Abstract
Quality control of duplex imaging involves consistency in performance of grey scale and Doppler frequency shift or velocity measurements. Phantoms are used to measure the accuracy of Duplex scanners, and many phantoms used for grey scale imaging quality control are available commercially. However, simplistic and inexpensive phantoms for velocity measurements are not available. The authors designed and tested one such phantom—an in-house pump that recirculates fluid in a bottle with inlet and outlet tubes. Different pump settings control the speed of circulating fluid. Initially, the authors used discarded blood from the blood bank. However, because of the associated risks with blood, they searched for a substitute with good reflective properties for ultrasound. Small air bubbles in soda pop worked very effectively, because air is the strongest reflector for ultrasound. To the author's knowledge, use of soda pop for this purpose has not been described previously. Three scanners, an HP 2000, Quantum 2000, and ATL 3000, were evaluated for accuracy of velocity measurements. A similar MHz transducer, 45-degree Doppler angle, and same segment of tube with flowing soda pop were used each time. The Quantum scanner consistently measured velocities as lower than the other two scaners by approximately 10-20% at all velocity ranges (50-350 cm/sec). At the higher end of the spectrum, the Quantum scanner consistently displayed aliasing. Therefore, velocities could not be measured.