title: Virtual touch tissue quantification of acoustic radiation force impulse: a new ultrasound elastic imaging in the diagnosis of thyroid nodules.
abstract: OBJECTIVE
  Virtual touch tissue quantification (VTQ) of acoustic radiation force impulse (ARFI) is a new quantitative technique to measure tissue stiffness. The study was aimed to assess the usefulness of VTQ in the diagnosis of thyroid nodules.
  
  
  METHODS
  173 pathologically proven thyroid nodules in 142 patients were included and all were examined by conventional ultrasound (US), conventional elasticity imaging (EI) and VTQ of ARFI. The tissue stiffness for VTQ was expressed as shear wave velocity (SWV) (m/s). Receiver-operating characteristic curve (ROC) analyses were performed to assess the diagnostic performance. Intra- and inter-observer reproducibility of VTQ measurement was assessed.
  
  
  RESULTS
  The SWVs of benign and malignant thyroid nodules were 2.34±1.17 m/s (range: 0.61-9.00 m/s) and 4.82±2.53 m/s (range: 2.32-9.00 m/s) respectively (P<0.001). The mean SWV ratios between each nodule and the adjacent thyroid tissue were 1.19±0.67 (range: 0.31-6.87) for benign and 2.50±1.54 (range: 0.85-6.69) for malignant nodules (P<0.001). ROC analyses indicated that the area under the curve was 0.861 (95% CI : 0.804, 0.918) (P<0.001) for SWV and 0.831(95% CI : 0.761, 0.900)(P<0.001) for the SWV ratio. The cutoff points for the differential diagnosis were 2.87 m/s for SWV and 1.59 for SWV ratio. The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value for EI were 65.9%, 66.7%, 66.5%, 40.3%, and 85.1%, respectively, and were 63.6%-75%, 82.2%-88.4%, 80.3%-82.1%, 58.9%-65.1%, and 87.7%-90.5%, respectively, for VTQ. The diagnostic value of VTQ is the highest for nodules >20 mm and lowest for those ≤10 mm. The correlation coefficients were 0.904 for intraobserver measurement and 0.864 for interobserver measurement.
  
  
  CONCLUSIONS
  VTQ of ARFI provides quantitative and reproducible information about the tissue stiffness, which is useful for the differentiation between benign and malignant thyroid nodules. The diagnostic performance of VTQ is higher than that of conventional EI.
authors.affiliation: Department of Medical Ultrasound, Tenth People's Hospital of Tongji University, Shanghai, People's Republic of China.
authors.forename: Yi-Feng
authors.initials: YF
authors.lastname: Zhang
authors.forename: Hui-Xiong
authors.initials: HX
authors.lastname: Xu
authors.forename: Yong
authors.initials: Y
authors.lastname: He
authors.forename: Chang
authors.initials: C
authors.lastname: Liu
authors.forename: Le-Hang
authors.initials: LH
authors.lastname: Guo
authors.forename: Lin-Na
authors.initials: LN
authors.lastname: Liu
authors.forename: Jun-Mei
authors.initials: JM
authors.lastname: Xu
mesh_terms: D000162:Acoustics; D000293:Adolescent; D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena; D002291:Carcinoma, Papillary / Q000000981:diagnostic imaging; D054459:Elasticity Imaging Techniques / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D033081:Shear Strength; D016606:Thyroid Nodule / Q000000981:diagnostic imaging*; D014110:Touch; D014584:User-Computer Interface; D055815:Young Adult