@article{SchreiberLohrBaltesetal.2023,
  author    = {Schreiber, Laura M. and Lohr, David and Baltes, Steffen and Vogel, Ulrich and Elabyad, Ibrahim A. and Bille, Maya and Reiter, Theresa and Kosmala, Aleksander and Gassenmaier, Tobias and Stefanescu, Maria R. and Kollmann, Alena and Aures, Julia and Schnitter, Florian and Pali, Mihaela and Ueda, Yuichiro and Williams, Tatiana and Christa, Martin and Hofmann, Ulrich and Bauer, Wolfgang and Gerull, Brenda and Zernecke, Alma and Erg{\"u}n, S{\"u}leyman and Terekhov, Maxim},
  title     = {Ultra-high field cardiac MRI in large animals and humans for translational cardiovascular research},
  series = {Frontiers in Cardiovascular Medicine},
  volume    = {10},
  journal   = {Frontiers in Cardiovascular Medicine},
  issn      = {2297-055X},
  doi       = {10.3389/fcvm.2023.1068390},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-317398},
  year      = {2023},
  abstract  = {A key step in translational cardiovascular research is the use of large animal models to better understand normal and abnormal physiology, to test drugs or interventions, or to perform studies which would be considered unethical in human subjects. Ultrahigh field magnetic resonance imaging (UHF-MRI) at 7 T field strength is becoming increasingly available for imaging of the heart and, when compared to clinically established field strengths, promises better image quality and image information content, more precise functional analysis, potentially new image contrasts, and as all in-vivo imaging techniques, a reduction of the number of animals per study because of the possibility to scan every animal repeatedly. We present here a solution to the dual use problem of whole-body UHF-MRI systems, which are typically installed in clinical environments, to both UHF-MRI in large animals and humans. Moreover, we provide evidence that in such a research infrastructure UHF-MRI, and ideally combined with a standard small-bore UHF-MRI system, can contribute to a variety of spatial scales in translational cardiovascular research: from cardiac organoids, Zebra fish and rodent hearts to large animal models such as pigs and humans. We present pilot data from serial CINE, late gadolinium enhancement, and susceptibility weighted UHF-MRI in a myocardial infarction model over eight weeks. In 14 pigs which were delivered from a breeding facility in a national SARS-CoV-2 hotspot, we found no infection in the incoming pigs. Human scanning using CINE and phase contrast flow measurements provided good image quality of the left and right ventricle. Agreement of functional analysis between CINE and phase contrast MRI was excellent. MRI in arrested hearts or excised vascular tissue for MRI-based histologic imaging, structural imaging of myofiber and vascular smooth muscle cell architecture using high-resolution diffusion tensor imaging, and UHF-MRI for monitoring free radicals as a surrogate for MRI of reactive oxygen species in studies of oxidative stress are demonstrated. We conclude that UHF-MRI has the potential to become an important precision imaging modality in translational cardiovascular research.},
  language  = {en}
}
@article{TerekhovElabyadSchreiber2021,
  author    = {Terekhov, Maxim and Elabyad, Ibrahim A. and Schreiber, Laura M.},
  title     = {Global optimization of default phases for parallel transmit coils for ultra-high-field cardiac MRI},
  series = {PLoS One},
  volume    = {16},
  journal   = {PLoS One},
  number    = {8},
  doi       = {10.1371/journal.pone.0255341},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-265737},
  year      = {2021},
  abstract  = {The development of novel multiple-element transmit-receive arrays is an essential factor for improving B\(_1\)\(^+\) field homogeneity in cardiac MRI at ultra-high magnetic field strength (B\(_0\) > = 7.0T). One of the key steps in the design and fine-tuning of such arrays during the development process is finding the default driving phases for individual coil elements providing the best possible homogeneity of the combined B\(_1\)\(^+\)-field that is achievable without (or before) subject-specific B\(_1\)\(^+\)-adjustment in the scanner. This task is often solved by time-consuming (brute-force) or by limited efficiency optimization methods. In this work, we propose a robust technique to find phase vectors providing optimization of the B-1-homogeneity in the default setup of multiple-element transceiver arrays. The key point of the described method is the pre-selection of starting vectors for the iterative solver-based search to maximize the probability of finding a global extremum for a cost function optimizing the homogeneity of a shaped B\(_1\)\(^+\)-field. This strategy allows for (i) drastic reduction of the computation time in comparison to a brute-force method and (ii) finding phase vectors providing a combined B\(_1\)\(^+\)-field with homogeneity characteristics superior to the one provided by the random-multi-start optimization approach. The method was efficiently used for optimizing the default phase settings in the in-house-built 8Tx/16Rx arrays designed for cMRI in pigs at 7T.},
  language  = {en}
}
@article{ElabyadTerekhovLohretal.2020,
  author    = {Elabyad, Ibrahim A. and Terekhov, Maxim and Lohr, David and Stefanescu, Maria R. and Baltes, Steffen and Schreiber, Laura M.},
  title     = {A Novel Mono-surface Antisymmetric 8Tx/16Rx Coil Array for Parallel Transmit Cardiac MRI in Pigs at 7T},
  series = {Scientific Reports},
  volume    = {10},
  journal   = {Scientific Reports},
  number    = {1},
  doi       = {10.1038/s41598-020-59949-6},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-229436},
  year      = {2020},
  abstract  = {A novel mono-surface antisymmetric 16-element transmit/receive (Tx/Rx) coil array was designed, simulated, constructed, and tested for cardiac magnetic resonance imaging (cMRI) in pigs at 7T. The cardiac array comprised of a mono-surface 16-loops with two central elements arranged antisymmetrically and flanked by seven elements on either side. The array was configured for parallel transmit (pTx) mode to have an eight channel transmit and 16-channel receive (8Tx/16Rx) coil array. Electromagnetic (EM) simulations, bench-top measurements, phantom, and MRI experiments with two pig cadavers (68 and 46 kg) were performed. Finally, the coil was used in pilot in-vivo measurements with a 60 kg pig. Flip angle (FA), geometry factor (g-factor), signal-to-noise ratio (SNR) maps, and high-resolution cardiac images were acquired with an in-plane resolution of 0.6 mm x 0.6 mm (in-vivo) and 0.3 mm x 0.3 mm (ex-vivo). The mean g-factor over the heart was 1.26 (R = 6). Static phase B-1(+) shimming in a pig body phantom with the optimal phase vectors makes possible to improve the B-1(+) homogeneity by factor > 2 and transmit efficiency by factor > 3 compared to zero phases (before RF shimming). Parallel imaging performed in the in-vivo measurements demonstrated well preserved diagnostic quality of the resulting images at acceleration factors up to R = 6. The described hardware design can be adapted for arrays optimized for animals and humans with a larger number of elements (32-64) while maintaining good decoupling for various MRI applications at UHF (e.g., cardiac, head, and spine).},
  language  = {en}
}