title: Diagnostic value of T1 and T2 * relaxation times and off-resonance saturation effects in the evaluation of Achilles tendinopathy by MRI at 3T.
abstract: OBJECTIVE
  To evaluate and compare the diagnostic value of T1 , T2 * relaxation times and off-resonance saturation ratios (OSR) in healthy controls and patients with different clinical and morphological stages of Achilles tendinopathy.
  
  
  METHODS
  Forty-two healthy Achilles tendons and 34 tendons of 17 patients with symptomatic and asymptomatic tendinopathy were investigated clinically with conventional magnetic resonance imaging (MRI) sequences on a 3T whole-body MR scanner and a dynamic ultrasound examination. In addition, T1 and T2 * relaxation times were assessed using an ultrashort echo time (UTE) imaging sequence with flip angle and echo time variation. For the calculation of OSR values a Gaussian off-resonance saturation pulse (frequency offset: 750-5000 Hz) was used. The diagnostic value of the derived MR values was assessed and compared using receiver operating characteristic (ROC) curves.
  
  
  RESULTS
  ROC curves demonstrate the highest overall test performance for OSR values at 2000 Hz off-resonance in differentiating slightly (OSR-2000 [AUC: 0.930] > T2 * [AUC: 0.884] > T1 [AUC: 0.737]) and more severe pathologically altered tendon areas (OSR-2000 [AUC: 0.964] > T2 * [AUC: 0.917] > T1 [AUC: 0.819]) from healthy ones.
  
  
  CONCLUSIONS
  OSR values at a frequency offset of 2000 Hz demonstrated a better sensitivity and specificity for detecting mild and severe stages of tendinopathy compared to T2 * and particularly when compared to T1 relaxation times.
authors.affiliation: Department of Diagnostic and Interventional Radiology, University Hospital Tuebingen, Tuebingen, Germany; Section on Experimental Radiology, University Hospital Tuebingen, Tuebingen, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Grosse
authors.forename: Roland
authors.initials: R
authors.lastname: Syha
authors.forename: Tobias
authors.initials: T
authors.lastname: Hein
authors.forename: Sergios
authors.initials: S
authors.lastname: Gatidis
authors.forename: Gerd
authors.initials: G
authors.lastname: Grözinger
authors.forename: Christoph
authors.initials: C
authors.lastname: Schabel
authors.forename: Petros
authors.initials: P
authors.lastname: Martirosian
authors.forename: Fritz
authors.initials: F
authors.lastname: Schick
authors.forename: Fabian
authors.initials: F
authors.lastname: Springer
mesh_terms: D000125:Achilles Tendon / Q000473:pathology*; D000465:Algorithms; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D052256:Tendinopathy / Q000473:pathology*; D013708:Tendon Injuries / Q000473:pathology*
keywords: Achilles tendon; T1 relaxation time; T2* relaxation time; magnetization transfer; off-resonance saturation ratios; tendinopathy