title: Imaging and T2relaxometry of short-T2connective tissues in the knee using ultrashort echo-time double-echo steady-state (UTEDESS).
abstract: OBJECTIVE
  To develop a radial, double-echo steady-state (DESS) sequence with ultra-short echo-time (UTE) capabilities for T2measurement of short-T2tissues along with simultaneous rapid, signal-to-noise ratio (SNR)-efficient, and high-isotropic-resolution morphological knee imaging.
  
  
  METHODS
  THe 3D radial UTE readouts were incorporated into DESS, termed UTEDESS. Multiple-echo-time UTEDESS was used for performing T2relaxometry for short-T2tendons, ligaments, and menisci; and for Dixon water-fat imaging. In vivo T2estimate repeatability and SNR efficiency for UTEDESS and Cartesian DESS were compared. The impact of coil combination methods on short-T2measurements was evaluated by means of simulations. UTEDESS T2measurements were compared with T2measurements from Cartesian DESS, multi-echo spin-echo (MESE), and fast spin-echo (FSE).
  
  
  RESULTS
  UTEDESS produced isotropic resolution images with high SNR efficiency in all short-T2tissues. Simulations and experiments demonstrated that sum-of-squares coil combinations overestimated short-T2measurements. UTEDESS measurements of meniscal T2were comparable to DESS, MESE, and FSE measurements while the tendon and ligament measurements were less biased than those from Cartesian DESS. Average UTEDESS T2repeatability variation was under 10% in all tissues.
  
  
  CONCLUSIONS
  The T2measurements of short-T2tissues and high-resolution morphological imaging provided by UTEDESS makes it promising for studying the whole knee, both in routine clinical examinations and longitudinal studies. Magn Reson Med 78:2136-2148, 2017. © 2017 International Society for Magnetic Resonance in Medicine.
authors.affiliation: Department of Radiology, Stanford University, Stanford, California, USA.|Department of Bioengineering, Stanford University, Stanford, California, USA.
authors.forename: Akshay S
authors.initials: AS
authors.lastname: Chaudhari
authors.affiliation: Department of Radiology, Stanford University, Stanford, California, USA.|Department of Electrical Engineering, Stanford University, Stanford, California, USA.
authors.forename: Bragi
authors.initials: B
authors.lastname: Sveinsson
authors.affiliation: Department of Radiology, Stanford University, Stanford, California, USA.
authors.forename: Catherine J
authors.initials: CJ
authors.lastname: Moran
authors.affiliation: Department of Mechanical Engineering, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
authors.forename: Emily J
authors.initials: EJ
authors.lastname: McWalter
authors.affiliation: Department of Electrical Engineering, Stanford University, Stanford, California, USA.
authors.forename: Ethan M
authors.initials: EM
authors.lastname: Johnson
authors.affiliation: Department of Radiology, Stanford University, Stanford, California, USA.|Department of Electrical Engineering, Stanford University, Stanford, California, USA.
authors.forename: Tao
authors.initials: T
authors.lastname: Zhang
authors.affiliation: Department of Radiology, Stanford University, Stanford, California, USA.|Department of Bioengineering, Stanford University, Stanford, California, USA.
authors.forename: Garry E
authors.initials: GE
authors.lastname: Gold
authors.affiliation: Department of Radiology, Stanford University, Stanford, California, USA.|Department of Bioengineering, Stanford University, Stanford, California, USA.|Department of Electrical Engineering, Stanford University, Stanford, California, USA.
authors.forename: Brian A
authors.initials: BA
authors.lastname: Hargreaves
mesh_terms: D000273:Adipose Tissue / Q000000981:diagnostic imaging; D000328:Adult; D000465:Algorithms; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D021621:Imaging, Three-Dimensional; D007717:Knee / Q000000981:diagnostic imaging*; D007719:Knee Joint / Q000000981:diagnostic imaging; D008022:Ligaments / Q000000981:diagnostic imaging; D008279:Magnetic Resonance Imaging; D008297:Male; D008592:Menisci, Tibial / Q000000981:diagnostic imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D059629:Signal-To-Noise Ratio; D013710:Tendons / Q000000981:diagnostic imaging
keywords: double-echo steady-state (DESS); isotropic resolution; osteoarthritis; relaxometry; short-T2; ultrashort echo time (UTE)