title: MRI assessment of experimental gliomas using 17.6 T.
abstract: BACKGROUND
  Using ultra-high-field contrast-enhanced magnetic resonance imaging (MRI), an increase of field strength is associated with a decrease of T 1 relaxivity. Yet, the impact of this effect on signal characteristics and contrast-enhanced pathology remains unclear. Hence, we evaluated the potential of a 17.6-T MRI to assess contrast-enhancing parts of experimentally induced rat gliomas compared to 3 T.
  
  
  METHODS
  A total of eight tumor-bearing rats were used for MRI assessments either at 17.6 T (four rats) or at 3 T (four rats) at 11 days after stereotactic implantation of F98 glioma cells into the right frontal lobe. T 1-weighted sequences were used to investigate signal-to-noise-ratios, contrast-to-noise-ratios, and relative contrast enhancement up to 16 min after double-dose contrast application. In addition, tumor volumes were calculated and compared to histology.
  
  
  RESULTS
  The 17.6-T-derived contrast-enhancing volumes were 31.5 ± 15.4 mm(3) at 4 min, 38.8 ± 12.7 mm(3) at 8 min, 51.1 ± 12.6 mm(3) at 12 min, and 61.5 ± 10.8 mm(3) at 16 min after gadobutrol injection. Corresponding histology-derived volumes were clearly higher (138.8 ± 8.4 mm(3); P < 0.01). At 3 T, contrast-enhancing volumes were 85.2 ± 11.7 mm(3) at 4 min, 107.3 ± 11.0 mm(3) at 8 min, 117.0 ± 10.5 mm(3) at 12 min, and 129.1 ± 10.0 mm(3) at 16 min after contrast agent application. Averaged histology-derived volumes (139.1 ± 13.4 mm(3)) in this group were comparable to the 16-min volume (P ↔16 min = 0.38). Compared to ultra-high-field MRI, all 3-T-derived volumes were significantly higher (P < 0.02).
  
  
  CONCLUSIONS
  Compared to 3-T-derived images and histology, tumor volumes were underestimated by approximately 50 % at 17.6 T. Hence, contrast-enhanced 17.6-T MRI provided no further benefits in tumor measurement compared to 3 T.
authors.affiliation: Department of Neuroradiology, University of Erlangen-Nuremberg, Schwabachanlage 6, 91054 Erlangen, Germany. marc.schwarz@uk-erlangen.de
authors.forename: Marc A
authors.initials: MA
authors.lastname: Schwarz
authors.forename: Mirko
authors.initials: M
authors.lastname: Pham
authors.forename: Xavier
authors.initials: X
authors.lastname: Helluy
authors.forename: Arnd
authors.initials: A
authors.lastname: Doerfler
authors.forename: Tobias
authors.initials: T
authors.lastname: Engelhorn
mesh_terms: D000465:Algorithms; D000818:Animals; D001932:Brain Neoplasms / Q000473:pathology*; D003287:Contrast Media; D005910:Glioma / Q000473:pathology*; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009374:Neoplasms, Experimental / Q000473:pathology*; D009942:Organometallic Compounds; D051381:Rats; D011916:Rats, Inbred F344; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D047368:Tumor Burden
chemical_list: D003287:Contrast Media; D009942:Organometallic Compounds; C090600:gadobutrol