performed routinely and within specific absorption rate limits at 7 T with an external transceive body array. Y1 - 2014 U6 - https://doi.org/10.1002/mrm.24818 SN - 1522-2594 VL - 71 IS - 5 SP - 1711 EP - 1719 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Umutlu, Lale A1 - Kraff, Oliver A1 - Fischer, Anja A1 - Kinner, Sonja A1 - Maderwald, Stefan A1 - Nassenstein, Kai A1 - Nensa, Felix A1 - Grüneisen, Johannes A1 - Orzada, Stephan A1 - Bitz, Andreas A1 - Forsting, Michael A1 - Ladd, Mark E. A1 - Lauenstein, Thomas C. T1 - Seven-Tesla MRI of the female pelvis JF - European Radiology Y1 - 2013 U6 - https://doi.org/10.1007/s00330-013-2868-0 SN - 1432-1084 VL - 23 IS - 9 SP - 2364 EP - 2373 PB - Springer CY - Berlin ER - TY - JOUR A1 - Bitz, Andreas A1 - Felder, Jorg A1 - Wittig, Tilmann T1 - Designing MRI Coils with Aid of Simulation JF - Microwaves & RF Y1 - 2013 SN - 0745-2993 VL - 52 IS - 7 SP - 56 PB - Penton CY - Cleveland, Ohio ER - TY - JOUR A1 - Kraff, Oliver A1 - Wrede, Karsten H. A1 - Schoemberg, Tobias A1 - Dammann, Philipp A1 - Noureddine, Yacine A1 - Orzada, Stephan A1 - Ladd, Mark E. A1 - Bitz, Andreas T1 - MR safety assessment of potential RF heating from cranial fixation plates at 7 T JF - Medical Physics Y1 - 2013 U6 - https://doi.org/10.1118/1.4795347 SN - 2473-4209 VL - 40 IS - 4 SP - 042302-1 EP - 042302-10 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Umutlu, L. A1 - Maderwald, S. A1 - Kinner, S. A1 - Kraff, O. A1 - Bitz, Andreas A1 - Orzada, S. A1 - Johst, S. A1 - Wrede, K. A1 - Forsting, M. A1 - Ladd, M. E. A1 - Lauenstein, T. C. A1 - Quick, H. H. T1 - First-pass contrast-enhanced renal MRA at 7 Tesla: initial results JF - European Radiology Y1 - 2013 U6 - https://doi.org/10.1007/s00330-012-2666-0 SN - 1432-1084 VL - 23 IS - 4 SP - 1059 EP - 1066 PB - Springer CY - Berlin ER - TY - JOUR A1 - Umutlu, Lale A1 - Orzada, Stephan A1 - Kinner, Sonja A1 - Maderwald, Stefan A1 - Bronte, Irina A1 - Bitz, Andreas A1 - Kraff, Oliver A1 - Ladd, Susanne C. A1 - Antoch, Gerald A1 - Ladd, Mark E. A1 - Quick, Harald H. A1 - Lauenstein, Thomas C. T1 - Renal imaging at 7 Tesla: preliminary results JF - European Radiology N2 - Objective To investigate the feasibility of 7T MR imaging of the kidneys utilising a custom-built 8-channel transmit/receive radiofrequency body coil. Methods In vivo unenhanced MR was performed in 8 healthy volunteers on a 7T whole-body MR system. After B0 shimming the following sequences were obtained: 1) 2D and 3D spoiled gradient-echo sequences (FLASH, VIBE), 2) T1-weighted 2D in and opposed phase 3) True-FISP imaging and 4) a T2-weighted turbo spin echo (TSE) sequence. Visual evaluation of the overall image quality was performed by two radiologists. Results Renal MRI at 7T was feasible in all eight subjects. Best image quality was found using T1-weighted gradient echo MRI, providing high anatomical details and excellent conspicuity of the non-enhanced vasculature. With successful shimming, B1 signal voids could be effectively reduced and/or shifted out of the region of interest in most sequence types. However, T2-weighted TSE imaging remained challenging and strongly impaired because of signal heterogeneities in three volunteers. Conclusion The results demonstrate the feasibility and diagnostic potential of dedicated 7T renal imaging. Further optimisation of imaging sequences and dedicated RF coil concepts are expected to improve the acquisition quality and ultimately provide high clinical diagnostic value. Y1 - 2011 SN - 1432-1084 VL - 21 IS - 4 SP - 841 EP - 849 PB - Springer CY - Berlin ER - TY - CHAP A1 - Essingholt, Felix A1 - Meyer, Frederic A1 - Kuhn, Peter A1 - Schmidt, Philip A1 - Benkner, Thorsten A1 - Grabmaier, Anton T1 - Non-invasive heart beat measurement using microwave resonators T2 - Proceedings, Vol. 2, Eurosensors 2018 Conference, Graz, Austria, 9–12 September 2018 Y1 - 2018 U6 - https://doi.org/10.3390/proceedings2131002 SN - 2504-3900 SP - 1002 PB - MDPI CY - Basel ER - TY - RPRT A1 - Jaekel, C. A1 - Klein, C. A1 - Barth, R. A1 - Roskos, H. A1 - Kyas, G. A1 - Schroeer, M. A1 - Hüning, Felix T1 - Dynamik von Nichtgleichgewichtszustaenden in Hochtemperatursupraleitern Abschlussbericht N2 - Im Projekt wurden mit Hilfe zeitaufgeloester optischer Messtechniken Relaxations-Dynamiken von optisch angeregten Ladungstraegern und Hochfrequenzeigenschaften von Hochtemperatursupraleitern untersucht. Oberhalb der Sprungtemperatur wurden die Elektron-Phonon-Kopplungskonstanten fuer YBCO und BSCCO bestimmt. Dabei wurde erstmalig ein direkter Zusammenhang zwischen der Sprungtemperatur und der Kopplungstaerke gefunden. Der Kopplungsmechanismus enthaelt sowohl phononische als auch elektronische (spindynamische) Anteile. Unterhalb von T_c wird die Dynamik durch Aufbrechen und Rekombination von Cooper-Paaren bestimmt. Bei den Arbeiten zu den kohaerenten Phononen wurde ein Modell entwickelt, das das 'Anwerfen' der Phononen und das Amplitudenverhalten unterhalb der Sprungtemperatur erklaert. Als begleitende Untersuchungen wurden breitbandige Hochfrequenz-Messungen vorgenommen. Die Methode erlaubt die Untersuchung von Ladungstraegerdichten und von Streumechanismen. Erstmalig wurde in verspannten YBCO-Duennfilmen eine starke temperaturabhaengige Resonanz-Absorption beobachtet, die als Josephson-Plasmaresonanz an intrinsischen Kontakten identifiziert werden konnte. Die Nutzbarkeit dieser Kontakte fuer Bauelemente wurde durch einen Mikrowellendetektor demonstriert. Durch den Nachweis von emittierter gepulster Strahlung aus einer stromdurchflossenen supraleitenden Bruecke nach optischer Anregung wurde erstmals die Einsatzmoeglichkeit von HTSL fuer schnelle optische Schalter demonstriert. Es wurde gezeigt, dass die Schaltgeschwindigkeit eine direkte Folge der Ladungstraegerdynamik ist. T2 - Dynamics of non-equilibrium states in HTSC. Final report KW - Relaxation KW - Phonons KW - Calcium oxides KW - Electron-phonon coupling Y1 - 1996 N1 - Foerderkennzeichen BMBF 13N6288; TRN: DE97FD184 ER - TY - CHAP A1 - Hoegen, Anne von A1 - Doncker, Rik W. De A1 - Rütters, René T1 - Teaching Digital Control of Operational Amplifier Processes with a LabVIEW Interface and Embedded Hardware T2 - 2020 23rd International Conference on Electrical Machines and Systems (ICEMS) N2 - Control engineering theory is hard to grasp for undergraduates during the first semesters, as it deals with the dynamical behavior of systems also in combination with control strategies on an abstract level. Therefore, operational amplifier (OpAmp) processes are reasonable and very effective systems to connect mathematical description with actual system’s behavior. In this paper, we present an experiment for a laboratory session in which an embedded system, driven by a LabVIEW human machine interface (HMI) via USB, controls the analog circuits.With this setup we want to show the possibility of firstly, analyzing a first order process and secondly, designing a P-and PI-controller. Thereby, the theory of control engineering is always applied to the empirical results in order to break down the abstract level for the students. Y1 - 2020 U6 - https://doi.org/10.23919/ICEMS50442.2020.9290928 N1 - 23rd International Conference on Electrical Machines and Systems (ICEMS), 24-27 November 2020, Hamamatsu, Japan SP - 1117 EP - 1122 PB - IEEE CY - New York, NY ER - TY - CHAP A1 - Schuba, Marko A1 - Höfken, Hans-Wilhelm T1 - Cybersicherheit