title: Prospective evaluation of acoustic radiation force impulse technology in the differentiation of thyroid nodules: accuracy and interobserver variability assessment.
abstract: OBJECTIVE
  The aim of this study is to assess the diagnostic efficacy and interobserver agreement of acoustic radiation force impulse (ARFI) elasticity imaging in differentiating thyroid nodules.
  
  
  METHODS
  In our study, 74 consecutive patients (52 females, 22 males; age range 27-77 years, mean: 41 years) with 82 thyroid nodules (60 benign nodules, and 22 malignant) were examined by two radiologists with different experience. Patients underwent either cytology using fine needle aspiration cytology or thyroid surgery. The diagnostic performance of the two operators at ARFI with sensitivity, specificity, positive predictive and negative predictive value, and ROC curves was estimated. Inter-reader variability between the two operators was defined using Cohen's k.
  
  
  RESULTS
  According to receiver operating characteristics ROC curves (AUROC = 0.86 for observer 1; 0.81 for observer 2) sensitivity, specificity, PPV and NPV of reader 1 and 2 were respectively: 90, 75, 90.91 and 96.55 %; (cut-off value of shear wave: 2.455 m/s); 90, 72, 90 and 96.90 % (cut-off value shear wave: 2.365 m/s). Concordance between the two operators was good (k = 0.755).
  
  
  CONCLUSIONS
  This work is a feasibility study evaluating ARFI imaging. Its results suggest that ARFI imaging is a reproducible method which can be utilized with good diagnostic performance in the thyroid for discriminating benign and malignant nodules using the cut-off value of 2.455 m/s. However, larger studies are needed to validate this method.
authors.affiliation: Department of Radiology, "Sapienza" University of Rome, Rome, Italy ; Department of Radiological, Oncological and Anatomopathological Sciences, "Sapienza" University of Rome, Policlinico Umberto I, Viale Regina Elena, 324, 00161 Rome, Italy.
authors.forename: Hektor
authors.initials: H
authors.lastname: Grazhdani
authors.affiliation: Department of Radiology, "Sapienza" University of Rome, Rome, Italy ; Department of Radiological, Oncological and Anatomopathological Sciences, "Sapienza" University of Rome, Policlinico Umberto I, Viale Regina Elena, 324, 00161 Rome, Italy.
authors.forename: Vito
authors.initials: V
authors.lastname: Cantisani
authors.affiliation: Department of Radiology, "Sapienza" University of Rome, Rome, Italy.
authors.forename: Pietro
authors.initials: P
authors.lastname: Lodise
authors.affiliation: Department of Surgical Sciences, "Sapienza" University of Rome, Rome, Italy.
authors.forename: Giorgio
authors.initials: G
authors.lastname: Di Rocco
authors.affiliation: Department of Radiology, "Sapienza" University of Rome, Rome, Italy.
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Proietto
authors.affiliation: Department of Radiology, "Sapienza" University of Rome, Rome, Italy.
authors.forename: Eloisa
authors.initials: E
authors.lastname: Fioravanti
authors.affiliation: Department of Radiology, "Sapienza" University of Rome, Rome, Italy.
authors.forename: Antonello
authors.initials: A
authors.lastname: Rubini
authors.affiliation: Department of Surgical Sciences, "Sapienza" University of Rome, Rome, Italy.
authors.forename: Adriano
authors.initials: A
authors.lastname: Redler
keywords: Acoustic radiation force impulse (ARFI); Benign thyroid nodules; Elastography; Malignant thyroid nodules; Ultrasound