@article{OrzadaFiedlerBitzetal.2020,
  author    = {Orzada, Stephan and Fiedler, Thomas M. and Bitz, Andreas and Ladd, Mark E. and Quick, Harald H.},
  title     = {Local SAR compression with overestimation control to reduce maximum relative SAR overestimation and improve multi-channel RF array performance},
  series = {Magnetic Resonance Materials in Physics, Biology and Medicine},
  journal   = {Magnetic Resonance Materials in Physics, Biology and Medicine},
  number    = {34 (2021)},
  publisher = {Springer},
  address   = {Heidelberg},
  isbn      = {1352-8661},
  doi       = {10.1007/s10334-020-00890-0},
  pages     = {153 -- 164},
  year      = {2020},
  abstract  = {Objective In local SAR compression algorithms, the overestimation is generally not linearly dependent on actual local SAR. This can lead to large relative overestimation at low actual SAR values, unnecessarily constraining transmit array performance. Method Two strategies are proposed to reduce maximum relative overestimation for a given number of VOPs. The first strategy uses an overestimation matrix that roughly approximates actual local SAR; the second strategy uses a small set of pre-calculated VOPs as the overestimation term for the compression. Result Comparison with a previous method shows that for a given maximum relative overestimation the number of VOPs can be reduced by around 20\% at the cost of a higher absolute overestimation at high actual local SAR values. Conclusion The proposed strategies outperform a previously published strategy and can improve the SAR compression where maximum relative overestimation constrains the performance of parallel transmission.},
  language  = {en}
}
@article{FiedlerLaddBitz2017,
  author    = {Fiedler, Thomas M. and Ladd, Mark E. and Bitz, Andreas},
  title     = {SAR Simulations \& Safety},
  series = {NeuroImage},
  journal   = {NeuroImage},
  number    = {Epub ahead of print},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {1053-8119},
  doi       = {10.1016/j.neuroimage.2017.03.035},
  year      = {2017},
  language  = {en}
}
@article{BayerTemizArtmannDigeletal.2020,
  author    = {Bayer, Robin and Temiz Artmann, Ayseg{\"u}l and Digel, Ilya and Falkenstein, Julia and Artmann, Gerhard and Creutz, Till and Hescheler, J{\"u}rgen},
  title     = {Mechano-pharmacological testing of L-Type Ca²⁺ channel modulators via human vascular celldrum model},
  series = {Cellular Physiology and Biochemistry},
  volume    = {54},
  journal   = {Cellular Physiology and Biochemistry},
  publisher = {Cell Physiol Biochem Press},
  address   = {D{\"u}sseldorf},
  issn      = {1421-9778},
  doi       = {10.33594/000000225},
  pages     = {371 -- 383},
  year      = {2020},
  abstract  = {Background/Aims: This study aimed to establish a precise and well-defined working model, assessing pharmaceutical effects on vascular smooth muscle cell monolayer in-vitro. It describes various analysis techniques to determine the most suitable to measure the biomechanical impact of vasoactive agents by using CellDrum technology. Methods: The so-called CellDrum technology was applied to analyse the biomechanical properties of confluent human aorta muscle cells (haSMC) in monolayer. The cell generated tensions deviations in the range of a few N/m² are evaluated by the CellDrum technology. This study focuses on the dilative and contractive effects of L-type Ca²⁺ channel agonists and antagonists, respectively. We analyzed the effects of Bay K8644, nifedipine and verapamil. Three different measurement modes were developed and applied to determine the most appropriate analysis technique for the study purpose. These three operation modes are called, particular time mode" (PTM), "long term mode" (LTM) and "real-time mode" (RTM). Results: It was possible to quantify the biomechanical response of haSMCs to the addition of vasoactive agents using CellDrum