title: Magnetization transfer in human Achilles tendon assessed by a 3D ultrashort echo time sequence: quantitative examinations in healthy volunteers at 3T.
abstract: OBJECTIVE
  Magnetization transfer contrast (MTC) imaging provides insight into interactions between free and bounded water. Newly developed ultrashort echo time (UTE) sequences implemented on whole-body magnetic resonance (MR) scanners allow MTC imaging in tissues with extremely fast signal decay such as tendons. The aim of this study was to develop a technique for the quantification of the MT effect in healthy Achilles tendons in-vivo at 3 Tesla.
  
  
  METHODS
  16 normal tendons of volunteers with no history of tendinopathy were examined using a 3D-UTE sequence with a rectangular on-resonant excitation pulse and a Fermi-shaped off-resonant MT preparation pulse. The frequency of the MT pulse was varied from 1 to 5 kHz. MT effects were calculated in terms of the MT ratio (MTR) between measurements without and with MT preparation. Direct saturation effects of MT preparation on the signal intensity were evaluated using numerical simulation of Bloch equations. One patient with tendinopathy was examined to exemplarily show changes of MTR under pathologic conditions.
  
  
  RESULTS
  Calculation of MTR data was feasible in all examined tendons and showed a decrease from 0.53 ± 0.05 to 0.25 ± 0.03 (1 kHz to 5 kHz) for healthy volunteers. Evaluation of variation with gender and dominance of ankle revealed no significant differences (p > 0.05). In contrast, the patient with confirmed tendinopathy showed MTR values between 0.36 (1 kHz) and 0.19 (5 kHz).
  
  
  CONCLUSIONS
  MT effects in human Achilles tendons can be reliably assessed in-vivo using a 3D UTE sequence at 3 T. All healthy tendons showed similar MTR values (coefficient of variation 10.0 ± 1.2 %). The examined patient showed a clearly different MT effect revealing a changed microstructure in the case of tendinopathy.
authors: Diagnostic and Interventional Radiology, Eberhard-Karls-University,Hoppe-Seyler-Str. 3,72076 Tübingen, Germany. roland.syha@gmx.net
authors: R
authors: R
authors: Syha
authors: P
authors: P
authors: Martirosian
authors: D
authors: D
authors: Ketelsen
authors: U
authors: U
authors: Grosse
authors: C D
authors: CD
authors: Claussen
authors: F
authors: F
authors: Schick
authors: F
authors: F
authors: Springer
mesh_terms: D000125:Achilles Tendon / Q000473:pathology*; D000328:Adult; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009716:Numerical Analysis, Computer-Assisted; D012016:Reference Values; D012680:Sensitivity and Specificity; D052256:Tendinopathy / Q000175:diagnosis* / Q000473:pathology; D055815:Young Adult