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 ARFIimaging
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.