Multidimensional Heart Imaging With Ultrasound

Project: Research project

Project Details


Description (provided by applicant): The long-term goal of this research
program continues: to evaluate myocardial function and physiology with high
temporal and spatial resolution using advanced multidimensional ultrasound
methods. The specific goals of this proposed project for the next five years
are: 1) to relate localized in-plane wall stress, to the vibroacoustography
signal in excised perfused slabs of myocardium and later, in open chest pigs,
2) to relate local myocardial in-plane strain, measured with tissue Doppler
gradients from our intra-cardiac ultrasound catheter, to vibro-acoustography
signals, 3) to measure myocardial perfusion (ml gram-1 min about') from
contrast bubble concentration, with vibro-acoustography using high ultrasound
intensity to clear out bubbles, and then 4) to apply these methods to
characterizing localized myocardial conditions of normal, ischemia, infarct,
and reperfusion, in the hearts of open chest pigs validated with gross vital
staining and histology. These specific goals will be accomplished with two new
imaging methods, both recently developed at Mayo Clinic. The first is an
intracardiac ultrasound imaging catheter developed in collaboration between the
Mayo echocardiography group and Acuson Corporation (AcuNav, Acuson, Inc.,
Mountain View, CA). The intracardiac catheter (ICE) can measure tissue
myocardial Doppler velocity gradients, which are a rough estimate of strain
rate along the direction of the ultrasound beam. The second recently developed
imaging method is "vibro-acoustographic emission" or VAE.
VAE uses radiation force induced vibration of myocardium, detected with
a hydrophone, to estimate stiffness with high spatial
and temporal resolution (-0.7cc, 200 samples/second, respectively). In
controlled in vitro and in vivo studies we will validate the ability of VAE to
estimate wall stress from measurements of stiffness and of ICE to estimate
strain. We also propose that VAE can assess inflow rates of contrast
microbubbles, and thus provide an estimate of blood perfusion, within localized
(-0.7cc) regions in the myocardium. When VAE, validated in this program, is
combined with the ICE catheter in a future clinical instrument, highly
localized stress, strain and perfusion could be estimated within the mvocardium.
StatusNot started


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