Cardiac elastography-a feasibility study

Early detection of cardiovascular diseases has been a very active research area in the medical imaging field. Assessment of the local and global mechanical functions is one of the major goals for accurate diagnosis. In this paper, we studied the use of elastography for estimation and imaging of the local cardiac muscle displacement and strain in vivo. In its noninvasive applications, elastography has been typically used to determine local tissue strain through the use of an externally applied compression. For our study, we utilized the cardiac muscle motion, i.e., contraction and relaxation, as the mechanical stimulus, and acquired successive RF data frames over a few cardiac cycles in parasternal and apical views. Best quality cine-loop elastograms were obtained at higher frame rates due to the relatively lower decorrelation noise while the expected tradeoff between signal-to-noise ratio and spatial resolution was also observed. Furthermore, the strain contrast was higher in the parasternal case, when solely the posterior wall was imaged while strain estimation was more robust in the apical case. High repeatability of the results was observed through elastographic measurements over several cardiac cycles. Finally, an M-mode version of elastography was used in order to follow a particular segment of the image in the course of two cardiac cycles. Not only do these preliminary results show that elastography is feasible in cardiac applications in vivo, but also that it can provide new information regarding the cardiac motion and mechanical function. Future prospects include the assessment of the role of elastography in the detection of ischemia as well as infarction.