Ultrasound elastography based on the normalized cross-correlation and the PSO algorithm

Ultrasound elastography is a common medical imaging applied in medical applications since it can provide the tissue hardness information. Most ultrasound elastography techniques are window based methods. The key of the quasi-static ultrasound elastography is to do the similarity measure between two windows from pre-and post-compression to compute the displacement. In view of this situation, the window size has an important influence on the strain images quality. In this paper, a reasonable method utilizing PSO algorithm to search for the optimal window length for different data is brought out to solve this problem. The displacement map can be estimated with the optimal window length using the normalized cross correlation method. And a spatial derivative operator is applied to estimate the strain map. The strain images with the fixed window length 12 and 50 and the optimal window length using PSO algorithm are compared in this paper. Results show that using PSO algorithm to search for the optimal window length can improve the SNR and CNR of strain images.