Modified Phase Zero Method for Ultrasound Freehand Strain Imaging

Ultrasound elastography is the technique of obtaining tissue stiffness information. In tumor diagnosis, the stiffness of the tissue is one of the most important parameters for tissue characterization, the more accurate stiffness information clinic doctors obtain, the more reliable diagnosis conclusion they can make. In ultrasound elastography, motion tracking between two successive frames plays a key role for strain estimation. Many algorithms have been presented recently; however, most of them are either inefficient for real time or not robust for general clinical applications. In this paper we developed an I/Q based freehand strain imaging technique including methods to handle decorrelation due to side slide, reduce the calculation from the phase zero method, provide a pre-processing for better strain imaging quality, and offer an interactive guidance for freehand manipulation of strain image acquisition. Our method has been integrated into a commercial ultrasound scanner and test imaging from a strain phantom has demonstrated that our method can consistently detect different level of lesion stiffness in real time.