Jonathan Ophir
Ignacio Cespedes
Hari Ponnekanti
Nabil Maklad
Univ. of Texas Med. School, Houston, TX 77030
The elastography technique is based on computing localized strain levels in tissue, which are produced in response to a small axial compression, and which are detected by subjecting pre- and post-compression radiofrequency a-line pairs to cross-correlation analysis. Additionally, the absolute stress field generated by the compressor is calculated from theory and from acoustic measurement of the applied stress. The local Young's moduli are estimated from the local axial stresses and strains, with reasonable sensitivity and resolution. Theoretical considerations and simulations were used to investigate the mechanical, acoustical, and signal processing tradeoffs which are encountered, and some of these have been studied experimentally in tissue mimicking phantoms and in tissues in vitro and in vivo. Some of the interesting results to date include improved signal-to-noise ratio in elasticity images (elastograms) as compared to sonograms, the possibility of imaging elasticity in certain acoustically shadowed areas, and the ability to observe certain structures that are invisible on sonograms. Several image artifacts have also been identified.