Fast surface and volume estimation from non-parallel cross-sections, for freehand 3-D ultrasound

Abstract

Volume measurements from ultrasound B-scans are useful in many clinical areas. It has previously been demonstrated that using 3-D ultrasound can greatly increase the accuracy of these measurements. Freehand 3-D ultrasound allows freedom of movement in scanning, but the processing is complicated by having non-parallel scan planes. Two techniques are proposed for volume measurement from such data, which also improve surface and volume estimation from data acquired on parallel planes. Cubic planimetry is a more accurate extension of a volume measurement technique involving vector areas and centroids of cross-sections. Maximal disc shape based interpolation is an extension of shape based interpolation which uses maximal disc representations to locally adjust the interpolation direction and hence improve the quality of the generated surface. Both methods are tested in simulation and on in-vivo data. Volumes estimated using cubic planimetry are more accurate than step-section planimetry, and require fewer cross-sections, even for complex objects. Maximal disc shape based interpolation is ideally suited for reconstructing surfaces from a handful of cross-sections, and can therefore be used to give confidence in the segmentation and hence also the cubic planimetry volume.