technology. Due to the supplementation of 100nM Bay K8644, the tension increased approximately 10.6\% from initial tension maximum, whereas, the treatment with nifedipine and verapamil caused a significant decrease in cellular tension: 10nM nifedipine decreased the biomechanical stress around 6,5\% and 50nM verapamil by 2,8\%, compared to the initial tension maximum. Additionally, all tested measurement modes provide similar results while focusing on different analysis parameters. Conclusion: The CellDrum technology allows highly sensitive biomechanical stress measurements of cultured haSMC monolayers. The mechanical stress responses evoked by the application of vasoactive calcium channel modulators were quantified functionally (N/m²). All tested operation modes resulted in equal findings, whereas each mode features operation-related data analysis.},
  language  = {en}
}
@article{OrzadaSolbachGratzetal.2019,
  author    = {Orzada, Stephan and Solbach, Klaus and Gratz, Marcel and Brunheim, Sascha and Fiedler, Thomas M. and Johst, S{\"o}ren and Bitz, Andreas and Shooshtary, Samaneh and Abuelhaija, Ashraf and Voelker, Maximilian N. and Rietsch, Stefan H. G. and Kraff, Oliver and Maderwald, Stefan and Fl{\"o}ser, Martina and Oehmingen, Mark and Quick, Harald H. and Ladd, Mark E.},
  title     = {A 32-channel parallel transmit system add-on for 7T MRI},
  series = {Plos one},
  journal   = {Plos one},
  doi       = {10.1371/journal.pone.0222452},
  year      = {2019},
  language  = {en}
}
@article{OrzadaBitzJohstetal.2017,
  author    = {Orzada, Stephan and Bitz, Andreas and Johst, S{\"o}ren and Gratz, Marcel and V{\"o}lker, Maximilian N. and Kraff, Oliver and Abuelhaija, Ashraf and Fiedler, Thomas M. and Solbach, Klaus and Quick, Harald H. and Ladd, Mark E.},
  title     = {Analysis of an integrated 8-Channel Tx/Rx body array for use as a body coil in 7-Tesla MRI},
  series = {Frontiers in Physics},
  volume    = {5},
  journal   = {Frontiers in Physics},
  number    = {Jun},
  issn      = {2296-424X},
  doi       = {10.3389/fphy.2017.00017},
  year      = {2017},
  language  = {en}
}
@article{SchollPalmLehmannetal.1998,
  author    = {Scholl, Ingrid and Palm, Christoph and Lehmann, Thomas Martin and Spitzer, Klaus},
  title     = {Quantitative Farbmessung in laryngoskopischen Bildern. Palm, C; Scholl, I; Lehmann, TM; Spitzer, K.},
  series = {Bildverarbeitung f{\"u}r die Medizin 1998. Hrsg.: Thomas Lehmann ...},
  journal   = {Bildverarbeitung f{\"u}r die Medizin 1998. Hrsg.: Thomas Lehmann ...},
  publisher = {Springer},
  address   = {Berlin},
  isbn      = {3-540-63885-7},
  pages     = {412 -- 416},
  year      = {1998},
  language  = {en}
}
@article{FiedlerLaddBitz2017,
  author    = {Fiedler, Thomas M. and Ladd, Mark E. and Bitz, Andreas},
  title     = {RF safety assessment of a bilateral four-channel transmit/receive 7 Tesla breast coil: SAR versus temperature limits},
  series = {Medical Physics},
  volume    = {44},
  journal   = {Medical Physics},
  number    = {1},
  doi       = {10.1002/mp.12034},
  pages     = {143 -- 157},
  year      = {2017},
  language  = {en}
}
@article{DieringerRenzLindeletal.2011,
  author    = {Dieringer, Matthias A. and Renz, Wolfgang and Lindel, Tomasz Dawid and Seifert, Frank and Frauenrath, Tobias and von Knobelsdorf-Brenkenhoff, Florian and Waiczies, Helmar and Hoffmann, Werner and Rieger, Jan and Pfeiffer, Harald and Ittermann, Bernd and Schulz-Menger, Jeanette and Niendorf, Thoralf},
  title     = {Design and application of a four-channel transmit/receive surface coil for functional cardiac imaging at 7T},
  series = {Journal of Magnetic Resonance Imaging},
  volume    = {33},
  journal   = {Journal of Magnetic Resonance Imaging},
  number    = {3},
  publisher = {Wiley-Liss},
  address   = {New York},
  issn      = {1522-2586},
  doi       = {10.1002/jmri.22451},
  pages     = {736 -- 741},
