Acoustic Radiation Force Impulse (ARFI) and Transient Elastography (TE) for evaluation of liver fibrosis in HIV-HCV co-infected patients

Abstract

Background: Transient elastography (TE) is widely used for non-invasive assessment of liver fibrosis in HIV-HCV co-infected patients. TE, however, cannot determine liver morphology. Acoustic radiation force impulse (ARFI) imaging is a novel procedure enabling assessment of liver fibrosis during a conventional ultrasonographic examination. This study evaluated the correlation between liver fibrosis measurements by TE and ARFI.

Methods: Each of 46 HIV-HCV patients underwent both ARFI and TE within 6 months. Patients were evaluated by the "equivalent METAVIR" scoring system, using previously established cut-off values. Agreements between the ARFI and TE scores were estimated by Kappa coefficients, with Kappa values ≥0.40, ≥0.60, and ≥0.80 defined as moderate, good and very good agreement, respectively.

Results: ARFI and TE yielded "Equivalent Metavir" fibrosis scores of F1 in 26 and 31 patients, respectively; F2 in nine and seven, respectively; F3 in three and two, respectively; and F4 in eight and six, respectively. The two methods showed very good agreement in predicting overall stages [Kappa = 0.82] and for F ≥3 [Kappa = 0.80] and moderate agreement in predicting significant fibrosis F ≥2 [Kappa = 0.50]. Morphologic ultrasound analysis concomitant to ARFI detected two hepatocarcinomas.

Conclusions: ARFI showed promising results in the non-invasive assessment of liver fibrosis in HIV-HCV patients, with liver fibrosis staging similar to that of TE. Moreover, ARFI can assess morphology and fibrosis during the same session.

Figure 1

Principle or ARFI quantitative measurement. a) Schematic of principles of ARFI imaging in virtual touch quantification mode – b) Example of a SWV measurement of the right liver. Transmission of a longitudinal acoustic pulse leads to tissue displacement, resulting in shear wave propagation away from the region of excitation. The shear wave velocity is measured within a defined region of interest (ROI) using ultrasound tracking beams laterally adjacent to the single push beam. The shear velocity is estimated in a graphically displayed ROI measuring 1 × 0.5 cm. The shear wave propagation velocity is proportional to the square root of tissue elasticity.

Figure 2

Scatterplot of the relationship between median ARFI (m/s) and TE (kPa) measurements.