Technical Note: Impact of Linear Array Transducer Doppler Aperture Location on Spectral Peak Velocity Measurements - A Phantom Study.

ABSTRACT

OBJECTIVE: Ultrasound beams sometimes need to be steered from the edge of linear array transducers to reach the sample volume with a desired Doppler angle in vascular exams. This phantom study aims to evaluate the impact of apertures located at the array edge on peak velocity (PV) measurements. METHODS: Three ultrasound scanner systems equipped with eight transducers from 3 major ultrasound vendors were tested using a flow phantom with a horizontal tube. Five spectral Doppler measurements with the aperture positioned at one edge of the array and 5 with the aperture at the center of the array were obtained using all available scanner-transducer combinations while maintaining all scan parameters and the sample volume in the same tube location. Differences in PVs between center and edge apertures were compared across 4 constant flow rates. RESULTS: The averaged PVs for all phantom flow rates ranged from 24.4 cm/s to 138.2 cm/s from the array center. The averaged PVs from the center aperture were significantly greater than the corresponding measurements from the edge aperture for each flow rate (all p < 0.001). The relative PV differences ranged from 6.7% to 19.4% across all transducers and flow rates. CONCLUSION: Significantly lower PVs were consistently shown with the Doppler beam aperture at the array edge compared to center among all tested systems. This may be due to a narrower aperture width, shifted central axis, and less intrinsic spectral broadening error at the array edge. Controlling variations in Doppler aperture location is important in clinical applications which depend on consistent velocity measurements.