title: Off-resonance saturation ratio obtained with ultrashort echo time-magnetization transfer techniques is sensitive to changes in static tensile loading of tendons and degeneration.
abstract: BACKGROUND
  To determine if off-saturation ratio (OSR) measured with the ultrashort echo time magnetization transfer (UTE-MT) sequence could differentiate between tendons under different states of tensile load and to compare these changes between normal versus degenerated tendons.
  
  
  METHODS
  Fourteen tendons were imaged at 3 Tesla before and during the application of 0.5-1 kg tension. A two-dimensional (2D) -UTE-MT sequence with 1.5, 3, and 5 kHz frequency offsets was used on nine tendons and a 3D-UTE-MT sequence with 1.5 kHz frequency offset was used on five tendons. OSR was calculated and compared for each condition. Histologic correlation was performed using light microscopy.
  
  
  RESULTS
  In general, OSR increased after the application of tension. Mean increase of 2D OSR was 0.035 (95% confidence interval [CI], 0.013-0.056) at 1.5 kHz offset (P < 0.01), 0.031 (95% CI, 0.023-0.040) at 3 kHz offset (P < 0.01), and 0.013 (95% CI, -0.013-0.027) at 5 kHz offset (P = 0.07) from pre- to posttension states. Mean increase of 3D OSR was 0.026 (95% CI, 0.008-0.044) at a 1.5 kHz offset (P = 0.02) from pre- to posttension states. Mean decrease of 2D OSR at 1.5 kHz offset was 0.074-0.087 when comparing normal versus degenerated tendons (P < 0.01).
  
  
  CONCLUSIONS
  OSR as measured with 2D or 3D UTE-MT sequences can detect the changes in hydration seen when tendons are placed under two different states of tensile load, but these changes are smaller than those encountered when comparing between normal versus pathologic tendons. Lower off-resonance saturation frequencies (3 kHz or less) are more sensitive to these changes than higher off-resonance saturation frequencies.
authors: Radiology Service, VA San Diego Healthcare System, San Diego, California, USA.|Department of Radiology, University of California, San Diego Medical Center, San Diego, California, USA.
authors: Eric Y
authors: EY
authors: Chang
authors: Department of Radiology, University of California, San Diego Medical Center, San Diego, California, USA.
authors: Jiang
authors: J
authors: Du
authors: Department of Radiology, University of California, San Diego Medical Center, San Diego, California, USA.
authors: Reni
authors: R
authors: Biswas
authors: Department of Radiology, University of California, San Diego Medical Center, San Diego, California, USA.
authors: Sheronda
authors: S
authors: Statum
authors: Institute of Surgical Pathology, University Hospital Zurich, Zurich, Switzerland.
authors: Chantal
authors: C
authors: Pauli
authors: Department of Radiology, University of California, San Diego Medical Center, San Diego, California, USA.
authors: Won C
authors: WC
authors: Bae
authors: Radiology Service, VA San Diego Healthcare System, San Diego, California, USA.|Department of Radiology, University of California, San Diego Medical Center, San Diego, California, USA.
authors: Christine B
authors: CB
authors: Chung
mesh_terms: D000369:Aged, 80 and over; D002102:Cadaver; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D066298:In Vitro Techniques; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013314:Stress, Mechanical; D052256:Tendinopathy / Q000473:pathology* / Q000503:physiopathology*; D013710:Tendons / Q000473:pathology* / Q000503:physiopathology*; D013718:Tensile Strength; D016474:Weight-Bearing
keywords: magnetization transfer; tendinosis; tendon; tension; ultrashort TE