Large Field-Of-View Shear Wave Elasticity Imaging with Combined On- and Off-Axis Stiffness Estimation for High Frame Rate Hepatic HCC Screening

Heptaocellular carcinoma (HCC) is a commonly occurring cancer and is currently detected using B-mode ultrasound scans in at-risk patients. However, B-mode ultrasound has low sensitivity for HCC, particularly for early stage disease. Ultrasound elasticity imaging methods have been used to demonstrate a stiffness contrast between HCC lesions and the surrounding liver, but currently, these elasticity methods are limited to small fields of view (3x3 cm2), such that full liver elasticity screenings would be excessively time consuming. Previous work has simulated a large field-of-view shear wave elasticity imaging sequence with on-axis reconstruction techniques. This work demonstrates this sequence and reconstruction strategy in phantoms, including an experimentally developed lookup table for the on-axis reconstruction. Results are presented for both a homogeneous and lesion-containing phantom. In the homogeneous phantom, the experimentally derived lookuptable exhibits less bias in the on-axis reconstruction than when using a simulation-based lookup table. In the lesion phantom, three lesions are measured and found to have similar shear wave speed values and contrasts to the manufacturer quoted values. Overall, a field of view of 68 cm2 is obtained using 3 overlapping SWEI reconstruction regions.