Peripheral vascular ARFI imaging: phantom and clinical results

Abstract

Non-invasive characterization of focal and dif- fuse atherosclerosis is difficult with existing techniques, but clinically important in guiding the selection of drug, surgical and other treatments. We describe new non-invasive tech- niques for monitoring vascular health with ARFI imaging. Custom ECG-gated beam sequencing was implemented on the Siemens SONOLINE Antares scanner to measure radiation force induced displacements for in vivo vascular tissue. We have developed layered polyvinyl alcohol cryogel (PVA- C) vessel phantoms to mimic arterial layers in the vascular wall. A custom phantom with layers of varying stiffness but homogeneous echogenicity is statically pressurized over the physiological range, and then imaged with acoustic radiation force. Layers are well visualized in the corresponding ARFI images with little contrast seen in the matched B-mode image. Displacement data is examined over the physiological range and suggests that PVA-C demonstrates some nonlinear behavior over physiologically realistic pressures. We present the preliminary results of a clinical pilot study involving twenty-four volunteers with no predisposition for peripheral vascular disease (PVD), and fifteen patients with diagnosed PVD. Both proximal and distal vascular walls are well visualized in the corresponding ARFI displacement images. Plaques that are present in the B-mode image are also well resolved in the corresponding ARFI image, with ARFI displacement images showing higher contrast between the plaque and surrounding vascular tissue than the conventional B-mode image.