Frequency Compounding for Ultrasound Freehand Elastography

Ultrasound elastography is the technique of obtaining the tissue relative stiffness information, which plays an important role in early diagnosis. Conventional elastography computes the strain from the gradient of the displacement estimates between gated pre- and post-compression echo signals. Although elastography has been proven to be a potential diagnosis tool for breast/prostate tumor, vascular stiffening and hepatocirrhosis diseases, the application of frequency compounding in elastography to reduce coherent artifact of elastic imaging has rarely been reported. In this paper, a new method called Transmit-side Frequency Compounding for Elastography (TSEC) is proposed, which involves using weighted compounding of different frequency sub-elastograms. The sub-elastograms are formed from the corresponding probe center frequency echo signal pairs reflected from the tissue ROI. Due to the frequency dependent reflection process, these sub-elastograms should have different speckle pattern. Upon compounding these sub-elastograms, the amount of speckle in the resultant strain image is reduced. The effect of TSFC are investigated through phantom experiments, which confirms the reduction in strain image artifact is accomplished with no sacrifice of real-time ultrasonic imaging as well as a measurable improvement in SNRe and CNRe.