Towards Non-Invasive Mapping of Blood Flow Velocity using Microwaves

Hemodynamic assessment is typically indicated for patients with a critical illness. Unstable hemodynamic conditions can lead to organ dysfunction and eventually death unless treated immediately. Vascular blood pressure and central venous pressure are vital parameters estimated with hemodynamic assessment. Non-invasive methods like ultrasound imaging measure blood velocity and derive pressure gradients. This paper presents an approach to assess the blood flow velocity fields using microwaves non-invasively. For this study, a through-plane blood velocity profile from a left ventricle is used in a 2D electromagnetic simulation at a frequency of 915 MHz. Dielectric properties of blood are assumed to vary linearly by 10% over a velocity range of 0 m/s to 0.2 m/s. Point sources placed around a blood-filled ventricle model act as transmitters and receivers. Distorted Born Iterative Method (DBIM) was used to reconstruct the dielectric parameters. Mapping these parameters back to velocities gives us a visual of the velocity field. The mapped blood flow velocity field from the reconstructed dielectric parameters resembles the velocity fields estimated using Computational Fluid Dynamics (CFD). This study demonstrates the conceptual feasibility of using microwaves for the non-invasive assessment of blood velocities.