Acoustic radiation force impulse elastography in distinguishing hepatic haemangiomata from metastases: preliminary observations.

OBJECTIVE: The increasing quality of diagnostic ultrasound has resulted in the detection of greater numbers of potentially benign hepatic lesions. Current radiological practice requires contrast enhanced ultrasound, CT or MRI to confirm the diagnosis. Acoustic radiation force impulse (ARFI) elastography is an imaging technique measuring the elasticity of biological tissues. Recent technical advances in ultrasound have made it possible to generate shear waves, whose velocity in the liver is proportional to the degree of hepatic elasticity.

METHODS: This shear wave velocity (SWV) may be used as a marker for both focal and diffuse liver pathology.We used this technique to examine patients with normal livers and those with haemangiomata and metastases.

RESULTS: Patients with normal ultrasound examinations and normal liver enzymes, n = 99, had SWVs of 1.24 ± 0.23 m s(-1) (mean ± standard deviation) independent of site of measurement, age or gender. Results of SWV measurements in haemangiomata, n = 35, produced values of the same order, 1.35 ± 0.48 m s(-1). In contrast, patients with metastases, n = 10, had SWVs of 4.23 ± 0.59 m s(-1). With a cut-off value of 2.5 m s(-1), the sensitivity and specificity for haemangiomata were 97.1% and 100%, respectively, with an area under the curve of 0.999.

CONCLUSION: ARFI elastography with SWV measurements is a promising new technique which could replace invasive investigations for benign hepatic lesions.