Fast displacement estimators for freehand ultrasonic strain imaging

Ultrasonic strain imaging aims to display mechanical stiffness parameters of soft tissue. This not yet commonly used medical imaging modality can help improve tumor detection and diagnosis based on the fact that many pathological changes are related to increases in tissue stiffness. Since real-time imaging is often indispensible for diagnostic purposes in clinical practice, fast estimation methods are needed. We investigated the performances of one novel and several established estimators with real-time capability and found that two are especially well-suited for freehand strain imaging. Results are from both Field II simulations and experiments using a commercial ultrasound scanner and a tissue-mimicking phantom that was designed to represent a typical tumor situation.