in Produktion, Automotive und intelligenten Gebäuden T2 - IT-Sicherheit - Technologien und Best Practices für die Umsetzung im Unternehmen Y1 - 2022 SN - 978-3-446-47223-5 SN - 978-3-446-47347-8 U6 - https://doi.org/10.3139/9783446473478.012 SP - 193 EP - 218 PB - Carl Hanser Verlag CY - München ER - TY - CHAP A1 - Engländer, Jacques A1 - Kaminski, Lars A1 - Schuba, Marko T1 - Informationssicherheitsmanagement T2 - Digitalisierungs- und Informationsmanagement N2 - Daten und Informationen sind die wichtigsten Ressourcen vieler Unternehmen und müssen daher entsprechend geschützt werden. Getrieben durch die erhöhte Vernetzung von Informationstechnologie, die höhere Offenheit infolge datengetriebener Dienstleistungen und eine starke Zunahme an Datenquellen, rücken die Gefahren von Informationsdiebstahl, -manipulation und -verlust in den Fokus von produzierenden Unternehmen. Auf dem Weg zum lern- und wandlungsfähigen Unternehmen kann dies zu einem großen Hindernis werden, da einerseits zu hohe Sicherheitsanforderungen neue Entwicklungen beschränken, andererseits wegen des Mangels an ausreichenden Informationssicherheitskonzepten Unternehmen weniger Innovationen wagen. Deshalb bedarf es individuell angepasster Konzepte für die Bereiche IT-Security, IT-Safety und Datenschutz für vernetzte Produkte, Produktion und Arbeitsplätze. Bei der Entwicklung und Durchsetzung dieser Konzepte steht der Faktor Mensch im Zentrum aller Überlegungen. In diesem Kapitel wird dargestellt, wie der Faktor Mensch bei der Erstellung von Informationssicherheitskonzepten in verschiedenen Phasen zu beachten ist. Beginnend mit der Integration von Informationssystemen und damit verbundenen Sicherheitsmaßnahmen, über die Administration, bis hin zur Anwendung durch den Endnutzer, werden Methoden beschrieben, die den Menschen, verbunden mit seinem Mehrwert wie auch den Risiken, einschließen. Dabei werden sowohl Grundlagen aufgezeigt als auch Konzepte vorgestellt, mit denen Entscheider in der Unternehmens-IT Leitlinien für die Informationssicherheit festlegen können. KW - Informationssicherheitsmanagement KW - Cybersicherheit KW - Cybersecurity KW - Informationssicherheit KW - IT-Sicherheit Y1 - 2022 SN - 978-3-662-63757-9 SN - 978-3-662-63758-6 U6 - https://doi.org/10.1007/978-3-662-63758-6_15 SP - 373 EP - 398 PB - Springer Vieweg CY - Berlin ER - TY - CHAP A1 - Schuba, Marko A1 - Höfken, Hans-Wilhelm A1 - Linzbach, Sophie T1 - An ICS Honeynet for Detecting and Analyzing Cyberattacks in Industrial Plants T2 - 2021 International Conference on Electrical, Computer and Energy Technologies (ICECET) N2 - Cybersecurity of Industrial Control Systems (ICS) is an important issue, as ICS incidents may have a direct impact on safety of people or the environment. At the same time the awareness and knowledge about cybersecurity, particularly in the context of ICS, is alarmingly low. Industrial honeypots offer a cheap and easy to implement way to raise cybersecurity awareness and to educate ICS staff about typical attack patterns. When integrated in a productive network, industrial honeypots may not only reveal attackers early but may also distract them from the actual important systems of the network. Implementing multiple honeypots as a honeynet, the systems can be used to emulate or simulate a whole Industrial Control System. This paper describes a network of honeypots emulating HTTP, SNMP, S7communication and the Modbus protocol using Conpot, IMUNES and SNAP7. The nodes mimic SIMATIC S7 programmable logic controllers (PLCs) which are widely used across the globe. The deployed honeypots' features will be compared with the features of real SIMATIC S7 PLCs. Furthermore, the honeynet has been made publicly available for ten days and occurring cyberattacks have been analyzed KW - Conpot KW - honeypot KW - honeynet KW - ICS KW - cybersecurity Y1 - 2022 SN - 978-1-6654-4231-2 SN - 978-1-6654-4232-9 U6 - https://doi.org/10.1109/ICECET52533.2021.9698746 N1 - 2021 International Conference on Electrical, Computer and Energy Technologies (ICECET). 