Calibration procedure for performance evaluation of clinical Pulsed Doppler Systems

This paper describes the analysis of an experimental setup for the performances evaluation of Pulsed Doppler feature in clinical ultrasound scanners. The equipment basically consist on a commercial flow phantom made by a straight tube having a known and constant cross sectional area in which a blood mimicking fluid is forced to flow at laminar conditions. Given the accuracy declared by the manufacturer (±0.7 cm/s), unsatisfactory for low flow rates, we calibrated the phantom using the gravimetric method. From the digitized images of the Pulsed Doppler spectra over time, the mean velocities have been computed with the software package developed by the authors. Moreover, to test the calibration procedure in effective conditions, we carried out performance test on five different ultrasound platforms, equipped with phased array and convex array probes with a nominal mean velocity of the blood mimicking fluid ranging from 1.1 cm/s to 12.7 cm/s. The pooled data showed an overestimation of the mean velocity, from over 200% down to about 50%, depending on nominal flow rate and ultrasound equipment. The same data, corrected via the calibration curve, showed a sensible recovery of the estimated accuracy of the tested platforms at low flow rates (<3 cm/s).