Fluid attenuated inversion recovery (FLAIR) MRI at 7.0 Tesla: comparison with 1.5 and 3.0 Tesla.
OBJECTIVE
To assess fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI) at three field strengths, regarding signal-to-noise ratio (SNR), contrast and signal homogeneity, in order to determine the potential gain and current challenges of FLAIR at ultra-high field strength (7 T).


METHODS
FLAIR images of five healthy volunteers (age 24 +/- 4 years, 4 male) were acquired at 1.5 T, 3 T and 7 T. Image homogeneity and visibility of normal brain structures were evaluated. SNR of grey matter (GM), white matter (WM) and cerebrospinal fluid (CSF) were measured in regions not affected by transmit field heterogeneity.


RESULTS
The SNR (mean +/- SD) at 7 T (GM 168 +/- 15, WM 125 +/- 11) increased slightly more than proportionally, compared with at 1.5 T (GM 30 +/- 3, WM 22 +/- 2) and 3 T (GM 62 +/- 7, WM 44 +/- 4). Relative contrast between GM and WM at 7 T (1.35 +/- 0.07) was slightly less than at 3 T (1.42 +/- 0.14) or 1.5 T (1.37 +/- 0.07). Several major fibre bundles became visible at 7 T. One incidentally observed white matter lesion was well visible at all field strengths.


CONCLUSIONS
Image homogeneity remains challenging and should be improved by future technical developments. FLAIR imaging at 7 T yields a high SNR,with better contrast for WM substructures and the iron-bearing basal ganglia, and has potential for good conspicuity of WM lesions.
Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands. J.J.M.Zwanenburg@umcutrecht.nl
Jaco J M
JJ
Zwanenburg
Jeroen
J
Hendrikse
Fredy
F
Visser
Taro
T
Takahara
Peter R
PR
Luijten
D000465:Algorithms; D001921:Brain / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055815:Young Adult