09-10 December 2021. Cape Town, South Africa. PB - IEEE ER - TY - CHAP A1 - Christian, Esser A1 - Montag, Tim A1 - Schuba, Marko A1 - Allhof, Manuel T1 - Future critical infrastructure and security - cyberattacks on charging stations T2 - 31st International Electric Vehicle Symposium & Exhibition and International Electric Vehicle Technology Conference (EVS31 & EVTeC 2018) Y1 - 2018 SN - 978-1-5108-9157-9 SP - 665 EP - 671 PB - Society of Automotive Engineers of Japan (JSAE) CY - Tokyo ER - TY - JOUR A1 - Fiedler, Thomas M. A1 - Orzada, Stephan A1 - Flöser, Martina A1 - Rietsch, Stefan H. G. A1 - Schmidt, Simon A1 - Stelter, Jonathan K. A1 - Wittrich, Marco A1 - Quick, Harald H. A1 - Bitz, Andreas A1 - Ladd, Mark E. T1 - Performance and safety assessment of an integrated transmit array for body imaging at 7 T under consideration of specificabsorption rate, tissue temperature, and thermal dose JF - NMR in Biomedicine N2 - In this study, the performance of an integrated body-imaging array for 7 T with 32 radiofrequency (RF) channels under consideration of local specific absorption rate (SAR), tissue temperature, and thermal dose limits was evaluated and the imaging performance was compared with a clinical 3 T body coil. Thirty-two transmit elements were placed in three rings between the bore liner and RF shield of the gradient coil. Slice-selective RF pulse optimizations for B1 shimming and spokes were performed for differently oriented slices in the body under consideration of realistic constraints for power and local SAR. To improve the B1+ homogeneity, safety assessments based on temperature and thermal dose were performed to possibly allow for higher input power for the pulse optimization than permissible with SAR limits. The results showed that using two spokes, the 7 T array outperformed the 3 T birdcage in all the considered regions of interest. However, a significantly higher SAR or lower duty cycle at 7 T is necessary in some cases to achieve similar B1+ homogeneity as at 3 T. The homogeneity in up to 50 cm-long coronal slices can particularly benefit from the high RF shim performance provided by the 32 RF channels. The thermal dose approach increases the allowable input power and the corresponding local SAR, in one example up to 100 W/kg, without limiting the exposure time necessary for an MR examination. In conclusion, the integrated antenna array at 7 T enables a clinical workflow for body imaging and comparable imaging performance to a conventional 3 T clinical body coil. KW - body imaging at 7 T MRI KW - thermal dose KW - tissue temperature KW - transmit antenna arrays Y1 - 2022 U6 - https://doi.org/10.1002/nbm.4656 SN - 0952-3480 (Print) SN - 1099-1492 (Online) VL - 35 IS - 5 SP - 1 EP - 17 PB - Wiley ER - TY - CHAP A1 - Alhaskir, Mohamed A1 - Tschesche, Matteo A1 - Linke, Florian A1 - Schriewer, Elisabeth A1 - Weber, Yvonne A1 - Wolking, Stefan A1 - Röhrig, Rainer A1 - Koch, Henner A1 - Kutafina, Ekaterina ED - Röhrig, Rainer ED - Grabe, Niels ED - Haag, Martin ED - Hübner, Ursula ED - Sax, Ulrich ED - Schmidt, Carsten Oliver ED - Sedlmayr, Martin ED - Zapf, Antonia T1 - ECG matching: an approach to synchronize ECG datasets for data quality comparisons T2 - Proceedings of the 68th Annual Meeting of the German Association of Medical Informatics, Biometry, and Epidemiology e.V. (gmds) 2023 N2 - Clinical