In vivo three-dimensional sonographic measurement of organ volume: validation in the urinary bladder

The purpose of this study was to assess the accuracy of in vivo measurement of organ volume using 3DUS and compare the results to 2D sonographic methods using the urinary bladder as the target organ and voided urine volume for validation. Fifty normal volunteers were studied. 2D volume measurements were based on length, width, and depth data and assumed a regular geometric model. 3D volume measurements were based on masked slices with the voxels integrated over the entire bladder. Voided urine volumes ranged from 35 ml to 701 ml. Residual urine volume was present in 48% of the subjects and ranged from 1% to 14% of the voided volume. 2D volume estimates for all 50 subjects had a mean absolute value of the error of 27.5% +/- 17.8%. 3D volume measurements had a mean absolute value of the error of 4.3% +/- 3.7% (transverse) and 5.6% +/- 3.8% (longitudinal). 3DUS provided more accurate volume measurements than 2DUS, particularly for irregularly shaped organs.