title: Experimental evaluation of accelerated T1rho relaxation quantification in human liver using limited spin-lock times.
abstract: OBJECTIVE
  It was reported lately that to obtain consistent liver T1rho measurement, at 3T MRI using six spin-lock times (SLTs), is feasible. In this study, the feasibility of using three or two SLT points to measure liver T1rho relaxation time was explored.
  
  
  METHODS
  Seventeen healthy volunteers underwent 36 examinations. Three representative axial slices were selected to cut through the upper, middle, and lower liver. A rotary echo spin-lock pulse was implemented in a 2D fast field echo sequence. Spin-lock frequency was 500 Hz and the spin-lock times of 1, 10, 20, 30, 40, and 50 milliseconds (ms) were used for T1rho mapping. T1rho maps were constructed by using all 6 SLT points, three SLT points of 1, 20, and 50 ms, or two SLTs of 1 and 50 ms, respectively. Intra-class correlation coefficient (ICC) and Bland and Altman plot were used to assess the measurement agreement.
  
  
  RESULTS
  Two examinations were excluded, due to motion artifact at the SLT of 50 ms. With the remaining 34 examinations, the ICC for 6-SLT vs. 3-SLT T1rho measurements was 0.922, while the ICC for 6-SLT vs. 2-SLT T1rho measurement was 0.756. The Bland and Altman analysis showed a mean difference of 0.19 (95% limits of agreement: -1.34, 1.73) for 6-SLT vs. 3-SLT T1rho measurement, and the mean difference of 0.89 (95% limits of agreement: -1.67, 3.45) for 6-SLT vs. 2-SLT T1rho measurement. The scan re-scan reproducibility ICC (n = 11 subjects) was 0.755, 0.727, and 0.528 for 6-SLT measurement, 3-SLT measurement, and 2-SLT measurement, respectively.
  
  
  CONCLUSIONS
  Adopting 3 SLTs of 1, 20, and 50 ms can be an acceptable alternative for the liver T1rho measurement, while 2 SLTs of 1 and 50 ms do not provide reliable measurement.
authors.affiliation: Department of Imaging and Interventional Radiology, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong SAR, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Zhao
authors.forename: Min
authors.initials: M
authors.lastname: Deng
authors.forename: Jing
authors.initials: J
authors.lastname: Yuan
authors.forename: Gao-Jun
authors.initials: GJ
authors.lastname: Teng
authors.forename: Anil T
authors.initials: AT
authors.lastname: Ahuja
authors.forename: Yi-Xiang J
authors.initials: YX
authors.lastname: Wang
mesh_terms: D000328:Adult; D004435:Eating; D017352:Echo-Planar Imaging / Q000379:methods*; D005215:Fasting; D005260:Female; D006801:Humans; D008099:Liver / Q000033:anatomy & histology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D055815:Young Adult
keywords: Liver; Magnetic resonance imaging; Spin-lock time; T1rho