  year      = {2011},
  abstract  = {Purpose To design and evaluate a four-channel cardiac transceiver coil array for functional cardiac imaging at 7T. Materials and Methods A four-element cardiac transceiver surface coil array was developed with two rectangular loops mounted on an anterior former and two rectangular loops on a posterior former. specific absorption rate (SAR) simulations were performed and a Burn:x-wiley:10531807:media:JMRI22451:tex2gif-stack-1 calibration method was applied prior to obtain 2D FLASH CINE (mSENSE, R = 2) images from nine healthy volunteers with a spatial resolution of up to 1 × 1 × 2.5 mm3. Results Tuning and matching was found to be better than 10 dB for all subjects. The decoupling (S21) was measured to be >18 dB between neighboring loops, >20 dB for opposite loops, and >30 dB for other loop combinations. SAR values were well within the limits provided by the IEC. Imaging provided clinically acceptable signal homogeneity with an excellent blood-myocardium contrast applying the Burn:x-wiley:10531807:media:JMRI22451:tex2gif-stack-2 calibration approach. Conclusion A four-channel cardiac transceiver coil array for 7T was built, allowing for cardiac imaging with clinically acceptable signal homogeneity and an excellent blood-myocardium contrast. Minor anatomic structures, such as pericardium, mitral, and tricuspid valves and their apparatus, as well as trabeculae, were accurately delineated.},
  language  = {en}
}
@article{FiedlerLaddClemensetal.2020,
  author    = {Fiedler, Thomas M. and Ladd, Mark E. and Clemens, Markus and Bitz, Andreas},
  title     = {Safety of subjects during radiofrequency exposure in ultra-high-field magnetic resonance imaging},
  series = {IEEE Letters on Electromagnetic Compatibility Practice and Applications},
  volume    = {2},
  journal   = {IEEE Letters on Electromagnetic Compatibility Practice and Applications},
  number    = {3},
  publisher = {IEEE},
  address   = {New York, NY},
  isbn      = {2637-6423},
  doi       = {10.1109/LEMCPA.2020.3029747},
  pages     = {1 -- 8},
  year      = {2020},
  abstract  = {Magnetic resonance imaging (MRI) is one of the most important medical imaging techniques. Since the introduction of MRI in the mid-1980s, there has been a continuous trend toward higher static magnetic fields to obtain i.a. a higher signal-to-noise ratio. The step toward ultra-high-field (UHF) MRI at 7 Tesla and higher, however, creates several challenges regarding the homogeneity of the spin excitation RF transmit field and the RF exposure of the subject. In UHF MRI systems, the wavelength of the RF field is in the range of the diameter of the human body, which can result in inhomogeneous spin excitation and local SAR hotspots. To optimize the homogeneity in a region of interest, UHF MRI systems use parallel transmit systems with multiple transmit antennas and time-dependent modulation of the RF signal in the individual transmit channels. Furthermore, SAR increases with increasing field strength, while the SAR limits remain unchanged. Two different approaches to generate the RF transmit field in UHF systems using antenna arrays close and remote to the body are investigated in this letter. Achievable imaging performance is evaluated compared to typical clinical RF transmit systems at lower field strength. The evaluation has been performed under consideration of RF exposure based on local SAR and tissue temperature. Furthermore, results for thermal dose as an alternative RF exposure metric are presented.},
  language  = {en}
}
@article{BlomeMashhoon1984,
  author    = {Blome, Hans-Joachim and Mashhoon, Bahram},
  title     = {Quasi-normal oscillations of a Schwarzschild black hole},
  series = {Physics Letters A. 100 (1984), H. 5},
  journal   = {Physics Letters A. 100 (1984), H. 5},
  isbn      = {0375-9601},
  pages     = {231 -- 234},
  year      = {1984},
  language  = {en}
}