Intravascular `power' flow imaging: Initial experience in vitro and in vivo

We present a novel power-mode method of IVUS blood flow imaging with in vitro and in vivo results. A 4.3F IVUS catheter was utilized to obtain echo signals from in vitro flow phantoms and from the carotid arteries of instrumented Yorkshire pigs, proximal to a electromagnetic flow probe. The normalized power of echo signals from blood after stationary echo subtraction was utilized to obtain the flow parameter. A range of pulse intervals and appropriate weightings can be used to tailor the power-to-flow response of the system. Power-mode images are sensitive to axial and transverse flow components, although the effect of flow along the beam direction is dominant. The spatial resolution of the technique approximates the ultrasonic counterpart. High sensitivity to low flow, ubiquitous near the vessel and catheter walls, allows good depiction of the free lumen. Low persistence requirements allows imaging of pulsatile flows. In addition to lumen visualization, extensions of this technique include automatic measurement of lumen geometry.