In vivo cardiac, acoustic-radiation-force-driven, shear wave velocimetry.
Shear wave elasticity imaging (SWEI) was employed to track acoustic radiation force impulse (ARFI)-induced shear waves in the mid-myocardium of the left ventricular free wall (LVFW) of a beating canine heart. Shear waves were generated and tracked with a linear ultrasound transducer that was placed directly on the exposed epicardium. Acquisition was ECG-gated and coincided with the mid-diastolic portion of the cardiac cycle. Axial displacement profiles consistent with shear wave propagation were clearly evident in all SWEI acquisitions (i.e., those including an ARFI excitation); displacement data from control cases (i.e., sequences lacking an ARFI excitation) offered no evidence of shear wave propagation and yielded a peak absolute mean displacement below 0.31 microm after motion filtering. Shear wave velocity estimates ranged from 0.82 to 2.65 m/s and were stable across multiple heartbeats for the same interrogation region, with coefficients of variation less than 19% for all matched acquisitions. Variations in velocity estimates suggest a spatial dependence of shear wave velocity through the mid-myocardium of the LVFW, with velocity estimates changing, in limited cases, through depth and lateral position.
Bouchard
Richard R
RR
Department of Biomedical Engineering, Duke University, Durham, NC, USA. rrb@duke.edu
Hsu
Stephen J
SJ
Wolf
Patrick D
PD
Trahey
Gregg E
GE
D000818:Animals; D004285:Dogs; D004452:Echocardiography / Q000379:methods*; D054459:Elasticity Imaging Techniques / Q000379:methods*; D004562:Electrocardiography; D006352:Heart Ventricles / Q000000981:diagnostic imaging; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D009200:Myocardial Contraction / Q000502:physiology; D012212:Rheology; D016276:Ventricular Function / Q000502:physiology