795–5 Digital Particle Image Velocimetry: A New Technique for Verification of Color Doppler Flow Mapping Data

Abstract

Many color Doppler flow mapping (CDFM) systems now provide direct access to digital velocity and variance data, thereby promising true flow quantitation. However, the accuracy of flow information thus obtained has not been adequately verified. We used laser based Digital Particle Image Velocimetry (DPIV) to measure two-dimensional velocity components proximal and distal to various sized orifices (0.1 cm 2 – 1 cm 2 ) for steady flows (0.2 – 3 L/min). Immediately after the DPIV studies and without changing flow conditions, digital CDFM velocity and variance measurements were obtained at identical proximal and distal points. CDFM/digital velocity data showed excellent agreement with the DPIV measurements although three main discrepancies were found: 1) CDFM velocities underestimated DPIV velocities at points of large angulation between ultrasound beam and flow direction although an angle correction algorithm significantly reduced this error. 2) CDFM velocity measurements underestimated DPIVvelocities to a maximum of 48% (mean = 21%) at points of high velocity shear such as the jet boundary, presumably due to the averaging nature and limited time envelope for CDFM velocity measurements. 3) Normalized variance as a percentage of maximum reflected Doppler signal bandwidth (0–1 00%) provided by the CDFM system was present in significant quantity (>30%) in locations of low turbulence intensity as measured by DPIV indicating substantial variation between CDFM variance and hydrodynamic turbulence. DPIV is a promising and highly accurate technique for in-vitro measurements of complex cardiac flow conditions. DPIV also provides an ideal gold-standard for verification of CDFM data and should lead to improved understanding of CDFM information obtained in patients.