In vitro evaluation of three-dimensional ultrasonography based on magnetic scanhead tracking

The objective of this study was to evaluate the accuracy and precision of a magnetic position sensor system for acquisition of three-dimensional (3D) ultrasound images in volume estimation of phantoms in vitro, Installation of either 0.9% solution of saline at 37 degrees C or distilled water at 20 degrees C to a condom was performed. Scanning was performed either by a continuous or stepwise acquisition. This 3D ultrasound system demonstrated good correlation (r = 0.99-1.0, n = 8) between estimated (EV) and true volumes (TV), The errors were in the. range 1.3% +/- 0.3% (SEM) to 1.9% +/- 0.6%, independent of sound velocity, Scanning through a porcine abdominal wall positioned at the fluid surface yielded a systematic underestimation of the volume: mean (EV - TV) = -7.2 +/- 0.8 mi, Eight repeated scans of the same volume yielded a coefficient of variation of 1.1%. Interobserver error of the tracing procedure was 2.6% +/- 0.9%. This 3D ultrasound system gave high accuracy and precision in volume estimation in vitro, and yielded low interobserver error. A change in ultrasound velocity of approximately 60 m/s did not influence the accuracy significantly. Scanning through an abdominal wall underestimated volumes slightly. (C) 1998 World Federation for Ultrasound in Medicine & Biology.