Download Doppler Vortography – Detection and Quantification of the Vortices

Doppler Vortography – Detection and Quantification of the Vortices in the Left Ventricle.
Forough Mehregan (maîtrise)
A vortex is a fluid pattern that has a rapid swirling motion around its center. The natural swirling flow
that occurs in the normal left ventricle (LV) during LV filling is optimized in terms of fluid energy
dissipation. In vivo findings revealed the formation of additional counter-rotating vortices in the presence
of cardiac disease. Such unnatural vortices may significantly impair the LV function due to important
kinetic dissipation. One ultrasound technique has generally been used to quantify the vortices in the LV:
optical flow carried out on B-mode frames (echo-PIV). Echo-PIV requires continuous intravenous
injection of contrast agents. Due to the unstable property of bubble aggregates in the LV, a complex finetuning of the contrast infusion before image acquisition is required. This seriously limits the application
of LV echo-PIV in clinical practice.
The objective of this study is to propose a new echocardiographic methodology, called Doppler
vortography, for a thorough quantification of intracardiac vortices based on conventional Doppler images.
Conventional color Doppler ultrasound imaging is a fully non-invasive and inexpensive modality for
imaging blood flow through the heart. This capability has generated great excitement about the use of this
technique to detect and quantify the intra-ventricular vortices that form during left ventricle filling.
Because the Doppler velocities have specific symmetry in the vortex position, we propose an index
“blood vortex signature” (BVS) obtained using a specific covariance-based Kernel filter to reflect the
intra-ventricular vorticity. This method can be easily implemented for routine checks to recognize
ventricular insufficiency and abnormal blood patterns at early stages of heart failure to decrease the
morbidity of cardiac disease.
The reliability of BVS measured by Doppler vortography was assessed in mock Doppler fields and
compared with the ground-truth vorticity mapping. Doppler vortography was also tested in a numerical
phantom with vortical moving ultrasound scatters simulated by Field II software. Field II allows modeling
arbitrary ultrasound transducer and image scan sequence to obtain the RF-signals resulting from the
rotating phantom. Some preliminary results issued from healthy subjects and patients with heart disease
will also be presented in this research project.