@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{HeiserUlrichsMuellerBuchholtz1994,
  author    = {Heiser, Axel and Ulrichs, Karin and M{\"u}ller-Buchholtz, Wolfgang},
  title     = {Isolation of porcine pancreatic islets: low trypsin activity during the isolation procedure guarantees reproducible high islet yields},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-44719},
  year      = {1994},
  abstract  = {During the past few years, interest in xenotransplantation of porcine islets of Langerhans for the future therapy of type I diabetes has Increased markedly. Therefore, we established a semiautomated digestion method for isolating islets from the porcine pancreas. However, although the isolation technique was standardized and collagenase of controlled quality was used, we were unable to attain high islet yields with a satisfactory degree of reproducibility. One hypothesis was that varying degrees of interference by donor pancreatic enzymes were responsible for this failure. The aim of this stUdy was to examine the kinetics of four types of enzymatic activity during the isolation procedure, as well as their effects on islet yield: collagenase, trypsin, neutral protease, and clostripaln. Our results indicate that while exogenous collagenase activity decreases slightly during the isolation procedure, the activity of the pancreas enzymes neutral protease and trypsin increases. In some cases, trypsin activity increases very strongly. A strong increase in trypsin activity correlates with poor islet yield, whereas low trypsin activity always correlates with high islet yield. Addition of the protease inhibitor Pefabloc to the isolation medium results in low trypsin activity and reproducible high islet yields.},
  subject      = {Langerhans-Inseln},
  language  = {en}
}
@article{HeiserUlrichsMuellerRuchholtz1994,
  author    = {Heiser, A. and Ulrichs, Karin and M{\"u}ller-Ruchholtz, W.},
  title     = {Prophylactic trypsin inhibition during the isolation procedure guarantees reproducible, high porcine islet yields},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-45531},
  year      = {1994},
  abstract  = {Abstract: For isolating islets from the porcine pancreas, we established a semiautomated digestion method. Although the isolation technique was standardized and collagenase of controlled quality was used, until now the reproducibility of high islet yields was unsatisfactory. Our hypothesis was that pancreatic trypsin was responsible for this failure. The aim of this study was to investigate the effect of endogenous trypsin on islet yield. Our results demonstrate that a high trypsin level correlates with poor islet yield, whereas low trypsin activity always correlates with high islet yield. Specific inhibition of trypsin results in low trypsin activity and reproducible, high islet yields.},
  language  = {en}
}