assessment of newly developed sensors is important for ensuring their validity. Comparing recordings of emerging electrocardiography (ECG) systems to a reference ECG system requires accurate synchronization of data from both devices. Current methods can be inefficient and prone to errors. To address this issue, three algorithms are presented to synchronize two ECG time series from different recording systems: Binned R-peak Correlation, R-R Interval Correlation, and Average R-peak Distance. These algorithms reduce ECG data to their cyclic features, mitigating inefficiencies and minimizing discrepancies between different recording systems. We evaluate the performance of these algorithms using high-quality data and then assess their robustness after manipulating the R-peaks. Our results show that R-R Interval Correlation was the most efficient, whereas the Average R-peak Distance and Binned R-peak Correlation were more robust against noisy data. KW - Electrocardiography KW - Wearable electronic device KW - Sensors comparison KW - Time-series synchronization Y1 - 2023 SN - 978-1-64368-428-4 (Print) SN - 978-1-64368-429-1 (Online) U6 - https://doi.org/10.3233/SHTI230718 N1 - Proceedings of the 68th Annual Meeting of the German Association of Medical Informatics, Biometry, and Epidemiology e.V. (gmds) 2023, 17. - 21.9.23, Heilbronn, Germany Part of the series: Studies in Health Technology and Informatics VL - 307 SP - 225 EP - 232 PB - IOS Press ER - TY - CHAP A1 - Tischbein, Franziska A1 - Kean, Kilian A1 - Vertgewall, Chris Martin A1 - Ulbig, Andreas A1 - Altherr, Lena T1 - Determination of the topology of low-voltage distribution grids using cluster methods T2 - 27th International Conference on Electricity Distribution (CIRED 2023) N2 - Due to the decarbonization of the energy sector, the electric distribution grids are undergoing a major transformation, which is expected to increase the load on the operating resources due to new electrical loads and distributed energy resources. Therefore, grid operators need to gradually move to active grid management in order to ensure safe and reliable grid operation. However, this requires knowledge of key grid variables, such as node voltages, which is why the mass integration of measurement technology (smart meters) is necessary. Another problem is the fact that a large part of the topology of the distribution grids is not sufficiently digitized and models are partly faulty, which means that active grid operation management today has to be carried out largely blindly. It is therefore part of current research to develop methods for determining unknown grid topologies based on measurement data. In this paper, different clustering algorithms are presented and their performance of topology detection of low voltage grids is compared. Furthermore, the influence of measurement uncertainties is investigated in the form of a sensitivity analysis. Y1 - 2023 SN - 978-1-83953-855-1 U6 - https://doi.org/10.1049/icp.2023.0478 N1 - 27th International Conference on Electricity Distribution (CIRED 2023), 12-15 June 2023, Rome, Italy. SP - 1 EP - 5 PB - IEEE ER - TY - JOUR A1 - Coll-Perales, Baldomero A1 - Schulte-Tigges, Joschua A1 - Rondinone, Michele A1 - Gozalvez, Javier A1 - Reke, Michael A1 - Matheis, Dominik A1 - Walter, Thomas T1 - Prototyping and evaluation of infrastructure-assisted transition of control for cooperative automated vehicles JF - IEEE Transactions on Intelligent Transportation Systems N2 - Automated driving is now possible in diverse road and traffic conditions. However, there are still situations that automated vehicles cannot handle safely and efficiently. In this case, a Transition of Control (ToC) is necessary