title: Brain tumor enhancement in MR imaging at 3 Tesla: comparison of SNR and CNR gain using TSE and GRE techniques.
abstract: OBJECTIVE
  The purpose of this study was to compare brain and tumor signal characteristics of T1-weighted turbo spin-echo (TSE) and gradient recalled echo (GRE) sequence techniques at 3 T compared to TSE at 1.5 T, focusing on the detection of contrast enhancement, in a standardized animal model of a brain glioma.
  
  
  METHODS
  Twelve rats with implanted brain gliomas were evaluated at 1.5 and 3 T using matched hardware configurations. At 1.5 T, scanning was performed using a TSE sequence optimized for field strength (480/15 milliseconds; 125 Hz/Px) with postcontrast scans acquired at multiple time points after gadoteridol injection (0.1 mmol/kg). At 3 T, scanning was performed using the 1.5 T equivalent TSE as well as with TSE and GRE techniques optimized for 3 T. Signal-to-noise ratio (SNR) of brain and tumor and tumor contrast-to-noise ratio (CNR) were evaluated for all techniques at both field strengths.
  
  
  RESULTS
  Postcontrast tumor SNR (63.7 +/- 10.8 vs. 29.5 +/- 4.3; P < 0.0001) and brain SNR (35.8 +/- 1.5 vs. 19.1 +/- 0.7; P < 0.0001) showed significant increase at 3 T using matched TSE. Comparing TSE optimized to each field strength (for optimized gray-white contrast), tumor and brain SNR still showed a significant increase at 3 T of 73% and 56%, respectively (both P < 0.0001). Comparing TSE at 1.5 T and GRE at 3 T, tumor SNR increased by 105%, whereas brain SNR increased by 141% (both P < 0.0001). Tumor CNR with matched TSE increased by 168% (P < 0.0001), with optimized TSE by 111% (P < 0.0001), and with GRE at 3 T versus TSE at 1.5 T by 36% (P < 0.001). With additional adjustments for echo time the gain in tumor CNR for 2D GRE may again reach 60%.
  
  
  CONCLUSIONS
  With TSE at 3 T, the SNR gain comes close to the theoretically expected doubling with an even higher tumor CNR increase. In a clinical like setting at 3 T, where a T1w GRE sequence is used, tumor CNR gain is limited. Contrast dose should therefore not be decreased at 3 T.
authors.affiliation: Department of Clinical Radiology, University Hospitals Grosshadern, Ludwig-Maximilians-University, Munich, Germany. bernd.wintersperger@med.uni-muenchen.de
authors.forename: Bernd J
authors.initials: BJ
authors.lastname: Wintersperger
authors.forename: Val M
authors.initials: VM
authors.lastname: Runge
authors.forename: Jonmenjoy
authors.initials: J
authors.lastname: Biswas
authors.forename: Maximilian F
authors.initials: MF
authors.lastname: Reiser
authors.forename: Stefan O
authors.initials: SO
authors.lastname: Schoenberg
mesh_terms: D000818:Animals; D001932:Brain Neoplasms / Q000175:diagnosis* / Q000473:pathology; D003287:Contrast Media; D005260:Female; D005682:Gadolinium; D005910:Glioma / Q000175:diagnosis* / Q000473:pathology; D007089:Image Enhancement / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D008280:Magnetics / Q000295:instrumentation; D051381:Rats; D011916:Rats, Inbred F344; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D003287:Contrast Media; D005682:Gadolinium