PERFORMANCE OPTIMIZATION IN ELASTOGRAPHY - MULTICOMPRESSION WITH TEMPORAL STRETCHING

A general theoretical framework known as the strain filter has been pr eviously used to evaluate the performance in elastography. The strain filter describes the relationship among the resolution, dynamic range, sensitivity and elastographic SNR (SNR(e)), and may be plotted as a g raph of the upper bound of the SNR(e) vs. the strain experienced by th e tissue, for a desired elastographic axial resolution as determined b y the data window length. The ideal strain filter has an infinitely hi gh, flat all-pass characteristic shape in the strain domain, which mea ns that all local tissue strains are displayed in the elastogram with infinite SNR(e); it also means that the strain dynamic range in the el astogram is infinite as well. Practical strain filters obtained using a single tissue compression have a bandpass characteristic shape in th e strain domain, where the -3 dB width of this bandpass characteristic may be defined as the elastographic dynamic range. In this paper, we present an optimal technique for stretching multicompression elastogra phy, practiced by selecting the optimum incremental applied strain usi ng the strain filter. Two techniques, temporal stretching and multicom pression elastography, are combined in this paper to improve elastogra m quality. Stretching multicompression elastography using the optimal applied strain increment alters the shape of the strain filter from it s bandpass characteristic to a more desirable high-emphasis filter. Th e dynamic range of optimal stretching multicompression elastography is limited only by tissue nonlinearities. This optimal applied strain in crement minimizes signal decorrelation and achieves the maximum achiev able elastographic SNR(e).