Background and aims: Three-dimensional (3D) ultrasound imaging of the total liver volume has not yet been achieved. The aim of this study was to investigate whether a magnetic position sensing system for free-hand acquisition of 3D ultrasound images could be used to estimate liver volumes, and to study the effect of a high-caloric meal on these volumes in healthy subjects.

Methods: A system for position and orientation measurement was interfaced to an ultrasound scanner. In vitro accuracy was evaluated by scanning porcine and rabbit livers. Ten healthy subjects were examined fasting and 30 minutes after ingesting a high-caloric liquid meal. Portal and hepatic blood flow were measured by 2D duplex sonography.

Results: The 3D system yielded a strong correlation (r = 0.98) between true and estimated volumes in vitro. The liver volumes were overestimated by an average of 25.9 +/- 24 ml over the range of 47-1185 ml, giving a mean error of 4.2 +/- 6%. No significant increase in liver volume in response to the meal was seen. The mean liver volume fasting was 1349 +/- 321 ml and 30 minutes postprandially it was 1367 +/- 334 ml (p = 0.5). Portal and hepatic vein flow volume increased, however, significantly from 508 +/- 183 ml/sec to 1038 +/- 369 ml/sec (p = 0.02), and 129.7 +/- 45 ml/min to 191.5 +/- 51 ml/min (p = 0.02), respectively.

Conclusions: Excellent in vitro accuracy was found. Experience in human subjects suggests that a complete 3D study of liver volumes can be obtained from multiple acoustic windows. In healthy subjects no significant increase in liver volume was seen in response to ingestion of a high-caloric liquid meal.