so that the driver takes control of the driving. Executing a ToC requires the driver to get full situation awareness of the driving environment. If the driver fails to get back the control in a limited time, a Minimum Risk Maneuver (MRM) is executed to bring the vehicle into a safe state (e.g., decelerating to full stop). The execution of ToCs requires some time and can cause traffic disruption and safety risks that increase if several vehicles execute ToCs/MRMs at similar times and in the same area. This study proposes to use novel C-ITS traffic management measures where the infrastructure exploits V2X communications to assist Connected and Automated Vehicles (CAVs) in the execution of ToCs. The infrastructure can suggest a spatial distribution of ToCs, and inform vehicles of the locations where they could execute a safe stop in case of MRM. This paper reports the first field operational tests that validate the feasibility and quantify the benefits of the proposed infrastructure-assisted ToC and MRM management. The paper also presents the CAV and roadside infrastructure prototypes implemented and used in the trials. The conducted field trials demonstrate that infrastructure-assisted traffic management solutions can reduce safety risks and traffic disruptions. KW - Automated driving KW - automated vehicles KW - connected automated vehicles KW - CAV KW - experimental evaluation Y1 - 2021 U6 - https://doi.org/10.1109/TITS.2021.3061085 SN - 1524-9050 (Print) SN - 1558-0016 (Online) VL - 23 IS - 7 SP - 6720 EP - 6736 PB - IEEE ER - TY - CHAP A1 - Schulte-Tigges, Joschua A1 - Matheis, Dominik A1 - Reke, Michael A1 - Walter, Thomas A1 - Kaszner, Daniel ED - Krömker, Heidi T1 - Demonstrating a V2X enabled system for transition of control and minimum risk manoeuvre when leaving the operational design domain T2 - HCII 2023: HCI in Mobility, Transport, and Automotive Systems N2 - Modern implementations of driver assistance systems are evolving from a pure driver assistance to a independently acting automation system. Still these systems are not covering the full vehicle usage range, also called operational design domain, which require the human driver as fall-back mechanism. Transition of control and potential minimum risk manoeuvres are currently research topics and will bridge the gap until full autonomous vehicles are available. The authors showed in a demonstration that the transition of control mechanisms can be further improved by usage of communication technology. Receiving the incident type and position information by usage of standardised vehicle to everything (V2X) messages can improve the driver safety and comfort level. The connected and automated vehicle’s software framework can take this information to plan areas where the driver should take back control by initiating a transition of control which can be followed by a minimum risk manoeuvre in case of an unresponsive driver. This transition of control has been implemented in a test vehicle and was presented to the public during the IEEE IV2022 (IEEE Intelligent Vehicle Symposium) in Aachen, Germany. KW - V2X KW - Transiton of Control KW - Minimum Risk Manoeuvre KW - Operational Design Domain KW - Connected Automated Vehicle Y1 - 2023 SN - 978-3-031-35677-3 (Print) SN - 978-3-031-35678-0 (Online) U6 - https://doi.org/10.1007/978-3-031-35678-0_12 N1 - 5th International Conference, MobiTAS 2023, Held as Part of the 25th HCI International Conference, HCII 2023, Copenhagen, Denmark, July 23–28, 2023. SP - 200 EP - 210 PB - Springer CY - Cham ER - TY - CHAP A1 - Galdi, Chiara A1 - Hartung, Frank A1 - Dugelay, Jean-Luc T1 - Videos versus still images: Asymmetric sensor pattern noise comparison on mobile phones