title: Acoustic radiation force impulse imaging for differentiation of thyroid nodules.
abstract: BACKGROUND
  Acoustic Radiation Force Impulse (ARFI)-Imaging is an ultrasound-based elastography method enabling quantitative measurement of tissue stiffness. The aim of the present study was to evaluate sensitivity and specificity of ARFI-imaging for differentiation of thyroid nodules and to compare it to the well evaluated qualitative real-time elastography (RTE).
  
  
  METHODS
  ARFI-imaging involves the mechanical excitation of tissue using acoustic pulses to generate localized displacements resulting in shear-wave propagation which is tracked using correlation-based methods and recorded in m/s. Inclusion criteria were: nodules ≥5 mm, and cytological/histological assessment. All patients received conventional ultrasound, real-time elastography (RTE) and ARFI-imaging.
  
  
  RESULTS
  One-hundred-fifty-eight nodules in 138 patients were available for analysis. One-hundred-thirty-seven nodules were benign on cytology/histology, and twenty-one nodules were malignant. The median velocity of ARFI-imaging in the healthy thyroid tissue, as well as in benign and malignant thyroid nodules was 1.76 m/s, 1.90 m/s, and 2.69 m/s, respectively. While no significant difference in median velocity was found between healthy thyroid tissue and benign thyroid nodules, a significant difference was found between malignant thyroid nodules on the one hand and healthy thyroid tissue (p = 0.0019) or benign thyroid nodules (p = 0.0039) on the other hand. No significant difference of diagnostic accuracy for the diagnosis of malignant thyroid nodules was found between RTE and ARFI-imaging (0.74 vs. 0.69, p = 0.54). The combination of RTE with ARFI did not improve diagnostic accuracy.
  
  
  CONCLUSIONS
  ARFI can be used as an additional tool in the diagnostic work up of thyroid nodules with high negative predictive value and comparable results to RTE.
authors.affiliation: Department of Internal Medicine 1, J.W. Goethe-University Hospital, Frankfurt, Germany.
authors.forename: Joerg
authors.initials: J
authors.lastname: Bojunga
authors.forename: Nina
authors.initials: N
authors.lastname: Dauth
authors.forename: Christian
authors.initials: C
authors.lastname: Berner
authors.forename: Gesine
authors.initials: G
authors.lastname: Meyer
authors.forename: Katharina
authors.initials: K
authors.lastname: Holzer
authors.forename: Lisa
authors.initials: L
authors.lastname: Voelkl
authors.forename: Eva
authors.initials: E
authors.lastname: Herrmann
authors.forename: Hartmut
authors.initials: H
authors.lastname: Schroeter
authors.forename: Stefan
authors.initials: S
authors.lastname: Zeuzem
authors.forename: Mireen
authors.initials: M
authors.lastname: Friedrich-Rust
mesh_terms: D000162:Acoustics; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D044963:Biopsy, Fine-Needle; D054459:Elasticity Imaging Techniques / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008495:Medical Oncology / Q000379:methods; D008875:Middle Aged; D011237:Predictive Value of Tests; D012372:ROC Curve; D015203:Reproducibility of Results; D016606:Thyroid Nodule / Q000175:diagnosis* / Q000000981:diagnostic imaging*; D014463:Ultrasonography / Q000379:methods