@article{NoureddineBitzLaddetal.2015,
  author    = {Noureddine, Yacine and Bitz, Andreas and Ladd, Mark E. and Th{\"u}rling, Markus and Ladd, Susanne C. and Schaefers, Gregor and Kraff, Oliver},
  title     = {Experience with magnetic resonance imaging of human subjects with passive implants and tattoos at 7 T: a retrospective study},
  series = {Magnetic Resonance Materials in Physics, Biology and Medicine},
  volume    = {28},
  journal   = {Magnetic Resonance Materials in Physics, Biology and Medicine},
  number    = {6},
  publisher = {Springer},
  address   = {Berlin},
  issn      = {1352-8661},
  doi       = {10.1007/s10334-015-0499-y},
  pages     = {577 -- 590},
  year      = {2015},
  language  = {en}
}
@article{NoureddineKraffLaddetal.2017,
  author    = {Noureddine, Yacine and Kraff, Oliver and Ladd, Mark E. and Wrede, Karsten H. and Chen, Bixia and Quick, Harald H. and Schaefers, Gregor and Bitz, Andreas},
  title     = {In vitro and in silico assessment of RF-induced heating around intracranial aneurysm clips at 7 Tesla},
  series = {Magnetic Resonance in Medicine},
  journal   = {Magnetic Resonance in Medicine},
  number    = {Early view},
  publisher = {Wiley},
  address   = {Weinheim},
  issn      = {1522-2594},
  doi       = {10.1002/mrm.26650},
  pages     = {14 Seiten},
  year      = {2017},
  language  = {en}
}
@article{ChenSchoembergKraffetal.2016,
  author    = {Chen, Bixia and Schoemberg, Tobias and Kraff, Oliver and Dammann, Philipp and Bitz, Andreas and Schlamann, Marc and Quick, Harald H. and Ladd, Mark E. and Sure, Ulrich and Wrede, Karsten H.},
  title     = {Cranial fixation plates in cerebral magnetic resonance imaging: a 3 and 7 Tesla in vivo image quality study},
  series = {Magnetic Resonance Materials in Physics, Biology and Medicine},
  volume    = {29},
  journal   = {Magnetic Resonance Materials in Physics, Biology and Medicine},
  number    = {3},
  publisher = {Springer},
  address   = {Berlin},
  issn      = {1352-8661},
  doi       = {10.1007/s10334-016-0548-1},
  pages     = {389 -- 398},
  year      = {2016},
  abstract  = {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.},
  language  = {en}
}
@article{MaasVosLagemaatetal.2014,
  author    = {Maas, Marnix C. and Vos, Eline K. and Lagemaat, Miriam W. and Bitz, Andreas and Orzada, Stephan and Kobus, Thiele and Kraff, Oliver and Maderwald, Stefan and Ladd, Mark E. and Scheenen, Tom W. J.},
  title     = {Feasibility of T₂-weighted turbo spin echo imaging of the human prostate at 7 tesla},
  series = {Magnetic Resonance in Medicine},
  volume    = {71},
  journal   = {Magnetic Resonance in Medicine},
  number    = {5},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {1522-2594},
  doi       = {10.1002/mrm.24818},
  pages     = {1711 -- 1719},
  year      = {2014},
  abstract  = {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.},
  language  = {en}
}
@article{UmutluKraffFischeretal.2013,
  author    = {Umutlu, Lale and Kraff, Oliver and Fischer, Anja and Kinner, Sonja and Maderwald, Stefan and Nassenstein, Kai and Nensa, Felix and Gr{\"u}neisen, Johannes and Orzada, Stephan and Bitz, Andreas and Forsting, Michael and Ladd, Mark E. and Lauenstein, Thomas C.},
  title     = {Seven-Tesla MRI of the female pelvis},
  series = {European Radiology},
  volume    = {23},
  journal   = {European Radiology},
  number    = {9},
  publisher = {Springer},
  address   = {Berlin},
