title: Carpal tunnel syndrome: US strain imaging for diagnosis.
abstract: OBJECTIVE
  To determine the feasibility of two-dimensional (2D) ultrasonographic (US) strain imaging for quantifying and mapping mechanical behaviors of the median nerve, flexor retinaculum, and flexor tendons within the carpal tunnel in normal and carpal tunnel syndrome (CTS) disease states during active finger motion.
  
  
  METHODS
  This prospective study was approved by the institutional review board; all subjects gave written informed consent and had both of their hands examined. Ten wrists in 10 healthy volunteers (age range, 35-51 years) and 16 wrists in 12 patients with CTS (age range, 37-55 years) were examined. In the patients, CTS had been confirmed on the basis of clinical symptoms and results of electrophysiologic studies. Raw US signals were acquired and were cross correlated to enable estimation of 2D incremental displacements, from which 2D strains were computed. The median nerve was characterized by the axial normal strain, while the flexor tendons and the flexor retinaculum were characterized by the shear strain. Temporal mean values (mean cumulative strain [MCS] values) and standard deviations (standard deviations of the cumulative strain [SDCS]) of the spatially averaged cumulative strains in each tissue region over the entire cycle of finger motion were compared by using an unpaired two-tailed Student t test.
  
  
  RESULTS
  MCS for patients with CTS and volunteers was similar. The SDCS for the shear strain of the flexor retinaculum was significantly lower (P < .001) in patients with CTS than in healthy volunteers, while that for the axial strain of the median nerve was higher in healthy volunteers than in patients with CTS (P = .0065).
  
  
  CONCLUSIONS
  US strain imaging can be used to quantify and map tissue kinematics in the carpal tunnel and to differentiate abnormal from normal median nerves in the wrist.
authors.affiliation: From the Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, No. 101, Section 2, Kuang-Fu Road, Hsinchu 30013, Taiwan, Republic of China (Y.Y.L., M.R.L., T.T.K., C.K.Y.); Department of Biomedical Engineering, Hungkuang University, Taichung, Taiwan, Republic of China (Y.Y.L.); Department of Electrical and Electronic Engineering, the University of Hong Kong, Hong Kong, SAR, People's Republic of China (W.N.L.); Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital, Taipei, Taiwan, Republic of China (W.S.C.); Department of Radiology, Taipei Veterans General Hospital, Taipei, Taiwan, Republic of China (H.J.C.); and Department of Neurosurgery, Hsin-chu Mackay Memorial Hospital, Hsinchu, Taiwan, Republic of China (T.T.K.).
authors.forename: Yin-Yin
authors.initials: YY
authors.lastname: Liao
authors.forename: Wei-Ning
authors.initials: WN
authors.lastname: Lee
authors.forename: Ming-Ru
authors.initials: MR
authors.lastname: Lee
authors.forename: Wen-Shiang
authors.initials: WS
authors.lastname: Chen
authors.forename: Hong-Jen
authors.initials: HJ
authors.lastname: Chiou
authors.forename: Tai-Tzung
authors.initials: TT
authors.lastname: Kuo
authors.forename: Chih-Kuang
authors.initials: CK
authors.lastname: Yeh
mesh_terms: D000328:Adult; D002349:Carpal Tunnel Syndrome / Q000000981:diagnostic imaging* / Q000503:physiopathology; D054459:Elasticity Imaging Techniques; D005260:Female; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008875:Middle Aged; D011446:Prospective Studies