title: Optimization and evaluation of reference region variable flip angle (RR-VFA) B1+ and T1Mapping in the Prostate at 3T.
abstract: To optimize and evaluate the reference region variable flip angle (RR-VFA) technique for simultaneous B1+ and T1mapping of the prostate at 3 Tesla (T).
  
  
  
  The fat region surrounding the prostate was first identified using a fractional fat segmentation constant (tF) and a signal fat-fraction threshold (rF), and the relative flip angle (FA) was characterized using an effective fat T1(T1f) within the fat region. Optimal values of tF, rF, and T1fwere chosen by comparing relative FA maps using RR-VFA (ARR-VFA) with a reference relative FA maps (AREF) in the surrounding fat and evaluating interpolation errors within the prostate. The optimized RR-VFA was evaluated in volunteers at 3T on a single scanner (n = 10) and across three scanners (n = 4).
  
  
  
  tF, rFand T1fwere optimized as 0.5, 90%, and 320 ms, respectively. Prostate ARR-VFAshowed differences of 30% among volunteers on one scanner, with no significant differences between ARR-VFAand AREF(P = 0.41). Prostate T1after B1+ correction was 1998 ± 113 ms with significantly (P = 0.004) lower standard deviation than T1before B1+ correction. The average coefficient of variation of prostate T1across multiple scanners decreased from 15% to 5% after B1+ correction.
  
  
  
  The optimized RR-VFA can simultaneously measure B1+ and T1in the prostate without the need for an additional scan and improve T1consistency within and across MRI scanners at 3T.
  
  
  
  3 J. Magn. Reson. Imaging 2017;45:751-760.
authors.affiliation: Department of Radiological Sciences, University of California Los Angeles, California, USA.
authors.forename: Novena A
authors.initials: NA
authors.lastname: Rangwala
authors.affiliation: Department of Radiological Sciences, University of California Los Angeles, California, USA.
authors.forename: Isabel
authors.initials: I
authors.lastname: Dregely
authors.affiliation: Department of Radiological Sciences, University of California Los Angeles, California, USA.
authors.forename: Holden H
authors.initials: HH
authors.lastname: Wu
authors.affiliation: Department of Radiological Sciences, University of California Los Angeles, California, USA.
authors.forename: Kyunghyun
authors.initials: K
authors.lastname: Sung
mesh_terms: D000273:Adipose Tissue / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D000328:Adult; D003198:Computer Simulation; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D011467:Prostate / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique
keywords: T1 mapping; B1 + mapping; variable flip angle; dynamic contrast-enhanced MRI; multi-parametric MRI; prostate