  issn      = {1432-1084},
  doi       = {10.1007/s00330-013-2868-0},
  pages     = {2364 -- 2373},
  year      = {2013},
  language  = {en}
}
@article{KraffWredeSchoembergetal.2013,
  author    = {Kraff, Oliver and Wrede, Karsten H. and Schoemberg, Tobias and Dammann, Philipp and Noureddine, Yacine and Orzada, Stephan and Ladd, Mark E. and Bitz, Andreas},
  title     = {MR safety assessment of potential RF heating from cranial fixation plates at 7 T},
  series = {Medical Physics},
  volume    = {40},
  journal   = {Medical Physics},
  number    = {4},
  publisher = {Wiley},
  address   = {Hoboken},
  issn      = {2473-4209},
  doi       = {10.1118/1.4795347},
  pages     = {042302-1 -- 042302-10},
  year      = {2013},
  language  = {en}
}
@article{UmutluOrzadaKinneretal.2011,
  author    = {Umutlu, Lale and Orzada, Stephan and Kinner, Sonja and Maderwald, Stefan and Bronte, Irina and Bitz, Andreas and Kraff, Oliver and Ladd, Susanne C. and Antoch, Gerald and Ladd, Mark E. and Quick, Harald H. and Lauenstein, Thomas C.},
  title     = {Renal imaging at 7 Tesla: preliminary results},
  series = {European Radiology},
  volume    = {21},
  journal   = {European Radiology},
  number    = {4},
  publisher = {Springer},
  address   = {Berlin},
  issn      = {1432-1084},
  pages     = {841 -- 849},
  year      = {2011},
  abstract  = {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.},
  language  = {en}
}
@article{UmutluBitzMaderwaldetal.2013,
  author    = {Umutlu, Lale and Bitz, Andreas and Maderwald, Stefan and Orzada, Stephan and Kinner, Sonja and Kraff, Oliver and Brote, Irina and Ladd, Susanne C. and Schroeder, Tobias and Forsting, Michael},
  title     = {Contrast-enhanced ultra-high-field liver MRI: a feasibility trial},
  series = {European Journal of Radiology},
  volume    = {82},
  journal   = {European Journal of Radiology},
  number    = {5},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0720-048X},
  doi       = {10.1016/j.ejrad.2011.07.004},
  pages     = {760 -- 767},
  year      = {2013},
  language  = {en}
}
@article{KraffBitzBreyeretal.2011,
  author    = {Kraff, Oliver and Bitz, Andreas and Breyer, Tobias and Kruszona, Stefan and Maderwald, Stefan and Brote, Irina and Gizewski, Elke R. and Ladd, Mark E. and Quick, Harald H.},
  title     = {A transmit/receive radiofrequency array for imaging the carotid arteries at 7 Tesla: coil design and first in vivo results},
  series = {Investigative Radiology},
  volume    = {46},
  journal   = {Investigative Radiology},
  number    = {4},
  publisher = {Wolters Kluwer},
  address   = {K{\"o}ln},
  issn      = {1536-0210},
  doi       = {10.1097/RLI.0b013e318206cee4},
  pages     = {246 -- 254},
  year      = {2011},
  abstract  = {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.},
  language  = {en}
}
@article{KraffBitzKruszonaetal.2009,
  author    = {Kraff, Oliver and Bitz, Andreas and Kruszona, Stefan and Orzada, Stephan and Schaefer, Lena C. and Theysohn, Jens M. and Maderwald, Stefan and Ladd, Mark E. and Quick, Harald H.},
  title     = {An eight-channel phased array RF coil for spine MR imaging at 7 T},
  series = {Investigative Radiology},
  volume    = {44},
  journal   = {Investigative Radiology},
  number    = {11},
  publisher = {Lippincott Williams \& Wilkins},
  issn      = {1536-0210},
  doi       = {10.1097/RLI.0b013e3181b24ab7},
  pages     = {734 -- 740},
  year      = {2009},
  language  = {en}
}