title: Dynamic contrast-enhanced renal MRI at 7 Tesla: preliminary results.
abstract: OBJECTIVE
  With the successful implementation of ultra-high-field imaging in neuro- and musculoskeletal imaging, the interest of scientific research expanded toward whole-body applications. The aim of this study was to assess the feasibility of dynamic contrast-enhanced renal magnetic resonance imaging (MRI) at 7 Tesla (T), with optimization and implementation of a dedicated examination protocol.
  
  
  METHODS
  In vivo dynamic contrast-enhanced high-field examinations were obtained in 10 healthy subjects on a 7 T whole-body MR scanner. A custom-built body transmit/receive reduced radiofrequency (RF) coil suitable for RF shimming was used for image acquisition. The examination protocol included (1) true fast imaging with steady-state precession imaging, (2) T2-weighted turbo spine echo imaging, (3) T1-weighted (T1w) in- and opposed-phase imaging, and (4) a fat-saturated 2D FLASH sequence. For dynamic imaging, gadobutrol was injected intravenously and T1w 3D FLASH images were obtained precontrast and at 20, 70, and 120 seconds delay. Qualitative image analysis was performed by 2 senior radiologists using a 3-point scale (1 = poor, 2 = moderate, 3 = good quality). Signal-to-noise ratio and contrast-to-noise ratio (CNR) of the renal cortex/medulla were measured for all sequences. For statistical analysis, a Wilcoxon Rank Test was used.
  
  
  RESULTS
  All examinations were performed successfully and were well tolerated by all subjects without any side effects. Best overall image quality was rated for the T1w 2D FLASH sequence with an average score of 2.57, followed by the contrast-enhanced 3D FLASH sequence in the equilibrium phase (mean, 2.22). T2-weighted turbo spine echo imaging provided the weakest overall image quality score (1.30) and was most impaired by artifacts. Quantitative analysis showed highest CNR between cortex and medulla for arterial phase 3D FLASH imaging (CNR = 12.2), providing a statistically significant difference to all other sequences, except for the in- and opposed-phase and the fat-saturated 2D FLASH sequence. Conversely, equilibrium phase FLASH imaging yielded the weakest CNR score of 3.6.
  
  
  CONCLUSIONS
  This feasibility study reveals the diagnostic potential and current constraints of ultra-high-field abdominal MRI. Our initial results demonstrate the potential of dedicated dynamic-contrast 7 T renal MRI and the need for further optimization of imaging sequences and RF coil concepts.
authors.affiliation: Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, University Duisburg-Essen, Essen, Germany. Lale.Umutlu@uk-essen.de
authors.forename: Lale
authors.initials: L
authors.lastname: Umutlu
authors.forename: Oliver
authors.initials: O
authors.lastname: Kraff
authors.forename: Stephan
authors.initials: S
authors.lastname: Orzada
authors.forename: Anja
authors.initials: A
authors.lastname: Fischer
authors.forename: Sonja
authors.initials: S
authors.lastname: Kinner
authors.forename: Stefan
authors.initials: S
authors.lastname: Maderwald
authors.forename: Gerald
authors.initials: G
authors.lastname: Antoch
authors.forename: Harald H
authors.initials: HH
authors.lastname: Quick
authors.forename: Michael
authors.initials: M
authors.lastname: Forsting
authors.forename: Mark E
authors.initials: ME
authors.lastname: Ladd
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Lauenstein
mesh_terms: D000311:Adrenal Glands / Q000473:pathology; D000328:Adult; D003287:Contrast Media; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007668:Kidney / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009942:Organometallic Compounds
chemical_list: D003287:Contrast Media; D009942:Organometallic Compounds; C090600:gadobutrol