A Handheld Probe for Focused Shear Wave Transient Elastography

Noninvasive liver stiffness assessment using shear wave elastography is often limited by wave attenuation in deep tissue. We introduce and validate a handheld focused shear wave transient elastography (fTE) device with interchangeable concave pistons to generate focused shear waves for enhanced elastography in deep tissues.

The device consists of a 3D-printed concave circular piston fit over the face of a phased ultrasound array driven by a mechanical vibrator. Benchtop setup validated shear wave speed (SWS) measurement against ground-truth linear array imaging. Handheld setup assessed measurement repeatability across three piston geometries in tissue-mimicking gelatin phantoms. Supersonic shear wave imaging (SSI) provided independent reference measurements to validate fTE SWS calculations. Shear wave amplitude at 45 mm depth and SWS measurement consistency were assessed.

Benchtop validation confirmed that fTE-measured SWS agreed within 10% of conventional flat piston TE measurements. Handheld setup demonstrated unbiased SWS across all piston geometries and against SSI. At a 45 mm depth, focused pistons produced approximately twofold to sevenfold greater shear wave amplitude than unfocused, depending on focusing gain and gelatin stiffness. Pairwise F-tests confirmed that SWS measurement using unfocused shear waves had significantly larger variance than using focused waves (p < 0.0001).

These results demonstrate the feasibility of surface-generated focused shear waves for robust stiffness assessment. By significantly increasing shear wave amplitude at depth and improving measurement consistency with focused shear waves, this handheld fTE device addresses a primary limitation of conventional transient elastography in patients with deep livers or high body mass index.