T2 - Electronic Imaging N2 - Nowadays, the most employed devices for recoding videos or capturing images are undoubtedly the smartphones. Our work investigates the application of source camera identification on mobile phones. We present a dataset entirely collected by mobile phones. The dataset contains both still images and videos collected by 67 different smartphones. Part of the images consists in photos of uniform backgrounds, especially collected for the computation of the RSPN. Identifying the source camera given a video is particularly challenging due to the strong video compression. The experiments reported in this paper, show the large variation in performance when testing an highly accurate technique on still images and videos. KW - Image Forensics KW - Mobile Phones KW - Image Database Y1 - 2017 U6 - https://doi.org/10.2352/ISSN.2470-1173.2017.7.MWSF-331 SN - 2470-1173 N1 - IS&T International Symposium on Electronic Imaging 2017 Media Watermarking, Security, and Forensics 2017 SP - 100 EP - 103 PB - Society for Imaging Science and Technology CY - Springfield, Virginia ER - TY - JOUR A1 - Fiedler, Thomas M. A1 - Orzada, Stephan A1 - Flöser, Martina A1 - Rietsch, Stefan H. G. A1 - Quick, Harald H. A1 - Ladd, Mark E. A1 - Bitz, Andreas T1 - Performance analysis of integrated RF microstrip transmit antenna arrays with high channel count for body imaging at 7 T JF - NMR in Biomedicine N2 - The aim of the current study was to investigate the performance of integrated RF transmit arrays with high channel count consisting of meander microstrip antennas for body imaging at 7 T and to optimize the position and number of transmit ele- ments. RF simulations using multiring antenna arrays placed behind the bore liner were performed for realistic exposure conditions for body imaging. Simulations were performed for arrays with as few as eight elements and for arrays with high channel counts of up to 48 elements. The B1+ field was evaluated regarding the degrees of freedom for RF shimming in the abdomen. Worst-case specific absorption rate (SARwc ), SAR overestimation in the matrix compression, the number of virtual obser- vation points (VOPs) and SAR efficiency were evaluated. Constrained RF shimming was performed in differently oriented regions of interest in the body, and the devia- tion from a target B1+ field was evaluated. Results show that integrated multiring arrays are able to generate homogeneous B1+ field distributions for large FOVs, espe- cially for coronal/sagittal slices, and thus enable body imaging at 7 T with a clinical workflow; however, a low duty cycle or a high SAR is required to achieve homoge- neous B1+ distributions and to exploit the full potential. In conclusion, integrated arrays allow for high element counts that have high degrees of freedom for the pulse optimization but also produce high SARwc , which reduces the SAR accuracy in the VOP compression for low-SAR protocols, leading to a potential reduction in array performance. Smaller SAR overestimations can increase SAR accuracy, but lead to a high number of VOPs, which increases the computational cost for VOP evaluation and makes online SAR monitoring or pulse optimization challenging. Arrays with interleaved rings showed the best results in the study. KW - body imaging at UHF MRI KW - integrated transmit coil arrays KW - VOP compression Y1 - 2021 U6 - https://doi.org/10.1002/nbm.4515 SN - 0952-3480 (ISSN) SN - 1099-1492 (eISSN) VL - 34 IS - 7 PB - Wiley CY - Weinheim ER - TY - PAT A1 - Lippoldt, Mario A1 - Ringbeck, Thorsten A1 - Hüning, Felix T1 - Verfahren und System zur Erkennung von unerlaubten Fahrzeug-Überholvorgängen in einer Überholverbotszone eines Fahrwegs Y1 - 2023 ER -